Download Anna University B-Tech ECE 5th Sem Communication Systems CS Lab Manual Question Paper

1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

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V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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--- Content provided by FirstRanker.com ---

Name : _______________________________________
Register No. : _______________________________________

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Section : _______________________________________

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LABORATORY MANUAL
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1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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DEPARTMENT OF

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ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

--- Content provided by FirstRanker.com ---

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

--- Content provided by FirstRanker.com ---

LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

--- Content provided by FirstRanker.com ---

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul

--- Content provided by FirstRanker.com ---

DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING


To impart professional education integrated with human values to the younger generation, so as to

--- Content provided by FirstRanker.com ---

shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity


? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics

--- Content provided by FirstRanker.com ---

industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

--- Content provided by FirstRanker.com ---

VISION

--- Content provided by FirstRanker.com ---

VISION
MISSION
MISSION
FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?

--- Content provided by FirstRanker.com ---

DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

--- Content provided by FirstRanker.com ---

V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

--- Content provided by FirstRanker.com ---

LABORATORY MANUAL

--- Content provided by FirstRanker.com ---

2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

DHANALAKSHMI

--- Content provided by FirstRanker.com ---

College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry

--- Content provided by FirstRanker.com ---

? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

--- Content provided by FirstRanker.com ---

To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

--- Content provided by FirstRanker.com ---

? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems

--- Content provided by FirstRanker.com ---

? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

--- Content provided by FirstRanker.com ---

VISION
VISION
MISSION
MISSION

--- Content provided by FirstRanker.com ---

3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,

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enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions

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3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students

--- Content provided by FirstRanker.com ---

to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


?

--- Content provided by FirstRanker.com ---

DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

--- Content provided by FirstRanker.com ---

V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

Name : _______________________________________

--- Content provided by FirstRanker.com ---

Register No. : _______________________________________
Section : _______________________________________

--- Content provided by FirstRanker.com ---

LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

DHANALAKSHMI

--- Content provided by FirstRanker.com ---

College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

--- Content provided by FirstRanker.com ---

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION

--- Content provided by FirstRanker.com ---

ENGINEERING


To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges

--- Content provided by FirstRanker.com ---

in deploying technology for the service of humanity


? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry

--- Content provided by FirstRanker.com ---

? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

--- Content provided by FirstRanker.com ---

VISION
VISION

--- Content provided by FirstRanker.com ---

MISSION
MISSION
3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)

--- Content provided by FirstRanker.com ---

1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence

--- Content provided by FirstRanker.com ---

To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products

--- Content provided by FirstRanker.com ---

4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics

--- Content provided by FirstRanker.com ---

To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints

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such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks

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f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities

--- Content provided by FirstRanker.com ---

j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


?

--- Content provided by FirstRanker.com ---

DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

--- Content provided by FirstRanker.com ---

V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

Name : _______________________________________

--- Content provided by FirstRanker.com ---

Register No. : _______________________________________
Section : _______________________________________

--- Content provided by FirstRanker.com ---

LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

DHANALAKSHMI

--- Content provided by FirstRanker.com ---

College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

--- Content provided by FirstRanker.com ---

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION

--- Content provided by FirstRanker.com ---

ENGINEERING


To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges

--- Content provided by FirstRanker.com ---

in deploying technology for the service of humanity


? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry

--- Content provided by FirstRanker.com ---

? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

--- Content provided by FirstRanker.com ---

VISION
VISION

--- Content provided by FirstRanker.com ---

MISSION
MISSION
3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)

--- Content provided by FirstRanker.com ---

1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence

--- Content provided by FirstRanker.com ---

To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products

--- Content provided by FirstRanker.com ---

4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics

--- Content provided by FirstRanker.com ---

To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints

--- Content provided by FirstRanker.com ---

such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks

--- Content provided by FirstRanker.com ---

f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities

--- Content provided by FirstRanker.com ---

j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM

--- Content provided by FirstRanker.com ---

? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes

--- Content provided by FirstRanker.com ---

LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator

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5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)

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10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

--- Content provided by FirstRanker.com ---

Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

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COURSE OBJECTIVES
COURSE OUTCOMES
FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?

--- Content provided by FirstRanker.com ---

DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

--- Content provided by FirstRanker.com ---

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

--- Content provided by FirstRanker.com ---

LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious

--- Content provided by FirstRanker.com ---

enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels

--- Content provided by FirstRanker.com ---

? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

--- Content provided by FirstRanker.com ---

To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

--- Content provided by FirstRanker.com ---

? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical

--- Content provided by FirstRanker.com ---

practices

--- Content provided by FirstRanker.com ---

VISION
VISION
MISSION
MISSION
3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher

--- Content provided by FirstRanker.com ---

education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth

--- Content provided by FirstRanker.com ---

To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social

--- Content provided by FirstRanker.com ---

context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics

--- Content provided by FirstRanker.com ---

Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits

--- Content provided by FirstRanker.com ---

d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness

--- Content provided by FirstRanker.com ---

of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 - COMMUNICATION SYSTEMS LABORATORY

--- Content provided by FirstRanker.com ---

To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes

--- Content provided by FirstRanker.com ---

? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing

--- Content provided by FirstRanker.com ---

3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM

--- Content provided by FirstRanker.com ---

8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

--- Content provided by FirstRanker.com ---

Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise

--- Content provided by FirstRanker.com ---

performance of communication system.

COURSE OBJECTIVES
COURSE OUTCOMES
6 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS

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1 Signal sampling reconstruction
7
2 Time division multiplexing
13
3 AM modulation demodulation

--- Content provided by FirstRanker.com ---

18
4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33

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6 Delta modulation demodulation
38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS

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8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB

--- Content provided by FirstRanker.com ---

55
11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59

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ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

?

--- Content provided by FirstRanker.com ---

DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

--- Content provided by FirstRanker.com ---

V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

--- Content provided by FirstRanker.com ---

LABORATORY MANUAL

--- Content provided by FirstRanker.com ---

2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

DHANALAKSHMI

--- Content provided by FirstRanker.com ---

College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry

--- Content provided by FirstRanker.com ---

? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

--- Content provided by FirstRanker.com ---

To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

--- Content provided by FirstRanker.com ---

? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems

--- Content provided by FirstRanker.com ---

? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

--- Content provided by FirstRanker.com ---

VISION
VISION
MISSION
MISSION

--- Content provided by FirstRanker.com ---

3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,

--- Content provided by FirstRanker.com ---

enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions

--- Content provided by FirstRanker.com ---

3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students

--- Content provided by FirstRanker.com ---

to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00



PROGRAMME OUTCOMES (POs)

--- Content provided by FirstRanker.com ---

a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics

--- Content provided by FirstRanker.com ---

communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large

--- Content provided by FirstRanker.com ---

h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM

--- Content provided by FirstRanker.com ---

? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction

--- Content provided by FirstRanker.com ---

2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation

--- Content provided by FirstRanker.com ---

7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation

--- Content provided by FirstRanker.com ---

12. Equalization ? Zero Forcing and LMS algorithms (simulation)


Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.

--- Content provided by FirstRanker.com ---

Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

COURSE OBJECTIVES
COURSE OUTCOMES

--- Content provided by FirstRanker.com ---

6 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.

--- Content provided by FirstRanker.com ---

CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7
2 Time division multiplexing
13

--- Content provided by FirstRanker.com ---

3 AM modulation demodulation
18
4 Frequency modulation demodulation
26
5 PCM modulation demodulation

--- Content provided by FirstRanker.com ---

33
6 Delta modulation demodulation
38
7 Line coding decoding techniques
45

--- Content provided by FirstRanker.com ---

CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB
53

--- Content provided by FirstRanker.com ---

10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB

--- Content provided by FirstRanker.com ---

59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

--- Content provided by FirstRanker.com ---

7 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit

--- Content provided by FirstRanker.com ---

Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.

--- Content provided by FirstRanker.com ---

Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For

--- Content provided by FirstRanker.com ---

reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known

--- Content provided by FirstRanker.com ---

as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the

--- Content provided by FirstRanker.com ---

sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
FirstRanker.com - FirstRanker's Choice

--- Content provided by FirstRanker.com ---

1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


?

--- Content provided by FirstRanker.com ---

DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

--- Content provided by FirstRanker.com ---

V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

Name : _______________________________________
Register No. : _______________________________________

--- Content provided by FirstRanker.com ---

Section : _______________________________________

--- Content provided by FirstRanker.com ---

LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

DHANALAKSHMI

--- Content provided by FirstRanker.com ---

College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

--- Content provided by FirstRanker.com ---

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

--- Content provided by FirstRanker.com ---

To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

--- Content provided by FirstRanker.com ---

? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in

--- Content provided by FirstRanker.com ---

communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

--- Content provided by FirstRanker.com ---

VISION
VISION
MISSION

--- Content provided by FirstRanker.com ---

MISSION
3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals

--- Content provided by FirstRanker.com ---

To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge

--- Content provided by FirstRanker.com ---

training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism

--- Content provided by FirstRanker.com ---

To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,

--- Content provided by FirstRanker.com ---

through commitment lifelong learning needed for successful professional career

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability

--- Content provided by FirstRanker.com ---

c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities

--- Content provided by FirstRanker.com ---

g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning

--- Content provided by FirstRanker.com ---

k) To participate succeed in competitive exams

--- Content provided by FirstRanker.com ---

5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation

--- Content provided by FirstRanker.com ---

? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS

--- Content provided by FirstRanker.com ---

1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation

--- Content provided by FirstRanker.com ---

6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)

--- Content provided by FirstRanker.com ---

11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)


Simulate end-to-end Communication Link

--- Content provided by FirstRanker.com ---

Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

COURSE OBJECTIVES

--- Content provided by FirstRanker.com ---

COURSE OUTCOMES
6 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS

--- Content provided by FirstRanker.com ---

Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7
2 Time division multiplexing

--- Content provided by FirstRanker.com ---

13
3 AM modulation demodulation
18
4 Frequency modulation demodulation
26

--- Content provided by FirstRanker.com ---

5 PCM modulation demodulation
33
6 Delta modulation demodulation
38
7 Line coding decoding techniques

--- Content provided by FirstRanker.com ---

45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB

--- Content provided by FirstRanker.com ---

53
10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB
57

--- Content provided by FirstRanker.com ---

12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

7 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:

--- Content provided by FirstRanker.com ---

To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.

--- Content provided by FirstRanker.com ---

4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.

--- Content provided by FirstRanker.com ---

A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the

--- Content provided by FirstRanker.com ---

signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals

--- Content provided by FirstRanker.com ---

The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.

--- Content provided by FirstRanker.com ---

8 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.

--- Content provided by FirstRanker.com ---

Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.

--- Content provided by FirstRanker.com ---

5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

Circuit Diagram

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

?

--- Content provided by FirstRanker.com ---

DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

--- Content provided by FirstRanker.com ---

V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

--- Content provided by FirstRanker.com ---

LABORATORY MANUAL

--- Content provided by FirstRanker.com ---

2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

DHANALAKSHMI

--- Content provided by FirstRanker.com ---

College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry

--- Content provided by FirstRanker.com ---

? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

--- Content provided by FirstRanker.com ---

To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

--- Content provided by FirstRanker.com ---

? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems

--- Content provided by FirstRanker.com ---

? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

--- Content provided by FirstRanker.com ---

VISION
VISION
MISSION
MISSION

--- Content provided by FirstRanker.com ---

3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,

--- Content provided by FirstRanker.com ---

enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions

--- Content provided by FirstRanker.com ---

3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students

--- Content provided by FirstRanker.com ---

to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00



PROGRAMME OUTCOMES (POs)

--- Content provided by FirstRanker.com ---

a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics

--- Content provided by FirstRanker.com ---

communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large

--- Content provided by FirstRanker.com ---

h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM

--- Content provided by FirstRanker.com ---

? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction

--- Content provided by FirstRanker.com ---

2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation

--- Content provided by FirstRanker.com ---

7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation

--- Content provided by FirstRanker.com ---

12. Equalization ? Zero Forcing and LMS algorithms (simulation)


Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.

--- Content provided by FirstRanker.com ---

Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

COURSE OBJECTIVES
COURSE OUTCOMES

--- Content provided by FirstRanker.com ---

6 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.

--- Content provided by FirstRanker.com ---

CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7
2 Time division multiplexing
13

--- Content provided by FirstRanker.com ---

3 AM modulation demodulation
18
4 Frequency modulation demodulation
26
5 PCM modulation demodulation

--- Content provided by FirstRanker.com ---

33
6 Delta modulation demodulation
38
7 Line coding decoding techniques
45

--- Content provided by FirstRanker.com ---

CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB
53

--- Content provided by FirstRanker.com ---

10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB

--- Content provided by FirstRanker.com ---

59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

--- Content provided by FirstRanker.com ---

7 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit

--- Content provided by FirstRanker.com ---

Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.

--- Content provided by FirstRanker.com ---

Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For

--- Content provided by FirstRanker.com ---

reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known

--- Content provided by FirstRanker.com ---

as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the

--- Content provided by FirstRanker.com ---

sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
8 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:

--- Content provided by FirstRanker.com ---

1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.

--- Content provided by FirstRanker.com ---

6. Integrate the sampling inputs.

Circuit Diagram

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

9 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

--- Content provided by FirstRanker.com ---

FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

?



DEPARTMENT OF

--- Content provided by FirstRanker.com ---

ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

--- Content provided by FirstRanker.com ---

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

--- Content provided by FirstRanker.com ---

LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

--- Content provided by FirstRanker.com ---

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul

--- Content provided by FirstRanker.com ---

DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING


To impart professional education integrated with human values to the younger generation, so as to

--- Content provided by FirstRanker.com ---

shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity


? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics

--- Content provided by FirstRanker.com ---

industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

--- Content provided by FirstRanker.com ---

VISION

--- Content provided by FirstRanker.com ---

VISION
MISSION
MISSION
3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education

--- Content provided by FirstRanker.com ---

2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to

--- Content provided by FirstRanker.com ---

find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context

--- Content provided by FirstRanker.com ---

5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field

--- Content provided by FirstRanker.com ---

b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems

--- Content provided by FirstRanker.com ---

e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility

--- Content provided by FirstRanker.com ---

i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 - COMMUNICATION SYSTEMS LABORATORY

--- Content provided by FirstRanker.com ---

To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms

--- Content provided by FirstRanker.com ---

? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator

--- Content provided by FirstRanker.com ---

4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes

--- Content provided by FirstRanker.com ---

9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

--- Content provided by FirstRanker.com ---

Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

--- Content provided by FirstRanker.com ---

COURSE OBJECTIVES
COURSE OUTCOMES
6 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction

--- Content provided by FirstRanker.com ---

7
2 Time division multiplexing
13
3 AM modulation demodulation
18

--- Content provided by FirstRanker.com ---

4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33
6 Delta modulation demodulation

--- Content provided by FirstRanker.com ---

38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB

--- Content provided by FirstRanker.com ---

51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB
55

--- Content provided by FirstRanker.com ---

11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS

--- Content provided by FirstRanker.com ---

13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

--- Content provided by FirstRanker.com ---

7 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

CYCLE 1 - EXPERIMENTS

--- Content provided by FirstRanker.com ---

Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.

--- Content provided by FirstRanker.com ---

2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at

--- Content provided by FirstRanker.com ---

which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.

--- Content provided by FirstRanker.com ---

Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples

--- Content provided by FirstRanker.com ---

taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To

--- Content provided by FirstRanker.com ---

recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
8 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit

--- Content provided by FirstRanker.com ---

works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.

--- Content provided by FirstRanker.com ---

3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

--- Content provided by FirstRanker.com ---

Circuit Diagram

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

9 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

10 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

Tabulation

Analog signal sampling and reconstruction trainer kit

--- Content provided by FirstRanker.com ---

Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

--- Content provided by FirstRanker.com ---

Signal Amplitude (V) Time period (s)
Message signal
Carrier signal
Sampled output

--- Content provided by FirstRanker.com ---

FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


?

--- Content provided by FirstRanker.com ---

DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

--- Content provided by FirstRanker.com ---

V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

Name : _______________________________________

--- Content provided by FirstRanker.com ---

Register No. : _______________________________________
Section : _______________________________________

--- Content provided by FirstRanker.com ---

LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

DHANALAKSHMI

--- Content provided by FirstRanker.com ---

College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

--- Content provided by FirstRanker.com ---

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION

--- Content provided by FirstRanker.com ---

ENGINEERING


To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges

--- Content provided by FirstRanker.com ---

in deploying technology for the service of humanity


? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry

--- Content provided by FirstRanker.com ---

? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

--- Content provided by FirstRanker.com ---

VISION
VISION

--- Content provided by FirstRanker.com ---

MISSION
MISSION
3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)

--- Content provided by FirstRanker.com ---

1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence

--- Content provided by FirstRanker.com ---

To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products

--- Content provided by FirstRanker.com ---

4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics

--- Content provided by FirstRanker.com ---

To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints

--- Content provided by FirstRanker.com ---

such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks

--- Content provided by FirstRanker.com ---

f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities

--- Content provided by FirstRanker.com ---

j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM

--- Content provided by FirstRanker.com ---

? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes

--- Content provided by FirstRanker.com ---

LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator

--- Content provided by FirstRanker.com ---

5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)

--- Content provided by FirstRanker.com ---

10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

--- Content provided by FirstRanker.com ---

Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

--- Content provided by FirstRanker.com ---

COURSE OBJECTIVES
COURSE OUTCOMES
6 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

--- Content provided by FirstRanker.com ---

CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7

--- Content provided by FirstRanker.com ---

2 Time division multiplexing
13
3 AM modulation demodulation
18
4 Frequency modulation demodulation

--- Content provided by FirstRanker.com ---

26
5 PCM modulation demodulation
33
6 Delta modulation demodulation
38

--- Content provided by FirstRanker.com ---

7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51

--- Content provided by FirstRanker.com ---

9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB

--- Content provided by FirstRanker.com ---

57
12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61

--- Content provided by FirstRanker.com ---

14 Amplitude modulation demodulation using LabVIEW 64

--- Content provided by FirstRanker.com ---

7 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION

--- Content provided by FirstRanker.com ---

Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.

--- Content provided by FirstRanker.com ---

3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are

--- Content provided by FirstRanker.com ---

natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem

--- Content provided by FirstRanker.com ---

If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.

--- Content provided by FirstRanker.com ---

Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz

--- Content provided by FirstRanker.com ---

and gain T.
8 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of

--- Content provided by FirstRanker.com ---

control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.

--- Content provided by FirstRanker.com ---

4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

Circuit Diagram

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

9 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

Natural Sampling and Flat Top Sampling Circuit Diagram

--- Content provided by FirstRanker.com ---

Model Graph:

10 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

Tabulation

Analog signal sampling and reconstruction trainer kit

--- Content provided by FirstRanker.com ---

Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

--- Content provided by FirstRanker.com ---

Signal Amplitude (V) Time period (s)
Message signal
Carrier signal
Sampled output
11 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.
Applications:

--- Content provided by FirstRanker.com ---

1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

--- Content provided by FirstRanker.com ---

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate
4. Define ? Nyquist interval

--- Content provided by FirstRanker.com ---

5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?

--- Content provided by FirstRanker.com ---

10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.

--- Content provided by FirstRanker.com ---

15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?

--- Content provided by FirstRanker.com ---

20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling


Viva - voce

--- Content provided by FirstRanker.com ---

FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


?

--- Content provided by FirstRanker.com ---

DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

--- Content provided by FirstRanker.com ---

V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

Name : _______________________________________

--- Content provided by FirstRanker.com ---

Register No. : _______________________________________
Section : _______________________________________

--- Content provided by FirstRanker.com ---

LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

DHANALAKSHMI

--- Content provided by FirstRanker.com ---

College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

--- Content provided by FirstRanker.com ---

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION

--- Content provided by FirstRanker.com ---

ENGINEERING


To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges

--- Content provided by FirstRanker.com ---

in deploying technology for the service of humanity


? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry

--- Content provided by FirstRanker.com ---

? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

--- Content provided by FirstRanker.com ---

VISION
VISION

--- Content provided by FirstRanker.com ---

MISSION
MISSION
3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)

--- Content provided by FirstRanker.com ---

1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence

--- Content provided by FirstRanker.com ---

To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products

--- Content provided by FirstRanker.com ---

4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics

--- Content provided by FirstRanker.com ---

To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints

--- Content provided by FirstRanker.com ---

such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks

--- Content provided by FirstRanker.com ---

f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities

--- Content provided by FirstRanker.com ---

j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM

--- Content provided by FirstRanker.com ---

? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes

--- Content provided by FirstRanker.com ---

LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator

--- Content provided by FirstRanker.com ---

5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)

--- Content provided by FirstRanker.com ---

10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

--- Content provided by FirstRanker.com ---

Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

--- Content provided by FirstRanker.com ---

COURSE OBJECTIVES
COURSE OUTCOMES
6 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

--- Content provided by FirstRanker.com ---

CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7

--- Content provided by FirstRanker.com ---

2 Time division multiplexing
13
3 AM modulation demodulation
18
4 Frequency modulation demodulation

--- Content provided by FirstRanker.com ---

26
5 PCM modulation demodulation
33
6 Delta modulation demodulation
38

--- Content provided by FirstRanker.com ---

7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51

--- Content provided by FirstRanker.com ---

9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB

--- Content provided by FirstRanker.com ---

57
12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61

--- Content provided by FirstRanker.com ---

14 Amplitude modulation demodulation using LabVIEW 64

--- Content provided by FirstRanker.com ---

7 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION

--- Content provided by FirstRanker.com ---

Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.

--- Content provided by FirstRanker.com ---

3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are

--- Content provided by FirstRanker.com ---

natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem

--- Content provided by FirstRanker.com ---

If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.

--- Content provided by FirstRanker.com ---

Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz

--- Content provided by FirstRanker.com ---

and gain T.
8 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of

--- Content provided by FirstRanker.com ---

control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.

--- Content provided by FirstRanker.com ---

4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

Circuit Diagram

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

9 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

Natural Sampling and Flat Top Sampling Circuit Diagram

--- Content provided by FirstRanker.com ---

Model Graph:

10 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

Tabulation

Analog signal sampling and reconstruction trainer kit

--- Content provided by FirstRanker.com ---

Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

--- Content provided by FirstRanker.com ---

Signal Amplitude (V) Time period (s)
Message signal
Carrier signal
Sampled output
11 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.
Applications:

--- Content provided by FirstRanker.com ---

1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

--- Content provided by FirstRanker.com ---

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate
4. Define ? Nyquist interval

--- Content provided by FirstRanker.com ---

5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?

--- Content provided by FirstRanker.com ---

10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.

--- Content provided by FirstRanker.com ---

15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?

--- Content provided by FirstRanker.com ---

20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling


Viva - voce

--- Content provided by FirstRanker.com ---

12 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit

--- Content provided by FirstRanker.com ---

Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.

--- Content provided by FirstRanker.com ---

Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.
Procedure:

--- Content provided by FirstRanker.com ---

1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on

--- Content provided by FirstRanker.com ---

channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)

--- Content provided by FirstRanker.com ---

on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .

--- Content provided by FirstRanker.com ---

FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

?



DEPARTMENT OF

--- Content provided by FirstRanker.com ---

ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

--- Content provided by FirstRanker.com ---

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

--- Content provided by FirstRanker.com ---

LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

--- Content provided by FirstRanker.com ---

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul

--- Content provided by FirstRanker.com ---

DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING


To impart professional education integrated with human values to the younger generation, so as to

--- Content provided by FirstRanker.com ---

shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity


? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics

--- Content provided by FirstRanker.com ---

industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

--- Content provided by FirstRanker.com ---

VISION

--- Content provided by FirstRanker.com ---

VISION
MISSION
MISSION
3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education

--- Content provided by FirstRanker.com ---

2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to

--- Content provided by FirstRanker.com ---

find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context

--- Content provided by FirstRanker.com ---

5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field

--- Content provided by FirstRanker.com ---

b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems

--- Content provided by FirstRanker.com ---

e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility

--- Content provided by FirstRanker.com ---

i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 - COMMUNICATION SYSTEMS LABORATORY

--- Content provided by FirstRanker.com ---

To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms

--- Content provided by FirstRanker.com ---

? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator

--- Content provided by FirstRanker.com ---

4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes

--- Content provided by FirstRanker.com ---

9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

--- Content provided by FirstRanker.com ---

Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

--- Content provided by FirstRanker.com ---

COURSE OBJECTIVES
COURSE OUTCOMES
6 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction

--- Content provided by FirstRanker.com ---

7
2 Time division multiplexing
13
3 AM modulation demodulation
18

--- Content provided by FirstRanker.com ---

4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33
6 Delta modulation demodulation

--- Content provided by FirstRanker.com ---

38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB

--- Content provided by FirstRanker.com ---

51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB
55

--- Content provided by FirstRanker.com ---

11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS

--- Content provided by FirstRanker.com ---

13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

--- Content provided by FirstRanker.com ---

7 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

CYCLE 1 - EXPERIMENTS

--- Content provided by FirstRanker.com ---

Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.

--- Content provided by FirstRanker.com ---

2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at

--- Content provided by FirstRanker.com ---

which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.

--- Content provided by FirstRanker.com ---

Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples

--- Content provided by FirstRanker.com ---

taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To

--- Content provided by FirstRanker.com ---

recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
8 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit

--- Content provided by FirstRanker.com ---

works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.

--- Content provided by FirstRanker.com ---

3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

--- Content provided by FirstRanker.com ---

Circuit Diagram

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

9 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

10 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

Tabulation

Analog signal sampling and reconstruction trainer kit

--- Content provided by FirstRanker.com ---

Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

--- Content provided by FirstRanker.com ---

Signal Amplitude (V) Time period (s)
Message signal
Carrier signal
Sampled output

--- Content provided by FirstRanker.com ---

11 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.

--- Content provided by FirstRanker.com ---

Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)

--- Content provided by FirstRanker.com ---

5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate

--- Content provided by FirstRanker.com ---

4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?

--- Content provided by FirstRanker.com ---

9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.

--- Content provided by FirstRanker.com ---

14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.

--- Content provided by FirstRanker.com ---

19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

--- Content provided by FirstRanker.com ---

Viva - voce
12 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:

--- Content provided by FirstRanker.com ---

To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.

--- Content provided by FirstRanker.com ---

4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.

--- Content provided by FirstRanker.com ---

Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .

--- Content provided by FirstRanker.com ---

3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .

--- Content provided by FirstRanker.com ---

6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .

--- Content provided by FirstRanker.com ---

13 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Circuit Diagram

--- Content provided by FirstRanker.com ---

Time division multiplexing

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

FirstRanker.com - FirstRanker's Choice

--- Content provided by FirstRanker.com ---

1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


?

--- Content provided by FirstRanker.com ---

DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

--- Content provided by FirstRanker.com ---

V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

Name : _______________________________________
Register No. : _______________________________________

--- Content provided by FirstRanker.com ---

Section : _______________________________________

--- Content provided by FirstRanker.com ---

LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

DHANALAKSHMI

--- Content provided by FirstRanker.com ---

College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

--- Content provided by FirstRanker.com ---

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

--- Content provided by FirstRanker.com ---

To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

--- Content provided by FirstRanker.com ---

? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in

--- Content provided by FirstRanker.com ---

communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

--- Content provided by FirstRanker.com ---

VISION
VISION
MISSION

--- Content provided by FirstRanker.com ---

MISSION
3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals

--- Content provided by FirstRanker.com ---

To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge

--- Content provided by FirstRanker.com ---

training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism

--- Content provided by FirstRanker.com ---

To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,

--- Content provided by FirstRanker.com ---

through commitment lifelong learning needed for successful professional career

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability

--- Content provided by FirstRanker.com ---

c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities

--- Content provided by FirstRanker.com ---

g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning

--- Content provided by FirstRanker.com ---

k) To participate succeed in competitive exams

--- Content provided by FirstRanker.com ---

5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation

--- Content provided by FirstRanker.com ---

? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS

--- Content provided by FirstRanker.com ---

1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation

--- Content provided by FirstRanker.com ---

6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)

--- Content provided by FirstRanker.com ---

11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)


Simulate end-to-end Communication Link

--- Content provided by FirstRanker.com ---

Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

COURSE OBJECTIVES

--- Content provided by FirstRanker.com ---

COURSE OUTCOMES
6 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS

--- Content provided by FirstRanker.com ---

Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7
2 Time division multiplexing

--- Content provided by FirstRanker.com ---

13
3 AM modulation demodulation
18
4 Frequency modulation demodulation
26

--- Content provided by FirstRanker.com ---

5 PCM modulation demodulation
33
6 Delta modulation demodulation
38
7 Line coding decoding techniques

--- Content provided by FirstRanker.com ---

45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB

--- Content provided by FirstRanker.com ---

53
10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB
57

--- Content provided by FirstRanker.com ---

12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

7 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:

--- Content provided by FirstRanker.com ---

To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.

--- Content provided by FirstRanker.com ---

4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.

--- Content provided by FirstRanker.com ---

A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the

--- Content provided by FirstRanker.com ---

signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals

--- Content provided by FirstRanker.com ---

The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.

--- Content provided by FirstRanker.com ---

8 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.

--- Content provided by FirstRanker.com ---

Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.

--- Content provided by FirstRanker.com ---

5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

Circuit Diagram

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

9 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

Natural Sampling and Flat Top Sampling Circuit Diagram

--- Content provided by FirstRanker.com ---

Model Graph:

10 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Tabulation

--- Content provided by FirstRanker.com ---

Analog signal sampling and reconstruction trainer kit


Result:

--- Content provided by FirstRanker.com ---

Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.


Signal Amplitude (V) Time period (s)

--- Content provided by FirstRanker.com ---

Message signal
Carrier signal
Sampled output
11 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)

--- Content provided by FirstRanker.com ---

2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

--- Content provided by FirstRanker.com ---

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?

--- Content provided by FirstRanker.com ---

6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?

--- Content provided by FirstRanker.com ---

11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?

--- Content provided by FirstRanker.com ---

16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.

--- Content provided by FirstRanker.com ---

21. Define ? Natural Sampling


Viva - voce
12 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:

--- Content provided by FirstRanker.com ---

1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:

--- Content provided by FirstRanker.com ---

Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.

--- Content provided by FirstRanker.com ---

2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.

--- Content provided by FirstRanker.com ---

4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .

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7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .

--- Content provided by FirstRanker.com ---

13 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Circuit Diagram
Time division multiplexing

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--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

14 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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TDM Trainer Kit

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FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


?

--- Content provided by FirstRanker.com ---

DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

--- Content provided by FirstRanker.com ---

V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

Name : _______________________________________

--- Content provided by FirstRanker.com ---

Register No. : _______________________________________
Section : _______________________________________

--- Content provided by FirstRanker.com ---

LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

DHANALAKSHMI

--- Content provided by FirstRanker.com ---

College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

--- Content provided by FirstRanker.com ---

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION

--- Content provided by FirstRanker.com ---

ENGINEERING


To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges

--- Content provided by FirstRanker.com ---

in deploying technology for the service of humanity


? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry

--- Content provided by FirstRanker.com ---

? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

--- Content provided by FirstRanker.com ---

VISION
VISION

--- Content provided by FirstRanker.com ---

MISSION
MISSION
3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)

--- Content provided by FirstRanker.com ---

1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence

--- Content provided by FirstRanker.com ---

To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products

--- Content provided by FirstRanker.com ---

4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics

--- Content provided by FirstRanker.com ---

To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints

--- Content provided by FirstRanker.com ---

such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks

--- Content provided by FirstRanker.com ---

f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities

--- Content provided by FirstRanker.com ---

j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM

--- Content provided by FirstRanker.com ---

? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes

--- Content provided by FirstRanker.com ---

LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator

--- Content provided by FirstRanker.com ---

5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)

--- Content provided by FirstRanker.com ---

10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

--- Content provided by FirstRanker.com ---

Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

--- Content provided by FirstRanker.com ---

COURSE OBJECTIVES
COURSE OUTCOMES
6 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

--- Content provided by FirstRanker.com ---

CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7

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2 Time division multiplexing
13
3 AM modulation demodulation
18
4 Frequency modulation demodulation

--- Content provided by FirstRanker.com ---

26
5 PCM modulation demodulation
33
6 Delta modulation demodulation
38

--- Content provided by FirstRanker.com ---

7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51

--- Content provided by FirstRanker.com ---

9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB

--- Content provided by FirstRanker.com ---

57
12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61

--- Content provided by FirstRanker.com ---

14 Amplitude modulation demodulation using LabVIEW 64

--- Content provided by FirstRanker.com ---

7 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION

--- Content provided by FirstRanker.com ---

Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.

--- Content provided by FirstRanker.com ---

3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are

--- Content provided by FirstRanker.com ---

natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem

--- Content provided by FirstRanker.com ---

If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.

--- Content provided by FirstRanker.com ---

Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz

--- Content provided by FirstRanker.com ---

and gain T.
8 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of

--- Content provided by FirstRanker.com ---

control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.

--- Content provided by FirstRanker.com ---

4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

Circuit Diagram

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9 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Natural Sampling and Flat Top Sampling Circuit Diagram

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Model Graph:

10 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

Tabulation

Analog signal sampling and reconstruction trainer kit

--- Content provided by FirstRanker.com ---

Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

--- Content provided by FirstRanker.com ---

Signal Amplitude (V) Time period (s)
Message signal
Carrier signal
Sampled output
11 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.
Applications:

--- Content provided by FirstRanker.com ---

1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

--- Content provided by FirstRanker.com ---

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate
4. Define ? Nyquist interval

--- Content provided by FirstRanker.com ---

5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?

--- Content provided by FirstRanker.com ---

10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.

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15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?

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20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling


Viva - voce

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12 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit

--- Content provided by FirstRanker.com ---

Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.

--- Content provided by FirstRanker.com ---

Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.
Procedure:

--- Content provided by FirstRanker.com ---

1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on

--- Content provided by FirstRanker.com ---

channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)

--- Content provided by FirstRanker.com ---

on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .

--- Content provided by FirstRanker.com ---

13 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Circuit Diagram
Time division multiplexing

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

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14 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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TDM Trainer Kit

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15 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Model Graph:

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Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1
2. Message Signal 2
3. TDM signal

--- Content provided by FirstRanker.com ---

Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the

--- Content provided by FirstRanker.com ---

signals.


FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

?

--- Content provided by FirstRanker.com ---

DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

--- Content provided by FirstRanker.com ---

V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

--- Content provided by FirstRanker.com ---

LABORATORY MANUAL

--- Content provided by FirstRanker.com ---

2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

DHANALAKSHMI

--- Content provided by FirstRanker.com ---

College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry

--- Content provided by FirstRanker.com ---

? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

--- Content provided by FirstRanker.com ---

To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

--- Content provided by FirstRanker.com ---

? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems

--- Content provided by FirstRanker.com ---

? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

--- Content provided by FirstRanker.com ---

VISION
VISION
MISSION
MISSION

--- Content provided by FirstRanker.com ---

3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,

--- Content provided by FirstRanker.com ---

enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions

--- Content provided by FirstRanker.com ---

3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students

--- Content provided by FirstRanker.com ---

to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00



PROGRAMME OUTCOMES (POs)

--- Content provided by FirstRanker.com ---

a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics

--- Content provided by FirstRanker.com ---

communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large

--- Content provided by FirstRanker.com ---

h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM

--- Content provided by FirstRanker.com ---

? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction

--- Content provided by FirstRanker.com ---

2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation

--- Content provided by FirstRanker.com ---

7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation

--- Content provided by FirstRanker.com ---

12. Equalization ? Zero Forcing and LMS algorithms (simulation)


Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.

--- Content provided by FirstRanker.com ---

Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

COURSE OBJECTIVES
COURSE OUTCOMES

--- Content provided by FirstRanker.com ---

6 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.

--- Content provided by FirstRanker.com ---

CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7
2 Time division multiplexing
13

--- Content provided by FirstRanker.com ---

3 AM modulation demodulation
18
4 Frequency modulation demodulation
26
5 PCM modulation demodulation

--- Content provided by FirstRanker.com ---

33
6 Delta modulation demodulation
38
7 Line coding decoding techniques
45

--- Content provided by FirstRanker.com ---

CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB
53

--- Content provided by FirstRanker.com ---

10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB

--- Content provided by FirstRanker.com ---

59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

--- Content provided by FirstRanker.com ---

7 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit

--- Content provided by FirstRanker.com ---

Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.

--- Content provided by FirstRanker.com ---

Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For

--- Content provided by FirstRanker.com ---

reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known

--- Content provided by FirstRanker.com ---

as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the

--- Content provided by FirstRanker.com ---

sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
8 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:

--- Content provided by FirstRanker.com ---

1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.

--- Content provided by FirstRanker.com ---

6. Integrate the sampling inputs.

Circuit Diagram

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

9 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

--- Content provided by FirstRanker.com ---

10 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Tabulation

--- Content provided by FirstRanker.com ---

Analog signal sampling and reconstruction trainer kit


Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer

--- Content provided by FirstRanker.com ---

kit.


Signal Amplitude (V) Time period (s)
Message signal

--- Content provided by FirstRanker.com ---

Carrier signal
Sampled output
11 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Outcome:

--- Content provided by FirstRanker.com ---

After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)

--- Content provided by FirstRanker.com ---

3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem

--- Content provided by FirstRanker.com ---

2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?

--- Content provided by FirstRanker.com ---

7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?

--- Content provided by FirstRanker.com ---

12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal

--- Content provided by FirstRanker.com ---

17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

--- Content provided by FirstRanker.com ---

Viva - voce
12 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.

--- Content provided by FirstRanker.com ---

2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common

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signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.

--- Content provided by FirstRanker.com ---

(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this

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sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of

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Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .


13 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Circuit Diagram
Time division multiplexing

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14 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


TDM Trainer Kit

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15 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Model Graph:

Tabulation
Sl. No. Signal Amplitude (V) Time period (s)

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1. Message signal 1
2. Message Signal 2
3. TDM signal

Result:

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Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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16 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital

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transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital

--- Content provided by FirstRanker.com ---

Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system

--- Content provided by FirstRanker.com ---

1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?

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6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce
FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?



DEPARTMENT OF

--- Content provided by FirstRanker.com ---

ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

--- Content provided by FirstRanker.com ---

LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

--- Content provided by FirstRanker.com ---

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul

--- Content provided by FirstRanker.com ---

DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING


To impart professional education integrated with human values to the younger generation, so as to

--- Content provided by FirstRanker.com ---

shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity


? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics

--- Content provided by FirstRanker.com ---

industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

--- Content provided by FirstRanker.com ---

VISION

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VISION
MISSION
MISSION
3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education

--- Content provided by FirstRanker.com ---

2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to

--- Content provided by FirstRanker.com ---

find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context

--- Content provided by FirstRanker.com ---

5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field

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b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems

--- Content provided by FirstRanker.com ---

e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility

--- Content provided by FirstRanker.com ---

i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 - COMMUNICATION SYSTEMS LABORATORY

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To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms

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? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator

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4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes

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9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

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COURSE OBJECTIVES
COURSE OUTCOMES
6 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction

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7
2 Time division multiplexing
13
3 AM modulation demodulation
18

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4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33
6 Delta modulation demodulation

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38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB

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51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB
55

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11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS

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13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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7 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

CYCLE 1 - EXPERIMENTS

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Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.

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2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at

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which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.

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Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples

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taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To

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recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
8 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit

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works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.

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3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

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Circuit Diagram

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9 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

10 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal
Sampled output

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11 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.

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Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)

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5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate

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4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?

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9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.

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14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.

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19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
12 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:

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To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.

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4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.

--- Content provided by FirstRanker.com ---

Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .

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3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .

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6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .

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13 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Circuit Diagram

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Time division multiplexing

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14 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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TDM Trainer Kit

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15 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Model Graph:

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Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1
2. Message Signal 2

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3. TDM signal

Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:

--- Content provided by FirstRanker.com ---

After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.


16 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network

--- Content provided by FirstRanker.com ---

2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis

--- Content provided by FirstRanker.com ---

5. The GSM telephone system


1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?

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3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?

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8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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--- Content provided by FirstRanker.com ---

Viva - voce
17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver

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Apparatus required:
.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.
3 Diode ? 2 No.

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4
AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.
6 Patch cards ? 6 No.

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Theory:

AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the

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instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.

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Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


?

--- Content provided by FirstRanker.com ---

DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

--- Content provided by FirstRanker.com ---

V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

Name : _______________________________________

--- Content provided by FirstRanker.com ---

Register No. : _______________________________________
Section : _______________________________________

--- Content provided by FirstRanker.com ---

LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

DHANALAKSHMI

--- Content provided by FirstRanker.com ---

College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

--- Content provided by FirstRanker.com ---

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION

--- Content provided by FirstRanker.com ---

ENGINEERING


To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges

--- Content provided by FirstRanker.com ---

in deploying technology for the service of humanity


? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry

--- Content provided by FirstRanker.com ---

? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

--- Content provided by FirstRanker.com ---

VISION
VISION

--- Content provided by FirstRanker.com ---

MISSION
MISSION
3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)

--- Content provided by FirstRanker.com ---

1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence

--- Content provided by FirstRanker.com ---

To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products

--- Content provided by FirstRanker.com ---

4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics

--- Content provided by FirstRanker.com ---

To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints

--- Content provided by FirstRanker.com ---

such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks

--- Content provided by FirstRanker.com ---

f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities

--- Content provided by FirstRanker.com ---

j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM

--- Content provided by FirstRanker.com ---

? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes

--- Content provided by FirstRanker.com ---

LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator

--- Content provided by FirstRanker.com ---

5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)

--- Content provided by FirstRanker.com ---

10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

--- Content provided by FirstRanker.com ---

Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

--- Content provided by FirstRanker.com ---

COURSE OBJECTIVES
COURSE OUTCOMES
6 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

--- Content provided by FirstRanker.com ---

CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7

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2 Time division multiplexing
13
3 AM modulation demodulation
18
4 Frequency modulation demodulation

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26
5 PCM modulation demodulation
33
6 Delta modulation demodulation
38

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7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51

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9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB

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57
12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61

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14 Amplitude modulation demodulation using LabVIEW 64

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7 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION

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Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.

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3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are

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natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem

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If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.

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Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz

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and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of

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control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.

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4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

Circuit Diagram

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9 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Natural Sampling and Flat Top Sampling Circuit Diagram

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Model Graph:

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Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal
Sampled output
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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.
Applications:

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1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

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1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate
4. Define ? Nyquist interval

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5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?

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10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.

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15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?

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20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling


Viva - voce

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12 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit

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Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.

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Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.
Procedure:

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1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on

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channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)

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on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .

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13 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Circuit Diagram
Time division multiplexing

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14 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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TDM Trainer Kit

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Model Graph:

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Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1
2. Message Signal 2
3. TDM signal

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Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the

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signals.


16 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network

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transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system

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1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?

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4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.

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9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce
17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver
Apparatus required:

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.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.
3 Diode ? 2 No.
4

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AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.
6 Patch cards ? 6 No.

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Theory:

AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.

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The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

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The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal

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Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index
Vmax = Maximum peak amplitude

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Vmin = Minimum peak amplitude
if
M < 1 Under modulation
M = 1 Critical modulation
M > 1 over modulation

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Procedure:
1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.

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4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

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V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL

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2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

DHANALAKSHMI

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College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry

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? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

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To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

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? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems

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? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION
VISION
MISSION
MISSION

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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,

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enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions

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3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students

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to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)

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a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics

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communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large

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h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM

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? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction

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2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation

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7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation

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12. Equalization ? Zero Forcing and LMS algorithms (simulation)


Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.

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Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

COURSE OBJECTIVES
COURSE OUTCOMES

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.

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CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7
2 Time division multiplexing
13

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3 AM modulation demodulation
18
4 Frequency modulation demodulation
26
5 PCM modulation demodulation

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33
6 Delta modulation demodulation
38
7 Line coding decoding techniques
45

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CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB
53

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10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB

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59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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7 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit

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Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.

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Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For

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reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known

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as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the

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sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
8 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:

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1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.

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6. Integrate the sampling inputs.

Circuit Diagram

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9 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

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Analog signal sampling and reconstruction trainer kit


Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer

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kit.


Signal Amplitude (V) Time period (s)
Message signal

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Carrier signal
Sampled output
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Outcome:

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After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)

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3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem

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2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?

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7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?

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12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal

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17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
12 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.

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2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common

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signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.

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(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this

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sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of

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Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .


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Circuit Diagram
Time division multiplexing

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14 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


TDM Trainer Kit

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Model Graph:

Tabulation
Sl. No. Signal Amplitude (V) Time period (s)

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1. Message signal 1
2. Message Signal 2
3. TDM signal

Result:

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Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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16 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital

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transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital

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Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system

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1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?

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6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce
17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 3 AM MODULATION & DEMODULATION
Aim:

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To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver
Apparatus required:
.
1 Resistor ? 4 No.

--- Content provided by FirstRanker.com ---

2 Capacitor ? 1 No.
3 Diode ? 2 No.
4
AM transmitter receiver
trainer kit ? 1 No.

--- Content provided by FirstRanker.com ---

5 CRO ? 1 No.
6 Patch cards ? 6 No.

Theory:

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AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt

--- Content provided by FirstRanker.com ---

VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,

--- Content provided by FirstRanker.com ---

VAM(t) = VC (1+ma sin ?mt) sin ?Ct

18 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Where

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Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:

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M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if

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M < 1 Under modulation
M = 1 Critical modulation
M > 1 over modulation

Procedure:

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1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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19 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Circuit Diagram
AM Modulation

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AM Demodulation

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FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

--- Content provided by FirstRanker.com ---

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

--- Content provided by FirstRanker.com ---

LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious

--- Content provided by FirstRanker.com ---

enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels

--- Content provided by FirstRanker.com ---

? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

--- Content provided by FirstRanker.com ---

To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

--- Content provided by FirstRanker.com ---

? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical

--- Content provided by FirstRanker.com ---

practices

--- Content provided by FirstRanker.com ---

VISION
VISION
MISSION
MISSION
3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher

--- Content provided by FirstRanker.com ---

education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth

--- Content provided by FirstRanker.com ---

To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social

--- Content provided by FirstRanker.com ---

context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics

--- Content provided by FirstRanker.com ---

Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits

--- Content provided by FirstRanker.com ---

d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness

--- Content provided by FirstRanker.com ---

of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 - COMMUNICATION SYSTEMS LABORATORY

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To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes

--- Content provided by FirstRanker.com ---

? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing

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3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM

--- Content provided by FirstRanker.com ---

8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise

--- Content provided by FirstRanker.com ---

performance of communication system.

COURSE OBJECTIVES
COURSE OUTCOMES
6 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS

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1 Signal sampling reconstruction
7
2 Time division multiplexing
13
3 AM modulation demodulation

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18
4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33

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6 Delta modulation demodulation
38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS

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8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB

--- Content provided by FirstRanker.com ---

55
11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59

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ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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7 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:

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1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:

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Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be

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sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.

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A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is

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accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
8 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.

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2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

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Circuit Diagram

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9 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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10 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal

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Sampled output
11 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Outcome:
After completion of this experiment, the students will be able to understand the discretization process of

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continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission

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4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?

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3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.

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8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits

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13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?

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18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
12 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 2 TIME DIVISION MULTIPLEXING

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Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.

--- Content provided by FirstRanker.com ---

3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears

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on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,

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(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.

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5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.

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8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .


13 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Circuit Diagram
Time division multiplexing

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14 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


TDM Trainer Kit

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15 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Model Graph:

Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1

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2. Message Signal 2
3. TDM signal

Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.

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Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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16 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)

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or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).

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4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system


1. What is meant by multiplexing technique ?

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2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.

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7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce

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17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after

--- Content provided by FirstRanker.com ---

demodulating using AM receiver
Apparatus required:
.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.

--- Content provided by FirstRanker.com ---

3 Diode ? 2 No.
4
AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.

--- Content provided by FirstRanker.com ---

6 Patch cards ? 6 No.

Theory:

AMPLITUDE MODULATION

--- Content provided by FirstRanker.com ---

Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct

--- Content provided by FirstRanker.com ---

The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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18 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Where
Vm = maximum amplitude of modulating signal

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VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100

--- Content provided by FirstRanker.com ---

Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if
M < 1 Under modulation

--- Content provided by FirstRanker.com ---

M = 1 Critical modulation
M > 1 over modulation

Procedure:
1. Give the modulating signal input to the Amplitude modulator.

--- Content provided by FirstRanker.com ---

2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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19 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Circuit Diagram
AM Modulation

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AM Demodulation

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20 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

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AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

--- Content provided by FirstRanker.com ---

FirstRanker.com - FirstRanker's Choice

--- Content provided by FirstRanker.com ---

1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


?

--- Content provided by FirstRanker.com ---

DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

--- Content provided by FirstRanker.com ---

V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

Name : _______________________________________
Register No. : _______________________________________

--- Content provided by FirstRanker.com ---

Section : _______________________________________

--- Content provided by FirstRanker.com ---

LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

DHANALAKSHMI

--- Content provided by FirstRanker.com ---

College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

--- Content provided by FirstRanker.com ---

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

--- Content provided by FirstRanker.com ---

To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

--- Content provided by FirstRanker.com ---

? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in

--- Content provided by FirstRanker.com ---

communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

--- Content provided by FirstRanker.com ---

VISION
VISION
MISSION

--- Content provided by FirstRanker.com ---

MISSION
3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals

--- Content provided by FirstRanker.com ---

To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge

--- Content provided by FirstRanker.com ---

training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism

--- Content provided by FirstRanker.com ---

To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,

--- Content provided by FirstRanker.com ---

through commitment lifelong learning needed for successful professional career

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability

--- Content provided by FirstRanker.com ---

c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities

--- Content provided by FirstRanker.com ---

g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning

--- Content provided by FirstRanker.com ---

k) To participate succeed in competitive exams

--- Content provided by FirstRanker.com ---

5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

--- Content provided by FirstRanker.com ---

EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation

--- Content provided by FirstRanker.com ---

? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS

--- Content provided by FirstRanker.com ---

1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation

--- Content provided by FirstRanker.com ---

6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)

--- Content provided by FirstRanker.com ---

11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)


Simulate end-to-end Communication Link

--- Content provided by FirstRanker.com ---

Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

COURSE OBJECTIVES

--- Content provided by FirstRanker.com ---

COURSE OUTCOMES
6 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS

--- Content provided by FirstRanker.com ---

Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7
2 Time division multiplexing

--- Content provided by FirstRanker.com ---

13
3 AM modulation demodulation
18
4 Frequency modulation demodulation
26

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5 PCM modulation demodulation
33
6 Delta modulation demodulation
38
7 Line coding decoding techniques

--- Content provided by FirstRanker.com ---

45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB

--- Content provided by FirstRanker.com ---

53
10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB
57

--- Content provided by FirstRanker.com ---

12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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7 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:

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To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.

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4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.

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A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the

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signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals

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The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.

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8 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.

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Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.

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5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

Circuit Diagram

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9 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Natural Sampling and Flat Top Sampling Circuit Diagram

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Model Graph:

10 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Tabulation

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Analog signal sampling and reconstruction trainer kit


Result:

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Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.


Signal Amplitude (V) Time period (s)

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Message signal
Carrier signal
Sampled output
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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)

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2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

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1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?

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6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?

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11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?

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16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.

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21. Define ? Natural Sampling


Viva - voce
12 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:

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1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:

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Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.

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2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.

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4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .

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7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .

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13 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Circuit Diagram
Time division multiplexing

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14 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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TDM Trainer Kit

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Model Graph:

Tabulation

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Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1
2. Message Signal 2
3. TDM signal

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Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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16 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Applications:

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1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.

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3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system

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1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?

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5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?

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10. Which type of modulation technique will be used in TDM?

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Viva - voce
17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 3 AM MODULATION & DEMODULATION

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Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver
Apparatus required:
.

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1 Resistor ? 4 No.
2 Capacitor ? 1 No.
3 Diode ? 2 No.
4
AM transmitter receiver

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trainer kit ? 1 No.
5 CRO ? 1 No.
6 Patch cards ? 6 No.

Theory:

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AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by

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Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

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The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal

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Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude

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if
M < 1 Under modulation
M = 1 Critical modulation
M > 1 over modulation

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Procedure:
1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .

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5. Calculate the modulation index

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Circuit Diagram

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AM Modulation


AM Demodulation

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20 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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21 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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AM Modulation demodulation trainer kit

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FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious

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enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels

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? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

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To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

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? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical

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practices

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VISION
VISION
MISSION
MISSION
3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher

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education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth

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To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social

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context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics

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Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits

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d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness

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of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

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To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes

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? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing

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3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM

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8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise

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performance of communication system.

COURSE OBJECTIVES
COURSE OUTCOMES
6 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS

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1 Signal sampling reconstruction
7
2 Time division multiplexing
13
3 AM modulation demodulation

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18
4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33

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6 Delta modulation demodulation
38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS

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8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB

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55
11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59

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ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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7 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:

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1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:

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Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be

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sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.

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A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is

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accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
8 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.

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2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

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Circuit Diagram

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9 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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10 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal

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Sampled output
11 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Outcome:
After completion of this experiment, the students will be able to understand the discretization process of

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continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission

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4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?

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3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.

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8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits

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13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?

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18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
12 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 2 TIME DIVISION MULTIPLEXING

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Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.

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3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears

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on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,

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(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.

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5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.

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8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .


13 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Circuit Diagram
Time division multiplexing

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14 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


TDM Trainer Kit

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15 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Model Graph:

Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1

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2. Message Signal 2
3. TDM signal

Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.

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Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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16 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)

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or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).

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4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system


1. What is meant by multiplexing technique ?

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2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.

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7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce

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17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after

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demodulating using AM receiver
Apparatus required:
.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.

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3 Diode ? 2 No.
4
AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.

--- Content provided by FirstRanker.com ---

6 Patch cards ? 6 No.

Theory:

AMPLITUDE MODULATION

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Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct

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The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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18 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Where
Vm = maximum amplitude of modulating signal

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VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100

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Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if
M < 1 Under modulation

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M = 1 Critical modulation
M > 1 over modulation

Procedure:
1. Give the modulating signal input to the Amplitude modulator.

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2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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19 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Circuit Diagram
AM Modulation

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AM Demodulation

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20 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

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AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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21 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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AM Modulation demodulation trainer kit

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22 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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AM Modulation and Demodulation trainer kit

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FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious

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enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels

--- Content provided by FirstRanker.com ---

? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

--- Content provided by FirstRanker.com ---

To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

--- Content provided by FirstRanker.com ---

? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical

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practices

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VISION
VISION
MISSION
MISSION
3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher

--- Content provided by FirstRanker.com ---

education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth

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To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social

--- Content provided by FirstRanker.com ---

context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics

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Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits

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d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness

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of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 - COMMUNICATION SYSTEMS LABORATORY

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To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes

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? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing

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3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM

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8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise

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performance of communication system.

COURSE OBJECTIVES
COURSE OUTCOMES
6 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS

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1 Signal sampling reconstruction
7
2 Time division multiplexing
13
3 AM modulation demodulation

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18
4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33

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6 Delta modulation demodulation
38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS

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8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB

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55
11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59

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ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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7 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:

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1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:

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Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be

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sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.

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A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is

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accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
8 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.

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2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

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Circuit Diagram

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9 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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10 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal

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Sampled output
11 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Outcome:
After completion of this experiment, the students will be able to understand the discretization process of

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continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission

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4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?

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3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.

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8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits

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13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?

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18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
12 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 2 TIME DIVISION MULTIPLEXING

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Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.

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3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears

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on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,

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(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.

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5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.

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8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .


13 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Circuit Diagram
Time division multiplexing

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14 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


TDM Trainer Kit

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15 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Model Graph:

Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1

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2. Message Signal 2
3. TDM signal

Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.

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Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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16 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)

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or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).

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4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system


1. What is meant by multiplexing technique ?

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2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.

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7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce

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17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after

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demodulating using AM receiver
Apparatus required:
.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.

--- Content provided by FirstRanker.com ---

3 Diode ? 2 No.
4
AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.

--- Content provided by FirstRanker.com ---

6 Patch cards ? 6 No.

Theory:

AMPLITUDE MODULATION

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Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct

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The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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18 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Where
Vm = maximum amplitude of modulating signal

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VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100

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Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if
M < 1 Under modulation

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M = 1 Critical modulation
M > 1 over modulation

Procedure:
1. Give the modulating signal input to the Amplitude modulator.

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2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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19 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Circuit Diagram
AM Modulation

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AM Demodulation

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20 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

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AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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21 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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AM Modulation demodulation trainer kit

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22 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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AM Modulation and Demodulation trainer kit

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23 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Tabulation

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Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.

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Applications:
1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?

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4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?

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9. What are the different types of AM generation?
10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce
FirstRanker.com - FirstRanker's Choice

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1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


?

--- Content provided by FirstRanker.com ---

DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

--- Content provided by FirstRanker.com ---

V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

--- Content provided by FirstRanker.com ---

--- Content provided by FirstRanker.com ---

Name : _______________________________________
Register No. : _______________________________________

--- Content provided by FirstRanker.com ---

Section : _______________________________________

--- Content provided by FirstRanker.com ---

LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

DHANALAKSHMI

--- Content provided by FirstRanker.com ---

College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

--- Content provided by FirstRanker.com ---

? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

--- Content provided by FirstRanker.com ---

To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

--- Content provided by FirstRanker.com ---

? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in

--- Content provided by FirstRanker.com ---

communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

--- Content provided by FirstRanker.com ---

VISION
VISION
MISSION

--- Content provided by FirstRanker.com ---

MISSION
3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals

--- Content provided by FirstRanker.com ---

To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge

--- Content provided by FirstRanker.com ---

training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism

--- Content provided by FirstRanker.com ---

To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,

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through commitment lifelong learning needed for successful professional career

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4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability

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c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities

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g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning

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k) To participate succeed in competitive exams

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5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation

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? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS

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1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation

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6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)

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11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)


Simulate end-to-end Communication Link

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Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

COURSE OBJECTIVES

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COURSE OUTCOMES
6 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS

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Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7
2 Time division multiplexing

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13
3 AM modulation demodulation
18
4 Frequency modulation demodulation
26

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5 PCM modulation demodulation
33
6 Delta modulation demodulation
38
7 Line coding decoding techniques

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45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB

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53
10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB
57

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12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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7 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:

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To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.

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4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.

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A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the

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signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals

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The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.

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8 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.

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Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.

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5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

Circuit Diagram

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9 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Natural Sampling and Flat Top Sampling Circuit Diagram

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Model Graph:

10 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Tabulation

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Analog signal sampling and reconstruction trainer kit


Result:

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Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.


Signal Amplitude (V) Time period (s)

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Message signal
Carrier signal
Sampled output
11 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)

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2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

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1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?

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6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?

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11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?

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16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.

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21. Define ? Natural Sampling


Viva - voce
12 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:

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1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:

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Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.

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2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.

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4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .

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7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .

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13 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Circuit Diagram
Time division multiplexing

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14 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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TDM Trainer Kit

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15 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Model Graph:

Tabulation

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Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1
2. Message Signal 2
3. TDM signal

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Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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16 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Applications:

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1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.

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3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system

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1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?

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5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?

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10. Which type of modulation technique will be used in TDM?

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Viva - voce
17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 3 AM MODULATION & DEMODULATION

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Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver
Apparatus required:
.

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1 Resistor ? 4 No.
2 Capacitor ? 1 No.
3 Diode ? 2 No.
4
AM transmitter receiver

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trainer kit ? 1 No.
5 CRO ? 1 No.
6 Patch cards ? 6 No.

Theory:

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AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by

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Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

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The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

18 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Where
Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal

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Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude

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if
M < 1 Under modulation
M = 1 Critical modulation
M > 1 over modulation

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Procedure:
1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .

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5. Calculate the modulation index

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19 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Circuit Diagram

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AM Modulation


AM Demodulation

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20 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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21 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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AM Modulation demodulation trainer kit

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22 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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AM Modulation and Demodulation trainer kit

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23 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

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Carrier

Modulated

Demodulated

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Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:

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After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.
Applications:
1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.

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3. Facsimile transmission



1. What is modulation and demodulation?

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2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?

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7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?
9. What are the different types of AM generation?
10. Define ? Modulation Index
11. What are different types of analog modulation techniques?

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Viva - voce
24 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.

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14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?

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18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.

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23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

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V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL

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2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

DHANALAKSHMI

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College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry

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? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

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To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

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? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems

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? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION
VISION
MISSION
MISSION

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3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,

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enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions

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3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students

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to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00



PROGRAMME OUTCOMES (POs)

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a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics

--- Content provided by FirstRanker.com ---

communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large

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h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM

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? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction

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2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation

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7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation

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12. Equalization ? Zero Forcing and LMS algorithms (simulation)


Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.

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Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

COURSE OBJECTIVES
COURSE OUTCOMES

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6 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.

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CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7
2 Time division multiplexing
13

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3 AM modulation demodulation
18
4 Frequency modulation demodulation
26
5 PCM modulation demodulation

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33
6 Delta modulation demodulation
38
7 Line coding decoding techniques
45

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CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB
53

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10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB

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59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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7 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit

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Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.

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Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For

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reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known

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as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the

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sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
8 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:

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1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.

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6. Integrate the sampling inputs.

Circuit Diagram

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9 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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10 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Tabulation

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Analog signal sampling and reconstruction trainer kit


Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer

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kit.


Signal Amplitude (V) Time period (s)
Message signal

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Carrier signal
Sampled output
11 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Outcome:

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After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)

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3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem

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2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?

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7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?

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12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal

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17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
12 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.

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2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common

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signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.

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(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this

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sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of

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Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .


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Circuit Diagram
Time division multiplexing

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TDM Trainer Kit

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Model Graph:

Tabulation
Sl. No. Signal Amplitude (V) Time period (s)

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1. Message signal 1
2. Message Signal 2
3. TDM signal

Result:

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Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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16 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital

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transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital

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Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system

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1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?

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6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce
17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 3 AM MODULATION & DEMODULATION
Aim:

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To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver
Apparatus required:
.
1 Resistor ? 4 No.

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2 Capacitor ? 1 No.
3 Diode ? 2 No.
4
AM transmitter receiver
trainer kit ? 1 No.

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5 CRO ? 1 No.
6 Patch cards ? 6 No.

Theory:

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AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt

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VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,

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VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where

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Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:

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M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if

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M < 1 Under modulation
M = 1 Critical modulation
M > 1 over modulation

Procedure:

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1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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19 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:

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1. AM Waveform (Ring diode Transistor based AM Modulator)

AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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21 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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AM Modulation demodulation trainer kit

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22 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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AM Modulation and Demodulation trainer kit

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23 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated

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demodulated wave.
Applications:
1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.

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3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?

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8. What is depth of modulation?
9. What are the different types of AM generation?
10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce

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24 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation

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15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.

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19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.

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.

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25 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 4 FREQUENCY MODULATION & DEMODULATION

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Aim:
To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver
Apparatus required:
.

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1. Resistor ? 4 No.
2. Capacitor ? 1 No.
3. Diode ? 2 No.
4.
AM transmitter Receiver

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trainer kit ? 1 No.
5. CRO ? 1 No.
6. Patch cards ? 6 No.

Theory:

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Frequency modulation (FM) is a form of modulation that represents information as variations in the
instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A

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narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used
in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
FirstRanker.com - FirstRanker's Choice

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1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

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V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________

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Section : _______________________________________

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LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

DHANALAKSHMI

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College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

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? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

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To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

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? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in

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communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION
VISION
MISSION

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MISSION
3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals

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To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge

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training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism

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To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,

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through commitment lifelong learning needed for successful professional career

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4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability

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c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities

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g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning

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k) To participate succeed in competitive exams

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5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation

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? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS

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1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation

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6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)

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11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)


Simulate end-to-end Communication Link

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Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

COURSE OBJECTIVES

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COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS

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Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7
2 Time division multiplexing

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13
3 AM modulation demodulation
18
4 Frequency modulation demodulation
26

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5 PCM modulation demodulation
33
6 Delta modulation demodulation
38
7 Line coding decoding techniques

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45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB

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53
10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB
57

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12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:

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To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.

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4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.

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A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the

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signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals

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The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.

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8 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.

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Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.

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5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

Circuit Diagram

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9 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Natural Sampling and Flat Top Sampling Circuit Diagram

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Model Graph:

10 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Tabulation

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Analog signal sampling and reconstruction trainer kit


Result:

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Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.


Signal Amplitude (V) Time period (s)

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Message signal
Carrier signal
Sampled output
11 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)

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2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

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1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?

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6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?

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11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?

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16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.

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21. Define ? Natural Sampling


Viva - voce
12 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:

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1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:

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Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.

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2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.

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4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .

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7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .

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Circuit Diagram
Time division multiplexing

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14 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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TDM Trainer Kit

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Model Graph:

Tabulation

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Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1
2. Message Signal 2
3. TDM signal

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Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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Applications:

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1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.

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3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system

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1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?

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5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?

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10. Which type of modulation technique will be used in TDM?

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Viva - voce
17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 3 AM MODULATION & DEMODULATION

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Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver
Apparatus required:
.

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1 Resistor ? 4 No.
2 Capacitor ? 1 No.
3 Diode ? 2 No.
4
AM transmitter receiver

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trainer kit ? 1 No.
5 CRO ? 1 No.
6 Patch cards ? 6 No.

Theory:

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AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by

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Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

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The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal

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Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude

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if
M < 1 Under modulation
M = 1 Critical modulation
M > 1 over modulation

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Procedure:
1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .

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5. Calculate the modulation index

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Circuit Diagram

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AM Modulation


AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

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Carrier

Modulated

Demodulated

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Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:

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After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.
Applications:
1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.

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3. Facsimile transmission



1. What is modulation and demodulation?

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2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?

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7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?
9. What are the different types of AM generation?
10. Define ? Modulation Index
11. What are different types of analog modulation techniques?

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Viva - voce
24 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.

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14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?

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18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.

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23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver
Apparatus required:

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.
1. Resistor ? 4 No.
2. Capacitor ? 1 No.
3. Diode ? 2 No.
4.

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AM transmitter Receiver
trainer kit ? 1 No.
5. CRO ? 1 No.
6. Patch cards ? 6 No.

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Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the
instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF

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radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used
in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.

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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of

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frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of
noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

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Procedure:
FM Modulator:
1. Switch ON the Power supply.

2. Connect the sine wave generator output to frequency modulator input.

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3. Select the low frequency carrier (or) high frequency carrier.

4. Connect the CRO input to the frequency modulator output.

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5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

6. Observe the frequency modulator output .

FM Demodulator:

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A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

2. Now set the DPDT switch in low frequency mode.

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3. Connect CRO input to PLL detector output.

4. Observe the Demodulated O/P compare with the original input.

B) Quadrature Detector

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1. Connect the frequency modulated output to Quadrature detector input.

2. Now set the DPDT switch in high frequency mode.

3. Connect the CRO input to Quadrature detector output.

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4. Observe the Demodulated O/P and compare with the original input.
FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
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DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious

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enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels

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? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

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To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

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? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical

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practices

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VISION
VISION
MISSION
MISSION
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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher

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education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth

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To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social

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context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics

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Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits

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d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness

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of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

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To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes

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? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing

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3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM

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8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise

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performance of communication system.

COURSE OBJECTIVES
COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS

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1 Signal sampling reconstruction
7
2 Time division multiplexing
13
3 AM modulation demodulation

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18
4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33

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6 Delta modulation demodulation
38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS

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8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB

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55
11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59

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ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:

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1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:

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Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be

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sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.

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A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is

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accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.

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2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

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Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal

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Sampled output
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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of

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continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission

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4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?

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3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.

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8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits

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13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?

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18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
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Expt. No. 2 TIME DIVISION MULTIPLEXING

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Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.

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3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears

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on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,

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(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.

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5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.

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8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .


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Circuit Diagram
Time division multiplexing

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14 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


TDM Trainer Kit

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Model Graph:

Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1

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2. Message Signal 2
3. TDM signal

Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.

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Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)

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or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).

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4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system


1. What is meant by multiplexing technique ?

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2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.

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7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce

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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after

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demodulating using AM receiver
Apparatus required:
.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.

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3 Diode ? 2 No.
4
AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.

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6 Patch cards ? 6 No.

Theory:

AMPLITUDE MODULATION

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Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct

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The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal

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VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100

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Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if
M < 1 Under modulation

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M = 1 Critical modulation
M > 1 over modulation

Procedure:
1. Give the modulating signal input to the Amplitude modulator.

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2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

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AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation

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Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.

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Applications:
1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?

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4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?

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9. What are the different types of AM generation?
10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce
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12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?

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16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.

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20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:

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To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver
Apparatus required:
.
1. Resistor ? 4 No.

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2. Capacitor ? 1 No.
3. Diode ? 2 No.
4.
AM transmitter Receiver
trainer kit ? 1 No.

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5. CRO ? 1 No.
6. Patch cards ? 6 No.

Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the

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instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used

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in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of

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noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

Procedure:
FM Modulator:

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1. Switch ON the Power supply.

2. Connect the sine wave generator output to frequency modulator input.

3. Select the low frequency carrier (or) high frequency carrier.

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4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

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6. Observe the frequency modulator output .

FM Demodulator:
A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

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2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

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4. Observe the Demodulated O/P compare with the original input.

B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

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2. Now set the DPDT switch in high frequency mode.

3. Connect the CRO input to Quadrature detector output.

4. Observe the Demodulated O/P and compare with the original input.

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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

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4. Observe the Demodulated O/P and then compare with the original input.

D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Ratio detector output.

4. Observe the Demodulated O/P and then compare with the original input.

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FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?



DEPARTMENT OF

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ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
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DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

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? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul

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DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING


To impart professional education integrated with human values to the younger generation, so as to

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shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity


? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics

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industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION

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VISION
MISSION
MISSION
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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education

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2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to

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find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context

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5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field

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b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems

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e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility

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i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

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To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms

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? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator

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4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes

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9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

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COURSE OBJECTIVES
COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction

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7
2 Time division multiplexing
13
3 AM modulation demodulation
18

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4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33
6 Delta modulation demodulation

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38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB

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51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB
55

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11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS

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13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS

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Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.

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2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at

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which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.

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Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples

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taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To

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recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit

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works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.

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3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

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Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal
Sampled output

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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.

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Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)

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5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate

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4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?

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9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.

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14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.

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19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
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Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:

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To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.

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4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.

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Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .

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3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .

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6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .

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Circuit Diagram

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Time division multiplexing

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TDM Trainer Kit

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Model Graph:

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Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1
2. Message Signal 2

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3. TDM signal

Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:

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After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.


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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network

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2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis

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5. The GSM telephone system


1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?

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3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?

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8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce
17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver

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Apparatus required:
.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.
3 Diode ? 2 No.

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4
AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.
6 Patch cards ? 6 No.

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Theory:

AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the

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instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.

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Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal

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Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index

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Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if
M < 1 Under modulation
M = 1 Critical modulation

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M > 1 over modulation

Procedure:
1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.

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3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

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AM Modulated wave



2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)

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Message

Carrier

Modulated

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Demodulated


Result:

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Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.
Applications:

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1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?

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5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?
9. What are the different types of AM generation?

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10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce
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12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?

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17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?

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21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after

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demodulating using FM receiver
Apparatus required:
.
1. Resistor ? 4 No.
2. Capacitor ? 1 No.

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3. Diode ? 2 No.
4.
AM transmitter Receiver
trainer kit ? 1 No.
5. CRO ? 1 No.

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6. Patch cards ? 6 No.

Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the
instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct

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proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used
in broadcast is generally called wide-FM, or W-FM.

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In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the

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luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of
noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes

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print-through pre-echo.

Procedure:
FM Modulator:
1. Switch ON the Power supply.

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2. Connect the sine wave generator output to frequency modulator input.

3. Select the low frequency carrier (or) high frequency carrier.

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4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

6. Observe the frequency modulator output .

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FM Demodulator:
A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

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2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

4. Observe the Demodulated O/P compare with the original input.

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B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

2. Now set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Quadrature detector output.

4. Observe the Demodulated O/P and compare with the original input.
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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

4. Observe the Demodulated O/P and then compare with the original input.

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D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

2. Set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Ratio detector output.

4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram
FM Modulator

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FM Demodulator

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FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
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DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious

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enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels

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? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

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To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

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? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical

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practices

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VISION
VISION
MISSION
MISSION
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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher

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education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth

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To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social

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context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics

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Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits

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d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness

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of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

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To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes

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? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing

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3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM

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8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise

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performance of communication system.

COURSE OBJECTIVES
COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS

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1 Signal sampling reconstruction
7
2 Time division multiplexing
13
3 AM modulation demodulation

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18
4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33

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6 Delta modulation demodulation
38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS

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8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB

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55
11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59

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ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:

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1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:

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Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be

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sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.

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A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is

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accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.

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2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

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Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal

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Sampled output
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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of

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continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission

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4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?

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3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.

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8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits

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13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?

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18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
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Expt. No. 2 TIME DIVISION MULTIPLEXING

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Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.

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3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears

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on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,

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(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.

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5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.

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8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .


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Circuit Diagram
Time division multiplexing

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TDM Trainer Kit

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Model Graph:

Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1

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2. Message Signal 2
3. TDM signal

Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.

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Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)

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or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).

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4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system


1. What is meant by multiplexing technique ?

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2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.

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7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce

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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after

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demodulating using AM receiver
Apparatus required:
.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.

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3 Diode ? 2 No.
4
AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.

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6 Patch cards ? 6 No.

Theory:

AMPLITUDE MODULATION

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Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct

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The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal

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VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100

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Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if
M < 1 Under modulation

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M = 1 Critical modulation
M > 1 over modulation

Procedure:
1. Give the modulating signal input to the Amplitude modulator.

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2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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19 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

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AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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21 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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AM Modulation demodulation trainer kit

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22 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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AM Modulation and Demodulation trainer kit

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Tabulation

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Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.

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Applications:
1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?

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4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?

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9. What are the different types of AM generation?
10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce
24 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?

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16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.

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20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:

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To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver
Apparatus required:
.
1. Resistor ? 4 No.

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2. Capacitor ? 1 No.
3. Diode ? 2 No.
4.
AM transmitter Receiver
trainer kit ? 1 No.

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5. CRO ? 1 No.
6. Patch cards ? 6 No.

Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the

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instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used

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in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of

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noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

Procedure:
FM Modulator:

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1. Switch ON the Power supply.

2. Connect the sine wave generator output to frequency modulator input.

3. Select the low frequency carrier (or) high frequency carrier.

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4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

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6. Observe the frequency modulator output .

FM Demodulator:
A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

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2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

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4. Observe the Demodulated O/P compare with the original input.

B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

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2. Now set the DPDT switch in high frequency mode.

3. Connect the CRO input to Quadrature detector output.

4. Observe the Demodulated O/P and compare with the original input.

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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

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4. Observe the Demodulated O/P and then compare with the original input.

D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Ratio detector output.

4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram

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FM Modulator

FM Demodulator

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FM Modulation and Demodulation Trainer kit

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FirstRanker.com - FirstRanker's Choice

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1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

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V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________

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Section : _______________________________________

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LABORATORY MANUAL
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DHANALAKSHMI

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College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

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? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

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To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

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? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in

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communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION
VISION
MISSION

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MISSION
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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals

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To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge

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training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism

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To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,

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through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability

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c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities

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g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning

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k) To participate succeed in competitive exams

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation

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? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS

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1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation

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6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)

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11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)


Simulate end-to-end Communication Link

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Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

COURSE OBJECTIVES

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COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS

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Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7
2 Time division multiplexing

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13
3 AM modulation demodulation
18
4 Frequency modulation demodulation
26

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5 PCM modulation demodulation
33
6 Delta modulation demodulation
38
7 Line coding decoding techniques

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45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB

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53
10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB
57

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12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:

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To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.

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4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.

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A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the

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signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals

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The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.

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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.

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Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.

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5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

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Model Graph:

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Tabulation

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Analog signal sampling and reconstruction trainer kit


Result:

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Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.


Signal Amplitude (V) Time period (s)

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Message signal
Carrier signal
Sampled output
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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)

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2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

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1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?

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6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?

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11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?

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16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.

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21. Define ? Natural Sampling


Viva - voce
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Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:

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1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:

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Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.

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2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.

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4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .

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7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .

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Circuit Diagram
Time division multiplexing

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14 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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TDM Trainer Kit

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Model Graph:

Tabulation

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Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1
2. Message Signal 2
3. TDM signal

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Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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Applications:

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1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.

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3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system

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1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?

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5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?

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10. Which type of modulation technique will be used in TDM?

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Viva - voce
17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 3 AM MODULATION & DEMODULATION

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Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver
Apparatus required:
.

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1 Resistor ? 4 No.
2 Capacitor ? 1 No.
3 Diode ? 2 No.
4
AM transmitter receiver

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trainer kit ? 1 No.
5 CRO ? 1 No.
6 Patch cards ? 6 No.

Theory:

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AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by

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Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

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The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal

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Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude

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if
M < 1 Under modulation
M = 1 Critical modulation
M > 1 over modulation

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Procedure:
1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .

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5. Calculate the modulation index

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Circuit Diagram

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AM Modulation


AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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22 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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AM Modulation and Demodulation trainer kit

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

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Carrier

Modulated

Demodulated

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Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:

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After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.
Applications:
1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.

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3. Facsimile transmission



1. What is modulation and demodulation?

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2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?

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7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?
9. What are the different types of AM generation?
10. Define ? Modulation Index
11. What are different types of analog modulation techniques?

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Viva - voce
24 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.

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14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?

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18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.

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23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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25 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver
Apparatus required:

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.
1. Resistor ? 4 No.
2. Capacitor ? 1 No.
3. Diode ? 2 No.
4.

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AM transmitter Receiver
trainer kit ? 1 No.
5. CRO ? 1 No.
6. Patch cards ? 6 No.

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Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the
instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF

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radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used
in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.

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26 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of

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frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of
noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

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Procedure:
FM Modulator:
1. Switch ON the Power supply.

2. Connect the sine wave generator output to frequency modulator input.

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3. Select the low frequency carrier (or) high frequency carrier.

4. Connect the CRO input to the frequency modulator output.

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5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

6. Observe the frequency modulator output .

FM Demodulator:

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A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

2. Now set the DPDT switch in low frequency mode.

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3. Connect CRO input to PLL detector output.

4. Observe the Demodulated O/P compare with the original input.

B) Quadrature Detector

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1. Connect the frequency modulated output to Quadrature detector input.

2. Now set the DPDT switch in high frequency mode.

3. Connect the CRO input to Quadrature detector output.

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4. Observe the Demodulated O/P and compare with the original input.
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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

2. Set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Phase discriminator output.

4. Observe the Demodulated O/P and then compare with the original input.

D) Ratio Detector

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1. Connect the frequency modulated output to Ratio detector input.

2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Ratio detector output.

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4. Observe the Demodulated O/P and then compare with the original input.

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28 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Circuit Diagram
FM Modulator

FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:


Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)

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Message

Carrier

Modulated

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Demodulated


Result:

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Thus the FM Modulation and Demodulation is performed for the given message signal.

FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious

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enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels

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? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

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To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

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? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical

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practices

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VISION
VISION
MISSION
MISSION
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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher

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education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth

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To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social

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context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics

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Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits

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d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness

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of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

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To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes

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? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing

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3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM

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8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise

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performance of communication system.

COURSE OBJECTIVES
COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS

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1 Signal sampling reconstruction
7
2 Time division multiplexing
13
3 AM modulation demodulation

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18
4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33

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6 Delta modulation demodulation
38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS

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8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB

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55
11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59

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ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:

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1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:

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Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be

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sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.

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A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is

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accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.

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2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

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Circuit Diagram

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9 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal

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Sampled output
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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of

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continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission

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4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?

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3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.

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8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits

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13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?

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18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
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Expt. No. 2 TIME DIVISION MULTIPLEXING

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Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.

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3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears

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on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,

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(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.

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5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.

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8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .


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Circuit Diagram
Time division multiplexing

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TDM Trainer Kit

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Model Graph:

Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1

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2. Message Signal 2
3. TDM signal

Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.

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Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)

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or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).

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4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system


1. What is meant by multiplexing technique ?

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2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.

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7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce

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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after

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demodulating using AM receiver
Apparatus required:
.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.

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3 Diode ? 2 No.
4
AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.

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6 Patch cards ? 6 No.

Theory:

AMPLITUDE MODULATION

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Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct

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The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal

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VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100

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Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if
M < 1 Under modulation

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M = 1 Critical modulation
M > 1 over modulation

Procedure:
1. Give the modulating signal input to the Amplitude modulator.

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2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

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AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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21 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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AM Modulation demodulation trainer kit

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22 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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AM Modulation and Demodulation trainer kit

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Tabulation

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Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.

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Applications:
1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?

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4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?

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9. What are the different types of AM generation?
10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce
24 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?

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16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.

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20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:

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To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver
Apparatus required:
.
1. Resistor ? 4 No.

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2. Capacitor ? 1 No.
3. Diode ? 2 No.
4.
AM transmitter Receiver
trainer kit ? 1 No.

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5. CRO ? 1 No.
6. Patch cards ? 6 No.

Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the

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instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used

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in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of

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noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

Procedure:
FM Modulator:

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1. Switch ON the Power supply.

2. Connect the sine wave generator output to frequency modulator input.

3. Select the low frequency carrier (or) high frequency carrier.

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4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

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6. Observe the frequency modulator output .

FM Demodulator:
A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

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2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

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4. Observe the Demodulated O/P compare with the original input.

B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

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2. Now set the DPDT switch in high frequency mode.

3. Connect the CRO input to Quadrature detector output.

4. Observe the Demodulated O/P and compare with the original input.

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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

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4. Observe the Demodulated O/P and then compare with the original input.

D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Ratio detector output.

4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram

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FM Modulator

FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

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Carrier

Modulated

Demodulated

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Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency
modulated and demodulated wave.

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Applications:
1. Television sound transmission
2. Two way mobile radio
3. Cellular Radio
4. Microwave

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5. Satellite Communication System


1. Define ? Frequency Modulation
2. How it is different from phase modulation?

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3. Write equation of FM wave, explain each parameter in it.
4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.
6. Define ? Modulation Index
7. Differentiate between Narrow band FM from Wide band FM.

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8. Draw message, carrier FM waves .
9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?
11. Give the practical applications of FM.
12. State advantages and disadvantages of FM.

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13. What is the range of speech signals?
14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation
17. Draw the phasor diagram of FM signal.

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18. What are the different types of FM generation?

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Viva - voce
FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?



DEPARTMENT OF

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ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
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DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

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? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul

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DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING


To impart professional education integrated with human values to the younger generation, so as to

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shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity


? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics

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industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION

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VISION
MISSION
MISSION
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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education

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2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to

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find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context

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5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field

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b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems

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e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility

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i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

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To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms

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? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator

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4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes

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9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

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COURSE OBJECTIVES
COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction

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7
2 Time division multiplexing
13
3 AM modulation demodulation
18

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4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33
6 Delta modulation demodulation

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38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB

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51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB
55

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11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS

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13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS

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Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.

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2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at

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which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.

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Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples

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taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To

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recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit

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works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.

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3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

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Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal
Sampled output

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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.

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Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)

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5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate

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4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?

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9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.

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14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.

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19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
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Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:

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To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.

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4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.

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Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .

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3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .

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6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .

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Circuit Diagram

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Time division multiplexing

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TDM Trainer Kit

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Model Graph:

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Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1
2. Message Signal 2

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3. TDM signal

Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:

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After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.


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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network

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2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis

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5. The GSM telephone system


1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?

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3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?

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8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce
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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver

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Apparatus required:
.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.
3 Diode ? 2 No.

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4
AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.
6 Patch cards ? 6 No.

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Theory:

AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the

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instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.

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Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal

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Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index

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Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if
M < 1 Under modulation
M = 1 Critical modulation

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M > 1 over modulation

Procedure:
1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.

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3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

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AM Modulated wave



2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)

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Message

Carrier

Modulated

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Demodulated


Result:

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Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.
Applications:

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1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?

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5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?
9. What are the different types of AM generation?

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10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce
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12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?

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17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?

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21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after

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demodulating using FM receiver
Apparatus required:
.
1. Resistor ? 4 No.
2. Capacitor ? 1 No.

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3. Diode ? 2 No.
4.
AM transmitter Receiver
trainer kit ? 1 No.
5. CRO ? 1 No.

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6. Patch cards ? 6 No.

Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the
instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct

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proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used
in broadcast is generally called wide-FM, or W-FM.

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In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the

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luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of
noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes

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print-through pre-echo.

Procedure:
FM Modulator:
1. Switch ON the Power supply.

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2. Connect the sine wave generator output to frequency modulator input.

3. Select the low frequency carrier (or) high frequency carrier.

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4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

6. Observe the frequency modulator output .

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FM Demodulator:
A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

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2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

4. Observe the Demodulated O/P compare with the original input.

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B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

2. Now set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Quadrature detector output.

4. Observe the Demodulated O/P and compare with the original input.
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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

4. Observe the Demodulated O/P and then compare with the original input.

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D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

2. Set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Ratio detector output.

4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram
FM Modulator

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FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency
modulated and demodulated wave.
Applications:

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1. Television sound transmission
2. Two way mobile radio
3. Cellular Radio
4. Microwave
5. Satellite Communication System

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1. Define ? Frequency Modulation
2. How it is different from phase modulation?
3. Write equation of FM wave, explain each parameter in it.

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4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.
6. Define ? Modulation Index
7. Differentiate between Narrow band FM from Wide band FM.
8. Draw message, carrier FM waves .

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9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?
11. Give the practical applications of FM.
12. State advantages and disadvantages of FM.
13. What is the range of speech signals?

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14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation
17. Draw the phasor diagram of FM signal.
18. What are the different types of FM generation?

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Viva - voce

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32 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 5 PCM MODULATION & DEMODULATION

Aim:

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To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator
Apparatus Required:
1. PCM trainer kit ? 1 No.
2. CRO ? 1 No.

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3. Connecting probes ? 4 No.
Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is
first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of
converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization

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can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization
the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel
serially.

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At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword
is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to
Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks

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for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:
1. Power on the PCM kit.
2. Measure the frequency of sampling clock.

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3. Apply the DC voltage as modulating signal.
FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?



DEPARTMENT OF

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ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
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DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

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? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul

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DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING


To impart professional education integrated with human values to the younger generation, so as to

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shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity


? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics

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industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION

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VISION
MISSION
MISSION
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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education

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2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to

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find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context

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5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field

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b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems

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e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility

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i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

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To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms

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? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator

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4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes

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9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

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COURSE OBJECTIVES
COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction

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7
2 Time division multiplexing
13
3 AM modulation demodulation
18

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4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33
6 Delta modulation demodulation

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38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB

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51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB
55

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11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS

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13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS

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Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.

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2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at

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which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.

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Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples

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taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To

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recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit

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works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.

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3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

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Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal
Sampled output

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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.

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Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)

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5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate

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4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?

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9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.

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14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.

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19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
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Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:

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To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.

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4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.

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Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .

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3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .

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6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .

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Circuit Diagram

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Time division multiplexing

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TDM Trainer Kit

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Model Graph:

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Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1
2. Message Signal 2

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3. TDM signal

Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:

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After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.


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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network

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2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis

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5. The GSM telephone system


1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?

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3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?

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8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce
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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver

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Apparatus required:
.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.
3 Diode ? 2 No.

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4
AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.
6 Patch cards ? 6 No.

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Theory:

AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the

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instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.

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Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal

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Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index

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Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if
M < 1 Under modulation
M = 1 Critical modulation

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M > 1 over modulation

Procedure:
1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.

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3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

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AM Modulated wave



2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)

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Message

Carrier

Modulated

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Demodulated


Result:

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Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.
Applications:

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1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?

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5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?
9. What are the different types of AM generation?

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10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce
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12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?

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17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?

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21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after

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demodulating using FM receiver
Apparatus required:
.
1. Resistor ? 4 No.
2. Capacitor ? 1 No.

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3. Diode ? 2 No.
4.
AM transmitter Receiver
trainer kit ? 1 No.
5. CRO ? 1 No.

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6. Patch cards ? 6 No.

Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the
instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct

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proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used
in broadcast is generally called wide-FM, or W-FM.

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In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the

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luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of
noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes

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print-through pre-echo.

Procedure:
FM Modulator:
1. Switch ON the Power supply.

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2. Connect the sine wave generator output to frequency modulator input.

3. Select the low frequency carrier (or) high frequency carrier.

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4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

6. Observe the frequency modulator output .

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FM Demodulator:
A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

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2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

4. Observe the Demodulated O/P compare with the original input.

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B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

2. Now set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Quadrature detector output.

4. Observe the Demodulated O/P and compare with the original input.
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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

4. Observe the Demodulated O/P and then compare with the original input.

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D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

2. Set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Ratio detector output.

4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram
FM Modulator

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FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency
modulated and demodulated wave.
Applications:

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1. Television sound transmission
2. Two way mobile radio
3. Cellular Radio
4. Microwave
5. Satellite Communication System

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1. Define ? Frequency Modulation
2. How it is different from phase modulation?
3. Write equation of FM wave, explain each parameter in it.

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4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.
6. Define ? Modulation Index
7. Differentiate between Narrow band FM from Wide band FM.
8. Draw message, carrier FM waves .

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9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?
11. Give the practical applications of FM.
12. State advantages and disadvantages of FM.
13. What is the range of speech signals?

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14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation
17. Draw the phasor diagram of FM signal.
18. What are the different types of FM generation?

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Viva - voce

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32 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 5 PCM MODULATION & DEMODULATION

Aim:

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To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator
Apparatus Required:
1. PCM trainer kit ? 1 No.
2. CRO ? 1 No.

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3. Connecting probes ? 4 No.
Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is
first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of
converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization

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can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization
the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel
serially.

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At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword
is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to
Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks

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for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:
1. Power on the PCM kit.
2. Measure the frequency of sampling clock.

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3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.
5. Connect the clock to the timing control circuit.

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6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.
9. Observe the waveform at the output of DAC.
10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the

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codeword graphically for a DC input.
Block diagram of PCM Transmission system

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FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?



DEPARTMENT OF

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ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
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DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

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? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul

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DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING


To impart professional education integrated with human values to the younger generation, so as to

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shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity


? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics

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industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION

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VISION
MISSION
MISSION
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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education

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2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to

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find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context

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5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field

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b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems

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e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility

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i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

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To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms

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? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator

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4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes

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9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

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COURSE OBJECTIVES
COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction

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7
2 Time division multiplexing
13
3 AM modulation demodulation
18

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4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33
6 Delta modulation demodulation

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38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB

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51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB
55

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11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS

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13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS

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Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.

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2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at

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which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.

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Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples

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taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To

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recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit

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works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.

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3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

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Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal
Sampled output

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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.

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Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)

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5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate

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4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?

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9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.

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14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.

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19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
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Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:

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To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.

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4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.

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Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .

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3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .

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6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .

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Circuit Diagram

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Time division multiplexing

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TDM Trainer Kit

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Model Graph:

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Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1
2. Message Signal 2

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3. TDM signal

Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:

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After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.


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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network

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2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis

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5. The GSM telephone system


1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?

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3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?

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8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce
17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver

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Apparatus required:
.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.
3 Diode ? 2 No.

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4
AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.
6 Patch cards ? 6 No.

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Theory:

AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the

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instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.

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Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal

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Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index

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Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if
M < 1 Under modulation
M = 1 Critical modulation

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M > 1 over modulation

Procedure:
1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.

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3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

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AM Modulated wave



2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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21 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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AM Modulation demodulation trainer kit

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22 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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AM Modulation and Demodulation trainer kit

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)

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Message

Carrier

Modulated

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Demodulated


Result:

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Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.
Applications:

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1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?

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5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?
9. What are the different types of AM generation?

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10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce
24 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?

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17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?

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21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after

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demodulating using FM receiver
Apparatus required:
.
1. Resistor ? 4 No.
2. Capacitor ? 1 No.

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3. Diode ? 2 No.
4.
AM transmitter Receiver
trainer kit ? 1 No.
5. CRO ? 1 No.

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6. Patch cards ? 6 No.

Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the
instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct

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proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used
in broadcast is generally called wide-FM, or W-FM.

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In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the

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luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of
noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes

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print-through pre-echo.

Procedure:
FM Modulator:
1. Switch ON the Power supply.

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2. Connect the sine wave generator output to frequency modulator input.

3. Select the low frequency carrier (or) high frequency carrier.

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4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

6. Observe the frequency modulator output .

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FM Demodulator:
A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

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2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

4. Observe the Demodulated O/P compare with the original input.

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B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

2. Now set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Quadrature detector output.

4. Observe the Demodulated O/P and compare with the original input.
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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

4. Observe the Demodulated O/P and then compare with the original input.

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D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

2. Set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Ratio detector output.

4. Observe the Demodulated O/P and then compare with the original input.

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28 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


Circuit Diagram
FM Modulator

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FM Demodulator

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29 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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FM Modulation and Demodulation Trainer kit

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30 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Model Graph:

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency
modulated and demodulated wave.
Applications:

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1. Television sound transmission
2. Two way mobile radio
3. Cellular Radio
4. Microwave
5. Satellite Communication System

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1. Define ? Frequency Modulation
2. How it is different from phase modulation?
3. Write equation of FM wave, explain each parameter in it.

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4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.
6. Define ? Modulation Index
7. Differentiate between Narrow band FM from Wide band FM.
8. Draw message, carrier FM waves .

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9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?
11. Give the practical applications of FM.
12. State advantages and disadvantages of FM.
13. What is the range of speech signals?

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14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation
17. Draw the phasor diagram of FM signal.
18. What are the different types of FM generation?

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Viva - voce

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32 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 5 PCM MODULATION & DEMODULATION

Aim:

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To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator
Apparatus Required:
1. PCM trainer kit ? 1 No.
2. CRO ? 1 No.

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3. Connecting probes ? 4 No.
Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is
first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of
converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization

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can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization
the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel
serially.

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At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword
is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to
Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks

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for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:
1. Power on the PCM kit.
2. Measure the frequency of sampling clock.

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3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.
5. Connect the clock to the timing control circuit.

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6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.
9. Observe the waveform at the output of DAC.
10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the

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codeword graphically for a DC input.
Block diagram of PCM Transmission system

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34 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PCM Modulation and Demodulation Trainer kit

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FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious

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enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels

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? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

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To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

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? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical

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practices

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VISION
VISION
MISSION
MISSION
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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher

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education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth

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To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social

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context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics

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Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits

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d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness

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of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 - COMMUNICATION SYSTEMS LABORATORY

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To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes

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? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing

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3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM

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8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise

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performance of communication system.

COURSE OBJECTIVES
COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS

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1 Signal sampling reconstruction
7
2 Time division multiplexing
13
3 AM modulation demodulation

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18
4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33

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6 Delta modulation demodulation
38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS

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8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB

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55
11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59

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ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:

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1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:

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Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be

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sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.

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A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is

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accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.

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2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

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Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal

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Sampled output
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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of

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continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission

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4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?

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3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.

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8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits

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13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?

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18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
12 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 2 TIME DIVISION MULTIPLEXING

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Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.

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3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears

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on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,

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(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.

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5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.

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8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .


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Circuit Diagram
Time division multiplexing

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TDM Trainer Kit

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Model Graph:

Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1

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2. Message Signal 2
3. TDM signal

Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.

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Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)

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or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).

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4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system


1. What is meant by multiplexing technique ?

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2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.

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7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce

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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after

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demodulating using AM receiver
Apparatus required:
.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.

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3 Diode ? 2 No.
4
AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.

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6 Patch cards ? 6 No.

Theory:

AMPLITUDE MODULATION

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Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct

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The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal

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VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100

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Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if
M < 1 Under modulation

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M = 1 Critical modulation
M > 1 over modulation

Procedure:
1. Give the modulating signal input to the Amplitude modulator.

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2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

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AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation

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Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.

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Applications:
1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?

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4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?

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9. What are the different types of AM generation?
10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce
24 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?

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16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.

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20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:

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To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver
Apparatus required:
.
1. Resistor ? 4 No.

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2. Capacitor ? 1 No.
3. Diode ? 2 No.
4.
AM transmitter Receiver
trainer kit ? 1 No.

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5. CRO ? 1 No.
6. Patch cards ? 6 No.

Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the

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instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used

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in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of

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noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

Procedure:
FM Modulator:

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1. Switch ON the Power supply.

2. Connect the sine wave generator output to frequency modulator input.

3. Select the low frequency carrier (or) high frequency carrier.

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4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

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6. Observe the frequency modulator output .

FM Demodulator:
A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

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2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

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4. Observe the Demodulated O/P compare with the original input.

B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

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2. Now set the DPDT switch in high frequency mode.

3. Connect the CRO input to Quadrature detector output.

4. Observe the Demodulated O/P and compare with the original input.

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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

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4. Observe the Demodulated O/P and then compare with the original input.

D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Ratio detector output.

4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram

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FM Modulator

FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

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Carrier

Modulated

Demodulated

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Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency
modulated and demodulated wave.

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Applications:
1. Television sound transmission
2. Two way mobile radio
3. Cellular Radio
4. Microwave

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5. Satellite Communication System


1. Define ? Frequency Modulation
2. How it is different from phase modulation?

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3. Write equation of FM wave, explain each parameter in it.
4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.
6. Define ? Modulation Index
7. Differentiate between Narrow band FM from Wide band FM.

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8. Draw message, carrier FM waves .
9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?
11. Give the practical applications of FM.
12. State advantages and disadvantages of FM.

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13. What is the range of speech signals?
14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation
17. Draw the phasor diagram of FM signal.

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18. What are the different types of FM generation?

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Viva - voce
32 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 5 PCM MODULATION & DEMODULATION

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Aim:
To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator
Apparatus Required:
1. PCM trainer kit ? 1 No.

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2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is
first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of

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converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization
can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization
the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel

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serially.
At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword
is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to

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Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks
for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:
1. Power on the PCM kit.

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2. Measure the frequency of sampling clock.
3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.

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5. Connect the clock to the timing control circuit.
6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.
9. Observe the waveform at the output of DAC.

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10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the
codeword graphically for a DC input.
Block diagram of PCM Transmission system

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34 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PCM Modulation and Demodulation Trainer kit

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35 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Model Graph:

Tabulation

Result:

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Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.
Outcome:
After the completion of this experiment the students will be able to design and construct the pulse code
modulated and demodulated wave.
Applications:

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1. Military Applications.
2. The PCM is used in the satellite transmission system.
SIGNALS AMPLITUDE (V) TIME PERIOD (s)
DC Input
Sampled Signal

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Clock Pulse
PCM Output
DC Output
FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

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V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL

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DHANALAKSHMI

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College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry

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? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

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To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

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? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems

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? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION
VISION
MISSION
MISSION

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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,

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enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions

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3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students

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to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)

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a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics

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communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large

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h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM

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? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction

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2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation

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7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation

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12. Equalization ? Zero Forcing and LMS algorithms (simulation)


Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.

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Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

COURSE OBJECTIVES
COURSE OUTCOMES

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.

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CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7
2 Time division multiplexing
13

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3 AM modulation demodulation
18
4 Frequency modulation demodulation
26
5 PCM modulation demodulation

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33
6 Delta modulation demodulation
38
7 Line coding decoding techniques
45

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CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB
53

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10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB

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59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit

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Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.

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Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For

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reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known

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as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the

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sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:

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1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.

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6. Integrate the sampling inputs.

Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

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Analog signal sampling and reconstruction trainer kit


Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer

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kit.


Signal Amplitude (V) Time period (s)
Message signal

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Carrier signal
Sampled output
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Outcome:

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After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)

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3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem

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2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?

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7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?

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12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal

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17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
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Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.

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2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common

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signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.

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(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this

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sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of

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Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .


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Circuit Diagram
Time division multiplexing

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TDM Trainer Kit

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Model Graph:

Tabulation
Sl. No. Signal Amplitude (V) Time period (s)

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1. Message signal 1
2. Message Signal 2
3. TDM signal

Result:

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Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital

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transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital

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Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system

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1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?

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6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce
17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 3 AM MODULATION & DEMODULATION
Aim:

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To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver
Apparatus required:
.
1 Resistor ? 4 No.

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2 Capacitor ? 1 No.
3 Diode ? 2 No.
4
AM transmitter receiver
trainer kit ? 1 No.

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5 CRO ? 1 No.
6 Patch cards ? 6 No.

Theory:

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AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt

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VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,

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VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where

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Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:

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M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if

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M < 1 Under modulation
M = 1 Critical modulation
M > 1 over modulation

Procedure:

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1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:

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1. AM Waveform (Ring diode Transistor based AM Modulator)

AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated

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demodulated wave.
Applications:
1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.

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3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?

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8. What is depth of modulation?
9. What are the different types of AM generation?
10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce

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24 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation

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15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.

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19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.

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.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION

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Aim:
To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver
Apparatus required:
.

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1. Resistor ? 4 No.
2. Capacitor ? 1 No.
3. Diode ? 2 No.
4.
AM transmitter Receiver

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trainer kit ? 1 No.
5. CRO ? 1 No.
6. Patch cards ? 6 No.

Theory:

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Frequency modulation (FM) is a form of modulation that represents information as variations in the
instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A

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narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used
in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to

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present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of
noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

Procedure:

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FM Modulator:
1. Switch ON the Power supply.

2. Connect the sine wave generator output to frequency modulator input.

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3. Select the low frequency carrier (or) high frequency carrier.

4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

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6. Observe the frequency modulator output .

FM Demodulator:
A) PLL Detector

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1. Connect frequency modulated output to the PLL detector input.

2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

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4. Observe the Demodulated O/P compare with the original input.

B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

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2. Now set the DPDT switch in high frequency mode.

3. Connect the CRO input to Quadrature detector output.

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4. Observe the Demodulated O/P and compare with the original input.
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C) Phase Discriminator (Foster-Seeley detector)

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1. Connect the frequency modulated output to Phase discriminator input.

2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

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4. Observe the Demodulated O/P and then compare with the original input.

D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Ratio detector output.

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4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram
FM Modulator

FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

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Carrier

Modulated

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Demodulated


Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency

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modulated and demodulated wave.
Applications:
1. Television sound transmission
2. Two way mobile radio
3. Cellular Radio

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4. Microwave
5. Satellite Communication System


1. Define ? Frequency Modulation

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2. How it is different from phase modulation?
3. Write equation of FM wave, explain each parameter in it.
4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.
6. Define ? Modulation Index

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7. Differentiate between Narrow band FM from Wide band FM.
8. Draw message, carrier FM waves .
9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?
11. Give the practical applications of FM.

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12. State advantages and disadvantages of FM.
13. What is the range of speech signals?
14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation

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17. Draw the phasor diagram of FM signal.
18. What are the different types of FM generation?

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Viva - voce
32 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 5 PCM MODULATION & DEMODULATION

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Aim:
To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator
Apparatus Required:

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1. PCM trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is

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first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of
converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization
can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization

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the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel
serially.
At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword

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is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to
Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks
for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:

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1. Power on the PCM kit.
2. Measure the frequency of sampling clock.
3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.
5. Connect the clock to the timing control circuit.
6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.

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9. Observe the waveform at the output of DAC.
10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the
codeword graphically for a DC input.
Block diagram of PCM Transmission system

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PCM Modulation and Demodulation Trainer kit

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Model Graph:

Tabulation

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Result:
Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.
Outcome:
After the completion of this experiment the students will be able to design and construct the pulse code
modulated and demodulated wave.

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Applications:
1. Military Applications.
2. The PCM is used in the satellite transmission system.
SIGNALS AMPLITUDE (V) TIME PERIOD (s)
DC Input

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Sampled Signal
Clock Pulse
PCM Output
DC Output
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3. It is used in space communication.
4. It is used in telephony.
5. The compact disc (CD) is a recent application of PCM.

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1. Define ? Modulation
2. State sampling theorem
3. Define ? Demodulation
4. Define ? Pulse Code Modulation

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5. What is aliasing effect?
6. What is quantization?
7. Define ? Bit Rate
8. Define ? Baud Rate
9. What are the advantages of PCM?

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10. Define ? Signal to Noise Ratio
11. What are the limitations of PCM?
12. What are the applications of PCM?
13. Define ? Encoding
14. Define ? Decoding

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15. Define ? Nyquist Rate
16. What is multiplexing?
17. What is de-multiplexing?
18. What are the types of pulse modulation?
19. What should be the minimum bandwidth required to transmit a PCM channel?

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20. What is the value of signal to noise ratio in PCM?

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Viva - voce
FirstRanker.com - FirstRanker's Choice

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?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

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V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________

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Section : _______________________________________

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LABORATORY MANUAL
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DHANALAKSHMI

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College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

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? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

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To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

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? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in

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communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION
VISION
MISSION

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MISSION
3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals

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To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge

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training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism

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To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,

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through commitment lifelong learning needed for successful professional career

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4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability

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c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities

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g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning

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k) To participate succeed in competitive exams

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation

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? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS

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1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation

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6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)

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11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)


Simulate end-to-end Communication Link

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Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

COURSE OBJECTIVES

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COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS

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Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7
2 Time division multiplexing

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13
3 AM modulation demodulation
18
4 Frequency modulation demodulation
26

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5 PCM modulation demodulation
33
6 Delta modulation demodulation
38
7 Line coding decoding techniques

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45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB

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53
10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB
57

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12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:

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To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.

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4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.

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A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the

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signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals

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The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.

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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.

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Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.

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5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

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Model Graph:

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Tabulation

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Analog signal sampling and reconstruction trainer kit


Result:

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Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.


Signal Amplitude (V) Time period (s)

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Message signal
Carrier signal
Sampled output
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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)

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2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

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1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?

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6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?

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11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?

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16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.

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21. Define ? Natural Sampling


Viva - voce
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Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:

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1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:

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Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.

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2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.

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4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .

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7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .

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Circuit Diagram
Time division multiplexing

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14 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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TDM Trainer Kit

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Model Graph:

Tabulation

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Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1
2. Message Signal 2
3. TDM signal

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Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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Applications:

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1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.

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3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system

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1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?

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5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?

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10. Which type of modulation technique will be used in TDM?

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Viva - voce
17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 3 AM MODULATION & DEMODULATION

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Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver
Apparatus required:
.

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1 Resistor ? 4 No.
2 Capacitor ? 1 No.
3 Diode ? 2 No.
4
AM transmitter receiver

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trainer kit ? 1 No.
5 CRO ? 1 No.
6 Patch cards ? 6 No.

Theory:

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AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by

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Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

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The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal

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Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude

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if
M < 1 Under modulation
M = 1 Critical modulation
M > 1 over modulation

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Procedure:
1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .

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5. Calculate the modulation index

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Circuit Diagram

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AM Modulation


AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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22 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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AM Modulation and Demodulation trainer kit

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

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Carrier

Modulated

Demodulated

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Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:

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After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.
Applications:
1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.

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3. Facsimile transmission



1. What is modulation and demodulation?

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2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?

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7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?
9. What are the different types of AM generation?
10. Define ? Modulation Index
11. What are different types of analog modulation techniques?

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Viva - voce
24 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.

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14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?

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18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.

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23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver
Apparatus required:

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.
1. Resistor ? 4 No.
2. Capacitor ? 1 No.
3. Diode ? 2 No.
4.

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AM transmitter Receiver
trainer kit ? 1 No.
5. CRO ? 1 No.
6. Patch cards ? 6 No.

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Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the
instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF

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radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used
in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.

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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of

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frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of
noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

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Procedure:
FM Modulator:
1. Switch ON the Power supply.

2. Connect the sine wave generator output to frequency modulator input.

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3. Select the low frequency carrier (or) high frequency carrier.

4. Connect the CRO input to the frequency modulator output.

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5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

6. Observe the frequency modulator output .

FM Demodulator:

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A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

2. Now set the DPDT switch in low frequency mode.

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3. Connect CRO input to PLL detector output.

4. Observe the Demodulated O/P compare with the original input.

B) Quadrature Detector

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1. Connect the frequency modulated output to Quadrature detector input.

2. Now set the DPDT switch in high frequency mode.

3. Connect the CRO input to Quadrature detector output.

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4. Observe the Demodulated O/P and compare with the original input.
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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

2. Set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Phase discriminator output.

4. Observe the Demodulated O/P and then compare with the original input.

D) Ratio Detector

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1. Connect the frequency modulated output to Ratio detector input.

2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Ratio detector output.

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4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram
FM Modulator

FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:


Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)

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Message

Carrier

Modulated

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Demodulated


Result:

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Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:

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After the completion of this experiment the students will be able to design and construct the frequency
modulated and demodulated wave.
Applications:
1. Television sound transmission
2. Two way mobile radio

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3. Cellular Radio
4. Microwave
5. Satellite Communication System

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1. Define ? Frequency Modulation
2. How it is different from phase modulation?
3. Write equation of FM wave, explain each parameter in it.
4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.

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6. Define ? Modulation Index
7. Differentiate between Narrow band FM from Wide band FM.
8. Draw message, carrier FM waves .
9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?

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11. Give the practical applications of FM.
12. State advantages and disadvantages of FM.
13. What is the range of speech signals?
14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?

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16. Define ? Phase Modulation
17. Draw the phasor diagram of FM signal.
18. What are the different types of FM generation?

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Viva - voce
32 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 5 PCM MODULATION & DEMODULATION

Aim:
To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator

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Apparatus Required:
1. PCM trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:

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Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is
first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of
converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization
can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are

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given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization
the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel
serially.
At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.

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In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword
is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to
Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks
for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.

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Procedure:
1. Power on the PCM kit.
2. Measure the frequency of sampling clock.
3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.
5. Connect the clock to the timing control circuit.
6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.

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8. Now apply the AC modulating signal at the input.
9. Observe the waveform at the output of DAC.
10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the
codeword graphically for a DC input.
Block diagram of PCM Transmission system

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PCM Modulation and Demodulation Trainer kit

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Model Graph:

Tabulation

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Result:
Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.
Outcome:
After the completion of this experiment the students will be able to design and construct the pulse code

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modulated and demodulated wave.
Applications:
1. Military Applications.
2. The PCM is used in the satellite transmission system.
SIGNALS AMPLITUDE (V) TIME PERIOD (s)

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DC Input
Sampled Signal
Clock Pulse
PCM Output
DC Output

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3. It is used in space communication.
4. It is used in telephony.
5. The compact disc (CD) is a recent application of PCM.

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1. Define ? Modulation
2. State sampling theorem
3. Define ? Demodulation

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4. Define ? Pulse Code Modulation
5. What is aliasing effect?
6. What is quantization?
7. Define ? Bit Rate
8. Define ? Baud Rate

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9. What are the advantages of PCM?
10. Define ? Signal to Noise Ratio
11. What are the limitations of PCM?
12. What are the applications of PCM?
13. Define ? Encoding

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14. Define ? Decoding
15. Define ? Nyquist Rate
16. What is multiplexing?
17. What is de-multiplexing?
18. What are the types of pulse modulation?

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19. What should be the minimum bandwidth required to transmit a PCM channel?
20. What is the value of signal to noise ratio in PCM?

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Viva - voce

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Expt. No. 6 DELTA MODULATION & DEMODULATION
Aim:
To transmit an analog message signal in its digital form and reconstruct back the original analog message

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signal at receiver by using Delta modulator
Apparatus required:
1. DM and ADM Trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.

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Theory:
Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The
difference signal between two successive samples is encoded into a single bit code. A present sample of the
analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level
(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.

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The comparison of samples is accomplished by converting the digital to analog form then comparing with the
present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to
a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.
Procedure:
1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.

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2. Observe the modulated signal in the CRO.
3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.
4. Also observe the DAC output on the CRO.
5. Change the amplitude of the modulating signal.
6. Observe the DAC output. Notice the slope overload distortion.

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7. Keep the tuning knob to minimize distortion.
8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope
overload distortion.
9. Calculate the sampling frequency required for no slope overload distortion.
10. Compare the calculated measured values of the sampling frequency.

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FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
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DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious

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enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels

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? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

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To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

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? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical

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practices

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VISION
VISION
MISSION
MISSION
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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher

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education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth

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To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social

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context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics

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Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits

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d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness

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of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

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To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes

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? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing

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3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM

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8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise

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performance of communication system.

COURSE OBJECTIVES
COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS

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1 Signal sampling reconstruction
7
2 Time division multiplexing
13
3 AM modulation demodulation

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18
4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33

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6 Delta modulation demodulation
38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS

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8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB

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55
11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59

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ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:

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1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:

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Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be

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sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.

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A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is

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accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.

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2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

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Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal

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Sampled output
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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of

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continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission

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4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?

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3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.

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8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits

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13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?

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18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
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Expt. No. 2 TIME DIVISION MULTIPLEXING

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Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.

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3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears

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on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,

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(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.

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5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.

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8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .


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Circuit Diagram
Time division multiplexing

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TDM Trainer Kit

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Model Graph:

Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1

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2. Message Signal 2
3. TDM signal

Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.

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Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)

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or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).

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4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system


1. What is meant by multiplexing technique ?

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2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.

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7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce

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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after

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demodulating using AM receiver
Apparatus required:
.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.

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3 Diode ? 2 No.
4
AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.

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6 Patch cards ? 6 No.

Theory:

AMPLITUDE MODULATION

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Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct

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The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal

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VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100

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Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if
M < 1 Under modulation

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M = 1 Critical modulation
M > 1 over modulation

Procedure:
1. Give the modulating signal input to the Amplitude modulator.

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2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

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AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation

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Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.

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Applications:
1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?

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4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?

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9. What are the different types of AM generation?
10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce
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12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?

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16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.

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20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:

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To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver
Apparatus required:
.
1. Resistor ? 4 No.

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2. Capacitor ? 1 No.
3. Diode ? 2 No.
4.
AM transmitter Receiver
trainer kit ? 1 No.

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5. CRO ? 1 No.
6. Patch cards ? 6 No.

Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the

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instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used

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in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of

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noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

Procedure:
FM Modulator:

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1. Switch ON the Power supply.

2. Connect the sine wave generator output to frequency modulator input.

3. Select the low frequency carrier (or) high frequency carrier.

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4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

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6. Observe the frequency modulator output .

FM Demodulator:
A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

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2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

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4. Observe the Demodulated O/P compare with the original input.

B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

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2. Now set the DPDT switch in high frequency mode.

3. Connect the CRO input to Quadrature detector output.

4. Observe the Demodulated O/P and compare with the original input.

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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

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4. Observe the Demodulated O/P and then compare with the original input.

D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Ratio detector output.

4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram

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FM Modulator

FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

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Carrier

Modulated

Demodulated

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Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency
modulated and demodulated wave.

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Applications:
1. Television sound transmission
2. Two way mobile radio
3. Cellular Radio
4. Microwave

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5. Satellite Communication System


1. Define ? Frequency Modulation
2. How it is different from phase modulation?

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3. Write equation of FM wave, explain each parameter in it.
4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.
6. Define ? Modulation Index
7. Differentiate between Narrow band FM from Wide band FM.

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8. Draw message, carrier FM waves .
9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?
11. Give the practical applications of FM.
12. State advantages and disadvantages of FM.

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13. What is the range of speech signals?
14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation
17. Draw the phasor diagram of FM signal.

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18. What are the different types of FM generation?

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Viva - voce
32 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 5 PCM MODULATION & DEMODULATION

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Aim:
To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator
Apparatus Required:
1. PCM trainer kit ? 1 No.

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2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is
first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of

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converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization
can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization
the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel

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serially.
At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword
is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to

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Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks
for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:
1. Power on the PCM kit.

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2. Measure the frequency of sampling clock.
3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.

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5. Connect the clock to the timing control circuit.
6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.
9. Observe the waveform at the output of DAC.

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10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the
codeword graphically for a DC input.
Block diagram of PCM Transmission system

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PCM Modulation and Demodulation Trainer kit

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35 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Model Graph:

Tabulation

Result:

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Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.
Outcome:
After the completion of this experiment the students will be able to design and construct the pulse code
modulated and demodulated wave.
Applications:

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1. Military Applications.
2. The PCM is used in the satellite transmission system.
SIGNALS AMPLITUDE (V) TIME PERIOD (s)
DC Input
Sampled Signal

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Clock Pulse
PCM Output
DC Output
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3. It is used in space communication.
4. It is used in telephony.
5. The compact disc (CD) is a recent application of PCM.

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1. Define ? Modulation
2. State sampling theorem
3. Define ? Demodulation
4. Define ? Pulse Code Modulation
5. What is aliasing effect?

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6. What is quantization?
7. Define ? Bit Rate
8. Define ? Baud Rate
9. What are the advantages of PCM?
10. Define ? Signal to Noise Ratio

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11. What are the limitations of PCM?
12. What are the applications of PCM?
13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate

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16. What is multiplexing?
17. What is de-multiplexing?
18. What are the types of pulse modulation?
19. What should be the minimum bandwidth required to transmit a PCM channel?
20. What is the value of signal to noise ratio in PCM?

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Viva - voce
37 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 6 DELTA MODULATION & DEMODULATION
Aim:
To transmit an analog message signal in its digital form and reconstruct back the original analog message
signal at receiver by using Delta modulator
Apparatus required:

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1. DM and ADM Trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The

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difference signal between two successive samples is encoded into a single bit code. A present sample of the
analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level
(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.
The comparison of samples is accomplished by converting the digital to analog form then comparing with the
present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to

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a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.
Procedure:
1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.
2. Observe the modulated signal in the CRO.
3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.

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4. Also observe the DAC output on the CRO.
5. Change the amplitude of the modulating signal.
6. Observe the DAC output. Notice the slope overload distortion.
7. Keep the tuning knob to minimize distortion.
8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope

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overload distortion.
9. Calculate the sampling frequency required for no slope overload distortion.
10. Compare the calculated measured values of the sampling frequency.

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38 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Block Diagram Delta modulator and demodulator

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Delta Modulator

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Delta Demodulator

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FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

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V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL

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2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

DHANALAKSHMI

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College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry

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? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

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To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

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? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems

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? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION
VISION
MISSION
MISSION

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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,

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enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions

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3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students

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to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)

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a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics

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communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large

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h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM

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? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction

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2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation

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7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation

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12. Equalization ? Zero Forcing and LMS algorithms (simulation)


Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.

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Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

COURSE OBJECTIVES
COURSE OUTCOMES

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.

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CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7
2 Time division multiplexing
13

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3 AM modulation demodulation
18
4 Frequency modulation demodulation
26
5 PCM modulation demodulation

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33
6 Delta modulation demodulation
38
7 Line coding decoding techniques
45

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CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB
53

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10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB

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59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit

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Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.

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Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For

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reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known

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as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the

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sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:

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1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.

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6. Integrate the sampling inputs.

Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

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Analog signal sampling and reconstruction trainer kit


Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer

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kit.


Signal Amplitude (V) Time period (s)
Message signal

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Carrier signal
Sampled output
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Outcome:

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After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)

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3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem

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2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?

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7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?

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12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal

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17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
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Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.

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2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common

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signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.

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(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this

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sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of

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Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .


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Circuit Diagram
Time division multiplexing

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TDM Trainer Kit

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Model Graph:

Tabulation
Sl. No. Signal Amplitude (V) Time period (s)

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1. Message signal 1
2. Message Signal 2
3. TDM signal

Result:

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Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital

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transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital

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Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system

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1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?

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6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce
17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 3 AM MODULATION & DEMODULATION
Aim:

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To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver
Apparatus required:
.
1 Resistor ? 4 No.

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2 Capacitor ? 1 No.
3 Diode ? 2 No.
4
AM transmitter receiver
trainer kit ? 1 No.

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5 CRO ? 1 No.
6 Patch cards ? 6 No.

Theory:

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AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt

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VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,

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VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where

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Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:

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M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if

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M < 1 Under modulation
M = 1 Critical modulation
M > 1 over modulation

Procedure:

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1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:

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1. AM Waveform (Ring diode Transistor based AM Modulator)

AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated

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demodulated wave.
Applications:
1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.

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3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?

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8. What is depth of modulation?
9. What are the different types of AM generation?
10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce

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12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation

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15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.

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19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.

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.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION

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Aim:
To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver
Apparatus required:
.

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1. Resistor ? 4 No.
2. Capacitor ? 1 No.
3. Diode ? 2 No.
4.
AM transmitter Receiver

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trainer kit ? 1 No.
5. CRO ? 1 No.
6. Patch cards ? 6 No.

Theory:

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Frequency modulation (FM) is a form of modulation that represents information as variations in the
instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A

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narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used
in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to

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present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of
noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

Procedure:

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FM Modulator:
1. Switch ON the Power supply.

2. Connect the sine wave generator output to frequency modulator input.

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3. Select the low frequency carrier (or) high frequency carrier.

4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

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6. Observe the frequency modulator output .

FM Demodulator:
A) PLL Detector

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1. Connect frequency modulated output to the PLL detector input.

2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

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4. Observe the Demodulated O/P compare with the original input.

B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

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2. Now set the DPDT switch in high frequency mode.

3. Connect the CRO input to Quadrature detector output.

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4. Observe the Demodulated O/P and compare with the original input.
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C) Phase Discriminator (Foster-Seeley detector)

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1. Connect the frequency modulated output to Phase discriminator input.

2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

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4. Observe the Demodulated O/P and then compare with the original input.

D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Ratio detector output.

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4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram
FM Modulator

FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

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Carrier

Modulated

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Demodulated


Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency

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modulated and demodulated wave.
Applications:
1. Television sound transmission
2. Two way mobile radio
3. Cellular Radio

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4. Microwave
5. Satellite Communication System


1. Define ? Frequency Modulation

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2. How it is different from phase modulation?
3. Write equation of FM wave, explain each parameter in it.
4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.
6. Define ? Modulation Index

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7. Differentiate between Narrow band FM from Wide band FM.
8. Draw message, carrier FM waves .
9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?
11. Give the practical applications of FM.

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12. State advantages and disadvantages of FM.
13. What is the range of speech signals?
14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation

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17. Draw the phasor diagram of FM signal.
18. What are the different types of FM generation?

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Viva - voce
32 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 5 PCM MODULATION & DEMODULATION

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Aim:
To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator
Apparatus Required:

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1. PCM trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is

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first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of
converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization
can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization

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the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel
serially.
At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword

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is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to
Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks
for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:

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1. Power on the PCM kit.
2. Measure the frequency of sampling clock.
3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.
5. Connect the clock to the timing control circuit.
6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.

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9. Observe the waveform at the output of DAC.
10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the
codeword graphically for a DC input.
Block diagram of PCM Transmission system

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PCM Modulation and Demodulation Trainer kit

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Model Graph:

Tabulation

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Result:
Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.
Outcome:
After the completion of this experiment the students will be able to design and construct the pulse code
modulated and demodulated wave.

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Applications:
1. Military Applications.
2. The PCM is used in the satellite transmission system.
SIGNALS AMPLITUDE (V) TIME PERIOD (s)
DC Input

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Sampled Signal
Clock Pulse
PCM Output
DC Output
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3. It is used in space communication.
4. It is used in telephony.
5. The compact disc (CD) is a recent application of PCM.

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1. Define ? Modulation
2. State sampling theorem
3. Define ? Demodulation
4. Define ? Pulse Code Modulation

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5. What is aliasing effect?
6. What is quantization?
7. Define ? Bit Rate
8. Define ? Baud Rate
9. What are the advantages of PCM?

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10. Define ? Signal to Noise Ratio
11. What are the limitations of PCM?
12. What are the applications of PCM?
13. Define ? Encoding
14. Define ? Decoding

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15. Define ? Nyquist Rate
16. What is multiplexing?
17. What is de-multiplexing?
18. What are the types of pulse modulation?
19. What should be the minimum bandwidth required to transmit a PCM channel?

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20. What is the value of signal to noise ratio in PCM?

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Viva - voce
37 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 6 DELTA MODULATION & DEMODULATION
Aim:
To transmit an analog message signal in its digital form and reconstruct back the original analog message
signal at receiver by using Delta modulator

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Apparatus required:
1. DM and ADM Trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:

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Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The
difference signal between two successive samples is encoded into a single bit code. A present sample of the
analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level
(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.
The comparison of samples is accomplished by converting the digital to analog form then comparing with the

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present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to
a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.
Procedure:
1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.
2. Observe the modulated signal in the CRO.

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3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.
4. Also observe the DAC output on the CRO.
5. Change the amplitude of the modulating signal.
6. Observe the DAC output. Notice the slope overload distortion.
7. Keep the tuning knob to minimize distortion.

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8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope
overload distortion.
9. Calculate the sampling frequency required for no slope overload distortion.
10. Compare the calculated measured values of the sampling frequency.

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Block Diagram Delta modulator and demodulator

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Delta Modulator

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Delta Demodulator



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Block diagram of Adaptive delta modulator and demodulator

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Adaptive Delta Modulator

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Adaptive Delta Demodulator

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FirstRanker.com - FirstRanker's Choice
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?



DEPARTMENT OF

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ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
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DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

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? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul

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DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING


To impart professional education integrated with human values to the younger generation, so as to

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shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity


? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics

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industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION

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VISION
MISSION
MISSION
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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education

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2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to

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find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context

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5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field

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b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems

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e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility

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i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

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To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms

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? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator

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4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes

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9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

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COURSE OBJECTIVES
COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction

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7
2 Time division multiplexing
13
3 AM modulation demodulation
18

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4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33
6 Delta modulation demodulation

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38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB

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51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB
55

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11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS

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13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS

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Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.

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2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at

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which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.

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Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples

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taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To

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recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit

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works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.

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3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

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Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal
Sampled output

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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.

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Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)

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5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate

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4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?

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9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.

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14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.

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19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
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Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:

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To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.

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4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.

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Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .

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3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .

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6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .

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Circuit Diagram

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Time division multiplexing

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TDM Trainer Kit

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Model Graph:

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Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1
2. Message Signal 2

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3. TDM signal

Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:

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After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.


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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network

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2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis

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5. The GSM telephone system


1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?

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3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?

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8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce
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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver

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Apparatus required:
.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.
3 Diode ? 2 No.

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4
AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.
6 Patch cards ? 6 No.

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Theory:

AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the

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instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.

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Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal

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Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index

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Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if
M < 1 Under modulation
M = 1 Critical modulation

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M > 1 over modulation

Procedure:
1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.

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3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

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AM Modulated wave



2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)

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Message

Carrier

Modulated

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Demodulated


Result:

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Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.
Applications:

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1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?

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5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?
9. What are the different types of AM generation?

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10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce
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12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?

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17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?

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21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after

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demodulating using FM receiver
Apparatus required:
.
1. Resistor ? 4 No.
2. Capacitor ? 1 No.

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3. Diode ? 2 No.
4.
AM transmitter Receiver
trainer kit ? 1 No.
5. CRO ? 1 No.

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6. Patch cards ? 6 No.

Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the
instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct

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proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used
in broadcast is generally called wide-FM, or W-FM.

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In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the

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luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of
noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes

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print-through pre-echo.

Procedure:
FM Modulator:
1. Switch ON the Power supply.

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2. Connect the sine wave generator output to frequency modulator input.

3. Select the low frequency carrier (or) high frequency carrier.

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4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

6. Observe the frequency modulator output .

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FM Demodulator:
A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

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2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

4. Observe the Demodulated O/P compare with the original input.

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B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

2. Now set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Quadrature detector output.

4. Observe the Demodulated O/P and compare with the original input.
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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

4. Observe the Demodulated O/P and then compare with the original input.

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D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

2. Set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Ratio detector output.

4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram
FM Modulator

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FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency
modulated and demodulated wave.
Applications:

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1. Television sound transmission
2. Two way mobile radio
3. Cellular Radio
4. Microwave
5. Satellite Communication System

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1. Define ? Frequency Modulation
2. How it is different from phase modulation?
3. Write equation of FM wave, explain each parameter in it.

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4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.
6. Define ? Modulation Index
7. Differentiate between Narrow band FM from Wide band FM.
8. Draw message, carrier FM waves .

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9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?
11. Give the practical applications of FM.
12. State advantages and disadvantages of FM.
13. What is the range of speech signals?

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14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation
17. Draw the phasor diagram of FM signal.
18. What are the different types of FM generation?

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Viva - voce

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Expt. No. 5 PCM MODULATION & DEMODULATION

Aim:

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To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator
Apparatus Required:
1. PCM trainer kit ? 1 No.
2. CRO ? 1 No.

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3. Connecting probes ? 4 No.
Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is
first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of
converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization

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can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization
the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel
serially.

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At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword
is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to
Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks

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for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:
1. Power on the PCM kit.
2. Measure the frequency of sampling clock.

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3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.
5. Connect the clock to the timing control circuit.

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6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.
9. Observe the waveform at the output of DAC.
10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the

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codeword graphically for a DC input.
Block diagram of PCM Transmission system

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PCM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation

Result:
Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.

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Outcome:
After the completion of this experiment the students will be able to design and construct the pulse code
modulated and demodulated wave.
Applications:
1. Military Applications.

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2. The PCM is used in the satellite transmission system.
SIGNALS AMPLITUDE (V) TIME PERIOD (s)
DC Input
Sampled Signal
Clock Pulse

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PCM Output
DC Output
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3. It is used in space communication.

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4. It is used in telephony.
5. The compact disc (CD) is a recent application of PCM.


1. Define ? Modulation

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2. State sampling theorem
3. Define ? Demodulation
4. Define ? Pulse Code Modulation
5. What is aliasing effect?
6. What is quantization?

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7. Define ? Bit Rate
8. Define ? Baud Rate
9. What are the advantages of PCM?
10. Define ? Signal to Noise Ratio
11. What are the limitations of PCM?

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12. What are the applications of PCM?
13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate
16. What is multiplexing?

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17. What is de-multiplexing?
18. What are the types of pulse modulation?
19. What should be the minimum bandwidth required to transmit a PCM channel?
20. What is the value of signal to noise ratio in PCM?

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Viva - voce
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Expt. No. 6 DELTA MODULATION & DEMODULATION

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Aim:
To transmit an analog message signal in its digital form and reconstruct back the original analog message
signal at receiver by using Delta modulator
Apparatus required:
1. DM and ADM Trainer kit ? 1 No.

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2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The
difference signal between two successive samples is encoded into a single bit code. A present sample of the

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analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level
(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.
The comparison of samples is accomplished by converting the digital to analog form then comparing with the
present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to
a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.

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Procedure:
1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.
2. Observe the modulated signal in the CRO.
3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.
4. Also observe the DAC output on the CRO.

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5. Change the amplitude of the modulating signal.
6. Observe the DAC output. Notice the slope overload distortion.
7. Keep the tuning knob to minimize distortion.
8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope
overload distortion.

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9. Calculate the sampling frequency required for no slope overload distortion.
10. Compare the calculated measured values of the sampling frequency.


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Block Diagram Delta modulator and demodulator

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Delta Modulator

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Delta Demodulator

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39 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Block diagram of Adaptive delta modulator and demodulator

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Adaptive Delta Modulator

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Adaptive Delta Demodulator

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Delta Modulation and Adaptive Delta Modulator Trainer kit

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FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

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V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________

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Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
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DHANALAKSHMI

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College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

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? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION

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ENGINEERING


To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges

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in deploying technology for the service of humanity


? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry

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? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION
VISION

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MISSION
MISSION
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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)

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1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence

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To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products

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4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics

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To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints

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such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks

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f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities

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j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM

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? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes

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LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator

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5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)

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10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

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COURSE OBJECTIVES
COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7

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2 Time division multiplexing
13
3 AM modulation demodulation
18
4 Frequency modulation demodulation

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26
5 PCM modulation demodulation
33
6 Delta modulation demodulation
38

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7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51

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9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB

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57
12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61

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14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION

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Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.

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3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are

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natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem

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If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.

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Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz

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and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of

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control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.

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4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

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Model Graph:

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Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal
Sampled output
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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.
Applications:

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1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

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1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate
4. Define ? Nyquist interval

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5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?

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10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.

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15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?

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20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling


Viva - voce

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Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit

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Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.

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Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.
Procedure:

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1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on

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channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)

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on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .

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Circuit Diagram
Time division multiplexing

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14 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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TDM Trainer Kit

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Model Graph:

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Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1
2. Message Signal 2
3. TDM signal

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Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the

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signals.


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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network

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transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system

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1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?

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4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.

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9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce
17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver
Apparatus required:

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.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.
3 Diode ? 2 No.
4

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AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.
6 Patch cards ? 6 No.

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Theory:

AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.

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The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

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The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal

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Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index
Vmax = Maximum peak amplitude

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Vmin = Minimum peak amplitude
if
M < 1 Under modulation
M = 1 Critical modulation
M > 1 over modulation

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Procedure:
1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.

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4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation


AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

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Carrier

Modulated

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Demodulated


Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.

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Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.
Applications:
1. Commercial broadcasting of both audio and video signals

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2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.

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6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?
9. What are the different types of AM generation?
10. Define ? Modulation Index

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11. What are different types of analog modulation techniques?
Viva - voce
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12. What are the other names of message signal? What are the other names of carrier signal?

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13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of

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demodulation of an AM wave?
18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation

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22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver

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Apparatus required:
.
1. Resistor ? 4 No.
2. Capacitor ? 1 No.
3. Diode ? 2 No.

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4.
AM transmitter Receiver
trainer kit ? 1 No.
5. CRO ? 1 No.
6. Patch cards ? 6 No.

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Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the
instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete

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values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used
in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into

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space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and

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retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of
noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

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Procedure:
FM Modulator:
1. Switch ON the Power supply.

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2. Connect the sine wave generator output to frequency modulator input.

3. Select the low frequency carrier (or) high frequency carrier.

4. Connect the CRO input to the frequency modulator output.

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5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

6. Observe the frequency modulator output .

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FM Demodulator:
A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

2. Now set the DPDT switch in low frequency mode.

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3. Connect CRO input to PLL detector output.

4. Observe the Demodulated O/P compare with the original input.

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B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

2. Now set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Quadrature detector output.

4. Observe the Demodulated O/P and compare with the original input.
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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

2. Set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Phase discriminator output.

4. Observe the Demodulated O/P and then compare with the original input.

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D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

2. Set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Ratio detector output.

4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram
FM Modulator

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FM Demodulator

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29 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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FM Modulation and Demodulation Trainer kit

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Model Graph:


Tabulation

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Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency
modulated and demodulated wave.
Applications:
1. Television sound transmission

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2. Two way mobile radio
3. Cellular Radio
4. Microwave
5. Satellite Communication System

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1. Define ? Frequency Modulation
2. How it is different from phase modulation?
3. Write equation of FM wave, explain each parameter in it.
4. Draw the amplitude spectrum of FM wave.

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5. Give the Carson?s rule in FM.
6. Define ? Modulation Index
7. Differentiate between Narrow band FM from Wide band FM.
8. Draw message, carrier FM waves .
9. Explain the methods for generation of FM its demodulation.

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10. How FM wave is different from PM wave?
11. Give the practical applications of FM.
12. State advantages and disadvantages of FM.
13. What is the range of speech signals?
14. What type of modulation is used in radios?

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15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation
17. Draw the phasor diagram of FM signal.
18. What are the different types of FM generation?

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Viva - voce
32 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 5 PCM MODULATION & DEMODULATION

Aim:
To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM

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demodulator
Apparatus Required:
1. PCM trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.

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Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is
first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of
converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization
can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in

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speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization
the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel
serially.
At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an

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equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword
is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to
Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks
for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be

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observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:
1. Power on the PCM kit.
2. Measure the frequency of sampling clock.
3. Apply the DC voltage as modulating signal.

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4. Connect the DC input to the ADC measure the voltage.
5. Connect the clock to the timing control circuit.
6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.

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7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.
9. Observe the waveform at the output of DAC.
10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the
codeword graphically for a DC input.

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Block diagram of PCM Transmission system

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PCM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation

Result:
Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.
Outcome:

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After the completion of this experiment the students will be able to design and construct the pulse code
modulated and demodulated wave.
Applications:
1. Military Applications.
2. The PCM is used in the satellite transmission system.

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SIGNALS AMPLITUDE (V) TIME PERIOD (s)
DC Input
Sampled Signal
Clock Pulse
PCM Output

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DC Output
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3. It is used in space communication.
4. It is used in telephony.

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5. The compact disc (CD) is a recent application of PCM.


1. Define ? Modulation
2. State sampling theorem

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3. Define ? Demodulation
4. Define ? Pulse Code Modulation
5. What is aliasing effect?
6. What is quantization?
7. Define ? Bit Rate

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8. Define ? Baud Rate
9. What are the advantages of PCM?
10. Define ? Signal to Noise Ratio
11. What are the limitations of PCM?
12. What are the applications of PCM?

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13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate
16. What is multiplexing?
17. What is de-multiplexing?

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18. What are the types of pulse modulation?
19. What should be the minimum bandwidth required to transmit a PCM channel?
20. What is the value of signal to noise ratio in PCM?

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Viva - voce
37 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 6 DELTA MODULATION & DEMODULATION
Aim:

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To transmit an analog message signal in its digital form and reconstruct back the original analog message
signal at receiver by using Delta modulator
Apparatus required:
1. DM and ADM Trainer kit ? 1 No.
2. CRO ? 1 No.

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3. Connecting probes ? 4 No.
Theory:
Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The
difference signal between two successive samples is encoded into a single bit code. A present sample of the
analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level

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(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.
The comparison of samples is accomplished by converting the digital to analog form then comparing with the
present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to
a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.
Procedure:

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1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.
2. Observe the modulated signal in the CRO.
3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.
4. Also observe the DAC output on the CRO.
5. Change the amplitude of the modulating signal.

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6. Observe the DAC output. Notice the slope overload distortion.
7. Keep the tuning knob to minimize distortion.
8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope
overload distortion.
9. Calculate the sampling frequency required for no slope overload distortion.

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10. Compare the calculated measured values of the sampling frequency.


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Block Diagram Delta modulator and demodulator

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Delta Modulator

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Delta Demodulator

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Block diagram of Adaptive delta modulator and demodulator

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Adaptive Delta Modulator

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Adaptive Delta Demodulator

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Delta Modulation and Adaptive Delta Modulator Trainer kit

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Model Graph:

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FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

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V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL

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DHANALAKSHMI

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College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry

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? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

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To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

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? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems

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? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION
VISION
MISSION
MISSION

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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,

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enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions

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3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students

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to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)

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a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics

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communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large

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h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM

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? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction

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2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation

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7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation

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12. Equalization ? Zero Forcing and LMS algorithms (simulation)


Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.

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Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

COURSE OBJECTIVES
COURSE OUTCOMES

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.

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CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7
2 Time division multiplexing
13

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3 AM modulation demodulation
18
4 Frequency modulation demodulation
26
5 PCM modulation demodulation

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33
6 Delta modulation demodulation
38
7 Line coding decoding techniques
45

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CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB
53

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10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB

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59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit

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Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.

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Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For

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reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known

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as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the

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sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:

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1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.

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6. Integrate the sampling inputs.

Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

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Analog signal sampling and reconstruction trainer kit


Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer

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kit.


Signal Amplitude (V) Time period (s)
Message signal

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Carrier signal
Sampled output
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Outcome:

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After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)

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3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem

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2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?

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7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?

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12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal

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17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
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Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.

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2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common

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signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.

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(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this

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sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of

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Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .


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Circuit Diagram
Time division multiplexing

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TDM Trainer Kit

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Model Graph:

Tabulation
Sl. No. Signal Amplitude (V) Time period (s)

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1. Message signal 1
2. Message Signal 2
3. TDM signal

Result:

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Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital

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transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital

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Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system

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1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?

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6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce
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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:

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To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver
Apparatus required:
.
1 Resistor ? 4 No.

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2 Capacitor ? 1 No.
3 Diode ? 2 No.
4
AM transmitter receiver
trainer kit ? 1 No.

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5 CRO ? 1 No.
6 Patch cards ? 6 No.

Theory:

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AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt

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VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,

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VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where

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Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:

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M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if

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M < 1 Under modulation
M = 1 Critical modulation
M > 1 over modulation

Procedure:

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1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:

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1. AM Waveform (Ring diode Transistor based AM Modulator)

AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated

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demodulated wave.
Applications:
1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.

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3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?

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8. What is depth of modulation?
9. What are the different types of AM generation?
10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce

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24 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation

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15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.

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19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.

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.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION

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Aim:
To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver
Apparatus required:
.

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1. Resistor ? 4 No.
2. Capacitor ? 1 No.
3. Diode ? 2 No.
4.
AM transmitter Receiver

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trainer kit ? 1 No.
5. CRO ? 1 No.
6. Patch cards ? 6 No.

Theory:

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Frequency modulation (FM) is a form of modulation that represents information as variations in the
instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A

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narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used
in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to

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present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of
noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

Procedure:

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FM Modulator:
1. Switch ON the Power supply.

2. Connect the sine wave generator output to frequency modulator input.

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3. Select the low frequency carrier (or) high frequency carrier.

4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

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6. Observe the frequency modulator output .

FM Demodulator:
A) PLL Detector

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1. Connect frequency modulated output to the PLL detector input.

2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

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4. Observe the Demodulated O/P compare with the original input.

B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

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2. Now set the DPDT switch in high frequency mode.

3. Connect the CRO input to Quadrature detector output.

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4. Observe the Demodulated O/P and compare with the original input.
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C) Phase Discriminator (Foster-Seeley detector)

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1. Connect the frequency modulated output to Phase discriminator input.

2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

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4. Observe the Demodulated O/P and then compare with the original input.

D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Ratio detector output.

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4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram
FM Modulator

FM Demodulator

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29 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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FM Modulation and Demodulation Trainer kit

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30 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00



Model Graph:

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

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Carrier

Modulated

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Demodulated


Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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31 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Outcome:
After the completion of this experiment the students will be able to design and construct the frequency

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modulated and demodulated wave.
Applications:
1. Television sound transmission
2. Two way mobile radio
3. Cellular Radio

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4. Microwave
5. Satellite Communication System


1. Define ? Frequency Modulation

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2. How it is different from phase modulation?
3. Write equation of FM wave, explain each parameter in it.
4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.
6. Define ? Modulation Index

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7. Differentiate between Narrow band FM from Wide band FM.
8. Draw message, carrier FM waves .
9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?
11. Give the practical applications of FM.

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12. State advantages and disadvantages of FM.
13. What is the range of speech signals?
14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation

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17. Draw the phasor diagram of FM signal.
18. What are the different types of FM generation?

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Viva - voce
32 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 5 PCM MODULATION & DEMODULATION

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Aim:
To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator
Apparatus Required:

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1. PCM trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is

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first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of
converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization
can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization

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the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel
serially.
At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword

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is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to
Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks
for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:

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1. Power on the PCM kit.
2. Measure the frequency of sampling clock.
3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.
5. Connect the clock to the timing control circuit.
6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.

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9. Observe the waveform at the output of DAC.
10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the
codeword graphically for a DC input.
Block diagram of PCM Transmission system

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34 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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PCM Modulation and Demodulation Trainer kit

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35 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Model Graph:

Tabulation

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Result:
Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.
Outcome:
After the completion of this experiment the students will be able to design and construct the pulse code
modulated and demodulated wave.

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Applications:
1. Military Applications.
2. The PCM is used in the satellite transmission system.
SIGNALS AMPLITUDE (V) TIME PERIOD (s)
DC Input

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Sampled Signal
Clock Pulse
PCM Output
DC Output
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3. It is used in space communication.
4. It is used in telephony.
5. The compact disc (CD) is a recent application of PCM.

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1. Define ? Modulation
2. State sampling theorem
3. Define ? Demodulation
4. Define ? Pulse Code Modulation

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5. What is aliasing effect?
6. What is quantization?
7. Define ? Bit Rate
8. Define ? Baud Rate
9. What are the advantages of PCM?

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10. Define ? Signal to Noise Ratio
11. What are the limitations of PCM?
12. What are the applications of PCM?
13. Define ? Encoding
14. Define ? Decoding

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15. Define ? Nyquist Rate
16. What is multiplexing?
17. What is de-multiplexing?
18. What are the types of pulse modulation?
19. What should be the minimum bandwidth required to transmit a PCM channel?

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20. What is the value of signal to noise ratio in PCM?

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Viva - voce
37 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 6 DELTA MODULATION & DEMODULATION
Aim:
To transmit an analog message signal in its digital form and reconstruct back the original analog message
signal at receiver by using Delta modulator

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Apparatus required:
1. DM and ADM Trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:

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Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The
difference signal between two successive samples is encoded into a single bit code. A present sample of the
analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level
(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.
The comparison of samples is accomplished by converting the digital to analog form then comparing with the

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present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to
a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.
Procedure:
1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.
2. Observe the modulated signal in the CRO.

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3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.
4. Also observe the DAC output on the CRO.
5. Change the amplitude of the modulating signal.
6. Observe the DAC output. Notice the slope overload distortion.
7. Keep the tuning knob to minimize distortion.

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8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope
overload distortion.
9. Calculate the sampling frequency required for no slope overload distortion.
10. Compare the calculated measured values of the sampling frequency.

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38 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Block Diagram Delta modulator and demodulator

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Delta Modulator

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Delta Demodulator



39 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Block diagram of Adaptive delta modulator and demodulator

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Adaptive Delta Modulator

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Adaptive Delta Demodulator

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40 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Delta Modulation and Adaptive Delta Modulator Trainer kit

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41 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Model Graph:

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42 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Tabulation 1
For Delta Modulation

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Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal
2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

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Tabulation 2
For Adaptive Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal

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2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

Result:

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Thus the output waveforms of Delta modulation and adaptive delta modulation circuit were observed.
Outcome:
After the completion of this experiment the students will be able to design and construct the delta modulation
adaptive delta modulation circuit.
Applications:

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1. Digital voice storage
2. Voice transmission
FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
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DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious

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enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels

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? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

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To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

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? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical

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practices

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VISION
VISION
MISSION
MISSION
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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher

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education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth

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To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social

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context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics

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Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits

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d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness

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of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

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To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes

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? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing

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3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM

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8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise

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performance of communication system.

COURSE OBJECTIVES
COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS

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1 Signal sampling reconstruction
7
2 Time division multiplexing
13
3 AM modulation demodulation

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18
4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33

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6 Delta modulation demodulation
38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS

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8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB

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55
11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59

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ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:

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1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:

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Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be

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sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.

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A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is

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accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.

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2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

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Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal

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Sampled output
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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of

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continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission

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4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?

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3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.

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8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits

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13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?

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18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
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Expt. No. 2 TIME DIVISION MULTIPLEXING

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Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.

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3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears

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on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,

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(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.

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5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.

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8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .


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Circuit Diagram
Time division multiplexing

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TDM Trainer Kit

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Model Graph:

Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1

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2. Message Signal 2
3. TDM signal

Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.

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Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)

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or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).

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4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system


1. What is meant by multiplexing technique ?

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2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.

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7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce

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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after

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demodulating using AM receiver
Apparatus required:
.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.

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3 Diode ? 2 No.
4
AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.

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6 Patch cards ? 6 No.

Theory:

AMPLITUDE MODULATION

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Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct

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The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal

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VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100

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Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if
M < 1 Under modulation

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M = 1 Critical modulation
M > 1 over modulation

Procedure:
1. Give the modulating signal input to the Amplitude modulator.

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2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

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AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation

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Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.

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Applications:
1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?

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4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?

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9. What are the different types of AM generation?
10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce
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12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?

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16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.

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20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:

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To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver
Apparatus required:
.
1. Resistor ? 4 No.

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2. Capacitor ? 1 No.
3. Diode ? 2 No.
4.
AM transmitter Receiver
trainer kit ? 1 No.

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5. CRO ? 1 No.
6. Patch cards ? 6 No.

Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the

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instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used

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in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of

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noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

Procedure:
FM Modulator:

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1. Switch ON the Power supply.

2. Connect the sine wave generator output to frequency modulator input.

3. Select the low frequency carrier (or) high frequency carrier.

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4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

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6. Observe the frequency modulator output .

FM Demodulator:
A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

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2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

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4. Observe the Demodulated O/P compare with the original input.

B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

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2. Now set the DPDT switch in high frequency mode.

3. Connect the CRO input to Quadrature detector output.

4. Observe the Demodulated O/P and compare with the original input.

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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

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4. Observe the Demodulated O/P and then compare with the original input.

D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Ratio detector output.

4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram

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FM Modulator

FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

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Carrier

Modulated

Demodulated

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Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency
modulated and demodulated wave.

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Applications:
1. Television sound transmission
2. Two way mobile radio
3. Cellular Radio
4. Microwave

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5. Satellite Communication System


1. Define ? Frequency Modulation
2. How it is different from phase modulation?

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3. Write equation of FM wave, explain each parameter in it.
4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.
6. Define ? Modulation Index
7. Differentiate between Narrow band FM from Wide band FM.

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8. Draw message, carrier FM waves .
9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?
11. Give the practical applications of FM.
12. State advantages and disadvantages of FM.

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13. What is the range of speech signals?
14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation
17. Draw the phasor diagram of FM signal.

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18. What are the different types of FM generation?

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Viva - voce
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Expt. No. 5 PCM MODULATION & DEMODULATION

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Aim:
To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator
Apparatus Required:
1. PCM trainer kit ? 1 No.

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2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is
first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of

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converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization
can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization
the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel

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serially.
At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword
is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to

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Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks
for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:
1. Power on the PCM kit.

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2. Measure the frequency of sampling clock.
3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.

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5. Connect the clock to the timing control circuit.
6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.
9. Observe the waveform at the output of DAC.

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10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the
codeword graphically for a DC input.
Block diagram of PCM Transmission system

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PCM Modulation and Demodulation Trainer kit

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Model Graph:

Tabulation

Result:

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Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.
Outcome:
After the completion of this experiment the students will be able to design and construct the pulse code
modulated and demodulated wave.
Applications:

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1. Military Applications.
2. The PCM is used in the satellite transmission system.
SIGNALS AMPLITUDE (V) TIME PERIOD (s)
DC Input
Sampled Signal

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Clock Pulse
PCM Output
DC Output
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3. It is used in space communication.
4. It is used in telephony.
5. The compact disc (CD) is a recent application of PCM.

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1. Define ? Modulation
2. State sampling theorem
3. Define ? Demodulation
4. Define ? Pulse Code Modulation
5. What is aliasing effect?

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6. What is quantization?
7. Define ? Bit Rate
8. Define ? Baud Rate
9. What are the advantages of PCM?
10. Define ? Signal to Noise Ratio

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11. What are the limitations of PCM?
12. What are the applications of PCM?
13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate

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16. What is multiplexing?
17. What is de-multiplexing?
18. What are the types of pulse modulation?
19. What should be the minimum bandwidth required to transmit a PCM channel?
20. What is the value of signal to noise ratio in PCM?

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Viva - voce
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Expt. No. 6 DELTA MODULATION & DEMODULATION
Aim:
To transmit an analog message signal in its digital form and reconstruct back the original analog message
signal at receiver by using Delta modulator
Apparatus required:

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1. DM and ADM Trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The

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difference signal between two successive samples is encoded into a single bit code. A present sample of the
analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level
(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.
The comparison of samples is accomplished by converting the digital to analog form then comparing with the
present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to

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a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.
Procedure:
1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.
2. Observe the modulated signal in the CRO.
3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.

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4. Also observe the DAC output on the CRO.
5. Change the amplitude of the modulating signal.
6. Observe the DAC output. Notice the slope overload distortion.
7. Keep the tuning knob to minimize distortion.
8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope

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overload distortion.
9. Calculate the sampling frequency required for no slope overload distortion.
10. Compare the calculated measured values of the sampling frequency.

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Block Diagram Delta modulator and demodulator

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Delta Modulator

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Delta Demodulator

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39 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Block diagram of Adaptive delta modulator and demodulator

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Adaptive Delta Modulator

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Adaptive Delta Demodulator

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Delta Modulation and Adaptive Delta Modulator Trainer kit

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Model Graph:

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Tabulation 1
For Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)

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1 Modulating Signal
2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

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Tabulation 2
For Adaptive Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal
2 Carrier Signal

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3 Modulated Signal
4 Demodulated Signal

Result:
Thus the output waveforms of Delta modulation and adaptive delta modulation circuit were observed.

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Outcome:
After the completion of this experiment the students will be able to design and construct the delta modulation
adaptive delta modulation circuit.
Applications:
1. Digital voice storage

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2. Voice transmission
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3. Radio communication devices such TV remotes.
4. Delta Modulation was used by Satellite Business Systems or SBS

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5. DM used in high resolution A/D and D/A converters.


1. What is delta modulation?
2. What is adaptive delta modulation?

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3. What are the advantages of adaptive delta modulation over delta modulation?
4. What is slope over load distortion?
5. What is granular noise effect?
6. What are the two limitations of delta modulation?
7. What is the function of integrator?

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8. What is comparator?
9. What is companding?
10. What is the advantage of delta modulation over pulse modulation?
11. Distinguish between DPCM and DM.
12. What are the different types of digital modulation?

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13. What is sampling rate?
14. Which kind of multiplexing used in digital communication?
15. Why is sample hold circuit used?
16. What are the advantages of digital transmission?
17. How is the performance corrupted in PCM?

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18. What are the different types of multiplexing?
19. What is aliasing effect?
20. How to avoid aliasing effect?

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Viva - voce
FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?



DEPARTMENT OF

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ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
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DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

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? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul

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DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING


To impart professional education integrated with human values to the younger generation, so as to

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shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity


? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics

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industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION

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VISION
MISSION
MISSION
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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education

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2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to

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find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context

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5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field

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b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems

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e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility

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i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

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To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms

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? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator

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4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes

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9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

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COURSE OBJECTIVES
COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction

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7
2 Time division multiplexing
13
3 AM modulation demodulation
18

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4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33
6 Delta modulation demodulation

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38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB

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51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB
55

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11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS

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13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS

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Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.

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2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at

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which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.

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Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples

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taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To

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recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit

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works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.

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3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

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Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal
Sampled output

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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.

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Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)

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5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate

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4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?

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9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.

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14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.

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19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
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Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:

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To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.

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4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.

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Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .

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3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .

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6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .

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Circuit Diagram

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Time division multiplexing

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14 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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TDM Trainer Kit

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Model Graph:

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Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1
2. Message Signal 2

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3. TDM signal

Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:

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After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.


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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network

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2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis

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5. The GSM telephone system


1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?

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3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?

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8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce
17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver

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Apparatus required:
.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.
3 Diode ? 2 No.

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4
AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.
6 Patch cards ? 6 No.

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Theory:

AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the

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instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.

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Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal

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Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index

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Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if
M < 1 Under modulation
M = 1 Critical modulation

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M > 1 over modulation

Procedure:
1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.

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3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

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AM Modulated wave



2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)

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Message

Carrier

Modulated

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Demodulated


Result:

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Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.
Applications:

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1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?

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5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?
9. What are the different types of AM generation?

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10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce
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12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?

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17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?

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21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after

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demodulating using FM receiver
Apparatus required:
.
1. Resistor ? 4 No.
2. Capacitor ? 1 No.

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3. Diode ? 2 No.
4.
AM transmitter Receiver
trainer kit ? 1 No.
5. CRO ? 1 No.

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6. Patch cards ? 6 No.

Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the
instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct

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proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used
in broadcast is generally called wide-FM, or W-FM.

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In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the

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luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of
noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes

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print-through pre-echo.

Procedure:
FM Modulator:
1. Switch ON the Power supply.

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2. Connect the sine wave generator output to frequency modulator input.

3. Select the low frequency carrier (or) high frequency carrier.

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4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

6. Observe the frequency modulator output .

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FM Demodulator:
A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

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2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

4. Observe the Demodulated O/P compare with the original input.

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B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

2. Now set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Quadrature detector output.

4. Observe the Demodulated O/P and compare with the original input.
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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

4. Observe the Demodulated O/P and then compare with the original input.

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D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

2. Set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Ratio detector output.

4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram
FM Modulator

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FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency
modulated and demodulated wave.
Applications:

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1. Television sound transmission
2. Two way mobile radio
3. Cellular Radio
4. Microwave
5. Satellite Communication System

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1. Define ? Frequency Modulation
2. How it is different from phase modulation?
3. Write equation of FM wave, explain each parameter in it.

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4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.
6. Define ? Modulation Index
7. Differentiate between Narrow band FM from Wide band FM.
8. Draw message, carrier FM waves .

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9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?
11. Give the practical applications of FM.
12. State advantages and disadvantages of FM.
13. What is the range of speech signals?

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14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation
17. Draw the phasor diagram of FM signal.
18. What are the different types of FM generation?

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Viva - voce

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32 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 5 PCM MODULATION & DEMODULATION

Aim:

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To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator
Apparatus Required:
1. PCM trainer kit ? 1 No.
2. CRO ? 1 No.

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3. Connecting probes ? 4 No.
Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is
first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of
converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization

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can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization
the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel
serially.

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At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword
is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to
Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks

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for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:
1. Power on the PCM kit.
2. Measure the frequency of sampling clock.

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3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.
5. Connect the clock to the timing control circuit.

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6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.
9. Observe the waveform at the output of DAC.
10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the

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codeword graphically for a DC input.
Block diagram of PCM Transmission system

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PCM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation

Result:
Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.

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Outcome:
After the completion of this experiment the students will be able to design and construct the pulse code
modulated and demodulated wave.
Applications:
1. Military Applications.

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2. The PCM is used in the satellite transmission system.
SIGNALS AMPLITUDE (V) TIME PERIOD (s)
DC Input
Sampled Signal
Clock Pulse

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PCM Output
DC Output
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3. It is used in space communication.

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4. It is used in telephony.
5. The compact disc (CD) is a recent application of PCM.


1. Define ? Modulation

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2. State sampling theorem
3. Define ? Demodulation
4. Define ? Pulse Code Modulation
5. What is aliasing effect?
6. What is quantization?

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7. Define ? Bit Rate
8. Define ? Baud Rate
9. What are the advantages of PCM?
10. Define ? Signal to Noise Ratio
11. What are the limitations of PCM?

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12. What are the applications of PCM?
13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate
16. What is multiplexing?

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17. What is de-multiplexing?
18. What are the types of pulse modulation?
19. What should be the minimum bandwidth required to transmit a PCM channel?
20. What is the value of signal to noise ratio in PCM?

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Viva - voce
37 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 6 DELTA MODULATION & DEMODULATION

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Aim:
To transmit an analog message signal in its digital form and reconstruct back the original analog message
signal at receiver by using Delta modulator
Apparatus required:
1. DM and ADM Trainer kit ? 1 No.

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2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The
difference signal between two successive samples is encoded into a single bit code. A present sample of the

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analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level
(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.
The comparison of samples is accomplished by converting the digital to analog form then comparing with the
present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to
a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.

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Procedure:
1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.
2. Observe the modulated signal in the CRO.
3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.
4. Also observe the DAC output on the CRO.

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5. Change the amplitude of the modulating signal.
6. Observe the DAC output. Notice the slope overload distortion.
7. Keep the tuning knob to minimize distortion.
8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope
overload distortion.

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9. Calculate the sampling frequency required for no slope overload distortion.
10. Compare the calculated measured values of the sampling frequency.


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Block Diagram Delta modulator and demodulator

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Delta Modulator

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Delta Demodulator

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Block diagram of Adaptive delta modulator and demodulator

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Adaptive Delta Modulator

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Adaptive Delta Demodulator

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Delta Modulation and Adaptive Delta Modulator Trainer kit

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Model Graph:

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Tabulation 1
For Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal

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2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

Tabulation 2

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For Adaptive Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal
2 Carrier Signal
3 Modulated Signal

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4 Demodulated Signal

Result:
Thus the output waveforms of Delta modulation and adaptive delta modulation circuit were observed.
Outcome:

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After the completion of this experiment the students will be able to design and construct the delta modulation
adaptive delta modulation circuit.
Applications:
1. Digital voice storage
2. Voice transmission

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3. Radio communication devices such TV remotes.
4. Delta Modulation was used by Satellite Business Systems or SBS
5. DM used in high resolution A/D and D/A converters.

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1. What is delta modulation?
2. What is adaptive delta modulation?
3. What are the advantages of adaptive delta modulation over delta modulation?

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4. What is slope over load distortion?
5. What is granular noise effect?
6. What are the two limitations of delta modulation?
7. What is the function of integrator?
8. What is comparator?

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9. What is companding?
10. What is the advantage of delta modulation over pulse modulation?
11. Distinguish between DPCM and DM.
12. What are the different types of digital modulation?
13. What is sampling rate?

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14. Which kind of multiplexing used in digital communication?
15. Why is sample hold circuit used?
16. What are the advantages of digital transmission?
17. How is the performance corrupted in PCM?
18. What are the different types of multiplexing?

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19. What is aliasing effect?
20. How to avoid aliasing effect?

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Viva - voce

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44 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 7 LINE CODING DECODING TECHNIQUES

Aim:

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To study different line coding techniques.
Apparatus required:
1. Line coding and decoding trainer kit ? 1 No.
2. Patch cords ? 6 No.
3. CRO ? 1 No.

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Theory:
Line coding refers to the process of representing the bit stream (1 ?s and 0 ?s) in the form of voltage or current
variations optimally tuned for the specific properties of the physical channel being used. The selection of a proper
line code can help in many ways. One possibility is to aid in clock recovery at the receiver. A clock signal is

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recovered by observing transitions in the received bit sequence, if enough transitions exist, a good recovery of
the clock is guaranteed, the signal is said to be self-clocking. Another advantage is to get rid of DC shifts. The
DC component in a line code is called the bias or the DC coefficient. Unfortunately, most long-distance
communication channels cannot transport a DC component. This is why most line codes try to eliminate the DC
component before being transmitted on the channel. Such codes are called DC balanced, zero-DC, zero-bias, or

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DC equalized. Some common types of line encoding in common-use nowadays are unipolar, polar, bipolar,
Manchester, MLT-3 Duo binary encoding.
Unipolar (Unipolar NRZ and Unipolar RZ):
Unipolar is the simplest line coding scheme. It has the advantage of being compatible with TTL logic. Unipolar
coding uses a positive rectangular pulse p(t) to represent binary 1, the absence of a pulse (i.e., zero voltage) to

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represent a binary 0. Two possibilities for the pulse p(t) exist3: Non-Return-to-Zero (NRZ) rectangular pulse
Return-to-Zero (RZ) rectangular pulse. The difference between Unipolar NRZ Unipolar RZ codes is that the
rectangular pulse in NRZ stays at a positive value (e.g., +5V) for the full duration of the logic 1 bit, while the pule
in RZ drops from +5V to 0V in the middle of the bit time.

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FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious

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enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels

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? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

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To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

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? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical

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practices

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VISION
VISION
MISSION
MISSION
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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher

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education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth

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To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social

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context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics

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Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits

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d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness

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of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 - COMMUNICATION SYSTEMS LABORATORY

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To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes

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? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing

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3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM

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8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise

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performance of communication system.

COURSE OBJECTIVES
COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS

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1 Signal sampling reconstruction
7
2 Time division multiplexing
13
3 AM modulation demodulation

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18
4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33

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6 Delta modulation demodulation
38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS

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8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB

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55
11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59

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ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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7 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:

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1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:

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Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be

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sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.

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A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is

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accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.

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2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

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Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal

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Sampled output
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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of

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continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission

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4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?

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3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.

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8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits

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13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?

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18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
12 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 2 TIME DIVISION MULTIPLEXING

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Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.

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3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears

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on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,

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(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.

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5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.

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8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .


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Circuit Diagram
Time division multiplexing

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TDM Trainer Kit

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Model Graph:

Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1

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2. Message Signal 2
3. TDM signal

Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.

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Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)

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or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).

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4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system


1. What is meant by multiplexing technique ?

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2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.

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7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce

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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after

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demodulating using AM receiver
Apparatus required:
.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.

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3 Diode ? 2 No.
4
AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.

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6 Patch cards ? 6 No.

Theory:

AMPLITUDE MODULATION

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Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct

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The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal

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VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100

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Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if
M < 1 Under modulation

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M = 1 Critical modulation
M > 1 over modulation

Procedure:
1. Give the modulating signal input to the Amplitude modulator.

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2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

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AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation

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Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.

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Applications:
1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?

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4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?

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9. What are the different types of AM generation?
10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce
24 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?

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16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.

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20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:

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To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver
Apparatus required:
.
1. Resistor ? 4 No.

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2. Capacitor ? 1 No.
3. Diode ? 2 No.
4.
AM transmitter Receiver
trainer kit ? 1 No.

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5. CRO ? 1 No.
6. Patch cards ? 6 No.

Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the

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instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used

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in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of

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noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

Procedure:
FM Modulator:

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1. Switch ON the Power supply.

2. Connect the sine wave generator output to frequency modulator input.

3. Select the low frequency carrier (or) high frequency carrier.

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4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

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6. Observe the frequency modulator output .

FM Demodulator:
A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

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2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

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4. Observe the Demodulated O/P compare with the original input.

B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

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2. Now set the DPDT switch in high frequency mode.

3. Connect the CRO input to Quadrature detector output.

4. Observe the Demodulated O/P and compare with the original input.

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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

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4. Observe the Demodulated O/P and then compare with the original input.

D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Ratio detector output.

4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram

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FM Modulator

FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

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Carrier

Modulated

Demodulated

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Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency
modulated and demodulated wave.

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Applications:
1. Television sound transmission
2. Two way mobile radio
3. Cellular Radio
4. Microwave

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5. Satellite Communication System


1. Define ? Frequency Modulation
2. How it is different from phase modulation?

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3. Write equation of FM wave, explain each parameter in it.
4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.
6. Define ? Modulation Index
7. Differentiate between Narrow band FM from Wide band FM.

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8. Draw message, carrier FM waves .
9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?
11. Give the practical applications of FM.
12. State advantages and disadvantages of FM.

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13. What is the range of speech signals?
14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation
17. Draw the phasor diagram of FM signal.

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18. What are the different types of FM generation?

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Viva - voce
32 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 5 PCM MODULATION & DEMODULATION

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Aim:
To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator
Apparatus Required:
1. PCM trainer kit ? 1 No.

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2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is
first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of

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converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization
can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization
the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel

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serially.
At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword
is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to

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Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks
for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:
1. Power on the PCM kit.

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2. Measure the frequency of sampling clock.
3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.

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5. Connect the clock to the timing control circuit.
6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.
9. Observe the waveform at the output of DAC.

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10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the
codeword graphically for a DC input.
Block diagram of PCM Transmission system

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34 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PCM Modulation and Demodulation Trainer kit

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35 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Model Graph:

Tabulation

Result:

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Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.
Outcome:
After the completion of this experiment the students will be able to design and construct the pulse code
modulated and demodulated wave.
Applications:

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1. Military Applications.
2. The PCM is used in the satellite transmission system.
SIGNALS AMPLITUDE (V) TIME PERIOD (s)
DC Input
Sampled Signal

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Clock Pulse
PCM Output
DC Output
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3. It is used in space communication.
4. It is used in telephony.
5. The compact disc (CD) is a recent application of PCM.

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1. Define ? Modulation
2. State sampling theorem
3. Define ? Demodulation
4. Define ? Pulse Code Modulation
5. What is aliasing effect?

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6. What is quantization?
7. Define ? Bit Rate
8. Define ? Baud Rate
9. What are the advantages of PCM?
10. Define ? Signal to Noise Ratio

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11. What are the limitations of PCM?
12. What are the applications of PCM?
13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate

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16. What is multiplexing?
17. What is de-multiplexing?
18. What are the types of pulse modulation?
19. What should be the minimum bandwidth required to transmit a PCM channel?
20. What is the value of signal to noise ratio in PCM?

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Viva - voce
37 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 6 DELTA MODULATION & DEMODULATION
Aim:
To transmit an analog message signal in its digital form and reconstruct back the original analog message
signal at receiver by using Delta modulator
Apparatus required:

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1. DM and ADM Trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The

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difference signal between two successive samples is encoded into a single bit code. A present sample of the
analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level
(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.
The comparison of samples is accomplished by converting the digital to analog form then comparing with the
present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to

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a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.
Procedure:
1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.
2. Observe the modulated signal in the CRO.
3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.

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4. Also observe the DAC output on the CRO.
5. Change the amplitude of the modulating signal.
6. Observe the DAC output. Notice the slope overload distortion.
7. Keep the tuning knob to minimize distortion.
8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope

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overload distortion.
9. Calculate the sampling frequency required for no slope overload distortion.
10. Compare the calculated measured values of the sampling frequency.

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38 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Block Diagram Delta modulator and demodulator

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Delta Modulator

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Delta Demodulator

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Block diagram of Adaptive delta modulator and demodulator

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Adaptive Delta Modulator

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Adaptive Delta Demodulator

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40 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Delta Modulation and Adaptive Delta Modulator Trainer kit

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41 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Model Graph:

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Tabulation 1
For Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)

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1 Modulating Signal
2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

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Tabulation 2
For Adaptive Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal
2 Carrier Signal

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3 Modulated Signal
4 Demodulated Signal

Result:
Thus the output waveforms of Delta modulation and adaptive delta modulation circuit were observed.

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Outcome:
After the completion of this experiment the students will be able to design and construct the delta modulation
adaptive delta modulation circuit.
Applications:
1. Digital voice storage

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2. Voice transmission
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3. Radio communication devices such TV remotes.
4. Delta Modulation was used by Satellite Business Systems or SBS

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5. DM used in high resolution A/D and D/A converters.


1. What is delta modulation?
2. What is adaptive delta modulation?

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3. What are the advantages of adaptive delta modulation over delta modulation?
4. What is slope over load distortion?
5. What is granular noise effect?
6. What are the two limitations of delta modulation?
7. What is the function of integrator?

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8. What is comparator?
9. What is companding?
10. What is the advantage of delta modulation over pulse modulation?
11. Distinguish between DPCM and DM.
12. What are the different types of digital modulation?

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13. What is sampling rate?
14. Which kind of multiplexing used in digital communication?
15. Why is sample hold circuit used?
16. What are the advantages of digital transmission?
17. How is the performance corrupted in PCM?

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18. What are the different types of multiplexing?
19. What is aliasing effect?
20. How to avoid aliasing effect?

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Viva - voce
44 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 7 LINE CODING DECODING TECHNIQUES

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Aim:
To study different line coding techniques.
Apparatus required:
1. Line coding and decoding trainer kit ? 1 No.
2. Patch cords ? 6 No.

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3. CRO ? 1 No.

Theory:
Line coding refers to the process of representing the bit stream (1 ?s and 0 ?s) in the form of voltage or current
variations optimally tuned for the specific properties of the physical channel being used. The selection of a proper

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line code can help in many ways. One possibility is to aid in clock recovery at the receiver. A clock signal is
recovered by observing transitions in the received bit sequence, if enough transitions exist, a good recovery of
the clock is guaranteed, the signal is said to be self-clocking. Another advantage is to get rid of DC shifts. The
DC component in a line code is called the bias or the DC coefficient. Unfortunately, most long-distance
communication channels cannot transport a DC component. This is why most line codes try to eliminate the DC

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component before being transmitted on the channel. Such codes are called DC balanced, zero-DC, zero-bias, or
DC equalized. Some common types of line encoding in common-use nowadays are unipolar, polar, bipolar,
Manchester, MLT-3 Duo binary encoding.
Unipolar (Unipolar NRZ and Unipolar RZ):
Unipolar is the simplest line coding scheme. It has the advantage of being compatible with TTL logic. Unipolar

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coding uses a positive rectangular pulse p(t) to represent binary 1, the absence of a pulse (i.e., zero voltage) to
represent a binary 0. Two possibilities for the pulse p(t) exist3: Non-Return-to-Zero (NRZ) rectangular pulse
Return-to-Zero (RZ) rectangular pulse. The difference between Unipolar NRZ Unipolar RZ codes is that the
rectangular pulse in NRZ stays at a positive value (e.g., +5V) for the full duration of the logic 1 bit, while the pule
in RZ drops from +5V to 0V in the middle of the bit time.

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Procedure:
1. Connect the PRBS (test point P5) to various line coding formats. Obtain the coded output as per the
requirement.
2. Connect coded signal test point to corresponding decoding test point as inputs.
3. Set the SW1 as per the requirement.

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4. Set the potentiometer P1 in minimum position.
5. Switch ON the power supply. Press the switch SW2 once.
6. Display the encoded signal on one channel of CRO and decoded signal on second channel of CRO.

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FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

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V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________

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Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
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DHANALAKSHMI

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College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

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? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION

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ENGINEERING


To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges

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in deploying technology for the service of humanity


? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry

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? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION
VISION

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MISSION
MISSION
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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)

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1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence

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To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products

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4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics

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To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints

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such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks

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f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities

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j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM

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? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes

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LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator

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5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)

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10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

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COURSE OBJECTIVES
COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7

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2 Time division multiplexing
13
3 AM modulation demodulation
18
4 Frequency modulation demodulation

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26
5 PCM modulation demodulation
33
6 Delta modulation demodulation
38

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7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51

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9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB

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57
12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61

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14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION

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Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.

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3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are

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natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem

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If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.

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Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz

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and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of

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control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.

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4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

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Model Graph:

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Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal
Sampled output
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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.
Applications:

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1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

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1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate
4. Define ? Nyquist interval

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5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?

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10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.

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15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?

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20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling


Viva - voce

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Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit

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Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.

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Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.
Procedure:

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1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on

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channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)

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on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .

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Circuit Diagram
Time division multiplexing

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14 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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TDM Trainer Kit

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Model Graph:

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Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1
2. Message Signal 2
3. TDM signal

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Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the

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signals.


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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network

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transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system

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1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?

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4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.

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9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce
17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver
Apparatus required:

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.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.
3 Diode ? 2 No.
4

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AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.
6 Patch cards ? 6 No.

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Theory:

AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.

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The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

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The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal

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Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index
Vmax = Maximum peak amplitude

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Vmin = Minimum peak amplitude
if
M < 1 Under modulation
M = 1 Critical modulation
M > 1 over modulation

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Procedure:
1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.

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4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation


AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

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Carrier

Modulated

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Demodulated


Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.

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Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.
Applications:
1. Commercial broadcasting of both audio and video signals

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2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.

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6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?
9. What are the different types of AM generation?
10. Define ? Modulation Index

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11. What are different types of analog modulation techniques?
Viva - voce
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12. What are the other names of message signal? What are the other names of carrier signal?

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13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of

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demodulation of an AM wave?
18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation

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22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver

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Apparatus required:
.
1. Resistor ? 4 No.
2. Capacitor ? 1 No.
3. Diode ? 2 No.

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4.
AM transmitter Receiver
trainer kit ? 1 No.
5. CRO ? 1 No.
6. Patch cards ? 6 No.

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Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the
instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete

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values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used
in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into

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space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and

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retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of
noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

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Procedure:
FM Modulator:
1. Switch ON the Power supply.

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2. Connect the sine wave generator output to frequency modulator input.

3. Select the low frequency carrier (or) high frequency carrier.

4. Connect the CRO input to the frequency modulator output.

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5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

6. Observe the frequency modulator output .

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FM Demodulator:
A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

2. Now set the DPDT switch in low frequency mode.

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3. Connect CRO input to PLL detector output.

4. Observe the Demodulated O/P compare with the original input.

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B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

2. Now set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Quadrature detector output.

4. Observe the Demodulated O/P and compare with the original input.
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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

2. Set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Phase discriminator output.

4. Observe the Demodulated O/P and then compare with the original input.

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D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

2. Set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Ratio detector output.

4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram
FM Modulator

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FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:


Tabulation

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Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency
modulated and demodulated wave.
Applications:
1. Television sound transmission

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2. Two way mobile radio
3. Cellular Radio
4. Microwave
5. Satellite Communication System

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1. Define ? Frequency Modulation
2. How it is different from phase modulation?
3. Write equation of FM wave, explain each parameter in it.
4. Draw the amplitude spectrum of FM wave.

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5. Give the Carson?s rule in FM.
6. Define ? Modulation Index
7. Differentiate between Narrow band FM from Wide band FM.
8. Draw message, carrier FM waves .
9. Explain the methods for generation of FM its demodulation.

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10. How FM wave is different from PM wave?
11. Give the practical applications of FM.
12. State advantages and disadvantages of FM.
13. What is the range of speech signals?
14. What type of modulation is used in radios?

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15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation
17. Draw the phasor diagram of FM signal.
18. What are the different types of FM generation?

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Viva - voce
32 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 5 PCM MODULATION & DEMODULATION

Aim:
To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM

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demodulator
Apparatus Required:
1. PCM trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.

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Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is
first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of
converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization
can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in

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speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization
the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel
serially.
At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an

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equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword
is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to
Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks
for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be

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observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:
1. Power on the PCM kit.
2. Measure the frequency of sampling clock.
3. Apply the DC voltage as modulating signal.

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4. Connect the DC input to the ADC measure the voltage.
5. Connect the clock to the timing control circuit.
6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.

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7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.
9. Observe the waveform at the output of DAC.
10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the
codeword graphically for a DC input.

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Block diagram of PCM Transmission system

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PCM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation

Result:
Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.
Outcome:

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After the completion of this experiment the students will be able to design and construct the pulse code
modulated and demodulated wave.
Applications:
1. Military Applications.
2. The PCM is used in the satellite transmission system.

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SIGNALS AMPLITUDE (V) TIME PERIOD (s)
DC Input
Sampled Signal
Clock Pulse
PCM Output

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DC Output
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3. It is used in space communication.
4. It is used in telephony.

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5. The compact disc (CD) is a recent application of PCM.


1. Define ? Modulation
2. State sampling theorem

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3. Define ? Demodulation
4. Define ? Pulse Code Modulation
5. What is aliasing effect?
6. What is quantization?
7. Define ? Bit Rate

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8. Define ? Baud Rate
9. What are the advantages of PCM?
10. Define ? Signal to Noise Ratio
11. What are the limitations of PCM?
12. What are the applications of PCM?

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13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate
16. What is multiplexing?
17. What is de-multiplexing?

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18. What are the types of pulse modulation?
19. What should be the minimum bandwidth required to transmit a PCM channel?
20. What is the value of signal to noise ratio in PCM?

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Viva - voce
37 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 6 DELTA MODULATION & DEMODULATION
Aim:

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To transmit an analog message signal in its digital form and reconstruct back the original analog message
signal at receiver by using Delta modulator
Apparatus required:
1. DM and ADM Trainer kit ? 1 No.
2. CRO ? 1 No.

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3. Connecting probes ? 4 No.
Theory:
Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The
difference signal between two successive samples is encoded into a single bit code. A present sample of the
analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level

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(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.
The comparison of samples is accomplished by converting the digital to analog form then comparing with the
present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to
a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.
Procedure:

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1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.
2. Observe the modulated signal in the CRO.
3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.
4. Also observe the DAC output on the CRO.
5. Change the amplitude of the modulating signal.

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6. Observe the DAC output. Notice the slope overload distortion.
7. Keep the tuning knob to minimize distortion.
8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope
overload distortion.
9. Calculate the sampling frequency required for no slope overload distortion.

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10. Compare the calculated measured values of the sampling frequency.


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Block Diagram Delta modulator and demodulator

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Delta Modulator

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Delta Demodulator

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Block diagram of Adaptive delta modulator and demodulator

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Adaptive Delta Modulator

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Adaptive Delta Demodulator

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40 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Delta Modulation and Adaptive Delta Modulator Trainer kit

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41 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Model Graph:

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Tabulation 1
For Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal
2 Carrier Signal

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3 Modulated Signal
4 Demodulated Signal

Tabulation 2
For Adaptive Delta Modulation

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Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal
2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

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Result:
Thus the output waveforms of Delta modulation and adaptive delta modulation circuit were observed.
Outcome:
After the completion of this experiment the students will be able to design and construct the delta modulation

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adaptive delta modulation circuit.
Applications:
1. Digital voice storage
2. Voice transmission
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3. Radio communication devices such TV remotes.
4. Delta Modulation was used by Satellite Business Systems or SBS
5. DM used in high resolution A/D and D/A converters.

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1. What is delta modulation?
2. What is adaptive delta modulation?
3. What are the advantages of adaptive delta modulation over delta modulation?
4. What is slope over load distortion?

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5. What is granular noise effect?
6. What are the two limitations of delta modulation?
7. What is the function of integrator?
8. What is comparator?
9. What is companding?

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10. What is the advantage of delta modulation over pulse modulation?
11. Distinguish between DPCM and DM.
12. What are the different types of digital modulation?
13. What is sampling rate?
14. Which kind of multiplexing used in digital communication?

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15. Why is sample hold circuit used?
16. What are the advantages of digital transmission?
17. How is the performance corrupted in PCM?
18. What are the different types of multiplexing?
19. What is aliasing effect?

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20. How to avoid aliasing effect?

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Viva - voce
44 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 7 LINE CODING DECODING TECHNIQUES

Aim:
To study different line coding techniques.

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Apparatus required:
1. Line coding and decoding trainer kit ? 1 No.
2. Patch cords ? 6 No.
3. CRO ? 1 No.

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Theory:
Line coding refers to the process of representing the bit stream (1 ?s and 0 ?s) in the form of voltage or current
variations optimally tuned for the specific properties of the physical channel being used. The selection of a proper
line code can help in many ways. One possibility is to aid in clock recovery at the receiver. A clock signal is
recovered by observing transitions in the received bit sequence, if enough transitions exist, a good recovery of

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the clock is guaranteed, the signal is said to be self-clocking. Another advantage is to get rid of DC shifts. The
DC component in a line code is called the bias or the DC coefficient. Unfortunately, most long-distance
communication channels cannot transport a DC component. This is why most line codes try to eliminate the DC
component before being transmitted on the channel. Such codes are called DC balanced, zero-DC, zero-bias, or
DC equalized. Some common types of line encoding in common-use nowadays are unipolar, polar, bipolar,

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Manchester, MLT-3 Duo binary encoding.
Unipolar (Unipolar NRZ and Unipolar RZ):
Unipolar is the simplest line coding scheme. It has the advantage of being compatible with TTL logic. Unipolar
coding uses a positive rectangular pulse p(t) to represent binary 1, the absence of a pulse (i.e., zero voltage) to
represent a binary 0. Two possibilities for the pulse p(t) exist3: Non-Return-to-Zero (NRZ) rectangular pulse

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Return-to-Zero (RZ) rectangular pulse. The difference between Unipolar NRZ Unipolar RZ codes is that the
rectangular pulse in NRZ stays at a positive value (e.g., +5V) for the full duration of the logic 1 bit, while the pule
in RZ drops from +5V to 0V in the middle of the bit time.

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Procedure:
1. Connect the PRBS (test point P5) to various line coding formats. Obtain the coded output as per the

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requirement.
2. Connect coded signal test point to corresponding decoding test point as inputs.
3. Set the SW1 as per the requirement.
4. Set the potentiometer P1 in minimum position.
5. Switch ON the power supply. Press the switch SW2 once.

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6. Display the encoded signal on one channel of CRO and decoded signal on second channel of CRO.

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46 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Line coding decoding trainer kit

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FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

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V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL

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2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

DHANALAKSHMI

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College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry

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? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

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To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

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? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems

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? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION
VISION
MISSION
MISSION

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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,

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enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions

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3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students

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to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)

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a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics

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communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large

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h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM

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? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction

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2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation

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7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation

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12. Equalization ? Zero Forcing and LMS algorithms (simulation)


Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.

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Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

COURSE OBJECTIVES
COURSE OUTCOMES

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.

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CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7
2 Time division multiplexing
13

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3 AM modulation demodulation
18
4 Frequency modulation demodulation
26
5 PCM modulation demodulation

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33
6 Delta modulation demodulation
38
7 Line coding decoding techniques
45

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CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB
53

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10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB

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59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit

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Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.

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Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For

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reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known

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as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the

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sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:

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1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.

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6. Integrate the sampling inputs.

Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

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Analog signal sampling and reconstruction trainer kit


Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer

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kit.


Signal Amplitude (V) Time period (s)
Message signal

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Carrier signal
Sampled output
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Outcome:

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After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)

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3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem

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2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?

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7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?

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12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal

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17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
12 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.

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2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common

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signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.

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(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this

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sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of

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Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .


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Circuit Diagram
Time division multiplexing

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TDM Trainer Kit

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Model Graph:

Tabulation
Sl. No. Signal Amplitude (V) Time period (s)

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1. Message signal 1
2. Message Signal 2
3. TDM signal

Result:

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Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital

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transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital

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Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system

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1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?

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6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce
17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 3 AM MODULATION & DEMODULATION
Aim:

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To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver
Apparatus required:
.
1 Resistor ? 4 No.

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2 Capacitor ? 1 No.
3 Diode ? 2 No.
4
AM transmitter receiver
trainer kit ? 1 No.

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5 CRO ? 1 No.
6 Patch cards ? 6 No.

Theory:

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AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt

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VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,

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VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where

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Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:

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M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if

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M < 1 Under modulation
M = 1 Critical modulation
M > 1 over modulation

Procedure:

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1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:

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1. AM Waveform (Ring diode Transistor based AM Modulator)

AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated

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demodulated wave.
Applications:
1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.

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3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?

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8. What is depth of modulation?
9. What are the different types of AM generation?
10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce

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24 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation

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15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.

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19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION

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Aim:
To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver
Apparatus required:
.

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1. Resistor ? 4 No.
2. Capacitor ? 1 No.
3. Diode ? 2 No.
4.
AM transmitter Receiver

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trainer kit ? 1 No.
5. CRO ? 1 No.
6. Patch cards ? 6 No.

Theory:

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Frequency modulation (FM) is a form of modulation that represents information as variations in the
instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A

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narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used
in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to

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present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of
noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

Procedure:

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FM Modulator:
1. Switch ON the Power supply.

2. Connect the sine wave generator output to frequency modulator input.

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3. Select the low frequency carrier (or) high frequency carrier.

4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

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6. Observe the frequency modulator output .

FM Demodulator:
A) PLL Detector

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1. Connect frequency modulated output to the PLL detector input.

2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

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4. Observe the Demodulated O/P compare with the original input.

B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

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2. Now set the DPDT switch in high frequency mode.

3. Connect the CRO input to Quadrature detector output.

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4. Observe the Demodulated O/P and compare with the original input.
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C) Phase Discriminator (Foster-Seeley detector)

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1. Connect the frequency modulated output to Phase discriminator input.

2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

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4. Observe the Demodulated O/P and then compare with the original input.

D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Ratio detector output.

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4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram
FM Modulator

FM Demodulator

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FM Modulation and Demodulation Trainer kit

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30 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00



Model Graph:

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

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Carrier

Modulated

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Demodulated


Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency

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modulated and demodulated wave.
Applications:
1. Television sound transmission
2. Two way mobile radio
3. Cellular Radio

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4. Microwave
5. Satellite Communication System


1. Define ? Frequency Modulation

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2. How it is different from phase modulation?
3. Write equation of FM wave, explain each parameter in it.
4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.
6. Define ? Modulation Index

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7. Differentiate between Narrow band FM from Wide band FM.
8. Draw message, carrier FM waves .
9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?
11. Give the practical applications of FM.

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12. State advantages and disadvantages of FM.
13. What is the range of speech signals?
14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation

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17. Draw the phasor diagram of FM signal.
18. What are the different types of FM generation?

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Viva - voce
32 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 5 PCM MODULATION & DEMODULATION

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Aim:
To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator
Apparatus Required:

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1. PCM trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is

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first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of
converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization
can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization

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the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel
serially.
At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword

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is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to
Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks
for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:

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1. Power on the PCM kit.
2. Measure the frequency of sampling clock.
3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.
5. Connect the clock to the timing control circuit.
6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.

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9. Observe the waveform at the output of DAC.
10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the
codeword graphically for a DC input.
Block diagram of PCM Transmission system

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34 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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PCM Modulation and Demodulation Trainer kit

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35 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Model Graph:

Tabulation

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Result:
Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.
Outcome:
After the completion of this experiment the students will be able to design and construct the pulse code
modulated and demodulated wave.

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Applications:
1. Military Applications.
2. The PCM is used in the satellite transmission system.
SIGNALS AMPLITUDE (V) TIME PERIOD (s)
DC Input

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Sampled Signal
Clock Pulse
PCM Output
DC Output
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3. It is used in space communication.
4. It is used in telephony.
5. The compact disc (CD) is a recent application of PCM.

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1. Define ? Modulation
2. State sampling theorem
3. Define ? Demodulation
4. Define ? Pulse Code Modulation

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5. What is aliasing effect?
6. What is quantization?
7. Define ? Bit Rate
8. Define ? Baud Rate
9. What are the advantages of PCM?

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10. Define ? Signal to Noise Ratio
11. What are the limitations of PCM?
12. What are the applications of PCM?
13. Define ? Encoding
14. Define ? Decoding

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15. Define ? Nyquist Rate
16. What is multiplexing?
17. What is de-multiplexing?
18. What are the types of pulse modulation?
19. What should be the minimum bandwidth required to transmit a PCM channel?

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20. What is the value of signal to noise ratio in PCM?

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Viva - voce
37 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 6 DELTA MODULATION & DEMODULATION
Aim:
To transmit an analog message signal in its digital form and reconstruct back the original analog message
signal at receiver by using Delta modulator

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Apparatus required:
1. DM and ADM Trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:

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Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The
difference signal between two successive samples is encoded into a single bit code. A present sample of the
analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level
(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.
The comparison of samples is accomplished by converting the digital to analog form then comparing with the

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present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to
a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.
Procedure:
1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.
2. Observe the modulated signal in the CRO.

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3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.
4. Also observe the DAC output on the CRO.
5. Change the amplitude of the modulating signal.
6. Observe the DAC output. Notice the slope overload distortion.
7. Keep the tuning knob to minimize distortion.

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8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope
overload distortion.
9. Calculate the sampling frequency required for no slope overload distortion.
10. Compare the calculated measured values of the sampling frequency.

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38 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Block Diagram Delta modulator and demodulator

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Delta Modulator

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Delta Demodulator



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Block diagram of Adaptive delta modulator and demodulator

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Adaptive Delta Modulator

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Adaptive Delta Demodulator

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40 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Delta Modulation and Adaptive Delta Modulator Trainer kit

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41 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Model Graph:

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42 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Tabulation 1
For Delta Modulation

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Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal
2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

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Tabulation 2
For Adaptive Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal

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2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

Result:

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Thus the output waveforms of Delta modulation and adaptive delta modulation circuit were observed.
Outcome:
After the completion of this experiment the students will be able to design and construct the delta modulation
adaptive delta modulation circuit.
Applications:

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1. Digital voice storage
2. Voice transmission
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3. Radio communication devices such TV remotes.

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4. Delta Modulation was used by Satellite Business Systems or SBS
5. DM used in high resolution A/D and D/A converters.


1. What is delta modulation?

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2. What is adaptive delta modulation?
3. What are the advantages of adaptive delta modulation over delta modulation?
4. What is slope over load distortion?
5. What is granular noise effect?
6. What are the two limitations of delta modulation?

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7. What is the function of integrator?
8. What is comparator?
9. What is companding?
10. What is the advantage of delta modulation over pulse modulation?
11. Distinguish between DPCM and DM.

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12. What are the different types of digital modulation?
13. What is sampling rate?
14. Which kind of multiplexing used in digital communication?
15. Why is sample hold circuit used?
16. What are the advantages of digital transmission?

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17. How is the performance corrupted in PCM?
18. What are the different types of multiplexing?
19. What is aliasing effect?
20. How to avoid aliasing effect?

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Viva - voce
44 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 7 LINE CODING DECODING TECHNIQUES

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Aim:
To study different line coding techniques.
Apparatus required:
1. Line coding and decoding trainer kit ? 1 No.

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2. Patch cords ? 6 No.
3. CRO ? 1 No.

Theory:
Line coding refers to the process of representing the bit stream (1 ?s and 0 ?s) in the form of voltage or current

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variations optimally tuned for the specific properties of the physical channel being used. The selection of a proper
line code can help in many ways. One possibility is to aid in clock recovery at the receiver. A clock signal is
recovered by observing transitions in the received bit sequence, if enough transitions exist, a good recovery of
the clock is guaranteed, the signal is said to be self-clocking. Another advantage is to get rid of DC shifts. The
DC component in a line code is called the bias or the DC coefficient. Unfortunately, most long-distance

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communication channels cannot transport a DC component. This is why most line codes try to eliminate the DC
component before being transmitted on the channel. Such codes are called DC balanced, zero-DC, zero-bias, or
DC equalized. Some common types of line encoding in common-use nowadays are unipolar, polar, bipolar,
Manchester, MLT-3 Duo binary encoding.
Unipolar (Unipolar NRZ and Unipolar RZ):

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Unipolar is the simplest line coding scheme. It has the advantage of being compatible with TTL logic. Unipolar
coding uses a positive rectangular pulse p(t) to represent binary 1, the absence of a pulse (i.e., zero voltage) to
represent a binary 0. Two possibilities for the pulse p(t) exist3: Non-Return-to-Zero (NRZ) rectangular pulse
Return-to-Zero (RZ) rectangular pulse. The difference between Unipolar NRZ Unipolar RZ codes is that the
rectangular pulse in NRZ stays at a positive value (e.g., +5V) for the full duration of the logic 1 bit, while the pule

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in RZ drops from +5V to 0V in the middle of the bit time.



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Procedure:
1. Connect the PRBS (test point P5) to various line coding formats. Obtain the coded output as per the
requirement.
2. Connect coded signal test point to corresponding decoding test point as inputs.

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3. Set the SW1 as per the requirement.
4. Set the potentiometer P1 in minimum position.
5. Switch ON the power supply. Press the switch SW2 once.
6. Display the encoded signal on one channel of CRO and decoded signal on second channel of CRO.

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Line coding decoding trainer kit

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Model Graph:

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FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
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DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious

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enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels

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? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

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To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

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? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical

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practices

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VISION
VISION
MISSION
MISSION
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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher

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education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth

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To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social

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context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics

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Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits

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d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness

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of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

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To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes

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? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing

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3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM

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8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise

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performance of communication system.

COURSE OBJECTIVES
COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS

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1 Signal sampling reconstruction
7
2 Time division multiplexing
13
3 AM modulation demodulation

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18
4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33

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6 Delta modulation demodulation
38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS

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8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB

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55
11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59

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ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:

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1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:

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Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be

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sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.

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A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is

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accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.

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2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

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Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal

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Sampled output
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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of

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continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission

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4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?

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3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.

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8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits

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13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?

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18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
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Expt. No. 2 TIME DIVISION MULTIPLEXING

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Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.

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3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears

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on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,

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(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.

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5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.

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8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .


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Circuit Diagram
Time division multiplexing

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TDM Trainer Kit

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Model Graph:

Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1

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2. Message Signal 2
3. TDM signal

Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.

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Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)

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or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).

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4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system


1. What is meant by multiplexing technique ?

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2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.

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7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce

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17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after

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demodulating using AM receiver
Apparatus required:
.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.

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3 Diode ? 2 No.
4
AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.

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6 Patch cards ? 6 No.

Theory:

AMPLITUDE MODULATION

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Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct

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The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal

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VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100

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Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if
M < 1 Under modulation

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M = 1 Critical modulation
M > 1 over modulation

Procedure:
1. Give the modulating signal input to the Amplitude modulator.

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2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

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AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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22 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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AM Modulation and Demodulation trainer kit

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Tabulation

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Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.

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Applications:
1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?

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4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?

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9. What are the different types of AM generation?
10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce
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12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?

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16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.

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20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:

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To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver
Apparatus required:
.
1. Resistor ? 4 No.

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2. Capacitor ? 1 No.
3. Diode ? 2 No.
4.
AM transmitter Receiver
trainer kit ? 1 No.

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5. CRO ? 1 No.
6. Patch cards ? 6 No.

Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the

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instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used

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in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of

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noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

Procedure:
FM Modulator:

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1. Switch ON the Power supply.

2. Connect the sine wave generator output to frequency modulator input.

3. Select the low frequency carrier (or) high frequency carrier.

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4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

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6. Observe the frequency modulator output .

FM Demodulator:
A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

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2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

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4. Observe the Demodulated O/P compare with the original input.

B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

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2. Now set the DPDT switch in high frequency mode.

3. Connect the CRO input to Quadrature detector output.

4. Observe the Demodulated O/P and compare with the original input.

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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

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4. Observe the Demodulated O/P and then compare with the original input.

D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Ratio detector output.

4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram

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FM Modulator

FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

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Carrier

Modulated

Demodulated

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Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency
modulated and demodulated wave.

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Applications:
1. Television sound transmission
2. Two way mobile radio
3. Cellular Radio
4. Microwave

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5. Satellite Communication System


1. Define ? Frequency Modulation
2. How it is different from phase modulation?

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3. Write equation of FM wave, explain each parameter in it.
4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.
6. Define ? Modulation Index
7. Differentiate between Narrow band FM from Wide band FM.

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8. Draw message, carrier FM waves .
9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?
11. Give the practical applications of FM.
12. State advantages and disadvantages of FM.

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13. What is the range of speech signals?
14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation
17. Draw the phasor diagram of FM signal.

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18. What are the different types of FM generation?

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Viva - voce
32 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 5 PCM MODULATION & DEMODULATION

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Aim:
To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator
Apparatus Required:
1. PCM trainer kit ? 1 No.

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2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is
first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of

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converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization
can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization
the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel

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serially.
At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword
is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to

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Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks
for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:
1. Power on the PCM kit.

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2. Measure the frequency of sampling clock.
3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.

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5. Connect the clock to the timing control circuit.
6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.
9. Observe the waveform at the output of DAC.

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10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the
codeword graphically for a DC input.
Block diagram of PCM Transmission system

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PCM Modulation and Demodulation Trainer kit

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Model Graph:

Tabulation

Result:

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Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.
Outcome:
After the completion of this experiment the students will be able to design and construct the pulse code
modulated and demodulated wave.
Applications:

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1. Military Applications.
2. The PCM is used in the satellite transmission system.
SIGNALS AMPLITUDE (V) TIME PERIOD (s)
DC Input
Sampled Signal

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Clock Pulse
PCM Output
DC Output
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3. It is used in space communication.
4. It is used in telephony.
5. The compact disc (CD) is a recent application of PCM.

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1. Define ? Modulation
2. State sampling theorem
3. Define ? Demodulation
4. Define ? Pulse Code Modulation
5. What is aliasing effect?

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6. What is quantization?
7. Define ? Bit Rate
8. Define ? Baud Rate
9. What are the advantages of PCM?
10. Define ? Signal to Noise Ratio

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11. What are the limitations of PCM?
12. What are the applications of PCM?
13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate

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16. What is multiplexing?
17. What is de-multiplexing?
18. What are the types of pulse modulation?
19. What should be the minimum bandwidth required to transmit a PCM channel?
20. What is the value of signal to noise ratio in PCM?

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Viva - voce
37 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 6 DELTA MODULATION & DEMODULATION
Aim:
To transmit an analog message signal in its digital form and reconstruct back the original analog message
signal at receiver by using Delta modulator
Apparatus required:

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1. DM and ADM Trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The

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difference signal between two successive samples is encoded into a single bit code. A present sample of the
analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level
(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.
The comparison of samples is accomplished by converting the digital to analog form then comparing with the
present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to

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a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.
Procedure:
1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.
2. Observe the modulated signal in the CRO.
3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.

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4. Also observe the DAC output on the CRO.
5. Change the amplitude of the modulating signal.
6. Observe the DAC output. Notice the slope overload distortion.
7. Keep the tuning knob to minimize distortion.
8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope

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overload distortion.
9. Calculate the sampling frequency required for no slope overload distortion.
10. Compare the calculated measured values of the sampling frequency.

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Block Diagram Delta modulator and demodulator

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Delta Modulator

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Delta Demodulator

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Block diagram of Adaptive delta modulator and demodulator

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Adaptive Delta Modulator

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Adaptive Delta Demodulator

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Delta Modulation and Adaptive Delta Modulator Trainer kit

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Model Graph:

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Tabulation 1
For Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)

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1 Modulating Signal
2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

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Tabulation 2
For Adaptive Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal
2 Carrier Signal

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3 Modulated Signal
4 Demodulated Signal

Result:
Thus the output waveforms of Delta modulation and adaptive delta modulation circuit were observed.

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Outcome:
After the completion of this experiment the students will be able to design and construct the delta modulation
adaptive delta modulation circuit.
Applications:
1. Digital voice storage

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2. Voice transmission
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3. Radio communication devices such TV remotes.
4. Delta Modulation was used by Satellite Business Systems or SBS

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5. DM used in high resolution A/D and D/A converters.


1. What is delta modulation?
2. What is adaptive delta modulation?

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3. What are the advantages of adaptive delta modulation over delta modulation?
4. What is slope over load distortion?
5. What is granular noise effect?
6. What are the two limitations of delta modulation?
7. What is the function of integrator?

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8. What is comparator?
9. What is companding?
10. What is the advantage of delta modulation over pulse modulation?
11. Distinguish between DPCM and DM.
12. What are the different types of digital modulation?

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13. What is sampling rate?
14. Which kind of multiplexing used in digital communication?
15. Why is sample hold circuit used?
16. What are the advantages of digital transmission?
17. How is the performance corrupted in PCM?

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18. What are the different types of multiplexing?
19. What is aliasing effect?
20. How to avoid aliasing effect?

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Viva - voce
44 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 7 LINE CODING DECODING TECHNIQUES

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Aim:
To study different line coding techniques.
Apparatus required:
1. Line coding and decoding trainer kit ? 1 No.
2. Patch cords ? 6 No.

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3. CRO ? 1 No.

Theory:
Line coding refers to the process of representing the bit stream (1 ?s and 0 ?s) in the form of voltage or current
variations optimally tuned for the specific properties of the physical channel being used. The selection of a proper

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line code can help in many ways. One possibility is to aid in clock recovery at the receiver. A clock signal is
recovered by observing transitions in the received bit sequence, if enough transitions exist, a good recovery of
the clock is guaranteed, the signal is said to be self-clocking. Another advantage is to get rid of DC shifts. The
DC component in a line code is called the bias or the DC coefficient. Unfortunately, most long-distance
communication channels cannot transport a DC component. This is why most line codes try to eliminate the DC

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component before being transmitted on the channel. Such codes are called DC balanced, zero-DC, zero-bias, or
DC equalized. Some common types of line encoding in common-use nowadays are unipolar, polar, bipolar,
Manchester, MLT-3 Duo binary encoding.
Unipolar (Unipolar NRZ and Unipolar RZ):
Unipolar is the simplest line coding scheme. It has the advantage of being compatible with TTL logic. Unipolar

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coding uses a positive rectangular pulse p(t) to represent binary 1, the absence of a pulse (i.e., zero voltage) to
represent a binary 0. Two possibilities for the pulse p(t) exist3: Non-Return-to-Zero (NRZ) rectangular pulse
Return-to-Zero (RZ) rectangular pulse. The difference between Unipolar NRZ Unipolar RZ codes is that the
rectangular pulse in NRZ stays at a positive value (e.g., +5V) for the full duration of the logic 1 bit, while the pule
in RZ drops from +5V to 0V in the middle of the bit time.

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Procedure:
1. Connect the PRBS (test point P5) to various line coding formats. Obtain the coded output as per the
requirement.
2. Connect coded signal test point to corresponding decoding test point as inputs.
3. Set the SW1 as per the requirement.

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4. Set the potentiometer P1 in minimum position.
5. Switch ON the power supply. Press the switch SW2 once.
6. Display the encoded signal on one channel of CRO and decoded signal on second channel of CRO.

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46 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


Line coding decoding trainer kit

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Model Graph:

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48 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Tabulation
Sl. No. Type of Coding AMPLITUDE (V) Time period (s)
1. Unipolar data(NZ NRZ )

2. Unipolar data (NRZ RZ)

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3. Bipolar Data(NRZ AMI)
4. Manchester


Result:

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Thus the different line coding techniques was studied and verified.
Outcome:
After the completion of this experiment the students will be able to understand implement the different line
coding schemes.
Applications:

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1. DC balance
2. embedded clock applications
3. computing applications
4. Manchester codes are commonly used for local area networks
5. Bipolar codes are commonly used for local area networks

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FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?



DEPARTMENT OF

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ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
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DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

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? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul

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DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING


To impart professional education integrated with human values to the younger generation, so as to

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shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity


? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics

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industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION

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VISION
MISSION
MISSION
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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education

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2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to

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find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context

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5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field

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b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems

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e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility

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i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

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To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms

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? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator

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4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes

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9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

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COURSE OBJECTIVES
COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction

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7
2 Time division multiplexing
13
3 AM modulation demodulation
18

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4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33
6 Delta modulation demodulation

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38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB

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51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB
55

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11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS

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13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS

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Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.

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2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at

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which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.

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Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples

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taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To

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recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit

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works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.

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3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

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Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal
Sampled output

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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.

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Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)

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5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate

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4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?

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9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.

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14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.

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19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
12 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:

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To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.

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4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.

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Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .

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3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .

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6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .

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Circuit Diagram

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Time division multiplexing

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TDM Trainer Kit

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Model Graph:

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Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1
2. Message Signal 2

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3. TDM signal

Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:

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After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.


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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network

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2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis

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5. The GSM telephone system


1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?

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3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?

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8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce
17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver

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Apparatus required:
.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.
3 Diode ? 2 No.

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4
AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.
6 Patch cards ? 6 No.

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Theory:

AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the

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instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.

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Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal

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Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index

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Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if
M < 1 Under modulation
M = 1 Critical modulation

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M > 1 over modulation

Procedure:
1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.

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3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

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AM Modulated wave



2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)

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Message

Carrier

Modulated

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Demodulated


Result:

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Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.
Applications:

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1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?

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5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?
9. What are the different types of AM generation?

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10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce
24 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?

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17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?

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21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after

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demodulating using FM receiver
Apparatus required:
.
1. Resistor ? 4 No.
2. Capacitor ? 1 No.

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3. Diode ? 2 No.
4.
AM transmitter Receiver
trainer kit ? 1 No.
5. CRO ? 1 No.

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6. Patch cards ? 6 No.

Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the
instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct

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proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used
in broadcast is generally called wide-FM, or W-FM.

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In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the

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luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of
noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes

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print-through pre-echo.

Procedure:
FM Modulator:
1. Switch ON the Power supply.

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2. Connect the sine wave generator output to frequency modulator input.

3. Select the low frequency carrier (or) high frequency carrier.

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4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

6. Observe the frequency modulator output .

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FM Demodulator:
A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

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2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

4. Observe the Demodulated O/P compare with the original input.

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B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

2. Now set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Quadrature detector output.

4. Observe the Demodulated O/P and compare with the original input.
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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

4. Observe the Demodulated O/P and then compare with the original input.

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D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

2. Set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Ratio detector output.

4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram
FM Modulator

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FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency
modulated and demodulated wave.
Applications:

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1. Television sound transmission
2. Two way mobile radio
3. Cellular Radio
4. Microwave
5. Satellite Communication System

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1. Define ? Frequency Modulation
2. How it is different from phase modulation?
3. Write equation of FM wave, explain each parameter in it.

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4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.
6. Define ? Modulation Index
7. Differentiate between Narrow band FM from Wide band FM.
8. Draw message, carrier FM waves .

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9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?
11. Give the practical applications of FM.
12. State advantages and disadvantages of FM.
13. What is the range of speech signals?

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14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation
17. Draw the phasor diagram of FM signal.
18. What are the different types of FM generation?

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Viva - voce

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32 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 5 PCM MODULATION & DEMODULATION

Aim:

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To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator
Apparatus Required:
1. PCM trainer kit ? 1 No.
2. CRO ? 1 No.

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3. Connecting probes ? 4 No.
Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is
first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of
converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization

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can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization
the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel
serially.

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At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword
is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to
Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks

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for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:
1. Power on the PCM kit.
2. Measure the frequency of sampling clock.

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3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.
5. Connect the clock to the timing control circuit.

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6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.
9. Observe the waveform at the output of DAC.
10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the

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codeword graphically for a DC input.
Block diagram of PCM Transmission system

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PCM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation

Result:
Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.

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Outcome:
After the completion of this experiment the students will be able to design and construct the pulse code
modulated and demodulated wave.
Applications:
1. Military Applications.

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2. The PCM is used in the satellite transmission system.
SIGNALS AMPLITUDE (V) TIME PERIOD (s)
DC Input
Sampled Signal
Clock Pulse

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PCM Output
DC Output
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3. It is used in space communication.

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4. It is used in telephony.
5. The compact disc (CD) is a recent application of PCM.


1. Define ? Modulation

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2. State sampling theorem
3. Define ? Demodulation
4. Define ? Pulse Code Modulation
5. What is aliasing effect?
6. What is quantization?

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7. Define ? Bit Rate
8. Define ? Baud Rate
9. What are the advantages of PCM?
10. Define ? Signal to Noise Ratio
11. What are the limitations of PCM?

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12. What are the applications of PCM?
13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate
16. What is multiplexing?

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17. What is de-multiplexing?
18. What are the types of pulse modulation?
19. What should be the minimum bandwidth required to transmit a PCM channel?
20. What is the value of signal to noise ratio in PCM?

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Viva - voce
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Expt. No. 6 DELTA MODULATION & DEMODULATION

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Aim:
To transmit an analog message signal in its digital form and reconstruct back the original analog message
signal at receiver by using Delta modulator
Apparatus required:
1. DM and ADM Trainer kit ? 1 No.

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2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The
difference signal between two successive samples is encoded into a single bit code. A present sample of the

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analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level
(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.
The comparison of samples is accomplished by converting the digital to analog form then comparing with the
present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to
a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.

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Procedure:
1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.
2. Observe the modulated signal in the CRO.
3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.
4. Also observe the DAC output on the CRO.

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5. Change the amplitude of the modulating signal.
6. Observe the DAC output. Notice the slope overload distortion.
7. Keep the tuning knob to minimize distortion.
8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope
overload distortion.

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9. Calculate the sampling frequency required for no slope overload distortion.
10. Compare the calculated measured values of the sampling frequency.


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Block Diagram Delta modulator and demodulator

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Delta Modulator

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Delta Demodulator

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39 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Block diagram of Adaptive delta modulator and demodulator

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Adaptive Delta Modulator

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Adaptive Delta Demodulator

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40 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Delta Modulation and Adaptive Delta Modulator Trainer kit

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41 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Model Graph:

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Tabulation 1
For Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal

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2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

Tabulation 2

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For Adaptive Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal
2 Carrier Signal
3 Modulated Signal

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4 Demodulated Signal

Result:
Thus the output waveforms of Delta modulation and adaptive delta modulation circuit were observed.
Outcome:

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After the completion of this experiment the students will be able to design and construct the delta modulation
adaptive delta modulation circuit.
Applications:
1. Digital voice storage
2. Voice transmission

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43 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

3. Radio communication devices such TV remotes.
4. Delta Modulation was used by Satellite Business Systems or SBS
5. DM used in high resolution A/D and D/A converters.

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1. What is delta modulation?
2. What is adaptive delta modulation?
3. What are the advantages of adaptive delta modulation over delta modulation?

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4. What is slope over load distortion?
5. What is granular noise effect?
6. What are the two limitations of delta modulation?
7. What is the function of integrator?
8. What is comparator?

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9. What is companding?
10. What is the advantage of delta modulation over pulse modulation?
11. Distinguish between DPCM and DM.
12. What are the different types of digital modulation?
13. What is sampling rate?

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14. Which kind of multiplexing used in digital communication?
15. Why is sample hold circuit used?
16. What are the advantages of digital transmission?
17. How is the performance corrupted in PCM?
18. What are the different types of multiplexing?

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19. What is aliasing effect?
20. How to avoid aliasing effect?

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Viva - voce

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44 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 7 LINE CODING DECODING TECHNIQUES

Aim:

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To study different line coding techniques.
Apparatus required:
1. Line coding and decoding trainer kit ? 1 No.
2. Patch cords ? 6 No.
3. CRO ? 1 No.

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Theory:
Line coding refers to the process of representing the bit stream (1 ?s and 0 ?s) in the form of voltage or current
variations optimally tuned for the specific properties of the physical channel being used. The selection of a proper
line code can help in many ways. One possibility is to aid in clock recovery at the receiver. A clock signal is

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recovered by observing transitions in the received bit sequence, if enough transitions exist, a good recovery of
the clock is guaranteed, the signal is said to be self-clocking. Another advantage is to get rid of DC shifts. The
DC component in a line code is called the bias or the DC coefficient. Unfortunately, most long-distance
communication channels cannot transport a DC component. This is why most line codes try to eliminate the DC
component before being transmitted on the channel. Such codes are called DC balanced, zero-DC, zero-bias, or

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DC equalized. Some common types of line encoding in common-use nowadays are unipolar, polar, bipolar,
Manchester, MLT-3 Duo binary encoding.
Unipolar (Unipolar NRZ and Unipolar RZ):
Unipolar is the simplest line coding scheme. It has the advantage of being compatible with TTL logic. Unipolar
coding uses a positive rectangular pulse p(t) to represent binary 1, the absence of a pulse (i.e., zero voltage) to

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represent a binary 0. Two possibilities for the pulse p(t) exist3: Non-Return-to-Zero (NRZ) rectangular pulse
Return-to-Zero (RZ) rectangular pulse. The difference between Unipolar NRZ Unipolar RZ codes is that the
rectangular pulse in NRZ stays at a positive value (e.g., +5V) for the full duration of the logic 1 bit, while the pule
in RZ drops from +5V to 0V in the middle of the bit time.

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45 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Procedure:

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1. Connect the PRBS (test point P5) to various line coding formats. Obtain the coded output as per the
requirement.
2. Connect coded signal test point to corresponding decoding test point as inputs.
3. Set the SW1 as per the requirement.
4. Set the potentiometer P1 in minimum position.

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5. Switch ON the power supply. Press the switch SW2 once.
6. Display the encoded signal on one channel of CRO and decoded signal on second channel of CRO.

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46 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Line coding decoding trainer kit

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47 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Model Graph:

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48 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00



Tabulation

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Sl. No. Type of Coding AMPLITUDE (V) Time period (s)
1. Unipolar data(NZ NRZ )

2. Unipolar data (NRZ RZ)
3. Bipolar Data(NRZ AMI)

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4. Manchester


Result:
Thus the different line coding techniques was studied and verified.

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Outcome:
After the completion of this experiment the students will be able to understand implement the different line
coding schemes.
Applications:
1. DC balance

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2. embedded clock applications
3. computing applications
4. Manchester codes are commonly used for local area networks
5. Bipolar codes are commonly used for local area networks

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49 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


1. What is line coding?
2. Define ? Polar Encoding

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3. Define ? Unipolar Encoding
4. Define ? Bipolar Encoding
5. Define ? Manchester Encoding
6. What are the two function of fast frequency hopping?
7. What is return to zero?

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8. What is Non-return to zero?
9. What is the difference between source coding and line coding?
10. What are the properties of line coding?
11. What is the effect of inter symbol interference?
12. How ISI can be reduced?

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13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate
16. Draw the NRZ and RZ code for the digital data 10110001.
17. Define ? Equalization

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18. What is PRBS?
19. Write the Boolean expression for X-NOR gate.
20. Define ? Digital demodulation

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Viva - voce

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FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

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V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________

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Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
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DHANALAKSHMI

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College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

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? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION

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ENGINEERING


To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges

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in deploying technology for the service of humanity


? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry

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? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION
VISION

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MISSION
MISSION
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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)

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1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence

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To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products

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4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics

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To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints

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such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks

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f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities

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j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM

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? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes

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LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator

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5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)

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10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

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COURSE OBJECTIVES
COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7

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2 Time division multiplexing
13
3 AM modulation demodulation
18
4 Frequency modulation demodulation

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26
5 PCM modulation demodulation
33
6 Delta modulation demodulation
38

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7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51

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9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB

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57
12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61

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14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION

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Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.

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3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are

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natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem

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If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.

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Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz

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and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of

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control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.

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4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

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Model Graph:

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Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal
Sampled output
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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.
Applications:

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1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

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1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate
4. Define ? Nyquist interval

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5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?

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10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.

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15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?

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20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling


Viva - voce

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Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit

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Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.

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Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.
Procedure:

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1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on

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channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)

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on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .

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Circuit Diagram
Time division multiplexing

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14 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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TDM Trainer Kit

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Model Graph:

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Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1
2. Message Signal 2
3. TDM signal

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Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the

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signals.


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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network

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transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system

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1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?

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4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.

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9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce
17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver
Apparatus required:

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.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.
3 Diode ? 2 No.
4

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AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.
6 Patch cards ? 6 No.

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Theory:

AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.

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The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

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The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal

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Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index
Vmax = Maximum peak amplitude

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Vmin = Minimum peak amplitude
if
M < 1 Under modulation
M = 1 Critical modulation
M > 1 over modulation

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Procedure:
1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.

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4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation


AM Demodulation

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20 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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21 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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AM Modulation demodulation trainer kit

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22 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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AM Modulation and Demodulation trainer kit

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23 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

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Carrier

Modulated

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Demodulated


Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.

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Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.
Applications:
1. Commercial broadcasting of both audio and video signals

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2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.

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6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?
9. What are the different types of AM generation?
10. Define ? Modulation Index

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11. What are different types of analog modulation techniques?
Viva - voce
24 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

12. What are the other names of message signal? What are the other names of carrier signal?

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13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of

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demodulation of an AM wave?
18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation

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22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver

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Apparatus required:
.
1. Resistor ? 4 No.
2. Capacitor ? 1 No.
3. Diode ? 2 No.

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4.
AM transmitter Receiver
trainer kit ? 1 No.
5. CRO ? 1 No.
6. Patch cards ? 6 No.

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Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the
instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete

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values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used
in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into

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space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and

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retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of
noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

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Procedure:
FM Modulator:
1. Switch ON the Power supply.

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2. Connect the sine wave generator output to frequency modulator input.

3. Select the low frequency carrier (or) high frequency carrier.

4. Connect the CRO input to the frequency modulator output.

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5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

6. Observe the frequency modulator output .

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FM Demodulator:
A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

2. Now set the DPDT switch in low frequency mode.

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3. Connect CRO input to PLL detector output.

4. Observe the Demodulated O/P compare with the original input.

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B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

2. Now set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Quadrature detector output.

4. Observe the Demodulated O/P and compare with the original input.
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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

2. Set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Phase discriminator output.

4. Observe the Demodulated O/P and then compare with the original input.

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D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

2. Set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Ratio detector output.

4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram
FM Modulator

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FM Demodulator

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29 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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FM Modulation and Demodulation Trainer kit

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Model Graph:


Tabulation

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Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency
modulated and demodulated wave.
Applications:
1. Television sound transmission

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2. Two way mobile radio
3. Cellular Radio
4. Microwave
5. Satellite Communication System

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1. Define ? Frequency Modulation
2. How it is different from phase modulation?
3. Write equation of FM wave, explain each parameter in it.
4. Draw the amplitude spectrum of FM wave.

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5. Give the Carson?s rule in FM.
6. Define ? Modulation Index
7. Differentiate between Narrow band FM from Wide band FM.
8. Draw message, carrier FM waves .
9. Explain the methods for generation of FM its demodulation.

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10. How FM wave is different from PM wave?
11. Give the practical applications of FM.
12. State advantages and disadvantages of FM.
13. What is the range of speech signals?
14. What type of modulation is used in radios?

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15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation
17. Draw the phasor diagram of FM signal.
18. What are the different types of FM generation?

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Viva - voce
32 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 5 PCM MODULATION & DEMODULATION

Aim:
To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM

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demodulator
Apparatus Required:
1. PCM trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.

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Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is
first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of
converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization
can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in

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speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization
the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel
serially.
At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an

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equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword
is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to
Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks
for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be

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observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:
1. Power on the PCM kit.
2. Measure the frequency of sampling clock.
3. Apply the DC voltage as modulating signal.

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4. Connect the DC input to the ADC measure the voltage.
5. Connect the clock to the timing control circuit.
6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.

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7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.
9. Observe the waveform at the output of DAC.
10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the
codeword graphically for a DC input.

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Block diagram of PCM Transmission system

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34 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PCM Modulation and Demodulation Trainer kit

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35 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Model Graph:

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Tabulation

Result:
Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.
Outcome:

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After the completion of this experiment the students will be able to design and construct the pulse code
modulated and demodulated wave.
Applications:
1. Military Applications.
2. The PCM is used in the satellite transmission system.

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SIGNALS AMPLITUDE (V) TIME PERIOD (s)
DC Input
Sampled Signal
Clock Pulse
PCM Output

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DC Output
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3. It is used in space communication.
4. It is used in telephony.

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5. The compact disc (CD) is a recent application of PCM.


1. Define ? Modulation
2. State sampling theorem

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3. Define ? Demodulation
4. Define ? Pulse Code Modulation
5. What is aliasing effect?
6. What is quantization?
7. Define ? Bit Rate

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8. Define ? Baud Rate
9. What are the advantages of PCM?
10. Define ? Signal to Noise Ratio
11. What are the limitations of PCM?
12. What are the applications of PCM?

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13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate
16. What is multiplexing?
17. What is de-multiplexing?

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18. What are the types of pulse modulation?
19. What should be the minimum bandwidth required to transmit a PCM channel?
20. What is the value of signal to noise ratio in PCM?

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Viva - voce
37 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 6 DELTA MODULATION & DEMODULATION
Aim:

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To transmit an analog message signal in its digital form and reconstruct back the original analog message
signal at receiver by using Delta modulator
Apparatus required:
1. DM and ADM Trainer kit ? 1 No.
2. CRO ? 1 No.

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3. Connecting probes ? 4 No.
Theory:
Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The
difference signal between two successive samples is encoded into a single bit code. A present sample of the
analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level

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(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.
The comparison of samples is accomplished by converting the digital to analog form then comparing with the
present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to
a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.
Procedure:

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1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.
2. Observe the modulated signal in the CRO.
3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.
4. Also observe the DAC output on the CRO.
5. Change the amplitude of the modulating signal.

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6. Observe the DAC output. Notice the slope overload distortion.
7. Keep the tuning knob to minimize distortion.
8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope
overload distortion.
9. Calculate the sampling frequency required for no slope overload distortion.

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10. Compare the calculated measured values of the sampling frequency.


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Block Diagram Delta modulator and demodulator

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Delta Modulator

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Delta Demodulator

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Block diagram of Adaptive delta modulator and demodulator

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Adaptive Delta Modulator

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Adaptive Delta Demodulator

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40 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Delta Modulation and Adaptive Delta Modulator Trainer kit

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41 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Model Graph:

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42 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Tabulation 1
For Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal
2 Carrier Signal

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3 Modulated Signal
4 Demodulated Signal

Tabulation 2
For Adaptive Delta Modulation

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Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal
2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

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Result:
Thus the output waveforms of Delta modulation and adaptive delta modulation circuit were observed.
Outcome:
After the completion of this experiment the students will be able to design and construct the delta modulation

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adaptive delta modulation circuit.
Applications:
1. Digital voice storage
2. Voice transmission
43 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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3. Radio communication devices such TV remotes.
4. Delta Modulation was used by Satellite Business Systems or SBS
5. DM used in high resolution A/D and D/A converters.

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1. What is delta modulation?
2. What is adaptive delta modulation?
3. What are the advantages of adaptive delta modulation over delta modulation?
4. What is slope over load distortion?

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5. What is granular noise effect?
6. What are the two limitations of delta modulation?
7. What is the function of integrator?
8. What is comparator?
9. What is companding?

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10. What is the advantage of delta modulation over pulse modulation?
11. Distinguish between DPCM and DM.
12. What are the different types of digital modulation?
13. What is sampling rate?
14. Which kind of multiplexing used in digital communication?

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15. Why is sample hold circuit used?
16. What are the advantages of digital transmission?
17. How is the performance corrupted in PCM?
18. What are the different types of multiplexing?
19. What is aliasing effect?

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20. How to avoid aliasing effect?

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Viva - voce
44 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 7 LINE CODING DECODING TECHNIQUES

Aim:
To study different line coding techniques.

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Apparatus required:
1. Line coding and decoding trainer kit ? 1 No.
2. Patch cords ? 6 No.
3. CRO ? 1 No.

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Theory:
Line coding refers to the process of representing the bit stream (1 ?s and 0 ?s) in the form of voltage or current
variations optimally tuned for the specific properties of the physical channel being used. The selection of a proper
line code can help in many ways. One possibility is to aid in clock recovery at the receiver. A clock signal is
recovered by observing transitions in the received bit sequence, if enough transitions exist, a good recovery of

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the clock is guaranteed, the signal is said to be self-clocking. Another advantage is to get rid of DC shifts. The
DC component in a line code is called the bias or the DC coefficient. Unfortunately, most long-distance
communication channels cannot transport a DC component. This is why most line codes try to eliminate the DC
component before being transmitted on the channel. Such codes are called DC balanced, zero-DC, zero-bias, or
DC equalized. Some common types of line encoding in common-use nowadays are unipolar, polar, bipolar,

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Manchester, MLT-3 Duo binary encoding.
Unipolar (Unipolar NRZ and Unipolar RZ):
Unipolar is the simplest line coding scheme. It has the advantage of being compatible with TTL logic. Unipolar
coding uses a positive rectangular pulse p(t) to represent binary 1, the absence of a pulse (i.e., zero voltage) to
represent a binary 0. Two possibilities for the pulse p(t) exist3: Non-Return-to-Zero (NRZ) rectangular pulse

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Return-to-Zero (RZ) rectangular pulse. The difference between Unipolar NRZ Unipolar RZ codes is that the
rectangular pulse in NRZ stays at a positive value (e.g., +5V) for the full duration of the logic 1 bit, while the pule
in RZ drops from +5V to 0V in the middle of the bit time.

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45 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Procedure:
1. Connect the PRBS (test point P5) to various line coding formats. Obtain the coded output as per the

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requirement.
2. Connect coded signal test point to corresponding decoding test point as inputs.
3. Set the SW1 as per the requirement.
4. Set the potentiometer P1 in minimum position.
5. Switch ON the power supply. Press the switch SW2 once.

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6. Display the encoded signal on one channel of CRO and decoded signal on second channel of CRO.

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46 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Line coding decoding trainer kit

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47 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Model Graph:

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48 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Tabulation
Sl. No. Type of Coding AMPLITUDE (V) Time period (s)

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1. Unipolar data(NZ NRZ )

2. Unipolar data (NRZ RZ)
3. Bipolar Data(NRZ AMI)
4. Manchester

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Result:
Thus the different line coding techniques was studied and verified.
Outcome:

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After the completion of this experiment the students will be able to understand implement the different line
coding schemes.
Applications:
1. DC balance
2. embedded clock applications

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3. computing applications
4. Manchester codes are commonly used for local area networks
5. Bipolar codes are commonly used for local area networks

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49 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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1. What is line coding?
2. Define ? Polar Encoding
3. Define ? Unipolar Encoding

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4. Define ? Bipolar Encoding
5. Define ? Manchester Encoding
6. What are the two function of fast frequency hopping?
7. What is return to zero?
8. What is Non-return to zero?

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9. What is the difference between source coding and line coding?
10. What are the properties of line coding?
11. What is the effect of inter symbol interference?
12. How ISI can be reduced?
13. Define ? Encoding

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14. Define ? Decoding
15. Define ? Nyquist Rate
16. Draw the NRZ and RZ code for the digital data 10110001.
17. Define ? Equalization
18. What is PRBS?

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19. Write the Boolean expression for X-NOR gate.
20. Define ? Digital demodulation

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Viva - voce
50 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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CYCLE 2 ? EXPERIMENTS
Expt. No.8 ERROR CONTROL CODING USING MATLAB
Aim:
To write a program in MATLAB for error control coding techniques

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Software required:
PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments comon prompt will appear.

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3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitiled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.

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6. After execution output will appear in the common window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

Result:

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Thus the error control coding techniques are executed using MATLAB programs.
Outcome:
After the completion of this experiment the students will be able to simulate the different error control coding
schemes using MATLAB.
Applications :

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1. Deep space communication
2. Satellite communication
3. Data transmission
4. Data storage
5. Mobile communication

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6. File transfer
7. digital audio/video transmission.
FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious

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enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels

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? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

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To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

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? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical

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practices

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VISION
VISION
MISSION
MISSION
3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher

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education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth

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To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social

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context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics

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Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits

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d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness

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of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

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To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes

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? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing

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3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM

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8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise

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performance of communication system.

COURSE OBJECTIVES
COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS

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1 Signal sampling reconstruction
7
2 Time division multiplexing
13
3 AM modulation demodulation

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18
4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33

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6 Delta modulation demodulation
38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS

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8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB

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55
11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59

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ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:

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1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:

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Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be

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sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.

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A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is

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accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.

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2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

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Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal

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Sampled output
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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of

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continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission

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4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?

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3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.

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8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits

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13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?

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18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
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Expt. No. 2 TIME DIVISION MULTIPLEXING

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Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.

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3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears

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on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,

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(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.

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5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.

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8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .


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Circuit Diagram
Time division multiplexing

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TDM Trainer Kit

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Model Graph:

Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1

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2. Message Signal 2
3. TDM signal

Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.

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Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)

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or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).

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4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system


1. What is meant by multiplexing technique ?

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2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.

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7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce

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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after

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demodulating using AM receiver
Apparatus required:
.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.

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3 Diode ? 2 No.
4
AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.

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6 Patch cards ? 6 No.

Theory:

AMPLITUDE MODULATION

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Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct

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The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal

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VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100

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Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if
M < 1 Under modulation

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M = 1 Critical modulation
M > 1 over modulation

Procedure:
1. Give the modulating signal input to the Amplitude modulator.

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2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

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AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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21 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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AM Modulation demodulation trainer kit

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22 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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AM Modulation and Demodulation trainer kit

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Tabulation

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Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.

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Applications:
1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?

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4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?

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9. What are the different types of AM generation?
10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce
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12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?

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16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.

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20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:

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To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver
Apparatus required:
.
1. Resistor ? 4 No.

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2. Capacitor ? 1 No.
3. Diode ? 2 No.
4.
AM transmitter Receiver
trainer kit ? 1 No.

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5. CRO ? 1 No.
6. Patch cards ? 6 No.

Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the

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instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used

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in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of

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noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

Procedure:
FM Modulator:

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1. Switch ON the Power supply.

2. Connect the sine wave generator output to frequency modulator input.

3. Select the low frequency carrier (or) high frequency carrier.

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4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

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6. Observe the frequency modulator output .

FM Demodulator:
A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

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2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

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4. Observe the Demodulated O/P compare with the original input.

B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

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2. Now set the DPDT switch in high frequency mode.

3. Connect the CRO input to Quadrature detector output.

4. Observe the Demodulated O/P and compare with the original input.

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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

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4. Observe the Demodulated O/P and then compare with the original input.

D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Ratio detector output.

4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram

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FM Modulator

FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

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Carrier

Modulated

Demodulated

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Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency
modulated and demodulated wave.

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Applications:
1. Television sound transmission
2. Two way mobile radio
3. Cellular Radio
4. Microwave

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5. Satellite Communication System


1. Define ? Frequency Modulation
2. How it is different from phase modulation?

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3. Write equation of FM wave, explain each parameter in it.
4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.
6. Define ? Modulation Index
7. Differentiate between Narrow band FM from Wide band FM.

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8. Draw message, carrier FM waves .
9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?
11. Give the practical applications of FM.
12. State advantages and disadvantages of FM.

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13. What is the range of speech signals?
14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation
17. Draw the phasor diagram of FM signal.

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18. What are the different types of FM generation?

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Viva - voce
32 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 5 PCM MODULATION & DEMODULATION

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Aim:
To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator
Apparatus Required:
1. PCM trainer kit ? 1 No.

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2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is
first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of

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converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization
can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization
the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel

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serially.
At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword
is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to

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Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks
for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:
1. Power on the PCM kit.

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2. Measure the frequency of sampling clock.
3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.

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5. Connect the clock to the timing control circuit.
6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.
9. Observe the waveform at the output of DAC.

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10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the
codeword graphically for a DC input.
Block diagram of PCM Transmission system

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34 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PCM Modulation and Demodulation Trainer kit

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Model Graph:

Tabulation

Result:

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Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.
Outcome:
After the completion of this experiment the students will be able to design and construct the pulse code
modulated and demodulated wave.
Applications:

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1. Military Applications.
2. The PCM is used in the satellite transmission system.
SIGNALS AMPLITUDE (V) TIME PERIOD (s)
DC Input
Sampled Signal

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Clock Pulse
PCM Output
DC Output
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3. It is used in space communication.
4. It is used in telephony.
5. The compact disc (CD) is a recent application of PCM.

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1. Define ? Modulation
2. State sampling theorem
3. Define ? Demodulation
4. Define ? Pulse Code Modulation
5. What is aliasing effect?

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6. What is quantization?
7. Define ? Bit Rate
8. Define ? Baud Rate
9. What are the advantages of PCM?
10. Define ? Signal to Noise Ratio

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11. What are the limitations of PCM?
12. What are the applications of PCM?
13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate

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16. What is multiplexing?
17. What is de-multiplexing?
18. What are the types of pulse modulation?
19. What should be the minimum bandwidth required to transmit a PCM channel?
20. What is the value of signal to noise ratio in PCM?

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Viva - voce
37 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 6 DELTA MODULATION & DEMODULATION
Aim:
To transmit an analog message signal in its digital form and reconstruct back the original analog message
signal at receiver by using Delta modulator
Apparatus required:

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1. DM and ADM Trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The

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difference signal between two successive samples is encoded into a single bit code. A present sample of the
analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level
(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.
The comparison of samples is accomplished by converting the digital to analog form then comparing with the
present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to

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a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.
Procedure:
1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.
2. Observe the modulated signal in the CRO.
3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.

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4. Also observe the DAC output on the CRO.
5. Change the amplitude of the modulating signal.
6. Observe the DAC output. Notice the slope overload distortion.
7. Keep the tuning knob to minimize distortion.
8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope

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overload distortion.
9. Calculate the sampling frequency required for no slope overload distortion.
10. Compare the calculated measured values of the sampling frequency.

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38 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Block Diagram Delta modulator and demodulator

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Delta Modulator

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Delta Demodulator

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Block diagram of Adaptive delta modulator and demodulator

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Adaptive Delta Modulator

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Adaptive Delta Demodulator

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40 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Delta Modulation and Adaptive Delta Modulator Trainer kit

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41 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Model Graph:

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Tabulation 1
For Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)

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1 Modulating Signal
2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

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Tabulation 2
For Adaptive Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal
2 Carrier Signal

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3 Modulated Signal
4 Demodulated Signal

Result:
Thus the output waveforms of Delta modulation and adaptive delta modulation circuit were observed.

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Outcome:
After the completion of this experiment the students will be able to design and construct the delta modulation
adaptive delta modulation circuit.
Applications:
1. Digital voice storage

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2. Voice transmission
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3. Radio communication devices such TV remotes.
4. Delta Modulation was used by Satellite Business Systems or SBS

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5. DM used in high resolution A/D and D/A converters.


1. What is delta modulation?
2. What is adaptive delta modulation?

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3. What are the advantages of adaptive delta modulation over delta modulation?
4. What is slope over load distortion?
5. What is granular noise effect?
6. What are the two limitations of delta modulation?
7. What is the function of integrator?

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8. What is comparator?
9. What is companding?
10. What is the advantage of delta modulation over pulse modulation?
11. Distinguish between DPCM and DM.
12. What are the different types of digital modulation?

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13. What is sampling rate?
14. Which kind of multiplexing used in digital communication?
15. Why is sample hold circuit used?
16. What are the advantages of digital transmission?
17. How is the performance corrupted in PCM?

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18. What are the different types of multiplexing?
19. What is aliasing effect?
20. How to avoid aliasing effect?

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Viva - voce
44 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 7 LINE CODING DECODING TECHNIQUES

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Aim:
To study different line coding techniques.
Apparatus required:
1. Line coding and decoding trainer kit ? 1 No.
2. Patch cords ? 6 No.

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3. CRO ? 1 No.

Theory:
Line coding refers to the process of representing the bit stream (1 ?s and 0 ?s) in the form of voltage or current
variations optimally tuned for the specific properties of the physical channel being used. The selection of a proper

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line code can help in many ways. One possibility is to aid in clock recovery at the receiver. A clock signal is
recovered by observing transitions in the received bit sequence, if enough transitions exist, a good recovery of
the clock is guaranteed, the signal is said to be self-clocking. Another advantage is to get rid of DC shifts. The
DC component in a line code is called the bias or the DC coefficient. Unfortunately, most long-distance
communication channels cannot transport a DC component. This is why most line codes try to eliminate the DC

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component before being transmitted on the channel. Such codes are called DC balanced, zero-DC, zero-bias, or
DC equalized. Some common types of line encoding in common-use nowadays are unipolar, polar, bipolar,
Manchester, MLT-3 Duo binary encoding.
Unipolar (Unipolar NRZ and Unipolar RZ):
Unipolar is the simplest line coding scheme. It has the advantage of being compatible with TTL logic. Unipolar

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coding uses a positive rectangular pulse p(t) to represent binary 1, the absence of a pulse (i.e., zero voltage) to
represent a binary 0. Two possibilities for the pulse p(t) exist3: Non-Return-to-Zero (NRZ) rectangular pulse
Return-to-Zero (RZ) rectangular pulse. The difference between Unipolar NRZ Unipolar RZ codes is that the
rectangular pulse in NRZ stays at a positive value (e.g., +5V) for the full duration of the logic 1 bit, while the pule
in RZ drops from +5V to 0V in the middle of the bit time.

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45 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Procedure:
1. Connect the PRBS (test point P5) to various line coding formats. Obtain the coded output as per the
requirement.
2. Connect coded signal test point to corresponding decoding test point as inputs.
3. Set the SW1 as per the requirement.

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4. Set the potentiometer P1 in minimum position.
5. Switch ON the power supply. Press the switch SW2 once.
6. Display the encoded signal on one channel of CRO and decoded signal on second channel of CRO.

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46 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


Line coding decoding trainer kit

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Model Graph:

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48 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Tabulation
Sl. No. Type of Coding AMPLITUDE (V) Time period (s)
1. Unipolar data(NZ NRZ )

2. Unipolar data (NRZ RZ)

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3. Bipolar Data(NRZ AMI)
4. Manchester


Result:

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Thus the different line coding techniques was studied and verified.
Outcome:
After the completion of this experiment the students will be able to understand implement the different line
coding schemes.
Applications:

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1. DC balance
2. embedded clock applications
3. computing applications
4. Manchester codes are commonly used for local area networks
5. Bipolar codes are commonly used for local area networks

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49 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


1. What is line coding?

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2. Define ? Polar Encoding
3. Define ? Unipolar Encoding
4. Define ? Bipolar Encoding
5. Define ? Manchester Encoding
6. What are the two function of fast frequency hopping?

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7. What is return to zero?
8. What is Non-return to zero?
9. What is the difference between source coding and line coding?
10. What are the properties of line coding?
11. What is the effect of inter symbol interference?

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12. How ISI can be reduced?
13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate
16. Draw the NRZ and RZ code for the digital data 10110001.

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17. Define ? Equalization
18. What is PRBS?
19. Write the Boolean expression for X-NOR gate.
20. Define ? Digital demodulation

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Viva - voce
50 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

CYCLE 2 ? EXPERIMENTS
Expt. No.8 ERROR CONTROL CODING USING MATLAB

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Aim:
To write a program in MATLAB for error control coding techniques
Software required:
PC with MATLAB version 7.0 software installed
Procedure:

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1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments comon prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitiled?.

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5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the common window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the error control coding techniques are executed using MATLAB programs.
Outcome:
After the completion of this experiment the students will be able to simulate the different error control coding

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schemes using MATLAB.
Applications :
1. Deep space communication
2. Satellite communication
3. Data transmission

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4. Data storage
5. Mobile communication
6. File transfer
7. digital audio/video transmission.
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1. What is the need for error control coding?
2. What is meant by linear code?
3. What is meant by cyclic code?

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4. Name some error control coding techniques.
5. Name the code which is used only for error detection.

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Viva - voce

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FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

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V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________

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Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

DHANALAKSHMI

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College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

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? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION

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ENGINEERING


To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges

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in deploying technology for the service of humanity


? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry

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? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION
VISION

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MISSION
MISSION
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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)

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1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence

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To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products

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4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics

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To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints

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such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks

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f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities

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j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM

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? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes

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LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator

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5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)

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10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

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COURSE OBJECTIVES
COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7

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2 Time division multiplexing
13
3 AM modulation demodulation
18
4 Frequency modulation demodulation

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26
5 PCM modulation demodulation
33
6 Delta modulation demodulation
38

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7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51

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9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB

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57
12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61

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14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION

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Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.

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3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are

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natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem

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If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.

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Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz

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and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of

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control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.

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4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

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Model Graph:

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Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal
Sampled output
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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.
Applications:

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1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

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1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate
4. Define ? Nyquist interval

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5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?

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10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.

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15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?

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20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling


Viva - voce

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12 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit

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Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.

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Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.
Procedure:

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1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on

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channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)

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on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .

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Circuit Diagram
Time division multiplexing

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14 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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TDM Trainer Kit

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Model Graph:

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Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1
2. Message Signal 2
3. TDM signal

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Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the

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signals.


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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network

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transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system

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1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?

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4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.

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9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce
17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver
Apparatus required:

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.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.
3 Diode ? 2 No.
4

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AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.
6 Patch cards ? 6 No.

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Theory:

AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.

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The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

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The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal

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Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index
Vmax = Maximum peak amplitude

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Vmin = Minimum peak amplitude
if
M < 1 Under modulation
M = 1 Critical modulation
M > 1 over modulation

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Procedure:
1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.

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4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation


AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

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Carrier

Modulated

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Demodulated


Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.

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Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.
Applications:
1. Commercial broadcasting of both audio and video signals

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2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.

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6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?
9. What are the different types of AM generation?
10. Define ? Modulation Index

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11. What are different types of analog modulation techniques?
Viva - voce
24 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

12. What are the other names of message signal? What are the other names of carrier signal?

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13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of

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demodulation of an AM wave?
18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation

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22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver

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Apparatus required:
.
1. Resistor ? 4 No.
2. Capacitor ? 1 No.
3. Diode ? 2 No.

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4.
AM transmitter Receiver
trainer kit ? 1 No.
5. CRO ? 1 No.
6. Patch cards ? 6 No.

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Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the
instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete

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values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used
in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into

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space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and

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retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of
noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

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Procedure:
FM Modulator:
1. Switch ON the Power supply.

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2. Connect the sine wave generator output to frequency modulator input.

3. Select the low frequency carrier (or) high frequency carrier.

4. Connect the CRO input to the frequency modulator output.

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5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

6. Observe the frequency modulator output .

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FM Demodulator:
A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

2. Now set the DPDT switch in low frequency mode.

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3. Connect CRO input to PLL detector output.

4. Observe the Demodulated O/P compare with the original input.

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B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

2. Now set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Quadrature detector output.

4. Observe the Demodulated O/P and compare with the original input.
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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

2. Set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Phase discriminator output.

4. Observe the Demodulated O/P and then compare with the original input.

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D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

2. Set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Ratio detector output.

4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram
FM Modulator

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FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:


Tabulation

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Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency
modulated and demodulated wave.
Applications:
1. Television sound transmission

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2. Two way mobile radio
3. Cellular Radio
4. Microwave
5. Satellite Communication System

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1. Define ? Frequency Modulation
2. How it is different from phase modulation?
3. Write equation of FM wave, explain each parameter in it.
4. Draw the amplitude spectrum of FM wave.

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5. Give the Carson?s rule in FM.
6. Define ? Modulation Index
7. Differentiate between Narrow band FM from Wide band FM.
8. Draw message, carrier FM waves .
9. Explain the methods for generation of FM its demodulation.

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10. How FM wave is different from PM wave?
11. Give the practical applications of FM.
12. State advantages and disadvantages of FM.
13. What is the range of speech signals?
14. What type of modulation is used in radios?

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15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation
17. Draw the phasor diagram of FM signal.
18. What are the different types of FM generation?

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Viva - voce
32 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 5 PCM MODULATION & DEMODULATION

Aim:
To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM

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demodulator
Apparatus Required:
1. PCM trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.

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Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is
first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of
converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization
can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in

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speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization
the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel
serially.
At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an

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equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword
is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to
Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks
for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be

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observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:
1. Power on the PCM kit.
2. Measure the frequency of sampling clock.
3. Apply the DC voltage as modulating signal.

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4. Connect the DC input to the ADC measure the voltage.
5. Connect the clock to the timing control circuit.
6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.

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7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.
9. Observe the waveform at the output of DAC.
10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the
codeword graphically for a DC input.

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Block diagram of PCM Transmission system

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34 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PCM Modulation and Demodulation Trainer kit

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35 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Model Graph:

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Tabulation

Result:
Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.
Outcome:

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After the completion of this experiment the students will be able to design and construct the pulse code
modulated and demodulated wave.
Applications:
1. Military Applications.
2. The PCM is used in the satellite transmission system.

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SIGNALS AMPLITUDE (V) TIME PERIOD (s)
DC Input
Sampled Signal
Clock Pulse
PCM Output

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DC Output
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3. It is used in space communication.
4. It is used in telephony.

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5. The compact disc (CD) is a recent application of PCM.


1. Define ? Modulation
2. State sampling theorem

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3. Define ? Demodulation
4. Define ? Pulse Code Modulation
5. What is aliasing effect?
6. What is quantization?
7. Define ? Bit Rate

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8. Define ? Baud Rate
9. What are the advantages of PCM?
10. Define ? Signal to Noise Ratio
11. What are the limitations of PCM?
12. What are the applications of PCM?

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13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate
16. What is multiplexing?
17. What is de-multiplexing?

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18. What are the types of pulse modulation?
19. What should be the minimum bandwidth required to transmit a PCM channel?
20. What is the value of signal to noise ratio in PCM?

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Viva - voce
37 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 6 DELTA MODULATION & DEMODULATION
Aim:

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To transmit an analog message signal in its digital form and reconstruct back the original analog message
signal at receiver by using Delta modulator
Apparatus required:
1. DM and ADM Trainer kit ? 1 No.
2. CRO ? 1 No.

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3. Connecting probes ? 4 No.
Theory:
Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The
difference signal between two successive samples is encoded into a single bit code. A present sample of the
analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level

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(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.
The comparison of samples is accomplished by converting the digital to analog form then comparing with the
present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to
a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.
Procedure:

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1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.
2. Observe the modulated signal in the CRO.
3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.
4. Also observe the DAC output on the CRO.
5. Change the amplitude of the modulating signal.

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6. Observe the DAC output. Notice the slope overload distortion.
7. Keep the tuning knob to minimize distortion.
8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope
overload distortion.
9. Calculate the sampling frequency required for no slope overload distortion.

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10. Compare the calculated measured values of the sampling frequency.


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Block Diagram Delta modulator and demodulator

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Delta Modulator

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Delta Demodulator

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Block diagram of Adaptive delta modulator and demodulator

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Adaptive Delta Modulator

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Adaptive Delta Demodulator

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Delta Modulation and Adaptive Delta Modulator Trainer kit

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41 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Model Graph:

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Tabulation 1
For Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal
2 Carrier Signal

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3 Modulated Signal
4 Demodulated Signal

Tabulation 2
For Adaptive Delta Modulation

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Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal
2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

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Result:
Thus the output waveforms of Delta modulation and adaptive delta modulation circuit were observed.
Outcome:
After the completion of this experiment the students will be able to design and construct the delta modulation

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adaptive delta modulation circuit.
Applications:
1. Digital voice storage
2. Voice transmission
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3. Radio communication devices such TV remotes.
4. Delta Modulation was used by Satellite Business Systems or SBS
5. DM used in high resolution A/D and D/A converters.

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1. What is delta modulation?
2. What is adaptive delta modulation?
3. What are the advantages of adaptive delta modulation over delta modulation?
4. What is slope over load distortion?

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5. What is granular noise effect?
6. What are the two limitations of delta modulation?
7. What is the function of integrator?
8. What is comparator?
9. What is companding?

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10. What is the advantage of delta modulation over pulse modulation?
11. Distinguish between DPCM and DM.
12. What are the different types of digital modulation?
13. What is sampling rate?
14. Which kind of multiplexing used in digital communication?

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15. Why is sample hold circuit used?
16. What are the advantages of digital transmission?
17. How is the performance corrupted in PCM?
18. What are the different types of multiplexing?
19. What is aliasing effect?

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20. How to avoid aliasing effect?

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Viva - voce
44 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 7 LINE CODING DECODING TECHNIQUES

Aim:
To study different line coding techniques.

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Apparatus required:
1. Line coding and decoding trainer kit ? 1 No.
2. Patch cords ? 6 No.
3. CRO ? 1 No.

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Theory:
Line coding refers to the process of representing the bit stream (1 ?s and 0 ?s) in the form of voltage or current
variations optimally tuned for the specific properties of the physical channel being used. The selection of a proper
line code can help in many ways. One possibility is to aid in clock recovery at the receiver. A clock signal is
recovered by observing transitions in the received bit sequence, if enough transitions exist, a good recovery of

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the clock is guaranteed, the signal is said to be self-clocking. Another advantage is to get rid of DC shifts. The
DC component in a line code is called the bias or the DC coefficient. Unfortunately, most long-distance
communication channels cannot transport a DC component. This is why most line codes try to eliminate the DC
component before being transmitted on the channel. Such codes are called DC balanced, zero-DC, zero-bias, or
DC equalized. Some common types of line encoding in common-use nowadays are unipolar, polar, bipolar,

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Manchester, MLT-3 Duo binary encoding.
Unipolar (Unipolar NRZ and Unipolar RZ):
Unipolar is the simplest line coding scheme. It has the advantage of being compatible with TTL logic. Unipolar
coding uses a positive rectangular pulse p(t) to represent binary 1, the absence of a pulse (i.e., zero voltage) to
represent a binary 0. Two possibilities for the pulse p(t) exist3: Non-Return-to-Zero (NRZ) rectangular pulse

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Return-to-Zero (RZ) rectangular pulse. The difference between Unipolar NRZ Unipolar RZ codes is that the
rectangular pulse in NRZ stays at a positive value (e.g., +5V) for the full duration of the logic 1 bit, while the pule
in RZ drops from +5V to 0V in the middle of the bit time.

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45 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Procedure:
1. Connect the PRBS (test point P5) to various line coding formats. Obtain the coded output as per the

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requirement.
2. Connect coded signal test point to corresponding decoding test point as inputs.
3. Set the SW1 as per the requirement.
4. Set the potentiometer P1 in minimum position.
5. Switch ON the power supply. Press the switch SW2 once.

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6. Display the encoded signal on one channel of CRO and decoded signal on second channel of CRO.

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46 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Line coding decoding trainer kit

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47 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Model Graph:

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48 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Tabulation
Sl. No. Type of Coding AMPLITUDE (V) Time period (s)

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1. Unipolar data(NZ NRZ )

2. Unipolar data (NRZ RZ)
3. Bipolar Data(NRZ AMI)
4. Manchester

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Result:
Thus the different line coding techniques was studied and verified.
Outcome:

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After the completion of this experiment the students will be able to understand implement the different line
coding schemes.
Applications:
1. DC balance
2. embedded clock applications

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3. computing applications
4. Manchester codes are commonly used for local area networks
5. Bipolar codes are commonly used for local area networks

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49 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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1. What is line coding?
2. Define ? Polar Encoding
3. Define ? Unipolar Encoding

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4. Define ? Bipolar Encoding
5. Define ? Manchester Encoding
6. What are the two function of fast frequency hopping?
7. What is return to zero?
8. What is Non-return to zero?

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9. What is the difference between source coding and line coding?
10. What are the properties of line coding?
11. What is the effect of inter symbol interference?
12. How ISI can be reduced?
13. Define ? Encoding

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14. Define ? Decoding
15. Define ? Nyquist Rate
16. Draw the NRZ and RZ code for the digital data 10110001.
17. Define ? Equalization
18. What is PRBS?

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19. Write the Boolean expression for X-NOR gate.
20. Define ? Digital demodulation

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Viva - voce
50 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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CYCLE 2 ? EXPERIMENTS
Expt. No.8 ERROR CONTROL CODING USING MATLAB
Aim:
To write a program in MATLAB for error control coding techniques

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Software required:
PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments comon prompt will appear.

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3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitiled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.

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6. After execution output will appear in the common window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

Result:

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Thus the error control coding techniques are executed using MATLAB programs.
Outcome:
After the completion of this experiment the students will be able to simulate the different error control coding
schemes using MATLAB.
Applications :

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1. Deep space communication
2. Satellite communication
3. Data transmission
4. Data storage
5. Mobile communication

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6. File transfer
7. digital audio/video transmission.
51 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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1. What is the need for error control coding?
2. What is meant by linear code?
3. What is meant by cyclic code?
4. Name some error control coding techniques.
5. Name the code which is used only for error detection.

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Viva - voce
52 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 9 DESIGN OF BPSK, QPSK, QAM USING MATLAB
Aim:
To write a program in MATLAB for design of BPSK, QPSK and QAM
Software required:
PC with MATLAB version 7.0 software installed

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Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.

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4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.

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7. Rectify the error, if any go to debug menu select run.

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FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

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V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL

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2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

DHANALAKSHMI

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College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry

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? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

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To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

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? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems

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? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION
VISION
MISSION
MISSION

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3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,

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enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions

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3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students

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to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00



PROGRAMME OUTCOMES (POs)

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a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics

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communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large

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h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM

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? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction

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2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation

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7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation

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12. Equalization ? Zero Forcing and LMS algorithms (simulation)


Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.

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Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

COURSE OBJECTIVES
COURSE OUTCOMES

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.

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CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7
2 Time division multiplexing
13

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3 AM modulation demodulation
18
4 Frequency modulation demodulation
26
5 PCM modulation demodulation

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33
6 Delta modulation demodulation
38
7 Line coding decoding techniques
45

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CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB
53

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10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB

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59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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7 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit

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Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.

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Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For

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reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known

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as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the

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sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:

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1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.

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6. Integrate the sampling inputs.

Circuit Diagram

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9 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

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Analog signal sampling and reconstruction trainer kit


Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer

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kit.


Signal Amplitude (V) Time period (s)
Message signal

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Carrier signal
Sampled output
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Outcome:

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After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)

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3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem

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2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?

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7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?

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12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal

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17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
12 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.

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2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common

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signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.

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(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this

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sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of

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Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .


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Circuit Diagram
Time division multiplexing

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14 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


TDM Trainer Kit

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Model Graph:

Tabulation
Sl. No. Signal Amplitude (V) Time period (s)

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1. Message signal 1
2. Message Signal 2
3. TDM signal

Result:

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Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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16 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital

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transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital

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Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system

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1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?

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6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce
17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 3 AM MODULATION & DEMODULATION
Aim:

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To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver
Apparatus required:
.
1 Resistor ? 4 No.

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2 Capacitor ? 1 No.
3 Diode ? 2 No.
4
AM transmitter receiver
trainer kit ? 1 No.

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5 CRO ? 1 No.
6 Patch cards ? 6 No.

Theory:

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AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt

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VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,

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VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where

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Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:

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M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if

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M < 1 Under modulation
M = 1 Critical modulation
M > 1 over modulation

Procedure:

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1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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19 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:

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1. AM Waveform (Ring diode Transistor based AM Modulator)

AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated

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demodulated wave.
Applications:
1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.

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3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?

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8. What is depth of modulation?
9. What are the different types of AM generation?
10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce

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12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation

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15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.

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19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION

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Aim:
To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver
Apparatus required:
.

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1. Resistor ? 4 No.
2. Capacitor ? 1 No.
3. Diode ? 2 No.
4.
AM transmitter Receiver

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trainer kit ? 1 No.
5. CRO ? 1 No.
6. Patch cards ? 6 No.

Theory:

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Frequency modulation (FM) is a form of modulation that represents information as variations in the
instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A

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narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used
in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to

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present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of
noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

Procedure:

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FM Modulator:
1. Switch ON the Power supply.

2. Connect the sine wave generator output to frequency modulator input.

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3. Select the low frequency carrier (or) high frequency carrier.

4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

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6. Observe the frequency modulator output .

FM Demodulator:
A) PLL Detector

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1. Connect frequency modulated output to the PLL detector input.

2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

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4. Observe the Demodulated O/P compare with the original input.

B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

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2. Now set the DPDT switch in high frequency mode.

3. Connect the CRO input to Quadrature detector output.

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4. Observe the Demodulated O/P and compare with the original input.
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C) Phase Discriminator (Foster-Seeley detector)

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1. Connect the frequency modulated output to Phase discriminator input.

2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

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4. Observe the Demodulated O/P and then compare with the original input.

D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Ratio detector output.

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4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram
FM Modulator

FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

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Carrier

Modulated

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Demodulated


Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency

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modulated and demodulated wave.
Applications:
1. Television sound transmission
2. Two way mobile radio
3. Cellular Radio

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4. Microwave
5. Satellite Communication System


1. Define ? Frequency Modulation

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2. How it is different from phase modulation?
3. Write equation of FM wave, explain each parameter in it.
4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.
6. Define ? Modulation Index

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7. Differentiate between Narrow band FM from Wide band FM.
8. Draw message, carrier FM waves .
9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?
11. Give the practical applications of FM.

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12. State advantages and disadvantages of FM.
13. What is the range of speech signals?
14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation

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17. Draw the phasor diagram of FM signal.
18. What are the different types of FM generation?

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Viva - voce
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Expt. No. 5 PCM MODULATION & DEMODULATION

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Aim:
To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator
Apparatus Required:

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1. PCM trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is

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first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of
converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization
can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization

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the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel
serially.
At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword

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is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to
Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks
for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:

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1. Power on the PCM kit.
2. Measure the frequency of sampling clock.
3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.
5. Connect the clock to the timing control circuit.
6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.

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9. Observe the waveform at the output of DAC.
10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the
codeword graphically for a DC input.
Block diagram of PCM Transmission system

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PCM Modulation and Demodulation Trainer kit

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Model Graph:

Tabulation

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Result:
Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.
Outcome:
After the completion of this experiment the students will be able to design and construct the pulse code
modulated and demodulated wave.

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Applications:
1. Military Applications.
2. The PCM is used in the satellite transmission system.
SIGNALS AMPLITUDE (V) TIME PERIOD (s)
DC Input

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Sampled Signal
Clock Pulse
PCM Output
DC Output
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3. It is used in space communication.
4. It is used in telephony.
5. The compact disc (CD) is a recent application of PCM.

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1. Define ? Modulation
2. State sampling theorem
3. Define ? Demodulation
4. Define ? Pulse Code Modulation

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5. What is aliasing effect?
6. What is quantization?
7. Define ? Bit Rate
8. Define ? Baud Rate
9. What are the advantages of PCM?

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10. Define ? Signal to Noise Ratio
11. What are the limitations of PCM?
12. What are the applications of PCM?
13. Define ? Encoding
14. Define ? Decoding

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15. Define ? Nyquist Rate
16. What is multiplexing?
17. What is de-multiplexing?
18. What are the types of pulse modulation?
19. What should be the minimum bandwidth required to transmit a PCM channel?

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20. What is the value of signal to noise ratio in PCM?

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Viva - voce
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Expt. No. 6 DELTA MODULATION & DEMODULATION
Aim:
To transmit an analog message signal in its digital form and reconstruct back the original analog message
signal at receiver by using Delta modulator

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Apparatus required:
1. DM and ADM Trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:

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Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The
difference signal between two successive samples is encoded into a single bit code. A present sample of the
analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level
(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.
The comparison of samples is accomplished by converting the digital to analog form then comparing with the

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present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to
a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.
Procedure:
1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.
2. Observe the modulated signal in the CRO.

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3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.
4. Also observe the DAC output on the CRO.
5. Change the amplitude of the modulating signal.
6. Observe the DAC output. Notice the slope overload distortion.
7. Keep the tuning knob to minimize distortion.

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8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope
overload distortion.
9. Calculate the sampling frequency required for no slope overload distortion.
10. Compare the calculated measured values of the sampling frequency.

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Block Diagram Delta modulator and demodulator

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Delta Modulator

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Delta Demodulator



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Block diagram of Adaptive delta modulator and demodulator

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Adaptive Delta Modulator

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Adaptive Delta Demodulator

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Delta Modulation and Adaptive Delta Modulator Trainer kit

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Model Graph:

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Tabulation 1
For Delta Modulation

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Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal
2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

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Tabulation 2
For Adaptive Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal

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2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

Result:

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Thus the output waveforms of Delta modulation and adaptive delta modulation circuit were observed.
Outcome:
After the completion of this experiment the students will be able to design and construct the delta modulation
adaptive delta modulation circuit.
Applications:

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1. Digital voice storage
2. Voice transmission
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3. Radio communication devices such TV remotes.

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4. Delta Modulation was used by Satellite Business Systems or SBS
5. DM used in high resolution A/D and D/A converters.


1. What is delta modulation?

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2. What is adaptive delta modulation?
3. What are the advantages of adaptive delta modulation over delta modulation?
4. What is slope over load distortion?
5. What is granular noise effect?
6. What are the two limitations of delta modulation?

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7. What is the function of integrator?
8. What is comparator?
9. What is companding?
10. What is the advantage of delta modulation over pulse modulation?
11. Distinguish between DPCM and DM.

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12. What are the different types of digital modulation?
13. What is sampling rate?
14. Which kind of multiplexing used in digital communication?
15. Why is sample hold circuit used?
16. What are the advantages of digital transmission?

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17. How is the performance corrupted in PCM?
18. What are the different types of multiplexing?
19. What is aliasing effect?
20. How to avoid aliasing effect?

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Viva - voce
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Expt. No. 7 LINE CODING DECODING TECHNIQUES

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Aim:
To study different line coding techniques.
Apparatus required:
1. Line coding and decoding trainer kit ? 1 No.

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2. Patch cords ? 6 No.
3. CRO ? 1 No.

Theory:
Line coding refers to the process of representing the bit stream (1 ?s and 0 ?s) in the form of voltage or current

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variations optimally tuned for the specific properties of the physical channel being used. The selection of a proper
line code can help in many ways. One possibility is to aid in clock recovery at the receiver. A clock signal is
recovered by observing transitions in the received bit sequence, if enough transitions exist, a good recovery of
the clock is guaranteed, the signal is said to be self-clocking. Another advantage is to get rid of DC shifts. The
DC component in a line code is called the bias or the DC coefficient. Unfortunately, most long-distance

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communication channels cannot transport a DC component. This is why most line codes try to eliminate the DC
component before being transmitted on the channel. Such codes are called DC balanced, zero-DC, zero-bias, or
DC equalized. Some common types of line encoding in common-use nowadays are unipolar, polar, bipolar,
Manchester, MLT-3 Duo binary encoding.
Unipolar (Unipolar NRZ and Unipolar RZ):

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Unipolar is the simplest line coding scheme. It has the advantage of being compatible with TTL logic. Unipolar
coding uses a positive rectangular pulse p(t) to represent binary 1, the absence of a pulse (i.e., zero voltage) to
represent a binary 0. Two possibilities for the pulse p(t) exist3: Non-Return-to-Zero (NRZ) rectangular pulse
Return-to-Zero (RZ) rectangular pulse. The difference between Unipolar NRZ Unipolar RZ codes is that the
rectangular pulse in NRZ stays at a positive value (e.g., +5V) for the full duration of the logic 1 bit, while the pule

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in RZ drops from +5V to 0V in the middle of the bit time.



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Procedure:
1. Connect the PRBS (test point P5) to various line coding formats. Obtain the coded output as per the
requirement.
2. Connect coded signal test point to corresponding decoding test point as inputs.

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3. Set the SW1 as per the requirement.
4. Set the potentiometer P1 in minimum position.
5. Switch ON the power supply. Press the switch SW2 once.
6. Display the encoded signal on one channel of CRO and decoded signal on second channel of CRO.

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Line coding decoding trainer kit

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Model Graph:

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Tabulation
Sl. No. Type of Coding AMPLITUDE (V) Time period (s)
1. Unipolar data(NZ NRZ )

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2. Unipolar data (NRZ RZ)
3. Bipolar Data(NRZ AMI)
4. Manchester

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Result:
Thus the different line coding techniques was studied and verified.
Outcome:
After the completion of this experiment the students will be able to understand implement the different line
coding schemes.

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Applications:
1. DC balance
2. embedded clock applications
3. computing applications
4. Manchester codes are commonly used for local area networks

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5. Bipolar codes are commonly used for local area networks

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1. What is line coding?
2. Define ? Polar Encoding
3. Define ? Unipolar Encoding
4. Define ? Bipolar Encoding
5. Define ? Manchester Encoding

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6. What are the two function of fast frequency hopping?
7. What is return to zero?
8. What is Non-return to zero?
9. What is the difference between source coding and line coding?
10. What are the properties of line coding?

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11. What is the effect of inter symbol interference?
12. How ISI can be reduced?
13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate

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16. Draw the NRZ and RZ code for the digital data 10110001.
17. Define ? Equalization
18. What is PRBS?
19. Write the Boolean expression for X-NOR gate.
20. Define ? Digital demodulation

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Viva - voce
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CYCLE 2 ? EXPERIMENTS

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Expt. No.8 ERROR CONTROL CODING USING MATLAB
Aim:
To write a program in MATLAB for error control coding techniques
Software required:
PC with MATLAB version 7.0 software installed

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Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments comon prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.

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4. A blank M ?file will appear with a title ?untitiled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the common window. If there is an error then with an alarm, type of error
will appear in red colour.

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7. Rectify the error if any go to debug menu select run.

Result:
Thus the error control coding techniques are executed using MATLAB programs.
Outcome:

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After the completion of this experiment the students will be able to simulate the different error control coding
schemes using MATLAB.
Applications :
1. Deep space communication
2. Satellite communication

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3. Data transmission
4. Data storage
5. Mobile communication
6. File transfer
7. digital audio/video transmission.

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1. What is the need for error control coding?
2. What is meant by linear code?

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3. What is meant by cyclic code?
4. Name some error control coding techniques.
5. Name the code which is used only for error detection.

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Viva - voce
52 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 9 DESIGN OF BPSK, QPSK, QAM USING MATLAB
Aim:

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To write a program in MATLAB for design of BPSK, QPSK and QAM
Software required:
PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.

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2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the

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program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error, if any go to debug menu select run.

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Result:
Thus the BPSK, QPSK and QAM were simulated using MATLAB.

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Outcome:
After the completion of this experiment the students will be able to simulate the various modulation schemes
such as BPSK, QPSK and QAM using MATLAB.
Applications:
QPSK

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1. Data transmission, mainly radio transmissions.
2. RTTY means radio teletype transmissions from amateur radio up to WiFi transmissions or Zigbees
QAM
1. Radio communications and data delivery applications.

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1. What is a correlator?
2. Define ? Constellation Diagram
3. What is BPSK ? Mention its significance.
4. Give the expression for bandwidth of BPSK scheme.

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5. What is QPSK mention its significance?
6. Give the expression for bandwidth of QPSK scheme.
7. Draw the constellation diagram of QPSK.
8. What is QAM ?
9. Give the expression for bandwidth of QAM scheme.

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10. What are the blocks in BPSK receiver?
11. What is the function of a decision device?
12. Draw the constellation diagram of QAM.
13. What are the types of QPSK?
14. What is the significance of Q-channel I channel in QPSK modulator?

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15. What is the minimum bandwidth requirement of QPSK?
16. Draw the output phase versus time relationship for a QPSK modulator.
17. Compare OQPSK with QPSK.
18. Identify the error in the matlab command Sin 3.
19. Draw the constellation diagram of QPSK.

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20. Give the applications of QPSK modulation scheme.
Viva - voce
FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
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DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious

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enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels

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? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

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To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

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? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical

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practices

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VISION
VISION
MISSION
MISSION
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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher

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education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth

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To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social

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context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics

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Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits

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d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness

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of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

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To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes

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? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing

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3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM

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8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise

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performance of communication system.

COURSE OBJECTIVES
COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS

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1 Signal sampling reconstruction
7
2 Time division multiplexing
13
3 AM modulation demodulation

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18
4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33

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6 Delta modulation demodulation
38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS

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8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB

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55
11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59

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ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:

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1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:

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Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be

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sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.

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A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is

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accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.

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2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

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Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal

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Sampled output
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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of

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continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission

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4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?

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3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.

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8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits

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13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?

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18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
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Expt. No. 2 TIME DIVISION MULTIPLEXING

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Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.

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3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears

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on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,

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(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.

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5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.

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8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .


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Circuit Diagram
Time division multiplexing

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TDM Trainer Kit

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Model Graph:

Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1

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2. Message Signal 2
3. TDM signal

Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.

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Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)

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or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).

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4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system


1. What is meant by multiplexing technique ?

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2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.

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7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce

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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after

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demodulating using AM receiver
Apparatus required:
.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.

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3 Diode ? 2 No.
4
AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.

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6 Patch cards ? 6 No.

Theory:

AMPLITUDE MODULATION

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Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct

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The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal

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VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100

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Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if
M < 1 Under modulation

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M = 1 Critical modulation
M > 1 over modulation

Procedure:
1. Give the modulating signal input to the Amplitude modulator.

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2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

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AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation

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Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.

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Applications:
1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?

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4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?

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9. What are the different types of AM generation?
10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce
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12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?

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16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.

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20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:

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To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver
Apparatus required:
.
1. Resistor ? 4 No.

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2. Capacitor ? 1 No.
3. Diode ? 2 No.
4.
AM transmitter Receiver
trainer kit ? 1 No.

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5. CRO ? 1 No.
6. Patch cards ? 6 No.

Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the

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instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used

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in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of

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noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

Procedure:
FM Modulator:

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1. Switch ON the Power supply.

2. Connect the sine wave generator output to frequency modulator input.

3. Select the low frequency carrier (or) high frequency carrier.

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4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

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6. Observe the frequency modulator output .

FM Demodulator:
A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

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2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

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4. Observe the Demodulated O/P compare with the original input.

B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

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2. Now set the DPDT switch in high frequency mode.

3. Connect the CRO input to Quadrature detector output.

4. Observe the Demodulated O/P and compare with the original input.

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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

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4. Observe the Demodulated O/P and then compare with the original input.

D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Ratio detector output.

4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram

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FM Modulator

FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

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Carrier

Modulated

Demodulated

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Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency
modulated and demodulated wave.

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Applications:
1. Television sound transmission
2. Two way mobile radio
3. Cellular Radio
4. Microwave

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5. Satellite Communication System


1. Define ? Frequency Modulation
2. How it is different from phase modulation?

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3. Write equation of FM wave, explain each parameter in it.
4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.
6. Define ? Modulation Index
7. Differentiate between Narrow band FM from Wide band FM.

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8. Draw message, carrier FM waves .
9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?
11. Give the practical applications of FM.
12. State advantages and disadvantages of FM.

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13. What is the range of speech signals?
14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation
17. Draw the phasor diagram of FM signal.

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18. What are the different types of FM generation?

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Viva - voce
32 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 5 PCM MODULATION & DEMODULATION

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Aim:
To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator
Apparatus Required:
1. PCM trainer kit ? 1 No.

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2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is
first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of

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converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization
can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization
the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel

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serially.
At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword
is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to

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Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks
for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:
1. Power on the PCM kit.

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2. Measure the frequency of sampling clock.
3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.

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5. Connect the clock to the timing control circuit.
6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.
9. Observe the waveform at the output of DAC.

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10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the
codeword graphically for a DC input.
Block diagram of PCM Transmission system

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34 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PCM Modulation and Demodulation Trainer kit

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35 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Model Graph:

Tabulation

Result:

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Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.
Outcome:
After the completion of this experiment the students will be able to design and construct the pulse code
modulated and demodulated wave.
Applications:

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1. Military Applications.
2. The PCM is used in the satellite transmission system.
SIGNALS AMPLITUDE (V) TIME PERIOD (s)
DC Input
Sampled Signal

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Clock Pulse
PCM Output
DC Output
36 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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3. It is used in space communication.
4. It is used in telephony.
5. The compact disc (CD) is a recent application of PCM.

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1. Define ? Modulation
2. State sampling theorem
3. Define ? Demodulation
4. Define ? Pulse Code Modulation
5. What is aliasing effect?

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6. What is quantization?
7. Define ? Bit Rate
8. Define ? Baud Rate
9. What are the advantages of PCM?
10. Define ? Signal to Noise Ratio

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11. What are the limitations of PCM?
12. What are the applications of PCM?
13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate

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16. What is multiplexing?
17. What is de-multiplexing?
18. What are the types of pulse modulation?
19. What should be the minimum bandwidth required to transmit a PCM channel?
20. What is the value of signal to noise ratio in PCM?

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Viva - voce
37 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 6 DELTA MODULATION & DEMODULATION
Aim:
To transmit an analog message signal in its digital form and reconstruct back the original analog message
signal at receiver by using Delta modulator
Apparatus required:

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1. DM and ADM Trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The

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difference signal between two successive samples is encoded into a single bit code. A present sample of the
analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level
(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.
The comparison of samples is accomplished by converting the digital to analog form then comparing with the
present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to

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a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.
Procedure:
1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.
2. Observe the modulated signal in the CRO.
3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.

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4. Also observe the DAC output on the CRO.
5. Change the amplitude of the modulating signal.
6. Observe the DAC output. Notice the slope overload distortion.
7. Keep the tuning knob to minimize distortion.
8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope

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overload distortion.
9. Calculate the sampling frequency required for no slope overload distortion.
10. Compare the calculated measured values of the sampling frequency.

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38 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Block Diagram Delta modulator and demodulator

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Delta Modulator

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Delta Demodulator

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Block diagram of Adaptive delta modulator and demodulator

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Adaptive Delta Modulator

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Adaptive Delta Demodulator

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40 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Delta Modulation and Adaptive Delta Modulator Trainer kit

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41 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Model Graph:

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42 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Tabulation 1
For Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)

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1 Modulating Signal
2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

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Tabulation 2
For Adaptive Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal
2 Carrier Signal

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3 Modulated Signal
4 Demodulated Signal

Result:
Thus the output waveforms of Delta modulation and adaptive delta modulation circuit were observed.

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Outcome:
After the completion of this experiment the students will be able to design and construct the delta modulation
adaptive delta modulation circuit.
Applications:
1. Digital voice storage

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2. Voice transmission
43 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

3. Radio communication devices such TV remotes.
4. Delta Modulation was used by Satellite Business Systems or SBS

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5. DM used in high resolution A/D and D/A converters.


1. What is delta modulation?
2. What is adaptive delta modulation?

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3. What are the advantages of adaptive delta modulation over delta modulation?
4. What is slope over load distortion?
5. What is granular noise effect?
6. What are the two limitations of delta modulation?
7. What is the function of integrator?

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8. What is comparator?
9. What is companding?
10. What is the advantage of delta modulation over pulse modulation?
11. Distinguish between DPCM and DM.
12. What are the different types of digital modulation?

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13. What is sampling rate?
14. Which kind of multiplexing used in digital communication?
15. Why is sample hold circuit used?
16. What are the advantages of digital transmission?
17. How is the performance corrupted in PCM?

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18. What are the different types of multiplexing?
19. What is aliasing effect?
20. How to avoid aliasing effect?

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Viva - voce
44 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 7 LINE CODING DECODING TECHNIQUES

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Aim:
To study different line coding techniques.
Apparatus required:
1. Line coding and decoding trainer kit ? 1 No.
2. Patch cords ? 6 No.

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3. CRO ? 1 No.

Theory:
Line coding refers to the process of representing the bit stream (1 ?s and 0 ?s) in the form of voltage or current
variations optimally tuned for the specific properties of the physical channel being used. The selection of a proper

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line code can help in many ways. One possibility is to aid in clock recovery at the receiver. A clock signal is
recovered by observing transitions in the received bit sequence, if enough transitions exist, a good recovery of
the clock is guaranteed, the signal is said to be self-clocking. Another advantage is to get rid of DC shifts. The
DC component in a line code is called the bias or the DC coefficient. Unfortunately, most long-distance
communication channels cannot transport a DC component. This is why most line codes try to eliminate the DC

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component before being transmitted on the channel. Such codes are called DC balanced, zero-DC, zero-bias, or
DC equalized. Some common types of line encoding in common-use nowadays are unipolar, polar, bipolar,
Manchester, MLT-3 Duo binary encoding.
Unipolar (Unipolar NRZ and Unipolar RZ):
Unipolar is the simplest line coding scheme. It has the advantage of being compatible with TTL logic. Unipolar

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coding uses a positive rectangular pulse p(t) to represent binary 1, the absence of a pulse (i.e., zero voltage) to
represent a binary 0. Two possibilities for the pulse p(t) exist3: Non-Return-to-Zero (NRZ) rectangular pulse
Return-to-Zero (RZ) rectangular pulse. The difference between Unipolar NRZ Unipolar RZ codes is that the
rectangular pulse in NRZ stays at a positive value (e.g., +5V) for the full duration of the logic 1 bit, while the pule
in RZ drops from +5V to 0V in the middle of the bit time.

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Procedure:
1. Connect the PRBS (test point P5) to various line coding formats. Obtain the coded output as per the
requirement.
2. Connect coded signal test point to corresponding decoding test point as inputs.
3. Set the SW1 as per the requirement.

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4. Set the potentiometer P1 in minimum position.
5. Switch ON the power supply. Press the switch SW2 once.
6. Display the encoded signal on one channel of CRO and decoded signal on second channel of CRO.

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46 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


Line coding decoding trainer kit

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Model Graph:

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48 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Tabulation
Sl. No. Type of Coding AMPLITUDE (V) Time period (s)
1. Unipolar data(NZ NRZ )

2. Unipolar data (NRZ RZ)

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3. Bipolar Data(NRZ AMI)
4. Manchester


Result:

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Thus the different line coding techniques was studied and verified.
Outcome:
After the completion of this experiment the students will be able to understand implement the different line
coding schemes.
Applications:

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1. DC balance
2. embedded clock applications
3. computing applications
4. Manchester codes are commonly used for local area networks
5. Bipolar codes are commonly used for local area networks

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49 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


1. What is line coding?

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2. Define ? Polar Encoding
3. Define ? Unipolar Encoding
4. Define ? Bipolar Encoding
5. Define ? Manchester Encoding
6. What are the two function of fast frequency hopping?

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7. What is return to zero?
8. What is Non-return to zero?
9. What is the difference between source coding and line coding?
10. What are the properties of line coding?
11. What is the effect of inter symbol interference?

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12. How ISI can be reduced?
13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate
16. Draw the NRZ and RZ code for the digital data 10110001.

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17. Define ? Equalization
18. What is PRBS?
19. Write the Boolean expression for X-NOR gate.
20. Define ? Digital demodulation

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Viva - voce
50 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

CYCLE 2 ? EXPERIMENTS
Expt. No.8 ERROR CONTROL CODING USING MATLAB

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Aim:
To write a program in MATLAB for error control coding techniques
Software required:
PC with MATLAB version 7.0 software installed
Procedure:

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1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments comon prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitiled?.

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5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the common window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the error control coding techniques are executed using MATLAB programs.
Outcome:
After the completion of this experiment the students will be able to simulate the different error control coding

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schemes using MATLAB.
Applications :
1. Deep space communication
2. Satellite communication
3. Data transmission

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4. Data storage
5. Mobile communication
6. File transfer
7. digital audio/video transmission.
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1. What is the need for error control coding?
2. What is meant by linear code?
3. What is meant by cyclic code?

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4. Name some error control coding techniques.
5. Name the code which is used only for error detection.

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Viva - voce

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52 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 9 DESIGN OF BPSK, QPSK, QAM USING MATLAB
Aim:
To write a program in MATLAB for design of BPSK, QPSK and QAM

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Software required:
PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.

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3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.

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6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error, if any go to debug menu select run.

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Result:
Thus the BPSK, QPSK and QAM were simulated using MATLAB.
Outcome:

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After the completion of this experiment the students will be able to simulate the various modulation schemes
such as BPSK, QPSK and QAM using MATLAB.
Applications:
QPSK
1. Data transmission, mainly radio transmissions.

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2. RTTY means radio teletype transmissions from amateur radio up to WiFi transmissions or Zigbees
QAM
1. Radio communications and data delivery applications.

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1. What is a correlator?
2. Define ? Constellation Diagram
3. What is BPSK ? Mention its significance.
4. Give the expression for bandwidth of BPSK scheme.
5. What is QPSK mention its significance?

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6. Give the expression for bandwidth of QPSK scheme.
7. Draw the constellation diagram of QPSK.
8. What is QAM ?
9. Give the expression for bandwidth of QAM scheme.
10. What are the blocks in BPSK receiver?

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11. What is the function of a decision device?
12. Draw the constellation diagram of QAM.
13. What are the types of QPSK?
14. What is the significance of Q-channel I channel in QPSK modulator?
15. What is the minimum bandwidth requirement of QPSK?

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16. Draw the output phase versus time relationship for a QPSK modulator.
17. Compare OQPSK with QPSK.
18. Identify the error in the matlab command Sin 3.
19. Draw the constellation diagram of QPSK.
20. Give the applications of QPSK modulation scheme.

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Viva - voce
54 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 10 DESIGN OF FSK, PSK, DPSK USING MATLAB
Aim:

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To write a program in MATLAB for design of FSK, PSK and DPSK
Software required:
PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.

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2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the

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program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the FSK, PSK and DPSK were simulated using MATLAB.
Outcome:

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After the completion of this experiment the students will be able to simulate the various modulation schemes
such as FSK, PSK and DPSK using MATLAB.
FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious

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enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels

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? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

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To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

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? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical

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practices

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VISION
VISION
MISSION
MISSION
3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher

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education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth

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To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social

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context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics

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Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits

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d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness

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of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

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To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes

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? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing

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3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM

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8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise

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performance of communication system.

COURSE OBJECTIVES
COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS

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1 Signal sampling reconstruction
7
2 Time division multiplexing
13
3 AM modulation demodulation

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18
4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33

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6 Delta modulation demodulation
38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS

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8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB

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55
11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59

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ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:

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1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:

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Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be

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sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.

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A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is

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accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.

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2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

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Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal

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Sampled output
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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of

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continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission

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4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?

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3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.

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8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits

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13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?

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18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
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Expt. No. 2 TIME DIVISION MULTIPLEXING

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Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.

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3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears

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on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,

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(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.

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5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.

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8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .


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Circuit Diagram
Time division multiplexing

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TDM Trainer Kit

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Model Graph:

Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1

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2. Message Signal 2
3. TDM signal

Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.

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Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)

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or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).

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4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system


1. What is meant by multiplexing technique ?

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2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.

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7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce

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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after

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demodulating using AM receiver
Apparatus required:
.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.

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3 Diode ? 2 No.
4
AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.

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6 Patch cards ? 6 No.

Theory:

AMPLITUDE MODULATION

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Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct

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The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal

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VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100

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Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if
M < 1 Under modulation

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M = 1 Critical modulation
M > 1 over modulation

Procedure:
1. Give the modulating signal input to the Amplitude modulator.

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2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

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AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation

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Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.

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Applications:
1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?

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4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?

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9. What are the different types of AM generation?
10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce
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12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?

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16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.

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20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:

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To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver
Apparatus required:
.
1. Resistor ? 4 No.

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2. Capacitor ? 1 No.
3. Diode ? 2 No.
4.
AM transmitter Receiver
trainer kit ? 1 No.

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5. CRO ? 1 No.
6. Patch cards ? 6 No.

Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the

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instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used

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in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of

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noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

Procedure:
FM Modulator:

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1. Switch ON the Power supply.

2. Connect the sine wave generator output to frequency modulator input.

3. Select the low frequency carrier (or) high frequency carrier.

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4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

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6. Observe the frequency modulator output .

FM Demodulator:
A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

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2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

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4. Observe the Demodulated O/P compare with the original input.

B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

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2. Now set the DPDT switch in high frequency mode.

3. Connect the CRO input to Quadrature detector output.

4. Observe the Demodulated O/P and compare with the original input.

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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

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4. Observe the Demodulated O/P and then compare with the original input.

D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Ratio detector output.

4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram

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FM Modulator

FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

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Carrier

Modulated

Demodulated

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Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency
modulated and demodulated wave.

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Applications:
1. Television sound transmission
2. Two way mobile radio
3. Cellular Radio
4. Microwave

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5. Satellite Communication System


1. Define ? Frequency Modulation
2. How it is different from phase modulation?

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3. Write equation of FM wave, explain each parameter in it.
4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.
6. Define ? Modulation Index
7. Differentiate between Narrow band FM from Wide band FM.

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8. Draw message, carrier FM waves .
9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?
11. Give the practical applications of FM.
12. State advantages and disadvantages of FM.

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13. What is the range of speech signals?
14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation
17. Draw the phasor diagram of FM signal.

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18. What are the different types of FM generation?

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Viva - voce
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Expt. No. 5 PCM MODULATION & DEMODULATION

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Aim:
To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator
Apparatus Required:
1. PCM trainer kit ? 1 No.

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2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is
first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of

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converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization
can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization
the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel

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serially.
At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword
is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to

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Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks
for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:
1. Power on the PCM kit.

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2. Measure the frequency of sampling clock.
3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.

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5. Connect the clock to the timing control circuit.
6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.
9. Observe the waveform at the output of DAC.

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10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the
codeword graphically for a DC input.
Block diagram of PCM Transmission system

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34 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PCM Modulation and Demodulation Trainer kit

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35 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Model Graph:

Tabulation

Result:

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Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.
Outcome:
After the completion of this experiment the students will be able to design and construct the pulse code
modulated and demodulated wave.
Applications:

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1. Military Applications.
2. The PCM is used in the satellite transmission system.
SIGNALS AMPLITUDE (V) TIME PERIOD (s)
DC Input
Sampled Signal

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Clock Pulse
PCM Output
DC Output
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3. It is used in space communication.
4. It is used in telephony.
5. The compact disc (CD) is a recent application of PCM.

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1. Define ? Modulation
2. State sampling theorem
3. Define ? Demodulation
4. Define ? Pulse Code Modulation
5. What is aliasing effect?

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6. What is quantization?
7. Define ? Bit Rate
8. Define ? Baud Rate
9. What are the advantages of PCM?
10. Define ? Signal to Noise Ratio

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11. What are the limitations of PCM?
12. What are the applications of PCM?
13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate

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16. What is multiplexing?
17. What is de-multiplexing?
18. What are the types of pulse modulation?
19. What should be the minimum bandwidth required to transmit a PCM channel?
20. What is the value of signal to noise ratio in PCM?

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Viva - voce
37 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 6 DELTA MODULATION & DEMODULATION
Aim:
To transmit an analog message signal in its digital form and reconstruct back the original analog message
signal at receiver by using Delta modulator
Apparatus required:

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1. DM and ADM Trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The

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difference signal between two successive samples is encoded into a single bit code. A present sample of the
analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level
(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.
The comparison of samples is accomplished by converting the digital to analog form then comparing with the
present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to

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a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.
Procedure:
1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.
2. Observe the modulated signal in the CRO.
3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.

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4. Also observe the DAC output on the CRO.
5. Change the amplitude of the modulating signal.
6. Observe the DAC output. Notice the slope overload distortion.
7. Keep the tuning knob to minimize distortion.
8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope

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overload distortion.
9. Calculate the sampling frequency required for no slope overload distortion.
10. Compare the calculated measured values of the sampling frequency.

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38 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Block Diagram Delta modulator and demodulator

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Delta Modulator

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Delta Demodulator

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Block diagram of Adaptive delta modulator and demodulator

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Adaptive Delta Modulator

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Adaptive Delta Demodulator

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40 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Delta Modulation and Adaptive Delta Modulator Trainer kit

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41 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Model Graph:

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42 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Tabulation 1
For Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)

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1 Modulating Signal
2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

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Tabulation 2
For Adaptive Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal
2 Carrier Signal

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3 Modulated Signal
4 Demodulated Signal

Result:
Thus the output waveforms of Delta modulation and adaptive delta modulation circuit were observed.

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Outcome:
After the completion of this experiment the students will be able to design and construct the delta modulation
adaptive delta modulation circuit.
Applications:
1. Digital voice storage

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2. Voice transmission
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3. Radio communication devices such TV remotes.
4. Delta Modulation was used by Satellite Business Systems or SBS

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5. DM used in high resolution A/D and D/A converters.


1. What is delta modulation?
2. What is adaptive delta modulation?

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3. What are the advantages of adaptive delta modulation over delta modulation?
4. What is slope over load distortion?
5. What is granular noise effect?
6. What are the two limitations of delta modulation?
7. What is the function of integrator?

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8. What is comparator?
9. What is companding?
10. What is the advantage of delta modulation over pulse modulation?
11. Distinguish between DPCM and DM.
12. What are the different types of digital modulation?

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13. What is sampling rate?
14. Which kind of multiplexing used in digital communication?
15. Why is sample hold circuit used?
16. What are the advantages of digital transmission?
17. How is the performance corrupted in PCM?

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18. What are the different types of multiplexing?
19. What is aliasing effect?
20. How to avoid aliasing effect?

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Viva - voce
44 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 7 LINE CODING DECODING TECHNIQUES

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Aim:
To study different line coding techniques.
Apparatus required:
1. Line coding and decoding trainer kit ? 1 No.
2. Patch cords ? 6 No.

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3. CRO ? 1 No.

Theory:
Line coding refers to the process of representing the bit stream (1 ?s and 0 ?s) in the form of voltage or current
variations optimally tuned for the specific properties of the physical channel being used. The selection of a proper

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line code can help in many ways. One possibility is to aid in clock recovery at the receiver. A clock signal is
recovered by observing transitions in the received bit sequence, if enough transitions exist, a good recovery of
the clock is guaranteed, the signal is said to be self-clocking. Another advantage is to get rid of DC shifts. The
DC component in a line code is called the bias or the DC coefficient. Unfortunately, most long-distance
communication channels cannot transport a DC component. This is why most line codes try to eliminate the DC

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component before being transmitted on the channel. Such codes are called DC balanced, zero-DC, zero-bias, or
DC equalized. Some common types of line encoding in common-use nowadays are unipolar, polar, bipolar,
Manchester, MLT-3 Duo binary encoding.
Unipolar (Unipolar NRZ and Unipolar RZ):
Unipolar is the simplest line coding scheme. It has the advantage of being compatible with TTL logic. Unipolar

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coding uses a positive rectangular pulse p(t) to represent binary 1, the absence of a pulse (i.e., zero voltage) to
represent a binary 0. Two possibilities for the pulse p(t) exist3: Non-Return-to-Zero (NRZ) rectangular pulse
Return-to-Zero (RZ) rectangular pulse. The difference between Unipolar NRZ Unipolar RZ codes is that the
rectangular pulse in NRZ stays at a positive value (e.g., +5V) for the full duration of the logic 1 bit, while the pule
in RZ drops from +5V to 0V in the middle of the bit time.

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Procedure:
1. Connect the PRBS (test point P5) to various line coding formats. Obtain the coded output as per the
requirement.
2. Connect coded signal test point to corresponding decoding test point as inputs.
3. Set the SW1 as per the requirement.

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4. Set the potentiometer P1 in minimum position.
5. Switch ON the power supply. Press the switch SW2 once.
6. Display the encoded signal on one channel of CRO and decoded signal on second channel of CRO.

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46 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


Line coding decoding trainer kit

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Model Graph:

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48 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Tabulation
Sl. No. Type of Coding AMPLITUDE (V) Time period (s)
1. Unipolar data(NZ NRZ )

2. Unipolar data (NRZ RZ)

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3. Bipolar Data(NRZ AMI)
4. Manchester


Result:

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Thus the different line coding techniques was studied and verified.
Outcome:
After the completion of this experiment the students will be able to understand implement the different line
coding schemes.
Applications:

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1. DC balance
2. embedded clock applications
3. computing applications
4. Manchester codes are commonly used for local area networks
5. Bipolar codes are commonly used for local area networks

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49 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


1. What is line coding?

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2. Define ? Polar Encoding
3. Define ? Unipolar Encoding
4. Define ? Bipolar Encoding
5. Define ? Manchester Encoding
6. What are the two function of fast frequency hopping?

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7. What is return to zero?
8. What is Non-return to zero?
9. What is the difference between source coding and line coding?
10. What are the properties of line coding?
11. What is the effect of inter symbol interference?

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12. How ISI can be reduced?
13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate
16. Draw the NRZ and RZ code for the digital data 10110001.

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17. Define ? Equalization
18. What is PRBS?
19. Write the Boolean expression for X-NOR gate.
20. Define ? Digital demodulation

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Viva - voce
50 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

CYCLE 2 ? EXPERIMENTS
Expt. No.8 ERROR CONTROL CODING USING MATLAB

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Aim:
To write a program in MATLAB for error control coding techniques
Software required:
PC with MATLAB version 7.0 software installed
Procedure:

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1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments comon prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitiled?.

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5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the common window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the error control coding techniques are executed using MATLAB programs.
Outcome:
After the completion of this experiment the students will be able to simulate the different error control coding

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schemes using MATLAB.
Applications :
1. Deep space communication
2. Satellite communication
3. Data transmission

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4. Data storage
5. Mobile communication
6. File transfer
7. digital audio/video transmission.
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1. What is the need for error control coding?
2. What is meant by linear code?
3. What is meant by cyclic code?

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4. Name some error control coding techniques.
5. Name the code which is used only for error detection.

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Viva - voce

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52 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 9 DESIGN OF BPSK, QPSK, QAM USING MATLAB
Aim:
To write a program in MATLAB for design of BPSK, QPSK and QAM

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Software required:
PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.

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3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.

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6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error, if any go to debug menu select run.

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53 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Result:
Thus the BPSK, QPSK and QAM were simulated using MATLAB.
Outcome:

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After the completion of this experiment the students will be able to simulate the various modulation schemes
such as BPSK, QPSK and QAM using MATLAB.
Applications:
QPSK
1. Data transmission, mainly radio transmissions.

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2. RTTY means radio teletype transmissions from amateur radio up to WiFi transmissions or Zigbees
QAM
1. Radio communications and data delivery applications.

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1. What is a correlator?
2. Define ? Constellation Diagram
3. What is BPSK ? Mention its significance.
4. Give the expression for bandwidth of BPSK scheme.
5. What is QPSK mention its significance?

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6. Give the expression for bandwidth of QPSK scheme.
7. Draw the constellation diagram of QPSK.
8. What is QAM ?
9. Give the expression for bandwidth of QAM scheme.
10. What are the blocks in BPSK receiver?

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11. What is the function of a decision device?
12. Draw the constellation diagram of QAM.
13. What are the types of QPSK?
14. What is the significance of Q-channel I channel in QPSK modulator?
15. What is the minimum bandwidth requirement of QPSK?

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16. Draw the output phase versus time relationship for a QPSK modulator.
17. Compare OQPSK with QPSK.
18. Identify the error in the matlab command Sin 3.
19. Draw the constellation diagram of QPSK.
20. Give the applications of QPSK modulation scheme.

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Viva - voce
54 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 10 DESIGN OF FSK, PSK, DPSK USING MATLAB
Aim:

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To write a program in MATLAB for design of FSK, PSK and DPSK
Software required:
PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.

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2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the

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program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the FSK, PSK and DPSK were simulated using MATLAB.
Outcome:

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After the completion of this experiment the students will be able to simulate the various modulation schemes
such as FSK, PSK and DPSK using MATLAB.
55 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Applications:

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ASK:
1. ASK is used to transmit digital data over optical fiber
PSK:
1. over voice lines
2. in high-freq. radio transmissions.

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1. What is FSK? Mention its significance.
2. What is PSK? Mention its significance.
3. What is DPSK? Mention its significance.

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4. What are the applications of DPSK?
5. Give the equation for average probability of symbol error for DPSK.
6. List the operations performed in DPSK transmitter.
7. Compare DPSK with QPSK modulation scheme.
8. What is differential encoding technique?

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9. Why do we make 180 degree phase shift in PSK why not 90 or 270?
10. What is the function of a decision device?
11. What is RZ?
12. What is NRZ?
13. What is Manchester encoding?

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14. Sketch the FSK waveform for the input a) 1010110 b) 1100101
15. Define modulation index.
16. Write a MATLAB program for generating PN sequence.
17. Differentiate coherent with non-coherent FSK.
18. Give the expression for bandwidth of FSK scheme.

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19. What is the difference between PSK and FSK?
20. What is the major advantage of coherent PSK over coherent ASK?

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Viva - voce
FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious

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enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels

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? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

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To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

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? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical

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practices

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VISION
VISION
MISSION
MISSION
3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher

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education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth

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To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social

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context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics

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Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits

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d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness

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of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 - COMMUNICATION SYSTEMS LABORATORY

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To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes

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? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing

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3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM

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8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise

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performance of communication system.

COURSE OBJECTIVES
COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS

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1 Signal sampling reconstruction
7
2 Time division multiplexing
13
3 AM modulation demodulation

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18
4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33

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6 Delta modulation demodulation
38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS

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8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB

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55
11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59

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ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:

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1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:

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Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be

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sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.

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A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is

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accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.

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2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

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Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal

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Sampled output
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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of

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continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission

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4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?

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3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.

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8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits

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13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?

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18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
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Expt. No. 2 TIME DIVISION MULTIPLEXING

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Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.

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3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears

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on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,

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(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.

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5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.

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8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .


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Circuit Diagram
Time division multiplexing

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TDM Trainer Kit

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Model Graph:

Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1

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2. Message Signal 2
3. TDM signal

Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.

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Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)

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or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).

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4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system


1. What is meant by multiplexing technique ?

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2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.

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7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce

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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after

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demodulating using AM receiver
Apparatus required:
.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.

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3 Diode ? 2 No.
4
AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.

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6 Patch cards ? 6 No.

Theory:

AMPLITUDE MODULATION

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Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct

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The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal

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VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100

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Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if
M < 1 Under modulation

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M = 1 Critical modulation
M > 1 over modulation

Procedure:
1. Give the modulating signal input to the Amplitude modulator.

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2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

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AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation

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Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.

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Applications:
1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?

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4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?

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9. What are the different types of AM generation?
10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce
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12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?

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16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.

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20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:

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To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver
Apparatus required:
.
1. Resistor ? 4 No.

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2. Capacitor ? 1 No.
3. Diode ? 2 No.
4.
AM transmitter Receiver
trainer kit ? 1 No.

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5. CRO ? 1 No.
6. Patch cards ? 6 No.

Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the

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instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used

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in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of

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noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

Procedure:
FM Modulator:

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1. Switch ON the Power supply.

2. Connect the sine wave generator output to frequency modulator input.

3. Select the low frequency carrier (or) high frequency carrier.

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4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

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6. Observe the frequency modulator output .

FM Demodulator:
A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

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2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

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4. Observe the Demodulated O/P compare with the original input.

B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

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2. Now set the DPDT switch in high frequency mode.

3. Connect the CRO input to Quadrature detector output.

4. Observe the Demodulated O/P and compare with the original input.

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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

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4. Observe the Demodulated O/P and then compare with the original input.

D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Ratio detector output.

4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram

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FM Modulator

FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

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Carrier

Modulated

Demodulated

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Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency
modulated and demodulated wave.

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Applications:
1. Television sound transmission
2. Two way mobile radio
3. Cellular Radio
4. Microwave

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5. Satellite Communication System


1. Define ? Frequency Modulation
2. How it is different from phase modulation?

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3. Write equation of FM wave, explain each parameter in it.
4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.
6. Define ? Modulation Index
7. Differentiate between Narrow band FM from Wide band FM.

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8. Draw message, carrier FM waves .
9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?
11. Give the practical applications of FM.
12. State advantages and disadvantages of FM.

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13. What is the range of speech signals?
14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation
17. Draw the phasor diagram of FM signal.

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18. What are the different types of FM generation?

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Viva - voce
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Expt. No. 5 PCM MODULATION & DEMODULATION

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Aim:
To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator
Apparatus Required:
1. PCM trainer kit ? 1 No.

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2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is
first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of

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converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization
can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization
the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel

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serially.
At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword
is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to

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Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks
for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:
1. Power on the PCM kit.

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2. Measure the frequency of sampling clock.
3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.

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5. Connect the clock to the timing control circuit.
6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.
9. Observe the waveform at the output of DAC.

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10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the
codeword graphically for a DC input.
Block diagram of PCM Transmission system

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PCM Modulation and Demodulation Trainer kit

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Model Graph:

Tabulation

Result:

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Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.
Outcome:
After the completion of this experiment the students will be able to design and construct the pulse code
modulated and demodulated wave.
Applications:

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1. Military Applications.
2. The PCM is used in the satellite transmission system.
SIGNALS AMPLITUDE (V) TIME PERIOD (s)
DC Input
Sampled Signal

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Clock Pulse
PCM Output
DC Output
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3. It is used in space communication.
4. It is used in telephony.
5. The compact disc (CD) is a recent application of PCM.

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1. Define ? Modulation
2. State sampling theorem
3. Define ? Demodulation
4. Define ? Pulse Code Modulation
5. What is aliasing effect?

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6. What is quantization?
7. Define ? Bit Rate
8. Define ? Baud Rate
9. What are the advantages of PCM?
10. Define ? Signal to Noise Ratio

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11. What are the limitations of PCM?
12. What are the applications of PCM?
13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate

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16. What is multiplexing?
17. What is de-multiplexing?
18. What are the types of pulse modulation?
19. What should be the minimum bandwidth required to transmit a PCM channel?
20. What is the value of signal to noise ratio in PCM?

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Viva - voce
37 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 6 DELTA MODULATION & DEMODULATION
Aim:
To transmit an analog message signal in its digital form and reconstruct back the original analog message
signal at receiver by using Delta modulator
Apparatus required:

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1. DM and ADM Trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The

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difference signal between two successive samples is encoded into a single bit code. A present sample of the
analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level
(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.
The comparison of samples is accomplished by converting the digital to analog form then comparing with the
present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to

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a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.
Procedure:
1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.
2. Observe the modulated signal in the CRO.
3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.

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4. Also observe the DAC output on the CRO.
5. Change the amplitude of the modulating signal.
6. Observe the DAC output. Notice the slope overload distortion.
7. Keep the tuning knob to minimize distortion.
8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope

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overload distortion.
9. Calculate the sampling frequency required for no slope overload distortion.
10. Compare the calculated measured values of the sampling frequency.

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38 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Block Diagram Delta modulator and demodulator

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Delta Modulator

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Delta Demodulator

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39 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Block diagram of Adaptive delta modulator and demodulator

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Adaptive Delta Modulator

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Adaptive Delta Demodulator

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40 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Delta Modulation and Adaptive Delta Modulator Trainer kit

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41 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Model Graph:

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42 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Tabulation 1
For Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)

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1 Modulating Signal
2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

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Tabulation 2
For Adaptive Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal
2 Carrier Signal

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3 Modulated Signal
4 Demodulated Signal

Result:
Thus the output waveforms of Delta modulation and adaptive delta modulation circuit were observed.

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Outcome:
After the completion of this experiment the students will be able to design and construct the delta modulation
adaptive delta modulation circuit.
Applications:
1. Digital voice storage

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2. Voice transmission
43 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

3. Radio communication devices such TV remotes.
4. Delta Modulation was used by Satellite Business Systems or SBS

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5. DM used in high resolution A/D and D/A converters.


1. What is delta modulation?
2. What is adaptive delta modulation?

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3. What are the advantages of adaptive delta modulation over delta modulation?
4. What is slope over load distortion?
5. What is granular noise effect?
6. What are the two limitations of delta modulation?
7. What is the function of integrator?

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8. What is comparator?
9. What is companding?
10. What is the advantage of delta modulation over pulse modulation?
11. Distinguish between DPCM and DM.
12. What are the different types of digital modulation?

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13. What is sampling rate?
14. Which kind of multiplexing used in digital communication?
15. Why is sample hold circuit used?
16. What are the advantages of digital transmission?
17. How is the performance corrupted in PCM?

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18. What are the different types of multiplexing?
19. What is aliasing effect?
20. How to avoid aliasing effect?

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Viva - voce
44 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 7 LINE CODING DECODING TECHNIQUES

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Aim:
To study different line coding techniques.
Apparatus required:
1. Line coding and decoding trainer kit ? 1 No.
2. Patch cords ? 6 No.

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3. CRO ? 1 No.

Theory:
Line coding refers to the process of representing the bit stream (1 ?s and 0 ?s) in the form of voltage or current
variations optimally tuned for the specific properties of the physical channel being used. The selection of a proper

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line code can help in many ways. One possibility is to aid in clock recovery at the receiver. A clock signal is
recovered by observing transitions in the received bit sequence, if enough transitions exist, a good recovery of
the clock is guaranteed, the signal is said to be self-clocking. Another advantage is to get rid of DC shifts. The
DC component in a line code is called the bias or the DC coefficient. Unfortunately, most long-distance
communication channels cannot transport a DC component. This is why most line codes try to eliminate the DC

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component before being transmitted on the channel. Such codes are called DC balanced, zero-DC, zero-bias, or
DC equalized. Some common types of line encoding in common-use nowadays are unipolar, polar, bipolar,
Manchester, MLT-3 Duo binary encoding.
Unipolar (Unipolar NRZ and Unipolar RZ):
Unipolar is the simplest line coding scheme. It has the advantage of being compatible with TTL logic. Unipolar

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coding uses a positive rectangular pulse p(t) to represent binary 1, the absence of a pulse (i.e., zero voltage) to
represent a binary 0. Two possibilities for the pulse p(t) exist3: Non-Return-to-Zero (NRZ) rectangular pulse
Return-to-Zero (RZ) rectangular pulse. The difference between Unipolar NRZ Unipolar RZ codes is that the
rectangular pulse in NRZ stays at a positive value (e.g., +5V) for the full duration of the logic 1 bit, while the pule
in RZ drops from +5V to 0V in the middle of the bit time.

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45 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Procedure:
1. Connect the PRBS (test point P5) to various line coding formats. Obtain the coded output as per the
requirement.
2. Connect coded signal test point to corresponding decoding test point as inputs.
3. Set the SW1 as per the requirement.

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4. Set the potentiometer P1 in minimum position.
5. Switch ON the power supply. Press the switch SW2 once.
6. Display the encoded signal on one channel of CRO and decoded signal on second channel of CRO.

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46 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


Line coding decoding trainer kit

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Model Graph:

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48 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Tabulation
Sl. No. Type of Coding AMPLITUDE (V) Time period (s)
1. Unipolar data(NZ NRZ )

2. Unipolar data (NRZ RZ)

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3. Bipolar Data(NRZ AMI)
4. Manchester


Result:

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Thus the different line coding techniques was studied and verified.
Outcome:
After the completion of this experiment the students will be able to understand implement the different line
coding schemes.
Applications:

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1. DC balance
2. embedded clock applications
3. computing applications
4. Manchester codes are commonly used for local area networks
5. Bipolar codes are commonly used for local area networks

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49 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


1. What is line coding?

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2. Define ? Polar Encoding
3. Define ? Unipolar Encoding
4. Define ? Bipolar Encoding
5. Define ? Manchester Encoding
6. What are the two function of fast frequency hopping?

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7. What is return to zero?
8. What is Non-return to zero?
9. What is the difference between source coding and line coding?
10. What are the properties of line coding?
11. What is the effect of inter symbol interference?

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12. How ISI can be reduced?
13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate
16. Draw the NRZ and RZ code for the digital data 10110001.

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17. Define ? Equalization
18. What is PRBS?
19. Write the Boolean expression for X-NOR gate.
20. Define ? Digital demodulation

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Viva - voce
50 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

CYCLE 2 ? EXPERIMENTS
Expt. No.8 ERROR CONTROL CODING USING MATLAB

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Aim:
To write a program in MATLAB for error control coding techniques
Software required:
PC with MATLAB version 7.0 software installed
Procedure:

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1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments comon prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitiled?.

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5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the common window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the error control coding techniques are executed using MATLAB programs.
Outcome:
After the completion of this experiment the students will be able to simulate the different error control coding

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schemes using MATLAB.
Applications :
1. Deep space communication
2. Satellite communication
3. Data transmission

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4. Data storage
5. Mobile communication
6. File transfer
7. digital audio/video transmission.
51 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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1. What is the need for error control coding?
2. What is meant by linear code?
3. What is meant by cyclic code?

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4. Name some error control coding techniques.
5. Name the code which is used only for error detection.

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Viva - voce

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52 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 9 DESIGN OF BPSK, QPSK, QAM USING MATLAB
Aim:
To write a program in MATLAB for design of BPSK, QPSK and QAM

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Software required:
PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.

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3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.

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6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error, if any go to debug menu select run.

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53 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Result:
Thus the BPSK, QPSK and QAM were simulated using MATLAB.
Outcome:

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After the completion of this experiment the students will be able to simulate the various modulation schemes
such as BPSK, QPSK and QAM using MATLAB.
Applications:
QPSK
1. Data transmission, mainly radio transmissions.

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2. RTTY means radio teletype transmissions from amateur radio up to WiFi transmissions or Zigbees
QAM
1. Radio communications and data delivery applications.

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1. What is a correlator?
2. Define ? Constellation Diagram
3. What is BPSK ? Mention its significance.
4. Give the expression for bandwidth of BPSK scheme.
5. What is QPSK mention its significance?

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6. Give the expression for bandwidth of QPSK scheme.
7. Draw the constellation diagram of QPSK.
8. What is QAM ?
9. Give the expression for bandwidth of QAM scheme.
10. What are the blocks in BPSK receiver?

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11. What is the function of a decision device?
12. Draw the constellation diagram of QAM.
13. What are the types of QPSK?
14. What is the significance of Q-channel I channel in QPSK modulator?
15. What is the minimum bandwidth requirement of QPSK?

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16. Draw the output phase versus time relationship for a QPSK modulator.
17. Compare OQPSK with QPSK.
18. Identify the error in the matlab command Sin 3.
19. Draw the constellation diagram of QPSK.
20. Give the applications of QPSK modulation scheme.

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Viva - voce
54 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 10 DESIGN OF FSK, PSK, DPSK USING MATLAB
Aim:

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To write a program in MATLAB for design of FSK, PSK and DPSK
Software required:
PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.

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2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the

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program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the FSK, PSK and DPSK were simulated using MATLAB.
Outcome:

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After the completion of this experiment the students will be able to simulate the various modulation schemes
such as FSK, PSK and DPSK using MATLAB.
55 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Applications:

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ASK:
1. ASK is used to transmit digital data over optical fiber
PSK:
1. over voice lines
2. in high-freq. radio transmissions.

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1. What is FSK? Mention its significance.
2. What is PSK? Mention its significance.
3. What is DPSK? Mention its significance.

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4. What are the applications of DPSK?
5. Give the equation for average probability of symbol error for DPSK.
6. List the operations performed in DPSK transmitter.
7. Compare DPSK with QPSK modulation scheme.
8. What is differential encoding technique?

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9. Why do we make 180 degree phase shift in PSK why not 90 or 270?
10. What is the function of a decision device?
11. What is RZ?
12. What is NRZ?
13. What is Manchester encoding?

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14. Sketch the FSK waveform for the input a) 1010110 b) 1100101
15. Define modulation index.
16. Write a MATLAB program for generating PN sequence.
17. Differentiate coherent with non-coherent FSK.
18. Give the expression for bandwidth of FSK scheme.

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19. What is the difference between PSK and FSK?
20. What is the major advantage of coherent PSK over coherent ASK?

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Viva - voce
56 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

sExpt. No. 11 COMMUNICATION LINK SIMULATION USING

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MATLAB
Aim:
To simulate the basic communication link using mat lab
Software required:
PC with MATLAB version 7.0 software installed

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Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.

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4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.

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7. Rectify the error if any go to debug menu select run.



Result:

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Thus the communication link simulation was designed using MATLAB.
Outcome:
After the completion of this experiment the students will be able to simulate and design the communication link
using MATLAB.

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FirstRanker.com - FirstRanker's Choice

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1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

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V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________

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Section : _______________________________________

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LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

DHANALAKSHMI

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College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

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? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

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To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

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? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in

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communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION
VISION
MISSION

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MISSION
3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals

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To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge

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training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism

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To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,

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through commitment lifelong learning needed for successful professional career

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4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability

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c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities

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g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning

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k) To participate succeed in competitive exams

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5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation

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? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS

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1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation

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6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)

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11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)


Simulate end-to-end Communication Link

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Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

COURSE OBJECTIVES

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COURSE OUTCOMES
6 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS

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Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7
2 Time division multiplexing

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13
3 AM modulation demodulation
18
4 Frequency modulation demodulation
26

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5 PCM modulation demodulation
33
6 Delta modulation demodulation
38
7 Line coding decoding techniques

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45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB

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53
10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB
57

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12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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7 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:

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To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.

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4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.

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A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the

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signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals

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The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.

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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.

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Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.

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5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

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Model Graph:

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Tabulation

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Analog signal sampling and reconstruction trainer kit


Result:

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Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.


Signal Amplitude (V) Time period (s)

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Message signal
Carrier signal
Sampled output
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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)

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2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

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1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?

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6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?

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11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?

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16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.

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21. Define ? Natural Sampling


Viva - voce
12 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:

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1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:

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Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.

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2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.

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4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .

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7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .

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Circuit Diagram
Time division multiplexing

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TDM Trainer Kit

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Model Graph:

Tabulation

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Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1
2. Message Signal 2
3. TDM signal

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Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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Applications:

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1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.

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3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system

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1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?

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5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?

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10. Which type of modulation technique will be used in TDM?

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Viva - voce
17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 3 AM MODULATION & DEMODULATION

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Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver
Apparatus required:
.

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1 Resistor ? 4 No.
2 Capacitor ? 1 No.
3 Diode ? 2 No.
4
AM transmitter receiver

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trainer kit ? 1 No.
5 CRO ? 1 No.
6 Patch cards ? 6 No.

Theory:

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AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by

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Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

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The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal

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Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude

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if
M < 1 Under modulation
M = 1 Critical modulation
M > 1 over modulation

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Procedure:
1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .

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5. Calculate the modulation index

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Circuit Diagram

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AM Modulation


AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

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Carrier

Modulated

Demodulated

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Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:

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After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.
Applications:
1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.

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3. Facsimile transmission



1. What is modulation and demodulation?

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2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?

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7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?
9. What are the different types of AM generation?
10. Define ? Modulation Index
11. What are different types of analog modulation techniques?

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Viva - voce
24 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.

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14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?

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18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.

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23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver
Apparatus required:

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.
1. Resistor ? 4 No.
2. Capacitor ? 1 No.
3. Diode ? 2 No.
4.

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AM transmitter Receiver
trainer kit ? 1 No.
5. CRO ? 1 No.
6. Patch cards ? 6 No.

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Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the
instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF

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radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used
in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.

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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of

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frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of
noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

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Procedure:
FM Modulator:
1. Switch ON the Power supply.

2. Connect the sine wave generator output to frequency modulator input.

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3. Select the low frequency carrier (or) high frequency carrier.

4. Connect the CRO input to the frequency modulator output.

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5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

6. Observe the frequency modulator output .

FM Demodulator:

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A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

2. Now set the DPDT switch in low frequency mode.

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3. Connect CRO input to PLL detector output.

4. Observe the Demodulated O/P compare with the original input.

B) Quadrature Detector

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1. Connect the frequency modulated output to Quadrature detector input.

2. Now set the DPDT switch in high frequency mode.

3. Connect the CRO input to Quadrature detector output.

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4. Observe the Demodulated O/P and compare with the original input.
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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

2. Set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Phase discriminator output.

4. Observe the Demodulated O/P and then compare with the original input.

D) Ratio Detector

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1. Connect the frequency modulated output to Ratio detector input.

2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Ratio detector output.

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4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram
FM Modulator

FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:


Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)

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Message

Carrier

Modulated

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Demodulated


Result:

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Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:

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After the completion of this experiment the students will be able to design and construct the frequency
modulated and demodulated wave.
Applications:
1. Television sound transmission
2. Two way mobile radio

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3. Cellular Radio
4. Microwave
5. Satellite Communication System

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1. Define ? Frequency Modulation
2. How it is different from phase modulation?
3. Write equation of FM wave, explain each parameter in it.
4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.

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6. Define ? Modulation Index
7. Differentiate between Narrow band FM from Wide band FM.
8. Draw message, carrier FM waves .
9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?

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11. Give the practical applications of FM.
12. State advantages and disadvantages of FM.
13. What is the range of speech signals?
14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?

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16. Define ? Phase Modulation
17. Draw the phasor diagram of FM signal.
18. What are the different types of FM generation?

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Viva - voce
32 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 5 PCM MODULATION & DEMODULATION

Aim:
To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator

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Apparatus Required:
1. PCM trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:

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Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is
first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of
converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization
can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are

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given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization
the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel
serially.
At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.

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In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword
is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to
Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks
for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.

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Procedure:
1. Power on the PCM kit.
2. Measure the frequency of sampling clock.
3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.
5. Connect the clock to the timing control circuit.
6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.

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8. Now apply the AC modulating signal at the input.
9. Observe the waveform at the output of DAC.
10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the
codeword graphically for a DC input.
Block diagram of PCM Transmission system

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34 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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PCM Modulation and Demodulation Trainer kit

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35 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Model Graph:

Tabulation

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Result:
Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.
Outcome:
After the completion of this experiment the students will be able to design and construct the pulse code

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modulated and demodulated wave.
Applications:
1. Military Applications.
2. The PCM is used in the satellite transmission system.
SIGNALS AMPLITUDE (V) TIME PERIOD (s)

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DC Input
Sampled Signal
Clock Pulse
PCM Output
DC Output

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3. It is used in space communication.
4. It is used in telephony.
5. The compact disc (CD) is a recent application of PCM.

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1. Define ? Modulation
2. State sampling theorem
3. Define ? Demodulation

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4. Define ? Pulse Code Modulation
5. What is aliasing effect?
6. What is quantization?
7. Define ? Bit Rate
8. Define ? Baud Rate

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9. What are the advantages of PCM?
10. Define ? Signal to Noise Ratio
11. What are the limitations of PCM?
12. What are the applications of PCM?
13. Define ? Encoding

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14. Define ? Decoding
15. Define ? Nyquist Rate
16. What is multiplexing?
17. What is de-multiplexing?
18. What are the types of pulse modulation?

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19. What should be the minimum bandwidth required to transmit a PCM channel?
20. What is the value of signal to noise ratio in PCM?

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Viva - voce

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37 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 6 DELTA MODULATION & DEMODULATION
Aim:
To transmit an analog message signal in its digital form and reconstruct back the original analog message

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signal at receiver by using Delta modulator
Apparatus required:
1. DM and ADM Trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.

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Theory:
Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The
difference signal between two successive samples is encoded into a single bit code. A present sample of the
analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level
(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.

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The comparison of samples is accomplished by converting the digital to analog form then comparing with the
present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to
a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.
Procedure:
1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.

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2. Observe the modulated signal in the CRO.
3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.
4. Also observe the DAC output on the CRO.
5. Change the amplitude of the modulating signal.
6. Observe the DAC output. Notice the slope overload distortion.

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7. Keep the tuning knob to minimize distortion.
8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope
overload distortion.
9. Calculate the sampling frequency required for no slope overload distortion.
10. Compare the calculated measured values of the sampling frequency.

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38 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Block Diagram Delta modulator and demodulator

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Delta Modulator

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Delta Demodulator

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39 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


Block diagram of Adaptive delta modulator and demodulator

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Adaptive Delta Modulator

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Adaptive Delta Demodulator

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40 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Delta Modulation and Adaptive Delta Modulator Trainer kit

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41 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Model Graph:

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42 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Tabulation 1

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For Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal
2 Carrier Signal
3 Modulated Signal

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4 Demodulated Signal

Tabulation 2
For Adaptive Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)

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1 Modulating Signal
2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

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Result:
Thus the output waveforms of Delta modulation and adaptive delta modulation circuit were observed.
Outcome:
After the completion of this experiment the students will be able to design and construct the delta modulation
adaptive delta modulation circuit.

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Applications:
1. Digital voice storage
2. Voice transmission
43 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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3. Radio communication devices such TV remotes.
4. Delta Modulation was used by Satellite Business Systems or SBS
5. DM used in high resolution A/D and D/A converters.

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1. What is delta modulation?
2. What is adaptive delta modulation?
3. What are the advantages of adaptive delta modulation over delta modulation?
4. What is slope over load distortion?
5. What is granular noise effect?

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6. What are the two limitations of delta modulation?
7. What is the function of integrator?
8. What is comparator?
9. What is companding?
10. What is the advantage of delta modulation over pulse modulation?

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11. Distinguish between DPCM and DM.
12. What are the different types of digital modulation?
13. What is sampling rate?
14. Which kind of multiplexing used in digital communication?
15. Why is sample hold circuit used?

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16. What are the advantages of digital transmission?
17. How is the performance corrupted in PCM?
18. What are the different types of multiplexing?
19. What is aliasing effect?
20. How to avoid aliasing effect?

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Viva - voce
44 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 7 LINE CODING DECODING TECHNIQUES

Aim:
To study different line coding techniques.
Apparatus required:

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1. Line coding and decoding trainer kit ? 1 No.
2. Patch cords ? 6 No.
3. CRO ? 1 No.

Theory:

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Line coding refers to the process of representing the bit stream (1 ?s and 0 ?s) in the form of voltage or current
variations optimally tuned for the specific properties of the physical channel being used. The selection of a proper
line code can help in many ways. One possibility is to aid in clock recovery at the receiver. A clock signal is
recovered by observing transitions in the received bit sequence, if enough transitions exist, a good recovery of
the clock is guaranteed, the signal is said to be self-clocking. Another advantage is to get rid of DC shifts. The

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DC component in a line code is called the bias or the DC coefficient. Unfortunately, most long-distance
communication channels cannot transport a DC component. This is why most line codes try to eliminate the DC
component before being transmitted on the channel. Such codes are called DC balanced, zero-DC, zero-bias, or
DC equalized. Some common types of line encoding in common-use nowadays are unipolar, polar, bipolar,
Manchester, MLT-3 Duo binary encoding.

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Unipolar (Unipolar NRZ and Unipolar RZ):
Unipolar is the simplest line coding scheme. It has the advantage of being compatible with TTL logic. Unipolar
coding uses a positive rectangular pulse p(t) to represent binary 1, the absence of a pulse (i.e., zero voltage) to
represent a binary 0. Two possibilities for the pulse p(t) exist3: Non-Return-to-Zero (NRZ) rectangular pulse
Return-to-Zero (RZ) rectangular pulse. The difference between Unipolar NRZ Unipolar RZ codes is that the

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rectangular pulse in NRZ stays at a positive value (e.g., +5V) for the full duration of the logic 1 bit, while the pule
in RZ drops from +5V to 0V in the middle of the bit time.

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Procedure:
1. Connect the PRBS (test point P5) to various line coding formats. Obtain the coded output as per the
requirement.

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2. Connect coded signal test point to corresponding decoding test point as inputs.
3. Set the SW1 as per the requirement.
4. Set the potentiometer P1 in minimum position.
5. Switch ON the power supply. Press the switch SW2 once.
6. Display the encoded signal on one channel of CRO and decoded signal on second channel of CRO.

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46 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Line coding decoding trainer kit

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Model Graph:

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48 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Tabulation
Sl. No. Type of Coding AMPLITUDE (V) Time period (s)
1. Unipolar data(NZ NRZ )

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2. Unipolar data (NRZ RZ)
3. Bipolar Data(NRZ AMI)
4. Manchester

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Result:
Thus the different line coding techniques was studied and verified.
Outcome:
After the completion of this experiment the students will be able to understand implement the different line

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coding schemes.
Applications:
1. DC balance
2. embedded clock applications
3. computing applications

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4. Manchester codes are commonly used for local area networks
5. Bipolar codes are commonly used for local area networks

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49 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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1. What is line coding?
2. Define ? Polar Encoding
3. Define ? Unipolar Encoding
4. Define ? Bipolar Encoding

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5. Define ? Manchester Encoding
6. What are the two function of fast frequency hopping?
7. What is return to zero?
8. What is Non-return to zero?
9. What is the difference between source coding and line coding?

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10. What are the properties of line coding?
11. What is the effect of inter symbol interference?
12. How ISI can be reduced?
13. Define ? Encoding
14. Define ? Decoding

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15. Define ? Nyquist Rate
16. Draw the NRZ and RZ code for the digital data 10110001.
17. Define ? Equalization
18. What is PRBS?
19. Write the Boolean expression for X-NOR gate.

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20. Define ? Digital demodulation

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Viva - voce
50 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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CYCLE 2 ? EXPERIMENTS
Expt. No.8 ERROR CONTROL CODING USING MATLAB
Aim:
To write a program in MATLAB for error control coding techniques
Software required:

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PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments comon prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper

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icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitiled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the common window. If there is an error then with an alarm, type of error

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will appear in red colour.
7. Rectify the error if any go to debug menu select run.

Result:
Thus the error control coding techniques are executed using MATLAB programs.

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Outcome:
After the completion of this experiment the students will be able to simulate the different error control coding
schemes using MATLAB.
Applications :
1. Deep space communication

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2. Satellite communication
3. Data transmission
4. Data storage
5. Mobile communication
6. File transfer

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7. digital audio/video transmission.
51 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


1. What is the need for error control coding?

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2. What is meant by linear code?
3. What is meant by cyclic code?
4. Name some error control coding techniques.
5. Name the code which is used only for error detection.

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Viva - voce
52 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 9 DESIGN OF BPSK, QPSK, QAM USING MATLAB

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Aim:
To write a program in MATLAB for design of BPSK, QPSK and QAM
Software required:
PC with MATLAB version 7.0 software installed
Procedure:

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1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.

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5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error, if any go to debug menu select run.

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Result:

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Thus the BPSK, QPSK and QAM were simulated using MATLAB.
Outcome:
After the completion of this experiment the students will be able to simulate the various modulation schemes
such as BPSK, QPSK and QAM using MATLAB.
Applications:

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QPSK
1. Data transmission, mainly radio transmissions.
2. RTTY means radio teletype transmissions from amateur radio up to WiFi transmissions or Zigbees
QAM
1. Radio communications and data delivery applications.

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1. What is a correlator?
2. Define ? Constellation Diagram
3. What is BPSK ? Mention its significance.

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4. Give the expression for bandwidth of BPSK scheme.
5. What is QPSK mention its significance?
6. Give the expression for bandwidth of QPSK scheme.
7. Draw the constellation diagram of QPSK.
8. What is QAM ?

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9. Give the expression for bandwidth of QAM scheme.
10. What are the blocks in BPSK receiver?
11. What is the function of a decision device?
12. Draw the constellation diagram of QAM.
13. What are the types of QPSK?

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14. What is the significance of Q-channel I channel in QPSK modulator?
15. What is the minimum bandwidth requirement of QPSK?
16. Draw the output phase versus time relationship for a QPSK modulator.
17. Compare OQPSK with QPSK.
18. Identify the error in the matlab command Sin 3.

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19. Draw the constellation diagram of QPSK.
20. Give the applications of QPSK modulation scheme.
Viva - voce
54 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 10 DESIGN OF FSK, PSK, DPSK USING MATLAB
Aim:
To write a program in MATLAB for design of FSK, PSK and DPSK
Software required:
PC with MATLAB version 7.0 software installed

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Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.

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4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.

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7. Rectify the error if any go to debug menu select run.

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Result:

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Thus the FSK, PSK and DPSK were simulated using MATLAB.
Outcome:
After the completion of this experiment the students will be able to simulate the various modulation schemes
such as FSK, PSK and DPSK using MATLAB.
55 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Applications:
ASK:
1. ASK is used to transmit digital data over optical fiber
PSK:

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1. over voice lines
2. in high-freq. radio transmissions.


1. What is FSK? Mention its significance.

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2. What is PSK? Mention its significance.
3. What is DPSK? Mention its significance.
4. What are the applications of DPSK?
5. Give the equation for average probability of symbol error for DPSK.
6. List the operations performed in DPSK transmitter.

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7. Compare DPSK with QPSK modulation scheme.
8. What is differential encoding technique?
9. Why do we make 180 degree phase shift in PSK why not 90 or 270?
10. What is the function of a decision device?
11. What is RZ?

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12. What is NRZ?
13. What is Manchester encoding?
14. Sketch the FSK waveform for the input a) 1010110 b) 1100101
15. Define modulation index.
16. Write a MATLAB program for generating PN sequence.

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17. Differentiate coherent with non-coherent FSK.
18. Give the expression for bandwidth of FSK scheme.
19. What is the difference between PSK and FSK?
20. What is the major advantage of coherent PSK over coherent ASK?

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Viva - voce
56 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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sExpt. No. 11 COMMUNICATION LINK SIMULATION USING
MATLAB
Aim:
To simulate the basic communication link using mat lab

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Software required:
PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.

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3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.

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6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the communication link simulation was designed using MATLAB.
Outcome:
After the completion of this experiment the students will be able to simulate and design the communication link

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using MATLAB.

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57 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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1. Give examples for digital modulation techniques.
2. What is meant by pass-b transmission?
3. What is meant by base-b transmission?
4. What is the meaning for error pattern?

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5. Differentiate systematic from non-systematic coding.

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Viva - voce
FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?



DEPARTMENT OF

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ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
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DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

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? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul

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DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING


To impart professional education integrated with human values to the younger generation, so as to

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shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity


? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics

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industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION

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VISION
MISSION
MISSION
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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education

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2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to

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find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context

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5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field

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b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems

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e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility

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i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 - COMMUNICATION SYSTEMS LABORATORY

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To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms

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? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator

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4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes

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9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

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COURSE OBJECTIVES
COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction

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7
2 Time division multiplexing
13
3 AM modulation demodulation
18

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4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33
6 Delta modulation demodulation

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38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB

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51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB
55

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11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS

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13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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7 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

CYCLE 1 - EXPERIMENTS

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Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.

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2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at

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which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.

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Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples

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taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To

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recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit

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works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.

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3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

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Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal
Sampled output

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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.

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Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)

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5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate

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4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?

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9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.

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14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.

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19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
12 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:

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To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.

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4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.

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Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .

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3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .

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6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .

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Circuit Diagram

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Time division multiplexing

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TDM Trainer Kit

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Model Graph:

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Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1
2. Message Signal 2

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3. TDM signal

Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:

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After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.


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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network

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2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis

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5. The GSM telephone system


1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?

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3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?

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8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce
17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver

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Apparatus required:
.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.
3 Diode ? 2 No.

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4
AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.
6 Patch cards ? 6 No.

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Theory:

AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the

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instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.

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Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal

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Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index

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Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if
M < 1 Under modulation
M = 1 Critical modulation

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M > 1 over modulation

Procedure:
1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.

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3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

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AM Modulated wave



2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)

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Message

Carrier

Modulated

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Demodulated


Result:

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Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.
Applications:

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1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?

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5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?
9. What are the different types of AM generation?

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10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce
24 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?

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17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?

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21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after

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demodulating using FM receiver
Apparatus required:
.
1. Resistor ? 4 No.
2. Capacitor ? 1 No.

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3. Diode ? 2 No.
4.
AM transmitter Receiver
trainer kit ? 1 No.
5. CRO ? 1 No.

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6. Patch cards ? 6 No.

Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the
instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct

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proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used
in broadcast is generally called wide-FM, or W-FM.

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In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the

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luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of
noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes

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print-through pre-echo.

Procedure:
FM Modulator:
1. Switch ON the Power supply.

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2. Connect the sine wave generator output to frequency modulator input.

3. Select the low frequency carrier (or) high frequency carrier.

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4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

6. Observe the frequency modulator output .

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FM Demodulator:
A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

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2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

4. Observe the Demodulated O/P compare with the original input.

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B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

2. Now set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Quadrature detector output.

4. Observe the Demodulated O/P and compare with the original input.
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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

4. Observe the Demodulated O/P and then compare with the original input.

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D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

2. Set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Ratio detector output.

4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram
FM Modulator

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FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency
modulated and demodulated wave.
Applications:

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1. Television sound transmission
2. Two way mobile radio
3. Cellular Radio
4. Microwave
5. Satellite Communication System

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1. Define ? Frequency Modulation
2. How it is different from phase modulation?
3. Write equation of FM wave, explain each parameter in it.

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4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.
6. Define ? Modulation Index
7. Differentiate between Narrow band FM from Wide band FM.
8. Draw message, carrier FM waves .

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9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?
11. Give the practical applications of FM.
12. State advantages and disadvantages of FM.
13. What is the range of speech signals?

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14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation
17. Draw the phasor diagram of FM signal.
18. What are the different types of FM generation?

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Viva - voce

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32 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 5 PCM MODULATION & DEMODULATION

Aim:

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To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator
Apparatus Required:
1. PCM trainer kit ? 1 No.
2. CRO ? 1 No.

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3. Connecting probes ? 4 No.
Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is
first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of
converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization

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can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization
the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel
serially.

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At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword
is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to
Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks

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for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:
1. Power on the PCM kit.
2. Measure the frequency of sampling clock.

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3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.
5. Connect the clock to the timing control circuit.

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6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.
9. Observe the waveform at the output of DAC.
10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the

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codeword graphically for a DC input.
Block diagram of PCM Transmission system

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34 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PCM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation

Result:
Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.

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Outcome:
After the completion of this experiment the students will be able to design and construct the pulse code
modulated and demodulated wave.
Applications:
1. Military Applications.

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2. The PCM is used in the satellite transmission system.
SIGNALS AMPLITUDE (V) TIME PERIOD (s)
DC Input
Sampled Signal
Clock Pulse

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PCM Output
DC Output
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3. It is used in space communication.

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4. It is used in telephony.
5. The compact disc (CD) is a recent application of PCM.


1. Define ? Modulation

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2. State sampling theorem
3. Define ? Demodulation
4. Define ? Pulse Code Modulation
5. What is aliasing effect?
6. What is quantization?

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7. Define ? Bit Rate
8. Define ? Baud Rate
9. What are the advantages of PCM?
10. Define ? Signal to Noise Ratio
11. What are the limitations of PCM?

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12. What are the applications of PCM?
13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate
16. What is multiplexing?

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17. What is de-multiplexing?
18. What are the types of pulse modulation?
19. What should be the minimum bandwidth required to transmit a PCM channel?
20. What is the value of signal to noise ratio in PCM?

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Viva - voce
37 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 6 DELTA MODULATION & DEMODULATION

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Aim:
To transmit an analog message signal in its digital form and reconstruct back the original analog message
signal at receiver by using Delta modulator
Apparatus required:
1. DM and ADM Trainer kit ? 1 No.

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2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The
difference signal between two successive samples is encoded into a single bit code. A present sample of the

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analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level
(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.
The comparison of samples is accomplished by converting the digital to analog form then comparing with the
present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to
a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.

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Procedure:
1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.
2. Observe the modulated signal in the CRO.
3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.
4. Also observe the DAC output on the CRO.

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5. Change the amplitude of the modulating signal.
6. Observe the DAC output. Notice the slope overload distortion.
7. Keep the tuning knob to minimize distortion.
8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope
overload distortion.

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9. Calculate the sampling frequency required for no slope overload distortion.
10. Compare the calculated measured values of the sampling frequency.


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Block Diagram Delta modulator and demodulator

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Delta Modulator

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Delta Demodulator

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Block diagram of Adaptive delta modulator and demodulator

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Adaptive Delta Modulator

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Adaptive Delta Demodulator

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Delta Modulation and Adaptive Delta Modulator Trainer kit

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Model Graph:

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42 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Tabulation 1
For Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal

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2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

Tabulation 2

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For Adaptive Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal
2 Carrier Signal
3 Modulated Signal

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4 Demodulated Signal

Result:
Thus the output waveforms of Delta modulation and adaptive delta modulation circuit were observed.
Outcome:

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After the completion of this experiment the students will be able to design and construct the delta modulation
adaptive delta modulation circuit.
Applications:
1. Digital voice storage
2. Voice transmission

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43 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

3. Radio communication devices such TV remotes.
4. Delta Modulation was used by Satellite Business Systems or SBS
5. DM used in high resolution A/D and D/A converters.

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1. What is delta modulation?
2. What is adaptive delta modulation?
3. What are the advantages of adaptive delta modulation over delta modulation?

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4. What is slope over load distortion?
5. What is granular noise effect?
6. What are the two limitations of delta modulation?
7. What is the function of integrator?
8. What is comparator?

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9. What is companding?
10. What is the advantage of delta modulation over pulse modulation?
11. Distinguish between DPCM and DM.
12. What are the different types of digital modulation?
13. What is sampling rate?

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14. Which kind of multiplexing used in digital communication?
15. Why is sample hold circuit used?
16. What are the advantages of digital transmission?
17. How is the performance corrupted in PCM?
18. What are the different types of multiplexing?

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19. What is aliasing effect?
20. How to avoid aliasing effect?

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Viva - voce

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44 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 7 LINE CODING DECODING TECHNIQUES

Aim:

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To study different line coding techniques.
Apparatus required:
1. Line coding and decoding trainer kit ? 1 No.
2. Patch cords ? 6 No.
3. CRO ? 1 No.

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Theory:
Line coding refers to the process of representing the bit stream (1 ?s and 0 ?s) in the form of voltage or current
variations optimally tuned for the specific properties of the physical channel being used. The selection of a proper
line code can help in many ways. One possibility is to aid in clock recovery at the receiver. A clock signal is

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recovered by observing transitions in the received bit sequence, if enough transitions exist, a good recovery of
the clock is guaranteed, the signal is said to be self-clocking. Another advantage is to get rid of DC shifts. The
DC component in a line code is called the bias or the DC coefficient. Unfortunately, most long-distance
communication channels cannot transport a DC component. This is why most line codes try to eliminate the DC
component before being transmitted on the channel. Such codes are called DC balanced, zero-DC, zero-bias, or

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DC equalized. Some common types of line encoding in common-use nowadays are unipolar, polar, bipolar,
Manchester, MLT-3 Duo binary encoding.
Unipolar (Unipolar NRZ and Unipolar RZ):
Unipolar is the simplest line coding scheme. It has the advantage of being compatible with TTL logic. Unipolar
coding uses a positive rectangular pulse p(t) to represent binary 1, the absence of a pulse (i.e., zero voltage) to

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represent a binary 0. Two possibilities for the pulse p(t) exist3: Non-Return-to-Zero (NRZ) rectangular pulse
Return-to-Zero (RZ) rectangular pulse. The difference between Unipolar NRZ Unipolar RZ codes is that the
rectangular pulse in NRZ stays at a positive value (e.g., +5V) for the full duration of the logic 1 bit, while the pule
in RZ drops from +5V to 0V in the middle of the bit time.

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45 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Procedure:

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1. Connect the PRBS (test point P5) to various line coding formats. Obtain the coded output as per the
requirement.
2. Connect coded signal test point to corresponding decoding test point as inputs.
3. Set the SW1 as per the requirement.
4. Set the potentiometer P1 in minimum position.

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5. Switch ON the power supply. Press the switch SW2 once.
6. Display the encoded signal on one channel of CRO and decoded signal on second channel of CRO.

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46 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Line coding decoding trainer kit

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47 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Model Graph:

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48 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00



Tabulation

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Sl. No. Type of Coding AMPLITUDE (V) Time period (s)
1. Unipolar data(NZ NRZ )

2. Unipolar data (NRZ RZ)
3. Bipolar Data(NRZ AMI)

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4. Manchester


Result:
Thus the different line coding techniques was studied and verified.

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Outcome:
After the completion of this experiment the students will be able to understand implement the different line
coding schemes.
Applications:
1. DC balance

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2. embedded clock applications
3. computing applications
4. Manchester codes are commonly used for local area networks
5. Bipolar codes are commonly used for local area networks

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49 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


1. What is line coding?
2. Define ? Polar Encoding

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3. Define ? Unipolar Encoding
4. Define ? Bipolar Encoding
5. Define ? Manchester Encoding
6. What are the two function of fast frequency hopping?
7. What is return to zero?

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8. What is Non-return to zero?
9. What is the difference between source coding and line coding?
10. What are the properties of line coding?
11. What is the effect of inter symbol interference?
12. How ISI can be reduced?

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13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate
16. Draw the NRZ and RZ code for the digital data 10110001.
17. Define ? Equalization

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18. What is PRBS?
19. Write the Boolean expression for X-NOR gate.
20. Define ? Digital demodulation

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Viva - voce

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50 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

CYCLE 2 ? EXPERIMENTS
Expt. No.8 ERROR CONTROL CODING USING MATLAB
Aim:

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To write a program in MATLAB for error control coding techniques
Software required:
PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.

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2. MATLAB logo will appear after few moments comon prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitiled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the

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program press F5 or go to debug menu select run.
6. After execution output will appear in the common window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the error control coding techniques are executed using MATLAB programs.
Outcome:
After the completion of this experiment the students will be able to simulate the different error control coding
schemes using MATLAB.

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Applications :
1. Deep space communication
2. Satellite communication
3. Data transmission
4. Data storage

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5. Mobile communication
6. File transfer
7. digital audio/video transmission.
51 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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1. What is the need for error control coding?
2. What is meant by linear code?
3. What is meant by cyclic code?
4. Name some error control coding techniques.

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5. Name the code which is used only for error detection.

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Viva - voce
52 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 9 DESIGN OF BPSK, QPSK, QAM USING MATLAB
Aim:
To write a program in MATLAB for design of BPSK, QPSK and QAM
Software required:

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PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper

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icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error

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will appear in red colour.
7. Rectify the error, if any go to debug menu select run.

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53 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Result:
Thus the BPSK, QPSK and QAM were simulated using MATLAB.
Outcome:
After the completion of this experiment the students will be able to simulate the various modulation schemes

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such as BPSK, QPSK and QAM using MATLAB.
Applications:
QPSK
1. Data transmission, mainly radio transmissions.
2. RTTY means radio teletype transmissions from amateur radio up to WiFi transmissions or Zigbees

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QAM
1. Radio communications and data delivery applications.


1. What is a correlator?

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2. Define ? Constellation Diagram
3. What is BPSK ? Mention its significance.
4. Give the expression for bandwidth of BPSK scheme.
5. What is QPSK mention its significance?
6. Give the expression for bandwidth of QPSK scheme.

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7. Draw the constellation diagram of QPSK.
8. What is QAM ?
9. Give the expression for bandwidth of QAM scheme.
10. What are the blocks in BPSK receiver?
11. What is the function of a decision device?

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12. Draw the constellation diagram of QAM.
13. What are the types of QPSK?
14. What is the significance of Q-channel I channel in QPSK modulator?
15. What is the minimum bandwidth requirement of QPSK?
16. Draw the output phase versus time relationship for a QPSK modulator.

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17. Compare OQPSK with QPSK.
18. Identify the error in the matlab command Sin 3.
19. Draw the constellation diagram of QPSK.
20. Give the applications of QPSK modulation scheme.
Viva - voce

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54 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 10 DESIGN OF FSK, PSK, DPSK USING MATLAB
Aim:
To write a program in MATLAB for design of FSK, PSK and DPSK

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Software required:
PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.

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3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.

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6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the FSK, PSK and DPSK were simulated using MATLAB.
Outcome:
After the completion of this experiment the students will be able to simulate the various modulation schemes

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such as FSK, PSK and DPSK using MATLAB.
55 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Applications:
ASK:

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1. ASK is used to transmit digital data over optical fiber
PSK:
1. over voice lines
2. in high-freq. radio transmissions.

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1. What is FSK? Mention its significance.
2. What is PSK? Mention its significance.
3. What is DPSK? Mention its significance.
4. What are the applications of DPSK?

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5. Give the equation for average probability of symbol error for DPSK.
6. List the operations performed in DPSK transmitter.
7. Compare DPSK with QPSK modulation scheme.
8. What is differential encoding technique?
9. Why do we make 180 degree phase shift in PSK why not 90 or 270?

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10. What is the function of a decision device?
11. What is RZ?
12. What is NRZ?
13. What is Manchester encoding?
14. Sketch the FSK waveform for the input a) 1010110 b) 1100101

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15. Define modulation index.
16. Write a MATLAB program for generating PN sequence.
17. Differentiate coherent with non-coherent FSK.
18. Give the expression for bandwidth of FSK scheme.
19. What is the difference between PSK and FSK?

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20. What is the major advantage of coherent PSK over coherent ASK?

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Viva - voce
56 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

sExpt. No. 11 COMMUNICATION LINK SIMULATION USING
MATLAB

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Aim:
To simulate the basic communication link using mat lab
Software required:
PC with MATLAB version 7.0 software installed
Procedure:

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1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.

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5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the communication link simulation was designed using MATLAB.

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Outcome:
After the completion of this experiment the students will be able to simulate and design the communication link
using MATLAB.

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57 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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1. Give examples for digital modulation techniques.
2. What is meant by pass-b transmission?

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3. What is meant by base-b transmission?
4. What is the meaning for error pattern?
5. Differentiate systematic from non-systematic coding.

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Viva - voce
58 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 12 ZERO FORCING LMS EQUALIZATION
ALGORITHMS USING MATLAB
Aim:
To write a program in MATLAB for design of zero forcing LMS algorithms
Software required:

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PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper

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icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error

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will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the equalization of zero forcing LMS algorithms was simulated using MATLAB.
Outcome:
After the completion of this experiment the students will be able to implement the various algorithms using

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MATLAB.



FirstRanker.com - FirstRanker's Choice

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1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

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V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________

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Section : _______________________________________

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LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

DHANALAKSHMI

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College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

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? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

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To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

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? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in

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communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION
VISION
MISSION

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MISSION
3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals

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To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge

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training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism

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To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,

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through commitment lifelong learning needed for successful professional career

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4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability

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c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities

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g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning

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k) To participate succeed in competitive exams

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5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation

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? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS

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1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation

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6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)

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11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)


Simulate end-to-end Communication Link

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Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

COURSE OBJECTIVES

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COURSE OUTCOMES
6 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS

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Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7
2 Time division multiplexing

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13
3 AM modulation demodulation
18
4 Frequency modulation demodulation
26

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5 PCM modulation demodulation
33
6 Delta modulation demodulation
38
7 Line coding decoding techniques

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45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB

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53
10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB
57

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12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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7 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:

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To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.

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4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.

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A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the

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signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals

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The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.

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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.

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Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.

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5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

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Model Graph:

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Tabulation

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Analog signal sampling and reconstruction trainer kit


Result:

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Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.


Signal Amplitude (V) Time period (s)

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Message signal
Carrier signal
Sampled output
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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)

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2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

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1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?

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6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?

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11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?

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16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.

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21. Define ? Natural Sampling


Viva - voce
12 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:

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1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:

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Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.

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2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.

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4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .

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7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .

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Circuit Diagram
Time division multiplexing

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TDM Trainer Kit

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Model Graph:

Tabulation

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Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1
2. Message Signal 2
3. TDM signal

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Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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Applications:

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1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.

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3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system

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1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?

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5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?

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10. Which type of modulation technique will be used in TDM?

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Viva - voce
17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 3 AM MODULATION & DEMODULATION

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Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver
Apparatus required:
.

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1 Resistor ? 4 No.
2 Capacitor ? 1 No.
3 Diode ? 2 No.
4
AM transmitter receiver

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trainer kit ? 1 No.
5 CRO ? 1 No.
6 Patch cards ? 6 No.

Theory:

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AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by

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Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

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The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal

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Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude

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if
M < 1 Under modulation
M = 1 Critical modulation
M > 1 over modulation

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Procedure:
1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .

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5. Calculate the modulation index

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Circuit Diagram

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AM Modulation


AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

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Carrier

Modulated

Demodulated

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Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:

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After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.
Applications:
1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.

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3. Facsimile transmission



1. What is modulation and demodulation?

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2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?

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7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?
9. What are the different types of AM generation?
10. Define ? Modulation Index
11. What are different types of analog modulation techniques?

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Viva - voce
24 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.

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14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?

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18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.

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23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver
Apparatus required:

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.
1. Resistor ? 4 No.
2. Capacitor ? 1 No.
3. Diode ? 2 No.
4.

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AM transmitter Receiver
trainer kit ? 1 No.
5. CRO ? 1 No.
6. Patch cards ? 6 No.

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Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the
instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF

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radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used
in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.

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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of

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frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of
noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

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Procedure:
FM Modulator:
1. Switch ON the Power supply.

2. Connect the sine wave generator output to frequency modulator input.

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3. Select the low frequency carrier (or) high frequency carrier.

4. Connect the CRO input to the frequency modulator output.

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5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

6. Observe the frequency modulator output .

FM Demodulator:

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A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

2. Now set the DPDT switch in low frequency mode.

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3. Connect CRO input to PLL detector output.

4. Observe the Demodulated O/P compare with the original input.

B) Quadrature Detector

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1. Connect the frequency modulated output to Quadrature detector input.

2. Now set the DPDT switch in high frequency mode.

3. Connect the CRO input to Quadrature detector output.

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4. Observe the Demodulated O/P and compare with the original input.
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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

2. Set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Phase discriminator output.

4. Observe the Demodulated O/P and then compare with the original input.

D) Ratio Detector

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1. Connect the frequency modulated output to Ratio detector input.

2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Ratio detector output.

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4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram
FM Modulator

FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:


Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)

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Message

Carrier

Modulated

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Demodulated


Result:

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Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:

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After the completion of this experiment the students will be able to design and construct the frequency
modulated and demodulated wave.
Applications:
1. Television sound transmission
2. Two way mobile radio

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3. Cellular Radio
4. Microwave
5. Satellite Communication System

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1. Define ? Frequency Modulation
2. How it is different from phase modulation?
3. Write equation of FM wave, explain each parameter in it.
4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.

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6. Define ? Modulation Index
7. Differentiate between Narrow band FM from Wide band FM.
8. Draw message, carrier FM waves .
9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?

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11. Give the practical applications of FM.
12. State advantages and disadvantages of FM.
13. What is the range of speech signals?
14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?

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16. Define ? Phase Modulation
17. Draw the phasor diagram of FM signal.
18. What are the different types of FM generation?

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Viva - voce
32 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 5 PCM MODULATION & DEMODULATION

Aim:
To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator

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Apparatus Required:
1. PCM trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:

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Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is
first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of
converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization
can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are

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given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization
the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel
serially.
At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.

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In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword
is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to
Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks
for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.

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Procedure:
1. Power on the PCM kit.
2. Measure the frequency of sampling clock.
3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.
5. Connect the clock to the timing control circuit.
6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.

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8. Now apply the AC modulating signal at the input.
9. Observe the waveform at the output of DAC.
10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the
codeword graphically for a DC input.
Block diagram of PCM Transmission system

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34 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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PCM Modulation and Demodulation Trainer kit

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35 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Model Graph:

Tabulation

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Result:
Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.
Outcome:
After the completion of this experiment the students will be able to design and construct the pulse code

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modulated and demodulated wave.
Applications:
1. Military Applications.
2. The PCM is used in the satellite transmission system.
SIGNALS AMPLITUDE (V) TIME PERIOD (s)

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DC Input
Sampled Signal
Clock Pulse
PCM Output
DC Output

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3. It is used in space communication.
4. It is used in telephony.
5. The compact disc (CD) is a recent application of PCM.

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1. Define ? Modulation
2. State sampling theorem
3. Define ? Demodulation

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4. Define ? Pulse Code Modulation
5. What is aliasing effect?
6. What is quantization?
7. Define ? Bit Rate
8. Define ? Baud Rate

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9. What are the advantages of PCM?
10. Define ? Signal to Noise Ratio
11. What are the limitations of PCM?
12. What are the applications of PCM?
13. Define ? Encoding

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14. Define ? Decoding
15. Define ? Nyquist Rate
16. What is multiplexing?
17. What is de-multiplexing?
18. What are the types of pulse modulation?

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19. What should be the minimum bandwidth required to transmit a PCM channel?
20. What is the value of signal to noise ratio in PCM?

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Viva - voce

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37 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 6 DELTA MODULATION & DEMODULATION
Aim:
To transmit an analog message signal in its digital form and reconstruct back the original analog message

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signal at receiver by using Delta modulator
Apparatus required:
1. DM and ADM Trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.

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Theory:
Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The
difference signal between two successive samples is encoded into a single bit code. A present sample of the
analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level
(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.

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The comparison of samples is accomplished by converting the digital to analog form then comparing with the
present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to
a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.
Procedure:
1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.

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2. Observe the modulated signal in the CRO.
3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.
4. Also observe the DAC output on the CRO.
5. Change the amplitude of the modulating signal.
6. Observe the DAC output. Notice the slope overload distortion.

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7. Keep the tuning knob to minimize distortion.
8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope
overload distortion.
9. Calculate the sampling frequency required for no slope overload distortion.
10. Compare the calculated measured values of the sampling frequency.

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38 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Block Diagram Delta modulator and demodulator

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Delta Modulator

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Delta Demodulator

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Block diagram of Adaptive delta modulator and demodulator

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Adaptive Delta Modulator

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Adaptive Delta Demodulator

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Delta Modulation and Adaptive Delta Modulator Trainer kit

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41 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Model Graph:

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42 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Tabulation 1

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For Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal
2 Carrier Signal
3 Modulated Signal

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4 Demodulated Signal

Tabulation 2
For Adaptive Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)

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1 Modulating Signal
2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

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Result:
Thus the output waveforms of Delta modulation and adaptive delta modulation circuit were observed.
Outcome:
After the completion of this experiment the students will be able to design and construct the delta modulation
adaptive delta modulation circuit.

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Applications:
1. Digital voice storage
2. Voice transmission
43 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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3. Radio communication devices such TV remotes.
4. Delta Modulation was used by Satellite Business Systems or SBS
5. DM used in high resolution A/D and D/A converters.

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1. What is delta modulation?
2. What is adaptive delta modulation?
3. What are the advantages of adaptive delta modulation over delta modulation?
4. What is slope over load distortion?
5. What is granular noise effect?

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6. What are the two limitations of delta modulation?
7. What is the function of integrator?
8. What is comparator?
9. What is companding?
10. What is the advantage of delta modulation over pulse modulation?

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11. Distinguish between DPCM and DM.
12. What are the different types of digital modulation?
13. What is sampling rate?
14. Which kind of multiplexing used in digital communication?
15. Why is sample hold circuit used?

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16. What are the advantages of digital transmission?
17. How is the performance corrupted in PCM?
18. What are the different types of multiplexing?
19. What is aliasing effect?
20. How to avoid aliasing effect?

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Viva - voce
44 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 7 LINE CODING DECODING TECHNIQUES

Aim:
To study different line coding techniques.
Apparatus required:

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1. Line coding and decoding trainer kit ? 1 No.
2. Patch cords ? 6 No.
3. CRO ? 1 No.

Theory:

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Line coding refers to the process of representing the bit stream (1 ?s and 0 ?s) in the form of voltage or current
variations optimally tuned for the specific properties of the physical channel being used. The selection of a proper
line code can help in many ways. One possibility is to aid in clock recovery at the receiver. A clock signal is
recovered by observing transitions in the received bit sequence, if enough transitions exist, a good recovery of
the clock is guaranteed, the signal is said to be self-clocking. Another advantage is to get rid of DC shifts. The

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DC component in a line code is called the bias or the DC coefficient. Unfortunately, most long-distance
communication channels cannot transport a DC component. This is why most line codes try to eliminate the DC
component before being transmitted on the channel. Such codes are called DC balanced, zero-DC, zero-bias, or
DC equalized. Some common types of line encoding in common-use nowadays are unipolar, polar, bipolar,
Manchester, MLT-3 Duo binary encoding.

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Unipolar (Unipolar NRZ and Unipolar RZ):
Unipolar is the simplest line coding scheme. It has the advantage of being compatible with TTL logic. Unipolar
coding uses a positive rectangular pulse p(t) to represent binary 1, the absence of a pulse (i.e., zero voltage) to
represent a binary 0. Two possibilities for the pulse p(t) exist3: Non-Return-to-Zero (NRZ) rectangular pulse
Return-to-Zero (RZ) rectangular pulse. The difference between Unipolar NRZ Unipolar RZ codes is that the

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rectangular pulse in NRZ stays at a positive value (e.g., +5V) for the full duration of the logic 1 bit, while the pule
in RZ drops from +5V to 0V in the middle of the bit time.

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Procedure:
1. Connect the PRBS (test point P5) to various line coding formats. Obtain the coded output as per the
requirement.

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2. Connect coded signal test point to corresponding decoding test point as inputs.
3. Set the SW1 as per the requirement.
4. Set the potentiometer P1 in minimum position.
5. Switch ON the power supply. Press the switch SW2 once.
6. Display the encoded signal on one channel of CRO and decoded signal on second channel of CRO.

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46 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Line coding decoding trainer kit

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47 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Model Graph:

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48 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Tabulation
Sl. No. Type of Coding AMPLITUDE (V) Time period (s)
1. Unipolar data(NZ NRZ )

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2. Unipolar data (NRZ RZ)
3. Bipolar Data(NRZ AMI)
4. Manchester

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Result:
Thus the different line coding techniques was studied and verified.
Outcome:
After the completion of this experiment the students will be able to understand implement the different line

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coding schemes.
Applications:
1. DC balance
2. embedded clock applications
3. computing applications

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4. Manchester codes are commonly used for local area networks
5. Bipolar codes are commonly used for local area networks

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49 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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1. What is line coding?
2. Define ? Polar Encoding
3. Define ? Unipolar Encoding
4. Define ? Bipolar Encoding

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5. Define ? Manchester Encoding
6. What are the two function of fast frequency hopping?
7. What is return to zero?
8. What is Non-return to zero?
9. What is the difference between source coding and line coding?

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10. What are the properties of line coding?
11. What is the effect of inter symbol interference?
12. How ISI can be reduced?
13. Define ? Encoding
14. Define ? Decoding

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15. Define ? Nyquist Rate
16. Draw the NRZ and RZ code for the digital data 10110001.
17. Define ? Equalization
18. What is PRBS?
19. Write the Boolean expression for X-NOR gate.

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20. Define ? Digital demodulation

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Viva - voce
50 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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CYCLE 2 ? EXPERIMENTS
Expt. No.8 ERROR CONTROL CODING USING MATLAB
Aim:
To write a program in MATLAB for error control coding techniques
Software required:

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PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments comon prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper

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icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitiled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the common window. If there is an error then with an alarm, type of error

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will appear in red colour.
7. Rectify the error if any go to debug menu select run.

Result:
Thus the error control coding techniques are executed using MATLAB programs.

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Outcome:
After the completion of this experiment the students will be able to simulate the different error control coding
schemes using MATLAB.
Applications :
1. Deep space communication

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2. Satellite communication
3. Data transmission
4. Data storage
5. Mobile communication
6. File transfer

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7. digital audio/video transmission.
51 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


1. What is the need for error control coding?

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2. What is meant by linear code?
3. What is meant by cyclic code?
4. Name some error control coding techniques.
5. Name the code which is used only for error detection.

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Viva - voce
52 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 9 DESIGN OF BPSK, QPSK, QAM USING MATLAB

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Aim:
To write a program in MATLAB for design of BPSK, QPSK and QAM
Software required:
PC with MATLAB version 7.0 software installed
Procedure:

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1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.

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5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error, if any go to debug menu select run.

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Result:

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Thus the BPSK, QPSK and QAM were simulated using MATLAB.
Outcome:
After the completion of this experiment the students will be able to simulate the various modulation schemes
such as BPSK, QPSK and QAM using MATLAB.
Applications:

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QPSK
1. Data transmission, mainly radio transmissions.
2. RTTY means radio teletype transmissions from amateur radio up to WiFi transmissions or Zigbees
QAM
1. Radio communications and data delivery applications.

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1. What is a correlator?
2. Define ? Constellation Diagram
3. What is BPSK ? Mention its significance.

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4. Give the expression for bandwidth of BPSK scheme.
5. What is QPSK mention its significance?
6. Give the expression for bandwidth of QPSK scheme.
7. Draw the constellation diagram of QPSK.
8. What is QAM ?

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9. Give the expression for bandwidth of QAM scheme.
10. What are the blocks in BPSK receiver?
11. What is the function of a decision device?
12. Draw the constellation diagram of QAM.
13. What are the types of QPSK?

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14. What is the significance of Q-channel I channel in QPSK modulator?
15. What is the minimum bandwidth requirement of QPSK?
16. Draw the output phase versus time relationship for a QPSK modulator.
17. Compare OQPSK with QPSK.
18. Identify the error in the matlab command Sin 3.

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19. Draw the constellation diagram of QPSK.
20. Give the applications of QPSK modulation scheme.
Viva - voce
54 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 10 DESIGN OF FSK, PSK, DPSK USING MATLAB
Aim:
To write a program in MATLAB for design of FSK, PSK and DPSK
Software required:
PC with MATLAB version 7.0 software installed

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Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.

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4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.

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7. Rectify the error if any go to debug menu select run.

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Result:

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Thus the FSK, PSK and DPSK were simulated using MATLAB.
Outcome:
After the completion of this experiment the students will be able to simulate the various modulation schemes
such as FSK, PSK and DPSK using MATLAB.
55 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Applications:
ASK:
1. ASK is used to transmit digital data over optical fiber
PSK:

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1. over voice lines
2. in high-freq. radio transmissions.


1. What is FSK? Mention its significance.

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2. What is PSK? Mention its significance.
3. What is DPSK? Mention its significance.
4. What are the applications of DPSK?
5. Give the equation for average probability of symbol error for DPSK.
6. List the operations performed in DPSK transmitter.

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7. Compare DPSK with QPSK modulation scheme.
8. What is differential encoding technique?
9. Why do we make 180 degree phase shift in PSK why not 90 or 270?
10. What is the function of a decision device?
11. What is RZ?

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12. What is NRZ?
13. What is Manchester encoding?
14. Sketch the FSK waveform for the input a) 1010110 b) 1100101
15. Define modulation index.
16. Write a MATLAB program for generating PN sequence.

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17. Differentiate coherent with non-coherent FSK.
18. Give the expression for bandwidth of FSK scheme.
19. What is the difference between PSK and FSK?
20. What is the major advantage of coherent PSK over coherent ASK?

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Viva - voce
56 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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sExpt. No. 11 COMMUNICATION LINK SIMULATION USING
MATLAB
Aim:
To simulate the basic communication link using mat lab

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Software required:
PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.

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3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.

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6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the communication link simulation was designed using MATLAB.
Outcome:
After the completion of this experiment the students will be able to simulate and design the communication link

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using MATLAB.

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57 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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1. Give examples for digital modulation techniques.
2. What is meant by pass-b transmission?
3. What is meant by base-b transmission?
4. What is the meaning for error pattern?

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5. Differentiate systematic from non-systematic coding.

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Viva - voce
58 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 12 ZERO FORCING LMS EQUALIZATION
ALGORITHMS USING MATLAB

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Aim:
To write a program in MATLAB for design of zero forcing LMS algorithms
Software required:
PC with MATLAB version 7.0 software installed
Procedure:

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1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.

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5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:

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Thus the equalization of zero forcing LMS algorithms was simulated using MATLAB.
Outcome:
After the completion of this experiment the students will be able to implement the various algorithms using
MATLAB.

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59 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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1. Define ? Equalization
2. What is meant by zero forcing algorithms?
3. Define ? LMS Algorithm

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4. What is meant by pass-b transmission?
5. What is meant by base-b transmission?
6. What is the meaning for error pattern?

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Viva - voce
FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?



DEPARTMENT OF

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ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

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? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul

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DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING


To impart professional education integrated with human values to the younger generation, so as to

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shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity


? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics

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industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION

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VISION
MISSION
MISSION
3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education

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2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to

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find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context

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5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field

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b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems

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e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility

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i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 - COMMUNICATION SYSTEMS LABORATORY

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To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms

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? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator

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4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes

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9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

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COURSE OBJECTIVES
COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction

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7
2 Time division multiplexing
13
3 AM modulation demodulation
18

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4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33
6 Delta modulation demodulation

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38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB

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51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB
55

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11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS

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13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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7 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

CYCLE 1 - EXPERIMENTS

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Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.

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2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at

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which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.

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Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples

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taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To

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recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit

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works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.

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3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

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Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal
Sampled output

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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.

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Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)

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5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate

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4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?

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9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.

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14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.

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19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
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Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:

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To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.

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4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.

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Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .

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3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .

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6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .

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Circuit Diagram

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Time division multiplexing

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TDM Trainer Kit

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Model Graph:

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Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1
2. Message Signal 2

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3. TDM signal

Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:

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After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.


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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network

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2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis

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5. The GSM telephone system


1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?

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3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?

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8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce
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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver

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Apparatus required:
.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.
3 Diode ? 2 No.

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4
AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.
6 Patch cards ? 6 No.

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Theory:

AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the

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instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.

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Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal

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Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index

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Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if
M < 1 Under modulation
M = 1 Critical modulation

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M > 1 over modulation

Procedure:
1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.

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3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

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AM Modulated wave



2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)

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Message

Carrier

Modulated

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Demodulated


Result:

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Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.
Applications:

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1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?

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5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?
9. What are the different types of AM generation?

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10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce
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12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?

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17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?

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21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after

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demodulating using FM receiver
Apparatus required:
.
1. Resistor ? 4 No.
2. Capacitor ? 1 No.

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3. Diode ? 2 No.
4.
AM transmitter Receiver
trainer kit ? 1 No.
5. CRO ? 1 No.

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6. Patch cards ? 6 No.

Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the
instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct

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proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used
in broadcast is generally called wide-FM, or W-FM.

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In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the

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luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of
noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes

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print-through pre-echo.

Procedure:
FM Modulator:
1. Switch ON the Power supply.

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2. Connect the sine wave generator output to frequency modulator input.

3. Select the low frequency carrier (or) high frequency carrier.

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4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

6. Observe the frequency modulator output .

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FM Demodulator:
A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

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2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

4. Observe the Demodulated O/P compare with the original input.

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B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

2. Now set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Quadrature detector output.

4. Observe the Demodulated O/P and compare with the original input.
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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

4. Observe the Demodulated O/P and then compare with the original input.

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D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

2. Set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Ratio detector output.

4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram
FM Modulator

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FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency
modulated and demodulated wave.
Applications:

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1. Television sound transmission
2. Two way mobile radio
3. Cellular Radio
4. Microwave
5. Satellite Communication System

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1. Define ? Frequency Modulation
2. How it is different from phase modulation?
3. Write equation of FM wave, explain each parameter in it.

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4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.
6. Define ? Modulation Index
7. Differentiate between Narrow band FM from Wide band FM.
8. Draw message, carrier FM waves .

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9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?
11. Give the practical applications of FM.
12. State advantages and disadvantages of FM.
13. What is the range of speech signals?

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14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation
17. Draw the phasor diagram of FM signal.
18. What are the different types of FM generation?

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Viva - voce

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32 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 5 PCM MODULATION & DEMODULATION

Aim:

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To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator
Apparatus Required:
1. PCM trainer kit ? 1 No.
2. CRO ? 1 No.

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3. Connecting probes ? 4 No.
Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is
first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of
converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization

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can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization
the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel
serially.

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At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword
is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to
Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks

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for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:
1. Power on the PCM kit.
2. Measure the frequency of sampling clock.

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3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.
5. Connect the clock to the timing control circuit.

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6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.
9. Observe the waveform at the output of DAC.
10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the

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codeword graphically for a DC input.
Block diagram of PCM Transmission system

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PCM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation

Result:
Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.

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Outcome:
After the completion of this experiment the students will be able to design and construct the pulse code
modulated and demodulated wave.
Applications:
1. Military Applications.

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2. The PCM is used in the satellite transmission system.
SIGNALS AMPLITUDE (V) TIME PERIOD (s)
DC Input
Sampled Signal
Clock Pulse

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PCM Output
DC Output
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3. It is used in space communication.

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4. It is used in telephony.
5. The compact disc (CD) is a recent application of PCM.


1. Define ? Modulation

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2. State sampling theorem
3. Define ? Demodulation
4. Define ? Pulse Code Modulation
5. What is aliasing effect?
6. What is quantization?

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7. Define ? Bit Rate
8. Define ? Baud Rate
9. What are the advantages of PCM?
10. Define ? Signal to Noise Ratio
11. What are the limitations of PCM?

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12. What are the applications of PCM?
13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate
16. What is multiplexing?

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17. What is de-multiplexing?
18. What are the types of pulse modulation?
19. What should be the minimum bandwidth required to transmit a PCM channel?
20. What is the value of signal to noise ratio in PCM?

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Viva - voce
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Expt. No. 6 DELTA MODULATION & DEMODULATION

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Aim:
To transmit an analog message signal in its digital form and reconstruct back the original analog message
signal at receiver by using Delta modulator
Apparatus required:
1. DM and ADM Trainer kit ? 1 No.

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2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The
difference signal between two successive samples is encoded into a single bit code. A present sample of the

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analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level
(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.
The comparison of samples is accomplished by converting the digital to analog form then comparing with the
present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to
a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.

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Procedure:
1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.
2. Observe the modulated signal in the CRO.
3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.
4. Also observe the DAC output on the CRO.

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5. Change the amplitude of the modulating signal.
6. Observe the DAC output. Notice the slope overload distortion.
7. Keep the tuning knob to minimize distortion.
8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope
overload distortion.

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9. Calculate the sampling frequency required for no slope overload distortion.
10. Compare the calculated measured values of the sampling frequency.


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Block Diagram Delta modulator and demodulator

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Delta Modulator

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Delta Demodulator

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Block diagram of Adaptive delta modulator and demodulator

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Adaptive Delta Modulator

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Adaptive Delta Demodulator

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Delta Modulation and Adaptive Delta Modulator Trainer kit

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Model Graph:

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Tabulation 1
For Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal

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2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

Tabulation 2

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For Adaptive Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal
2 Carrier Signal
3 Modulated Signal

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4 Demodulated Signal

Result:
Thus the output waveforms of Delta modulation and adaptive delta modulation circuit were observed.
Outcome:

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After the completion of this experiment the students will be able to design and construct the delta modulation
adaptive delta modulation circuit.
Applications:
1. Digital voice storage
2. Voice transmission

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3. Radio communication devices such TV remotes.
4. Delta Modulation was used by Satellite Business Systems or SBS
5. DM used in high resolution A/D and D/A converters.

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1. What is delta modulation?
2. What is adaptive delta modulation?
3. What are the advantages of adaptive delta modulation over delta modulation?

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4. What is slope over load distortion?
5. What is granular noise effect?
6. What are the two limitations of delta modulation?
7. What is the function of integrator?
8. What is comparator?

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9. What is companding?
10. What is the advantage of delta modulation over pulse modulation?
11. Distinguish between DPCM and DM.
12. What are the different types of digital modulation?
13. What is sampling rate?

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14. Which kind of multiplexing used in digital communication?
15. Why is sample hold circuit used?
16. What are the advantages of digital transmission?
17. How is the performance corrupted in PCM?
18. What are the different types of multiplexing?

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19. What is aliasing effect?
20. How to avoid aliasing effect?

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Viva - voce

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44 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 7 LINE CODING DECODING TECHNIQUES

Aim:

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To study different line coding techniques.
Apparatus required:
1. Line coding and decoding trainer kit ? 1 No.
2. Patch cords ? 6 No.
3. CRO ? 1 No.

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Theory:
Line coding refers to the process of representing the bit stream (1 ?s and 0 ?s) in the form of voltage or current
variations optimally tuned for the specific properties of the physical channel being used. The selection of a proper
line code can help in many ways. One possibility is to aid in clock recovery at the receiver. A clock signal is

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recovered by observing transitions in the received bit sequence, if enough transitions exist, a good recovery of
the clock is guaranteed, the signal is said to be self-clocking. Another advantage is to get rid of DC shifts. The
DC component in a line code is called the bias or the DC coefficient. Unfortunately, most long-distance
communication channels cannot transport a DC component. This is why most line codes try to eliminate the DC
component before being transmitted on the channel. Such codes are called DC balanced, zero-DC, zero-bias, or

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DC equalized. Some common types of line encoding in common-use nowadays are unipolar, polar, bipolar,
Manchester, MLT-3 Duo binary encoding.
Unipolar (Unipolar NRZ and Unipolar RZ):
Unipolar is the simplest line coding scheme. It has the advantage of being compatible with TTL logic. Unipolar
coding uses a positive rectangular pulse p(t) to represent binary 1, the absence of a pulse (i.e., zero voltage) to

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represent a binary 0. Two possibilities for the pulse p(t) exist3: Non-Return-to-Zero (NRZ) rectangular pulse
Return-to-Zero (RZ) rectangular pulse. The difference between Unipolar NRZ Unipolar RZ codes is that the
rectangular pulse in NRZ stays at a positive value (e.g., +5V) for the full duration of the logic 1 bit, while the pule
in RZ drops from +5V to 0V in the middle of the bit time.

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Procedure:

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1. Connect the PRBS (test point P5) to various line coding formats. Obtain the coded output as per the
requirement.
2. Connect coded signal test point to corresponding decoding test point as inputs.
3. Set the SW1 as per the requirement.
4. Set the potentiometer P1 in minimum position.

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5. Switch ON the power supply. Press the switch SW2 once.
6. Display the encoded signal on one channel of CRO and decoded signal on second channel of CRO.

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46 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Line coding decoding trainer kit

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Model Graph:

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Tabulation

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Sl. No. Type of Coding AMPLITUDE (V) Time period (s)
1. Unipolar data(NZ NRZ )

2. Unipolar data (NRZ RZ)
3. Bipolar Data(NRZ AMI)

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4. Manchester


Result:
Thus the different line coding techniques was studied and verified.

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Outcome:
After the completion of this experiment the students will be able to understand implement the different line
coding schemes.
Applications:
1. DC balance

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2. embedded clock applications
3. computing applications
4. Manchester codes are commonly used for local area networks
5. Bipolar codes are commonly used for local area networks

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1. What is line coding?
2. Define ? Polar Encoding

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3. Define ? Unipolar Encoding
4. Define ? Bipolar Encoding
5. Define ? Manchester Encoding
6. What are the two function of fast frequency hopping?
7. What is return to zero?

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8. What is Non-return to zero?
9. What is the difference between source coding and line coding?
10. What are the properties of line coding?
11. What is the effect of inter symbol interference?
12. How ISI can be reduced?

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13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate
16. Draw the NRZ and RZ code for the digital data 10110001.
17. Define ? Equalization

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18. What is PRBS?
19. Write the Boolean expression for X-NOR gate.
20. Define ? Digital demodulation

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Viva - voce

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CYCLE 2 ? EXPERIMENTS
Expt. No.8 ERROR CONTROL CODING USING MATLAB
Aim:

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To write a program in MATLAB for error control coding techniques
Software required:
PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.

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2. MATLAB logo will appear after few moments comon prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitiled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the

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program press F5 or go to debug menu select run.
6. After execution output will appear in the common window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the error control coding techniques are executed using MATLAB programs.
Outcome:
After the completion of this experiment the students will be able to simulate the different error control coding
schemes using MATLAB.

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Applications :
1. Deep space communication
2. Satellite communication
3. Data transmission
4. Data storage

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5. Mobile communication
6. File transfer
7. digital audio/video transmission.
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1. What is the need for error control coding?
2. What is meant by linear code?
3. What is meant by cyclic code?
4. Name some error control coding techniques.

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5. Name the code which is used only for error detection.

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Viva - voce
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Expt. No. 9 DESIGN OF BPSK, QPSK, QAM USING MATLAB
Aim:
To write a program in MATLAB for design of BPSK, QPSK and QAM
Software required:

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PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper

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icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error

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will appear in red colour.
7. Rectify the error, if any go to debug menu select run.

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Result:
Thus the BPSK, QPSK and QAM were simulated using MATLAB.
Outcome:
After the completion of this experiment the students will be able to simulate the various modulation schemes

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such as BPSK, QPSK and QAM using MATLAB.
Applications:
QPSK
1. Data transmission, mainly radio transmissions.
2. RTTY means radio teletype transmissions from amateur radio up to WiFi transmissions or Zigbees

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QAM
1. Radio communications and data delivery applications.


1. What is a correlator?

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2. Define ? Constellation Diagram
3. What is BPSK ? Mention its significance.
4. Give the expression for bandwidth of BPSK scheme.
5. What is QPSK mention its significance?
6. Give the expression for bandwidth of QPSK scheme.

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7. Draw the constellation diagram of QPSK.
8. What is QAM ?
9. Give the expression for bandwidth of QAM scheme.
10. What are the blocks in BPSK receiver?
11. What is the function of a decision device?

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12. Draw the constellation diagram of QAM.
13. What are the types of QPSK?
14. What is the significance of Q-channel I channel in QPSK modulator?
15. What is the minimum bandwidth requirement of QPSK?
16. Draw the output phase versus time relationship for a QPSK modulator.

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17. Compare OQPSK with QPSK.
18. Identify the error in the matlab command Sin 3.
19. Draw the constellation diagram of QPSK.
20. Give the applications of QPSK modulation scheme.
Viva - voce

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54 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 10 DESIGN OF FSK, PSK, DPSK USING MATLAB
Aim:
To write a program in MATLAB for design of FSK, PSK and DPSK

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Software required:
PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.

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3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.

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6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the FSK, PSK and DPSK were simulated using MATLAB.
Outcome:
After the completion of this experiment the students will be able to simulate the various modulation schemes

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such as FSK, PSK and DPSK using MATLAB.
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Applications:
ASK:

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1. ASK is used to transmit digital data over optical fiber
PSK:
1. over voice lines
2. in high-freq. radio transmissions.

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1. What is FSK? Mention its significance.
2. What is PSK? Mention its significance.
3. What is DPSK? Mention its significance.
4. What are the applications of DPSK?

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5. Give the equation for average probability of symbol error for DPSK.
6. List the operations performed in DPSK transmitter.
7. Compare DPSK with QPSK modulation scheme.
8. What is differential encoding technique?
9. Why do we make 180 degree phase shift in PSK why not 90 or 270?

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10. What is the function of a decision device?
11. What is RZ?
12. What is NRZ?
13. What is Manchester encoding?
14. Sketch the FSK waveform for the input a) 1010110 b) 1100101

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15. Define modulation index.
16. Write a MATLAB program for generating PN sequence.
17. Differentiate coherent with non-coherent FSK.
18. Give the expression for bandwidth of FSK scheme.
19. What is the difference between PSK and FSK?

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20. What is the major advantage of coherent PSK over coherent ASK?

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Viva - voce
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sExpt. No. 11 COMMUNICATION LINK SIMULATION USING
MATLAB

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Aim:
To simulate the basic communication link using mat lab
Software required:
PC with MATLAB version 7.0 software installed
Procedure:

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1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.

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5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the communication link simulation was designed using MATLAB.

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Outcome:
After the completion of this experiment the students will be able to simulate and design the communication link
using MATLAB.

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1. Give examples for digital modulation techniques.
2. What is meant by pass-b transmission?

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3. What is meant by base-b transmission?
4. What is the meaning for error pattern?
5. Differentiate systematic from non-systematic coding.

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Viva - voce
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Expt. No. 12 ZERO FORCING LMS EQUALIZATION
ALGORITHMS USING MATLAB
Aim:
To write a program in MATLAB for design of zero forcing LMS algorithms
Software required:

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PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper

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icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error

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will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the equalization of zero forcing LMS algorithms was simulated using MATLAB.
Outcome:
After the completion of this experiment the students will be able to implement the various algorithms using

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MATLAB.



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1. Define ? Equalization

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2. What is meant by zero forcing algorithms?
3. Define ? LMS Algorithm
4. What is meant by pass-b transmission?
5. What is meant by base-b transmission?
6. What is the meaning for error pattern?

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Viva - voce
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ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS

Expt. No. 13 PULSE AMPLITUDE MODULATION
Aim:
To study the Pulse Amplitude Modulation technique and observe the output waveform

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Apparatus required:
Sl. No. Name of the Apparatus Range Quantity
1 Function generator 0-3 MHz 1
2 Diode 1N4007 2
3 Resistors, 3.3 k? 2

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4 Bread Board 1
5 Power supply (0-30) V 1
6 CRO 30 MHz 1
7 Probe few
8 Connecting Wires few

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Procedure:
1. Measure the amplitude of each pulse, no. of pulses in one cycle, frequency of pulses.
2. Vary the modulating input signal observe its effect on the output.
3. Observe compare the output waveform with input waveform/

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4. See the input and output that are same in frequency, amplitude phase.
5. Draw the waveform of the modulating signal, sampling signal, pulse amplitude a modulated signal.

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FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

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V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL

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DHANALAKSHMI

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College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry

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? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

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To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

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? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems

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? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION
VISION
MISSION
MISSION

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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,

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enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions

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3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students

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to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)

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a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics

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communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large

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h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM

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? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction

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2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation

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7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation

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12. Equalization ? Zero Forcing and LMS algorithms (simulation)


Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.

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Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

COURSE OBJECTIVES
COURSE OUTCOMES

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.

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CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7
2 Time division multiplexing
13

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3 AM modulation demodulation
18
4 Frequency modulation demodulation
26
5 PCM modulation demodulation

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33
6 Delta modulation demodulation
38
7 Line coding decoding techniques
45

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CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB
53

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10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB

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59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit

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Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.

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Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For

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reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known

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as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the

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sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:

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1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.

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6. Integrate the sampling inputs.

Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

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Analog signal sampling and reconstruction trainer kit


Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer

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kit.


Signal Amplitude (V) Time period (s)
Message signal

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Carrier signal
Sampled output
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Outcome:

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After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)

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3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem

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2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?

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7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?

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12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal

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17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
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Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.

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2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common

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signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.

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(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this

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sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of

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Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .


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Circuit Diagram
Time division multiplexing

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TDM Trainer Kit

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Model Graph:

Tabulation
Sl. No. Signal Amplitude (V) Time period (s)

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1. Message signal 1
2. Message Signal 2
3. TDM signal

Result:

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Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital

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transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital

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Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system

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1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?

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6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce
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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:

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To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver
Apparatus required:
.
1 Resistor ? 4 No.

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2 Capacitor ? 1 No.
3 Diode ? 2 No.
4
AM transmitter receiver
trainer kit ? 1 No.

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5 CRO ? 1 No.
6 Patch cards ? 6 No.

Theory:

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AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt

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VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,

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VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where

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Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:

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M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if

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M < 1 Under modulation
M = 1 Critical modulation
M > 1 over modulation

Procedure:

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1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:

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1. AM Waveform (Ring diode Transistor based AM Modulator)

AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated

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demodulated wave.
Applications:
1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.

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3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?

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8. What is depth of modulation?
9. What are the different types of AM generation?
10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce

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12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation

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15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.

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19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION

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Aim:
To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver
Apparatus required:
.

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1. Resistor ? 4 No.
2. Capacitor ? 1 No.
3. Diode ? 2 No.
4.
AM transmitter Receiver

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trainer kit ? 1 No.
5. CRO ? 1 No.
6. Patch cards ? 6 No.

Theory:

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Frequency modulation (FM) is a form of modulation that represents information as variations in the
instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A

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narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used
in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to

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present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of
noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

Procedure:

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FM Modulator:
1. Switch ON the Power supply.

2. Connect the sine wave generator output to frequency modulator input.

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3. Select the low frequency carrier (or) high frequency carrier.

4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

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6. Observe the frequency modulator output .

FM Demodulator:
A) PLL Detector

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1. Connect frequency modulated output to the PLL detector input.

2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

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4. Observe the Demodulated O/P compare with the original input.

B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

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2. Now set the DPDT switch in high frequency mode.

3. Connect the CRO input to Quadrature detector output.

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4. Observe the Demodulated O/P and compare with the original input.
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C) Phase Discriminator (Foster-Seeley detector)

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1. Connect the frequency modulated output to Phase discriminator input.

2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

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4. Observe the Demodulated O/P and then compare with the original input.

D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Ratio detector output.

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4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram
FM Modulator

FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

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Carrier

Modulated

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Demodulated


Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency

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modulated and demodulated wave.
Applications:
1. Television sound transmission
2. Two way mobile radio
3. Cellular Radio

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4. Microwave
5. Satellite Communication System


1. Define ? Frequency Modulation

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2. How it is different from phase modulation?
3. Write equation of FM wave, explain each parameter in it.
4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.
6. Define ? Modulation Index

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7. Differentiate between Narrow band FM from Wide band FM.
8. Draw message, carrier FM waves .
9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?
11. Give the practical applications of FM.

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12. State advantages and disadvantages of FM.
13. What is the range of speech signals?
14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation

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17. Draw the phasor diagram of FM signal.
18. What are the different types of FM generation?

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Viva - voce
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Expt. No. 5 PCM MODULATION & DEMODULATION

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Aim:
To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator
Apparatus Required:

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1. PCM trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is

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first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of
converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization
can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization

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the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel
serially.
At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword

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is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to
Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks
for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:

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1. Power on the PCM kit.
2. Measure the frequency of sampling clock.
3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.
5. Connect the clock to the timing control circuit.
6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.

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9. Observe the waveform at the output of DAC.
10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the
codeword graphically for a DC input.
Block diagram of PCM Transmission system

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PCM Modulation and Demodulation Trainer kit

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Model Graph:

Tabulation

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Result:
Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.
Outcome:
After the completion of this experiment the students will be able to design and construct the pulse code
modulated and demodulated wave.

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Applications:
1. Military Applications.
2. The PCM is used in the satellite transmission system.
SIGNALS AMPLITUDE (V) TIME PERIOD (s)
DC Input

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Sampled Signal
Clock Pulse
PCM Output
DC Output
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3. It is used in space communication.
4. It is used in telephony.
5. The compact disc (CD) is a recent application of PCM.

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1. Define ? Modulation
2. State sampling theorem
3. Define ? Demodulation
4. Define ? Pulse Code Modulation

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5. What is aliasing effect?
6. What is quantization?
7. Define ? Bit Rate
8. Define ? Baud Rate
9. What are the advantages of PCM?

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10. Define ? Signal to Noise Ratio
11. What are the limitations of PCM?
12. What are the applications of PCM?
13. Define ? Encoding
14. Define ? Decoding

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15. Define ? Nyquist Rate
16. What is multiplexing?
17. What is de-multiplexing?
18. What are the types of pulse modulation?
19. What should be the minimum bandwidth required to transmit a PCM channel?

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20. What is the value of signal to noise ratio in PCM?

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Viva - voce
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Expt. No. 6 DELTA MODULATION & DEMODULATION
Aim:
To transmit an analog message signal in its digital form and reconstruct back the original analog message
signal at receiver by using Delta modulator

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Apparatus required:
1. DM and ADM Trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:

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Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The
difference signal between two successive samples is encoded into a single bit code. A present sample of the
analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level
(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.
The comparison of samples is accomplished by converting the digital to analog form then comparing with the

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present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to
a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.
Procedure:
1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.
2. Observe the modulated signal in the CRO.

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3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.
4. Also observe the DAC output on the CRO.
5. Change the amplitude of the modulating signal.
6. Observe the DAC output. Notice the slope overload distortion.
7. Keep the tuning knob to minimize distortion.

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8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope
overload distortion.
9. Calculate the sampling frequency required for no slope overload distortion.
10. Compare the calculated measured values of the sampling frequency.

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38 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Block Diagram Delta modulator and demodulator

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Delta Modulator

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Delta Demodulator



39 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Block diagram of Adaptive delta modulator and demodulator

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Adaptive Delta Modulator

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Adaptive Delta Demodulator

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40 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Delta Modulation and Adaptive Delta Modulator Trainer kit

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41 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Model Graph:

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42 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Tabulation 1
For Delta Modulation

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Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal
2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

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Tabulation 2
For Adaptive Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal

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2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

Result:

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Thus the output waveforms of Delta modulation and adaptive delta modulation circuit were observed.
Outcome:
After the completion of this experiment the students will be able to design and construct the delta modulation
adaptive delta modulation circuit.
Applications:

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1. Digital voice storage
2. Voice transmission
43 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

3. Radio communication devices such TV remotes.

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4. Delta Modulation was used by Satellite Business Systems or SBS
5. DM used in high resolution A/D and D/A converters.


1. What is delta modulation?

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2. What is adaptive delta modulation?
3. What are the advantages of adaptive delta modulation over delta modulation?
4. What is slope over load distortion?
5. What is granular noise effect?
6. What are the two limitations of delta modulation?

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7. What is the function of integrator?
8. What is comparator?
9. What is companding?
10. What is the advantage of delta modulation over pulse modulation?
11. Distinguish between DPCM and DM.

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12. What are the different types of digital modulation?
13. What is sampling rate?
14. Which kind of multiplexing used in digital communication?
15. Why is sample hold circuit used?
16. What are the advantages of digital transmission?

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17. How is the performance corrupted in PCM?
18. What are the different types of multiplexing?
19. What is aliasing effect?
20. How to avoid aliasing effect?

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Viva - voce
44 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 7 LINE CODING DECODING TECHNIQUES

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Aim:
To study different line coding techniques.
Apparatus required:
1. Line coding and decoding trainer kit ? 1 No.

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2. Patch cords ? 6 No.
3. CRO ? 1 No.

Theory:
Line coding refers to the process of representing the bit stream (1 ?s and 0 ?s) in the form of voltage or current

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variations optimally tuned for the specific properties of the physical channel being used. The selection of a proper
line code can help in many ways. One possibility is to aid in clock recovery at the receiver. A clock signal is
recovered by observing transitions in the received bit sequence, if enough transitions exist, a good recovery of
the clock is guaranteed, the signal is said to be self-clocking. Another advantage is to get rid of DC shifts. The
DC component in a line code is called the bias or the DC coefficient. Unfortunately, most long-distance

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communication channels cannot transport a DC component. This is why most line codes try to eliminate the DC
component before being transmitted on the channel. Such codes are called DC balanced, zero-DC, zero-bias, or
DC equalized. Some common types of line encoding in common-use nowadays are unipolar, polar, bipolar,
Manchester, MLT-3 Duo binary encoding.
Unipolar (Unipolar NRZ and Unipolar RZ):

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Unipolar is the simplest line coding scheme. It has the advantage of being compatible with TTL logic. Unipolar
coding uses a positive rectangular pulse p(t) to represent binary 1, the absence of a pulse (i.e., zero voltage) to
represent a binary 0. Two possibilities for the pulse p(t) exist3: Non-Return-to-Zero (NRZ) rectangular pulse
Return-to-Zero (RZ) rectangular pulse. The difference between Unipolar NRZ Unipolar RZ codes is that the
rectangular pulse in NRZ stays at a positive value (e.g., +5V) for the full duration of the logic 1 bit, while the pule

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in RZ drops from +5V to 0V in the middle of the bit time.



45 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Procedure:
1. Connect the PRBS (test point P5) to various line coding formats. Obtain the coded output as per the
requirement.
2. Connect coded signal test point to corresponding decoding test point as inputs.

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3. Set the SW1 as per the requirement.
4. Set the potentiometer P1 in minimum position.
5. Switch ON the power supply. Press the switch SW2 once.
6. Display the encoded signal on one channel of CRO and decoded signal on second channel of CRO.

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46 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


Line coding decoding trainer kit

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47 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


Model Graph:

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48 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Tabulation
Sl. No. Type of Coding AMPLITUDE (V) Time period (s)
1. Unipolar data(NZ NRZ )

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2. Unipolar data (NRZ RZ)
3. Bipolar Data(NRZ AMI)
4. Manchester

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Result:
Thus the different line coding techniques was studied and verified.
Outcome:
After the completion of this experiment the students will be able to understand implement the different line
coding schemes.

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Applications:
1. DC balance
2. embedded clock applications
3. computing applications
4. Manchester codes are commonly used for local area networks

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5. Bipolar codes are commonly used for local area networks

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49 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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1. What is line coding?
2. Define ? Polar Encoding
3. Define ? Unipolar Encoding
4. Define ? Bipolar Encoding
5. Define ? Manchester Encoding

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6. What are the two function of fast frequency hopping?
7. What is return to zero?
8. What is Non-return to zero?
9. What is the difference between source coding and line coding?
10. What are the properties of line coding?

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11. What is the effect of inter symbol interference?
12. How ISI can be reduced?
13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate

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16. Draw the NRZ and RZ code for the digital data 10110001.
17. Define ? Equalization
18. What is PRBS?
19. Write the Boolean expression for X-NOR gate.
20. Define ? Digital demodulation

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Viva - voce
50 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

CYCLE 2 ? EXPERIMENTS

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Expt. No.8 ERROR CONTROL CODING USING MATLAB
Aim:
To write a program in MATLAB for error control coding techniques
Software required:
PC with MATLAB version 7.0 software installed

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Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments comon prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.

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4. A blank M ?file will appear with a title ?untitiled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the common window. If there is an error then with an alarm, type of error
will appear in red colour.

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7. Rectify the error if any go to debug menu select run.

Result:
Thus the error control coding techniques are executed using MATLAB programs.
Outcome:

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After the completion of this experiment the students will be able to simulate the different error control coding
schemes using MATLAB.
Applications :
1. Deep space communication
2. Satellite communication

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3. Data transmission
4. Data storage
5. Mobile communication
6. File transfer
7. digital audio/video transmission.

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51 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


1. What is the need for error control coding?
2. What is meant by linear code?

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3. What is meant by cyclic code?
4. Name some error control coding techniques.
5. Name the code which is used only for error detection.

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Viva - voce
52 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 9 DESIGN OF BPSK, QPSK, QAM USING MATLAB
Aim:

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To write a program in MATLAB for design of BPSK, QPSK and QAM
Software required:
PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.

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2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the

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program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error, if any go to debug menu select run.

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53 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Result:
Thus the BPSK, QPSK and QAM were simulated using MATLAB.

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Outcome:
After the completion of this experiment the students will be able to simulate the various modulation schemes
such as BPSK, QPSK and QAM using MATLAB.
Applications:
QPSK

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1. Data transmission, mainly radio transmissions.
2. RTTY means radio teletype transmissions from amateur radio up to WiFi transmissions or Zigbees
QAM
1. Radio communications and data delivery applications.

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1. What is a correlator?
2. Define ? Constellation Diagram
3. What is BPSK ? Mention its significance.
4. Give the expression for bandwidth of BPSK scheme.

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5. What is QPSK mention its significance?
6. Give the expression for bandwidth of QPSK scheme.
7. Draw the constellation diagram of QPSK.
8. What is QAM ?
9. Give the expression for bandwidth of QAM scheme.

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10. What are the blocks in BPSK receiver?
11. What is the function of a decision device?
12. Draw the constellation diagram of QAM.
13. What are the types of QPSK?
14. What is the significance of Q-channel I channel in QPSK modulator?

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15. What is the minimum bandwidth requirement of QPSK?
16. Draw the output phase versus time relationship for a QPSK modulator.
17. Compare OQPSK with QPSK.
18. Identify the error in the matlab command Sin 3.
19. Draw the constellation diagram of QPSK.

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20. Give the applications of QPSK modulation scheme.
Viva - voce
54 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 10 DESIGN OF FSK, PSK, DPSK USING MATLAB

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Aim:
To write a program in MATLAB for design of FSK, PSK and DPSK
Software required:
PC with MATLAB version 7.0 software installed
Procedure:

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1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.

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5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the FSK, PSK and DPSK were simulated using MATLAB.

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Outcome:
After the completion of this experiment the students will be able to simulate the various modulation schemes
such as FSK, PSK and DPSK using MATLAB.
55 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Applications:
ASK:
1. ASK is used to transmit digital data over optical fiber
PSK:
1. over voice lines

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2. in high-freq. radio transmissions.


1. What is FSK? Mention its significance.
2. What is PSK? Mention its significance.

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3. What is DPSK? Mention its significance.
4. What are the applications of DPSK?
5. Give the equation for average probability of symbol error for DPSK.
6. List the operations performed in DPSK transmitter.
7. Compare DPSK with QPSK modulation scheme.

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8. What is differential encoding technique?
9. Why do we make 180 degree phase shift in PSK why not 90 or 270?
10. What is the function of a decision device?
11. What is RZ?
12. What is NRZ?

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13. What is Manchester encoding?
14. Sketch the FSK waveform for the input a) 1010110 b) 1100101
15. Define modulation index.
16. Write a MATLAB program for generating PN sequence.
17. Differentiate coherent with non-coherent FSK.

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18. Give the expression for bandwidth of FSK scheme.
19. What is the difference between PSK and FSK?
20. What is the major advantage of coherent PSK over coherent ASK?

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Viva - voce
56 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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sExpt. No. 11 COMMUNICATION LINK SIMULATION USING
MATLAB
Aim:
To simulate the basic communication link using mat lab
Software required:

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PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper

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icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error

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will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the communication link simulation was designed using MATLAB.
Outcome:
After the completion of this experiment the students will be able to simulate and design the communication link
using MATLAB.

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57 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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1. Give examples for digital modulation techniques.
2. What is meant by pass-b transmission?
3. What is meant by base-b transmission?
4. What is the meaning for error pattern?
5. Differentiate systematic from non-systematic coding.

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Viva - voce

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58 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 12 ZERO FORCING LMS EQUALIZATION
ALGORITHMS USING MATLAB
Aim:

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To write a program in MATLAB for design of zero forcing LMS algorithms
Software required:
PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.

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2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the

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program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the equalization of zero forcing LMS algorithms was simulated using MATLAB.

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Outcome:
After the completion of this experiment the students will be able to implement the various algorithms using
MATLAB.

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59 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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1. Define ? Equalization
2. What is meant by zero forcing algorithms?
3. Define ? LMS Algorithm
4. What is meant by pass-b transmission?

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5. What is meant by base-b transmission?
6. What is the meaning for error pattern?

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Viva - voce

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60 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS

Expt. No. 13 PULSE AMPLITUDE MODULATION

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Aim:
To study the Pulse Amplitude Modulation technique and observe the output waveform
Apparatus required:
Sl. No. Name of the Apparatus Range Quantity
1 Function generator 0-3 MHz 1

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2 Diode 1N4007 2
3 Resistors, 3.3 k? 2
4 Bread Board 1
5 Power supply (0-30) V 1
6 CRO 30 MHz 1

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7 Probe few
8 Connecting Wires few

Procedure:
1. Measure the amplitude of each pulse, no. of pulses in one cycle, frequency of pulses.

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2. Vary the modulating input signal observe its effect on the output.
3. Observe compare the output waveform with input waveform/
4. See the input and output that are same in frequency, amplitude phase.
5. Draw the waveform of the modulating signal, sampling signal, pulse amplitude a modulated signal.

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61 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


Circuit Diagram
Pulse amplitude modulation

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Model Graph:

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FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?



DEPARTMENT OF

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ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

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? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul

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DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING


To impart professional education integrated with human values to the younger generation, so as to

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shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity


? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics

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industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION

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VISION
MISSION
MISSION
3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education

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2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to

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find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context

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5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field

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b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems

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e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility

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i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

EC6512 - COMMUNICATION SYSTEMS LABORATORY

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To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms

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? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator

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4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes

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9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

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COURSE OBJECTIVES
COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction

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7
2 Time division multiplexing
13
3 AM modulation demodulation
18

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4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33
6 Delta modulation demodulation

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38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB

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51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB
55

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11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS

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13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS

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Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.

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2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at

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which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.

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Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples

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taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To

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recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit

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works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.

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3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

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Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal
Sampled output

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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.

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Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)

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5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate

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4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?

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9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.

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14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.

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19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
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Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:

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To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.

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4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.

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Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .

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3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .

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6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .

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Circuit Diagram

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Time division multiplexing

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TDM Trainer Kit

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Model Graph:

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Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1
2. Message Signal 2

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3. TDM signal

Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:

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After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.


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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network

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2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis

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5. The GSM telephone system


1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?

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3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?

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8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce
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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver

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Apparatus required:
.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.
3 Diode ? 2 No.

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4
AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.
6 Patch cards ? 6 No.

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Theory:

AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the

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instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.

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Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal

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Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index

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Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if
M < 1 Under modulation
M = 1 Critical modulation

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M > 1 over modulation

Procedure:
1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.

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3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

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AM Modulated wave



2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)

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Message

Carrier

Modulated

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Demodulated


Result:

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Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.
Applications:

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1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?

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5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?
9. What are the different types of AM generation?

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10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce
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12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?

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17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?

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21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after

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demodulating using FM receiver
Apparatus required:
.
1. Resistor ? 4 No.
2. Capacitor ? 1 No.

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3. Diode ? 2 No.
4.
AM transmitter Receiver
trainer kit ? 1 No.
5. CRO ? 1 No.

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6. Patch cards ? 6 No.

Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the
instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct

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proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used
in broadcast is generally called wide-FM, or W-FM.

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In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the

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luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of
noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes

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print-through pre-echo.

Procedure:
FM Modulator:
1. Switch ON the Power supply.

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2. Connect the sine wave generator output to frequency modulator input.

3. Select the low frequency carrier (or) high frequency carrier.

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4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

6. Observe the frequency modulator output .

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FM Demodulator:
A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

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2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

4. Observe the Demodulated O/P compare with the original input.

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B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

2. Now set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Quadrature detector output.

4. Observe the Demodulated O/P and compare with the original input.
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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

4. Observe the Demodulated O/P and then compare with the original input.

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D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

2. Set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Ratio detector output.

4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram
FM Modulator

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FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency
modulated and demodulated wave.
Applications:

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1. Television sound transmission
2. Two way mobile radio
3. Cellular Radio
4. Microwave
5. Satellite Communication System

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1. Define ? Frequency Modulation
2. How it is different from phase modulation?
3. Write equation of FM wave, explain each parameter in it.

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4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.
6. Define ? Modulation Index
7. Differentiate between Narrow band FM from Wide band FM.
8. Draw message, carrier FM waves .

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9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?
11. Give the practical applications of FM.
12. State advantages and disadvantages of FM.
13. What is the range of speech signals?

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14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation
17. Draw the phasor diagram of FM signal.
18. What are the different types of FM generation?

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Viva - voce

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32 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 5 PCM MODULATION & DEMODULATION

Aim:

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To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator
Apparatus Required:
1. PCM trainer kit ? 1 No.
2. CRO ? 1 No.

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3. Connecting probes ? 4 No.
Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is
first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of
converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization

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can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization
the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel
serially.

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At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword
is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to
Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks

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for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:
1. Power on the PCM kit.
2. Measure the frequency of sampling clock.

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3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.
5. Connect the clock to the timing control circuit.

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6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.
9. Observe the waveform at the output of DAC.
10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the

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codeword graphically for a DC input.
Block diagram of PCM Transmission system

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PCM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation

Result:
Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.

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Outcome:
After the completion of this experiment the students will be able to design and construct the pulse code
modulated and demodulated wave.
Applications:
1. Military Applications.

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2. The PCM is used in the satellite transmission system.
SIGNALS AMPLITUDE (V) TIME PERIOD (s)
DC Input
Sampled Signal
Clock Pulse

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PCM Output
DC Output
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3. It is used in space communication.

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4. It is used in telephony.
5. The compact disc (CD) is a recent application of PCM.


1. Define ? Modulation

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2. State sampling theorem
3. Define ? Demodulation
4. Define ? Pulse Code Modulation
5. What is aliasing effect?
6. What is quantization?

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7. Define ? Bit Rate
8. Define ? Baud Rate
9. What are the advantages of PCM?
10. Define ? Signal to Noise Ratio
11. What are the limitations of PCM?

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12. What are the applications of PCM?
13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate
16. What is multiplexing?

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17. What is de-multiplexing?
18. What are the types of pulse modulation?
19. What should be the minimum bandwidth required to transmit a PCM channel?
20. What is the value of signal to noise ratio in PCM?

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Viva - voce
37 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 6 DELTA MODULATION & DEMODULATION

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Aim:
To transmit an analog message signal in its digital form and reconstruct back the original analog message
signal at receiver by using Delta modulator
Apparatus required:
1. DM and ADM Trainer kit ? 1 No.

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2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The
difference signal between two successive samples is encoded into a single bit code. A present sample of the

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analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level
(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.
The comparison of samples is accomplished by converting the digital to analog form then comparing with the
present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to
a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.

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Procedure:
1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.
2. Observe the modulated signal in the CRO.
3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.
4. Also observe the DAC output on the CRO.

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5. Change the amplitude of the modulating signal.
6. Observe the DAC output. Notice the slope overload distortion.
7. Keep the tuning knob to minimize distortion.
8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope
overload distortion.

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9. Calculate the sampling frequency required for no slope overload distortion.
10. Compare the calculated measured values of the sampling frequency.


38 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Block Diagram Delta modulator and demodulator

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Delta Modulator

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Delta Demodulator

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39 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Block diagram of Adaptive delta modulator and demodulator

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Adaptive Delta Modulator

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Adaptive Delta Demodulator

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40 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Delta Modulation and Adaptive Delta Modulator Trainer kit

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41 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Model Graph:

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42 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Tabulation 1
For Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal

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2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

Tabulation 2

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For Adaptive Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal
2 Carrier Signal
3 Modulated Signal

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4 Demodulated Signal

Result:
Thus the output waveforms of Delta modulation and adaptive delta modulation circuit were observed.
Outcome:

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After the completion of this experiment the students will be able to design and construct the delta modulation
adaptive delta modulation circuit.
Applications:
1. Digital voice storage
2. Voice transmission

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43 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

3. Radio communication devices such TV remotes.
4. Delta Modulation was used by Satellite Business Systems or SBS
5. DM used in high resolution A/D and D/A converters.

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1. What is delta modulation?
2. What is adaptive delta modulation?
3. What are the advantages of adaptive delta modulation over delta modulation?

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4. What is slope over load distortion?
5. What is granular noise effect?
6. What are the two limitations of delta modulation?
7. What is the function of integrator?
8. What is comparator?

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9. What is companding?
10. What is the advantage of delta modulation over pulse modulation?
11. Distinguish between DPCM and DM.
12. What are the different types of digital modulation?
13. What is sampling rate?

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14. Which kind of multiplexing used in digital communication?
15. Why is sample hold circuit used?
16. What are the advantages of digital transmission?
17. How is the performance corrupted in PCM?
18. What are the different types of multiplexing?

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19. What is aliasing effect?
20. How to avoid aliasing effect?

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Viva - voce

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44 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 7 LINE CODING DECODING TECHNIQUES

Aim:

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To study different line coding techniques.
Apparatus required:
1. Line coding and decoding trainer kit ? 1 No.
2. Patch cords ? 6 No.
3. CRO ? 1 No.

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Theory:
Line coding refers to the process of representing the bit stream (1 ?s and 0 ?s) in the form of voltage or current
variations optimally tuned for the specific properties of the physical channel being used. The selection of a proper
line code can help in many ways. One possibility is to aid in clock recovery at the receiver. A clock signal is

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recovered by observing transitions in the received bit sequence, if enough transitions exist, a good recovery of
the clock is guaranteed, the signal is said to be self-clocking. Another advantage is to get rid of DC shifts. The
DC component in a line code is called the bias or the DC coefficient. Unfortunately, most long-distance
communication channels cannot transport a DC component. This is why most line codes try to eliminate the DC
component before being transmitted on the channel. Such codes are called DC balanced, zero-DC, zero-bias, or

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DC equalized. Some common types of line encoding in common-use nowadays are unipolar, polar, bipolar,
Manchester, MLT-3 Duo binary encoding.
Unipolar (Unipolar NRZ and Unipolar RZ):
Unipolar is the simplest line coding scheme. It has the advantage of being compatible with TTL logic. Unipolar
coding uses a positive rectangular pulse p(t) to represent binary 1, the absence of a pulse (i.e., zero voltage) to

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represent a binary 0. Two possibilities for the pulse p(t) exist3: Non-Return-to-Zero (NRZ) rectangular pulse
Return-to-Zero (RZ) rectangular pulse. The difference between Unipolar NRZ Unipolar RZ codes is that the
rectangular pulse in NRZ stays at a positive value (e.g., +5V) for the full duration of the logic 1 bit, while the pule
in RZ drops from +5V to 0V in the middle of the bit time.

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45 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Procedure:

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1. Connect the PRBS (test point P5) to various line coding formats. Obtain the coded output as per the
requirement.
2. Connect coded signal test point to corresponding decoding test point as inputs.
3. Set the SW1 as per the requirement.
4. Set the potentiometer P1 in minimum position.

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5. Switch ON the power supply. Press the switch SW2 once.
6. Display the encoded signal on one channel of CRO and decoded signal on second channel of CRO.

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46 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Line coding decoding trainer kit

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47 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Model Graph:

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48 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00



Tabulation

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Sl. No. Type of Coding AMPLITUDE (V) Time period (s)
1. Unipolar data(NZ NRZ )

2. Unipolar data (NRZ RZ)
3. Bipolar Data(NRZ AMI)

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4. Manchester


Result:
Thus the different line coding techniques was studied and verified.

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Outcome:
After the completion of this experiment the students will be able to understand implement the different line
coding schemes.
Applications:
1. DC balance

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2. embedded clock applications
3. computing applications
4. Manchester codes are commonly used for local area networks
5. Bipolar codes are commonly used for local area networks

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49 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


1. What is line coding?
2. Define ? Polar Encoding

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3. Define ? Unipolar Encoding
4. Define ? Bipolar Encoding
5. Define ? Manchester Encoding
6. What are the two function of fast frequency hopping?
7. What is return to zero?

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8. What is Non-return to zero?
9. What is the difference between source coding and line coding?
10. What are the properties of line coding?
11. What is the effect of inter symbol interference?
12. How ISI can be reduced?

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13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate
16. Draw the NRZ and RZ code for the digital data 10110001.
17. Define ? Equalization

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18. What is PRBS?
19. Write the Boolean expression for X-NOR gate.
20. Define ? Digital demodulation

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Viva - voce

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50 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

CYCLE 2 ? EXPERIMENTS
Expt. No.8 ERROR CONTROL CODING USING MATLAB
Aim:

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To write a program in MATLAB for error control coding techniques
Software required:
PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.

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2. MATLAB logo will appear after few moments comon prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitiled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the

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program press F5 or go to debug menu select run.
6. After execution output will appear in the common window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the error control coding techniques are executed using MATLAB programs.
Outcome:
After the completion of this experiment the students will be able to simulate the different error control coding
schemes using MATLAB.

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Applications :
1. Deep space communication
2. Satellite communication
3. Data transmission
4. Data storage

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5. Mobile communication
6. File transfer
7. digital audio/video transmission.
51 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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1. What is the need for error control coding?
2. What is meant by linear code?
3. What is meant by cyclic code?
4. Name some error control coding techniques.

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5. Name the code which is used only for error detection.

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Viva - voce
52 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 9 DESIGN OF BPSK, QPSK, QAM USING MATLAB
Aim:
To write a program in MATLAB for design of BPSK, QPSK and QAM
Software required:

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PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper

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icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error

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will appear in red colour.
7. Rectify the error, if any go to debug menu select run.

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53 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Result:
Thus the BPSK, QPSK and QAM were simulated using MATLAB.
Outcome:
After the completion of this experiment the students will be able to simulate the various modulation schemes

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such as BPSK, QPSK and QAM using MATLAB.
Applications:
QPSK
1. Data transmission, mainly radio transmissions.
2. RTTY means radio teletype transmissions from amateur radio up to WiFi transmissions or Zigbees

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QAM
1. Radio communications and data delivery applications.


1. What is a correlator?

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2. Define ? Constellation Diagram
3. What is BPSK ? Mention its significance.
4. Give the expression for bandwidth of BPSK scheme.
5. What is QPSK mention its significance?
6. Give the expression for bandwidth of QPSK scheme.

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7. Draw the constellation diagram of QPSK.
8. What is QAM ?
9. Give the expression for bandwidth of QAM scheme.
10. What are the blocks in BPSK receiver?
11. What is the function of a decision device?

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12. Draw the constellation diagram of QAM.
13. What are the types of QPSK?
14. What is the significance of Q-channel I channel in QPSK modulator?
15. What is the minimum bandwidth requirement of QPSK?
16. Draw the output phase versus time relationship for a QPSK modulator.

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17. Compare OQPSK with QPSK.
18. Identify the error in the matlab command Sin 3.
19. Draw the constellation diagram of QPSK.
20. Give the applications of QPSK modulation scheme.
Viva - voce

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54 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 10 DESIGN OF FSK, PSK, DPSK USING MATLAB
Aim:
To write a program in MATLAB for design of FSK, PSK and DPSK

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Software required:
PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.

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3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.

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6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the FSK, PSK and DPSK were simulated using MATLAB.
Outcome:
After the completion of this experiment the students will be able to simulate the various modulation schemes

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such as FSK, PSK and DPSK using MATLAB.
55 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Applications:
ASK:

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1. ASK is used to transmit digital data over optical fiber
PSK:
1. over voice lines
2. in high-freq. radio transmissions.

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1. What is FSK? Mention its significance.
2. What is PSK? Mention its significance.
3. What is DPSK? Mention its significance.
4. What are the applications of DPSK?

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5. Give the equation for average probability of symbol error for DPSK.
6. List the operations performed in DPSK transmitter.
7. Compare DPSK with QPSK modulation scheme.
8. What is differential encoding technique?
9. Why do we make 180 degree phase shift in PSK why not 90 or 270?

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10. What is the function of a decision device?
11. What is RZ?
12. What is NRZ?
13. What is Manchester encoding?
14. Sketch the FSK waveform for the input a) 1010110 b) 1100101

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15. Define modulation index.
16. Write a MATLAB program for generating PN sequence.
17. Differentiate coherent with non-coherent FSK.
18. Give the expression for bandwidth of FSK scheme.
19. What is the difference between PSK and FSK?

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20. What is the major advantage of coherent PSK over coherent ASK?

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Viva - voce
56 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

sExpt. No. 11 COMMUNICATION LINK SIMULATION USING
MATLAB

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Aim:
To simulate the basic communication link using mat lab
Software required:
PC with MATLAB version 7.0 software installed
Procedure:

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1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.

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5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the communication link simulation was designed using MATLAB.

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Outcome:
After the completion of this experiment the students will be able to simulate and design the communication link
using MATLAB.

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57 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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1. Give examples for digital modulation techniques.
2. What is meant by pass-b transmission?

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3. What is meant by base-b transmission?
4. What is the meaning for error pattern?
5. Differentiate systematic from non-systematic coding.

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Viva - voce
58 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 12 ZERO FORCING LMS EQUALIZATION
ALGORITHMS USING MATLAB
Aim:
To write a program in MATLAB for design of zero forcing LMS algorithms
Software required:

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PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper

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icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error

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will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the equalization of zero forcing LMS algorithms was simulated using MATLAB.
Outcome:
After the completion of this experiment the students will be able to implement the various algorithms using

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MATLAB.



59 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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1. Define ? Equalization

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2. What is meant by zero forcing algorithms?
3. Define ? LMS Algorithm
4. What is meant by pass-b transmission?
5. What is meant by base-b transmission?
6. What is the meaning for error pattern?

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Viva - voce
60 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS

Expt. No. 13 PULSE AMPLITUDE MODULATION
Aim:
To study the Pulse Amplitude Modulation technique and observe the output waveform

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Apparatus required:
Sl. No. Name of the Apparatus Range Quantity
1 Function generator 0-3 MHz 1
2 Diode 1N4007 2
3 Resistors, 3.3 k? 2

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4 Bread Board 1
5 Power supply (0-30) V 1
6 CRO 30 MHz 1
7 Probe few
8 Connecting Wires few

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Procedure:
1. Measure the amplitude of each pulse, no. of pulses in one cycle, frequency of pulses.
2. Vary the modulating input signal observe its effect on the output.
3. Observe compare the output waveform with input waveform/

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4. See the input and output that are same in frequency, amplitude phase.
5. Draw the waveform of the modulating signal, sampling signal, pulse amplitude a modulated signal.

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61 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Circuit Diagram
Pulse amplitude modulation

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Model Graph:

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62 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Tabulation
Signal Amplitude (V) Time Period (s)
Message

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Carrier

PAM wave

Demodulated

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Result:
Thus the pulse amplitude modulation (PAM) output waveform was generated.
Outcome:

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After the completion of this experiment the students will be able to design and construct the PAM modulated
wave.


1. What is PAM?

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2. Differentiate PAM from PCM.
3. Write the application of PAM.
4. Draw the PAM signal.
5. Compare PAM, PPM and PWM.
6. What are the advantage of PAM and PWM?

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7. What is the advantage of PPM over PWM and PAM?
8. What is Pulse position modulation?
9. Mention the applications of PAM.
10. What are the disadvantages of PAM?
11. What is PWM or Pulse length modulation or pulse duration modulation?

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12. Define ? Pulse Modulation


Viva ? voce
FirstRanker.com - FirstRanker's Choice

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1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

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V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________

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Section : _______________________________________

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LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

DHANALAKSHMI

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College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

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? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

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To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

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? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in

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communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION
VISION
MISSION

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MISSION
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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals

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To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge

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training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism

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To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,

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through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability

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c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities

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g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning

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k) To participate succeed in competitive exams

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation

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? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS

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1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation

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6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)

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11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)


Simulate end-to-end Communication Link

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Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

COURSE OBJECTIVES

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COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS

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Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7
2 Time division multiplexing

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13
3 AM modulation demodulation
18
4 Frequency modulation demodulation
26

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5 PCM modulation demodulation
33
6 Delta modulation demodulation
38
7 Line coding decoding techniques

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45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB

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53
10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB
57

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12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:

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To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.

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4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.

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A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the

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signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals

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The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.

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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.

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Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.

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5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

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Model Graph:

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Tabulation

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Analog signal sampling and reconstruction trainer kit


Result:

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Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.


Signal Amplitude (V) Time period (s)

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Message signal
Carrier signal
Sampled output
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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)

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2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

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1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?

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6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?

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11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?

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16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.

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21. Define ? Natural Sampling


Viva - voce
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Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:

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1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:

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Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.

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2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.

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4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .

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7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .

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Circuit Diagram
Time division multiplexing

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TDM Trainer Kit

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Model Graph:

Tabulation

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Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1
2. Message Signal 2
3. TDM signal

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Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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Applications:

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1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.

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3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system

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1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?

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5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?

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10. Which type of modulation technique will be used in TDM?

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Viva - voce
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Expt. No. 3 AM MODULATION & DEMODULATION

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Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver
Apparatus required:
.

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1 Resistor ? 4 No.
2 Capacitor ? 1 No.
3 Diode ? 2 No.
4
AM transmitter receiver

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trainer kit ? 1 No.
5 CRO ? 1 No.
6 Patch cards ? 6 No.

Theory:

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AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by

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Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

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The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal

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Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude

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if
M < 1 Under modulation
M = 1 Critical modulation
M > 1 over modulation

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Procedure:
1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .

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5. Calculate the modulation index

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Circuit Diagram

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AM Modulation


AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

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Carrier

Modulated

Demodulated

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Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:

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After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.
Applications:
1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.

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3. Facsimile transmission



1. What is modulation and demodulation?

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2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?

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7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?
9. What are the different types of AM generation?
10. Define ? Modulation Index
11. What are different types of analog modulation techniques?

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Viva - voce
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12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.

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14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?

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18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.

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23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver
Apparatus required:

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.
1. Resistor ? 4 No.
2. Capacitor ? 1 No.
3. Diode ? 2 No.
4.

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AM transmitter Receiver
trainer kit ? 1 No.
5. CRO ? 1 No.
6. Patch cards ? 6 No.

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Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the
instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF

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radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used
in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.

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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of

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frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of
noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

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Procedure:
FM Modulator:
1. Switch ON the Power supply.

2. Connect the sine wave generator output to frequency modulator input.

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3. Select the low frequency carrier (or) high frequency carrier.

4. Connect the CRO input to the frequency modulator output.

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5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

6. Observe the frequency modulator output .

FM Demodulator:

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A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

2. Now set the DPDT switch in low frequency mode.

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3. Connect CRO input to PLL detector output.

4. Observe the Demodulated O/P compare with the original input.

B) Quadrature Detector

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1. Connect the frequency modulated output to Quadrature detector input.

2. Now set the DPDT switch in high frequency mode.

3. Connect the CRO input to Quadrature detector output.

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4. Observe the Demodulated O/P and compare with the original input.
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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

2. Set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Phase discriminator output.

4. Observe the Demodulated O/P and then compare with the original input.

D) Ratio Detector

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1. Connect the frequency modulated output to Ratio detector input.

2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Ratio detector output.

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4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram
FM Modulator

FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:


Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)

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Message

Carrier

Modulated

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Demodulated


Result:

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Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:

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After the completion of this experiment the students will be able to design and construct the frequency
modulated and demodulated wave.
Applications:
1. Television sound transmission
2. Two way mobile radio

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3. Cellular Radio
4. Microwave
5. Satellite Communication System

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1. Define ? Frequency Modulation
2. How it is different from phase modulation?
3. Write equation of FM wave, explain each parameter in it.
4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.

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6. Define ? Modulation Index
7. Differentiate between Narrow band FM from Wide band FM.
8. Draw message, carrier FM waves .
9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?

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11. Give the practical applications of FM.
12. State advantages and disadvantages of FM.
13. What is the range of speech signals?
14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?

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16. Define ? Phase Modulation
17. Draw the phasor diagram of FM signal.
18. What are the different types of FM generation?

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Viva - voce
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Expt. No. 5 PCM MODULATION & DEMODULATION

Aim:
To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator

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Apparatus Required:
1. PCM trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:

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Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is
first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of
converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization
can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are

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given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization
the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel
serially.
At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.

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In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword
is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to
Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks
for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.

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Procedure:
1. Power on the PCM kit.
2. Measure the frequency of sampling clock.
3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.
5. Connect the clock to the timing control circuit.
6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.

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8. Now apply the AC modulating signal at the input.
9. Observe the waveform at the output of DAC.
10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the
codeword graphically for a DC input.
Block diagram of PCM Transmission system

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34 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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PCM Modulation and Demodulation Trainer kit

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35 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Model Graph:

Tabulation

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Result:
Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.
Outcome:
After the completion of this experiment the students will be able to design and construct the pulse code

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modulated and demodulated wave.
Applications:
1. Military Applications.
2. The PCM is used in the satellite transmission system.
SIGNALS AMPLITUDE (V) TIME PERIOD (s)

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DC Input
Sampled Signal
Clock Pulse
PCM Output
DC Output

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3. It is used in space communication.
4. It is used in telephony.
5. The compact disc (CD) is a recent application of PCM.

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1. Define ? Modulation
2. State sampling theorem
3. Define ? Demodulation

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4. Define ? Pulse Code Modulation
5. What is aliasing effect?
6. What is quantization?
7. Define ? Bit Rate
8. Define ? Baud Rate

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9. What are the advantages of PCM?
10. Define ? Signal to Noise Ratio
11. What are the limitations of PCM?
12. What are the applications of PCM?
13. Define ? Encoding

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14. Define ? Decoding
15. Define ? Nyquist Rate
16. What is multiplexing?
17. What is de-multiplexing?
18. What are the types of pulse modulation?

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19. What should be the minimum bandwidth required to transmit a PCM channel?
20. What is the value of signal to noise ratio in PCM?

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Viva - voce

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37 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 6 DELTA MODULATION & DEMODULATION
Aim:
To transmit an analog message signal in its digital form and reconstruct back the original analog message

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signal at receiver by using Delta modulator
Apparatus required:
1. DM and ADM Trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.

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Theory:
Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The
difference signal between two successive samples is encoded into a single bit code. A present sample of the
analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level
(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.

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The comparison of samples is accomplished by converting the digital to analog form then comparing with the
present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to
a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.
Procedure:
1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.

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2. Observe the modulated signal in the CRO.
3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.
4. Also observe the DAC output on the CRO.
5. Change the amplitude of the modulating signal.
6. Observe the DAC output. Notice the slope overload distortion.

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7. Keep the tuning knob to minimize distortion.
8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope
overload distortion.
9. Calculate the sampling frequency required for no slope overload distortion.
10. Compare the calculated measured values of the sampling frequency.

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Block Diagram Delta modulator and demodulator

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Delta Modulator

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Delta Demodulator

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Block diagram of Adaptive delta modulator and demodulator

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Adaptive Delta Modulator

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Adaptive Delta Demodulator

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Delta Modulation and Adaptive Delta Modulator Trainer kit

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41 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Model Graph:

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42 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Tabulation 1

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For Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal
2 Carrier Signal
3 Modulated Signal

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4 Demodulated Signal

Tabulation 2
For Adaptive Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)

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1 Modulating Signal
2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

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Result:
Thus the output waveforms of Delta modulation and adaptive delta modulation circuit were observed.
Outcome:
After the completion of this experiment the students will be able to design and construct the delta modulation
adaptive delta modulation circuit.

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Applications:
1. Digital voice storage
2. Voice transmission
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3. Radio communication devices such TV remotes.
4. Delta Modulation was used by Satellite Business Systems or SBS
5. DM used in high resolution A/D and D/A converters.

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1. What is delta modulation?
2. What is adaptive delta modulation?
3. What are the advantages of adaptive delta modulation over delta modulation?
4. What is slope over load distortion?
5. What is granular noise effect?

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6. What are the two limitations of delta modulation?
7. What is the function of integrator?
8. What is comparator?
9. What is companding?
10. What is the advantage of delta modulation over pulse modulation?

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11. Distinguish between DPCM and DM.
12. What are the different types of digital modulation?
13. What is sampling rate?
14. Which kind of multiplexing used in digital communication?
15. Why is sample hold circuit used?

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16. What are the advantages of digital transmission?
17. How is the performance corrupted in PCM?
18. What are the different types of multiplexing?
19. What is aliasing effect?
20. How to avoid aliasing effect?

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Viva - voce
44 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 7 LINE CODING DECODING TECHNIQUES

Aim:
To study different line coding techniques.
Apparatus required:

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1. Line coding and decoding trainer kit ? 1 No.
2. Patch cords ? 6 No.
3. CRO ? 1 No.

Theory:

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Line coding refers to the process of representing the bit stream (1 ?s and 0 ?s) in the form of voltage or current
variations optimally tuned for the specific properties of the physical channel being used. The selection of a proper
line code can help in many ways. One possibility is to aid in clock recovery at the receiver. A clock signal is
recovered by observing transitions in the received bit sequence, if enough transitions exist, a good recovery of
the clock is guaranteed, the signal is said to be self-clocking. Another advantage is to get rid of DC shifts. The

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DC component in a line code is called the bias or the DC coefficient. Unfortunately, most long-distance
communication channels cannot transport a DC component. This is why most line codes try to eliminate the DC
component before being transmitted on the channel. Such codes are called DC balanced, zero-DC, zero-bias, or
DC equalized. Some common types of line encoding in common-use nowadays are unipolar, polar, bipolar,
Manchester, MLT-3 Duo binary encoding.

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Unipolar (Unipolar NRZ and Unipolar RZ):
Unipolar is the simplest line coding scheme. It has the advantage of being compatible with TTL logic. Unipolar
coding uses a positive rectangular pulse p(t) to represent binary 1, the absence of a pulse (i.e., zero voltage) to
represent a binary 0. Two possibilities for the pulse p(t) exist3: Non-Return-to-Zero (NRZ) rectangular pulse
Return-to-Zero (RZ) rectangular pulse. The difference between Unipolar NRZ Unipolar RZ codes is that the

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rectangular pulse in NRZ stays at a positive value (e.g., +5V) for the full duration of the logic 1 bit, while the pule
in RZ drops from +5V to 0V in the middle of the bit time.

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Procedure:
1. Connect the PRBS (test point P5) to various line coding formats. Obtain the coded output as per the
requirement.

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2. Connect coded signal test point to corresponding decoding test point as inputs.
3. Set the SW1 as per the requirement.
4. Set the potentiometer P1 in minimum position.
5. Switch ON the power supply. Press the switch SW2 once.
6. Display the encoded signal on one channel of CRO and decoded signal on second channel of CRO.

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46 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Line coding decoding trainer kit

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Model Graph:

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48 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Tabulation
Sl. No. Type of Coding AMPLITUDE (V) Time period (s)
1. Unipolar data(NZ NRZ )

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2. Unipolar data (NRZ RZ)
3. Bipolar Data(NRZ AMI)
4. Manchester

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Result:
Thus the different line coding techniques was studied and verified.
Outcome:
After the completion of this experiment the students will be able to understand implement the different line

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coding schemes.
Applications:
1. DC balance
2. embedded clock applications
3. computing applications

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4. Manchester codes are commonly used for local area networks
5. Bipolar codes are commonly used for local area networks

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49 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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1. What is line coding?
2. Define ? Polar Encoding
3. Define ? Unipolar Encoding
4. Define ? Bipolar Encoding

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5. Define ? Manchester Encoding
6. What are the two function of fast frequency hopping?
7. What is return to zero?
8. What is Non-return to zero?
9. What is the difference between source coding and line coding?

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10. What are the properties of line coding?
11. What is the effect of inter symbol interference?
12. How ISI can be reduced?
13. Define ? Encoding
14. Define ? Decoding

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15. Define ? Nyquist Rate
16. Draw the NRZ and RZ code for the digital data 10110001.
17. Define ? Equalization
18. What is PRBS?
19. Write the Boolean expression for X-NOR gate.

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20. Define ? Digital demodulation

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Viva - voce
50 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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CYCLE 2 ? EXPERIMENTS
Expt. No.8 ERROR CONTROL CODING USING MATLAB
Aim:
To write a program in MATLAB for error control coding techniques
Software required:

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PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments comon prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper

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icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitiled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the common window. If there is an error then with an alarm, type of error

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will appear in red colour.
7. Rectify the error if any go to debug menu select run.

Result:
Thus the error control coding techniques are executed using MATLAB programs.

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Outcome:
After the completion of this experiment the students will be able to simulate the different error control coding
schemes using MATLAB.
Applications :
1. Deep space communication

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2. Satellite communication
3. Data transmission
4. Data storage
5. Mobile communication
6. File transfer

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7. digital audio/video transmission.
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1. What is the need for error control coding?

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2. What is meant by linear code?
3. What is meant by cyclic code?
4. Name some error control coding techniques.
5. Name the code which is used only for error detection.

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Viva - voce
52 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 9 DESIGN OF BPSK, QPSK, QAM USING MATLAB

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Aim:
To write a program in MATLAB for design of BPSK, QPSK and QAM
Software required:
PC with MATLAB version 7.0 software installed
Procedure:

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1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.

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5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error, if any go to debug menu select run.

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Result:

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Thus the BPSK, QPSK and QAM were simulated using MATLAB.
Outcome:
After the completion of this experiment the students will be able to simulate the various modulation schemes
such as BPSK, QPSK and QAM using MATLAB.
Applications:

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QPSK
1. Data transmission, mainly radio transmissions.
2. RTTY means radio teletype transmissions from amateur radio up to WiFi transmissions or Zigbees
QAM
1. Radio communications and data delivery applications.

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1. What is a correlator?
2. Define ? Constellation Diagram
3. What is BPSK ? Mention its significance.

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4. Give the expression for bandwidth of BPSK scheme.
5. What is QPSK mention its significance?
6. Give the expression for bandwidth of QPSK scheme.
7. Draw the constellation diagram of QPSK.
8. What is QAM ?

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9. Give the expression for bandwidth of QAM scheme.
10. What are the blocks in BPSK receiver?
11. What is the function of a decision device?
12. Draw the constellation diagram of QAM.
13. What are the types of QPSK?

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14. What is the significance of Q-channel I channel in QPSK modulator?
15. What is the minimum bandwidth requirement of QPSK?
16. Draw the output phase versus time relationship for a QPSK modulator.
17. Compare OQPSK with QPSK.
18. Identify the error in the matlab command Sin 3.

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19. Draw the constellation diagram of QPSK.
20. Give the applications of QPSK modulation scheme.
Viva - voce
54 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 10 DESIGN OF FSK, PSK, DPSK USING MATLAB
Aim:
To write a program in MATLAB for design of FSK, PSK and DPSK
Software required:
PC with MATLAB version 7.0 software installed

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Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.

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4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.

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7. Rectify the error if any go to debug menu select run.

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Result:

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Thus the FSK, PSK and DPSK were simulated using MATLAB.
Outcome:
After the completion of this experiment the students will be able to simulate the various modulation schemes
such as FSK, PSK and DPSK using MATLAB.
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Applications:
ASK:
1. ASK is used to transmit digital data over optical fiber
PSK:

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1. over voice lines
2. in high-freq. radio transmissions.


1. What is FSK? Mention its significance.

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2. What is PSK? Mention its significance.
3. What is DPSK? Mention its significance.
4. What are the applications of DPSK?
5. Give the equation for average probability of symbol error for DPSK.
6. List the operations performed in DPSK transmitter.

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7. Compare DPSK with QPSK modulation scheme.
8. What is differential encoding technique?
9. Why do we make 180 degree phase shift in PSK why not 90 or 270?
10. What is the function of a decision device?
11. What is RZ?

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12. What is NRZ?
13. What is Manchester encoding?
14. Sketch the FSK waveform for the input a) 1010110 b) 1100101
15. Define modulation index.
16. Write a MATLAB program for generating PN sequence.

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17. Differentiate coherent with non-coherent FSK.
18. Give the expression for bandwidth of FSK scheme.
19. What is the difference between PSK and FSK?
20. What is the major advantage of coherent PSK over coherent ASK?

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Viva - voce
56 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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sExpt. No. 11 COMMUNICATION LINK SIMULATION USING
MATLAB
Aim:
To simulate the basic communication link using mat lab

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Software required:
PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.

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3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.

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6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the communication link simulation was designed using MATLAB.
Outcome:
After the completion of this experiment the students will be able to simulate and design the communication link

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using MATLAB.

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57 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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1. Give examples for digital modulation techniques.
2. What is meant by pass-b transmission?
3. What is meant by base-b transmission?
4. What is the meaning for error pattern?

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5. Differentiate systematic from non-systematic coding.

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Viva - voce
58 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 12 ZERO FORCING LMS EQUALIZATION
ALGORITHMS USING MATLAB

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Aim:
To write a program in MATLAB for design of zero forcing LMS algorithms
Software required:
PC with MATLAB version 7.0 software installed
Procedure:

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1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.

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5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:

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Thus the equalization of zero forcing LMS algorithms was simulated using MATLAB.
Outcome:
After the completion of this experiment the students will be able to implement the various algorithms using
MATLAB.

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59 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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1. Define ? Equalization
2. What is meant by zero forcing algorithms?
3. Define ? LMS Algorithm

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4. What is meant by pass-b transmission?
5. What is meant by base-b transmission?
6. What is the meaning for error pattern?

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Viva - voce
60 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS

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Expt. No. 13 PULSE AMPLITUDE MODULATION
Aim:
To study the Pulse Amplitude Modulation technique and observe the output waveform
Apparatus required:
Sl. No. Name of the Apparatus Range Quantity

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1 Function generator 0-3 MHz 1
2 Diode 1N4007 2
3 Resistors, 3.3 k? 2
4 Bread Board 1
5 Power supply (0-30) V 1

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6 CRO 30 MHz 1
7 Probe few
8 Connecting Wires few

Procedure:

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1. Measure the amplitude of each pulse, no. of pulses in one cycle, frequency of pulses.
2. Vary the modulating input signal observe its effect on the output.
3. Observe compare the output waveform with input waveform/
4. See the input and output that are same in frequency, amplitude phase.
5. Draw the waveform of the modulating signal, sampling signal, pulse amplitude a modulated signal.

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Circuit Diagram

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Pulse amplitude modulation

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Model Graph:

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Tabulation

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Signal Amplitude (V) Time Period (s)
Message

Carrier

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PAM wave

Demodulated

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Result:
Thus the pulse amplitude modulation (PAM) output waveform was generated.
Outcome:
After the completion of this experiment the students will be able to design and construct the PAM modulated
wave.

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1. What is PAM?
2. Differentiate PAM from PCM.
3. Write the application of PAM.

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4. Draw the PAM signal.
5. Compare PAM, PPM and PWM.
6. What are the advantage of PAM and PWM?
7. What is the advantage of PPM over PWM and PAM?
8. What is Pulse position modulation?

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9. Mention the applications of PAM.
10. What are the disadvantages of PAM?
11. What is PWM or Pulse length modulation or pulse duration modulation?
12. Define ? Pulse Modulation

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Viva ? voce
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Expt. No. 14 AMPLITUDE MODULATION DEMODULATION

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USING Lab VIEW
Aim:
To generate amplitude modulated wave using NI LabVIEW demodulate the AM wave
using envelope detector
Apparatus required:

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1. Windows XP or Later Version
2. LabVIEW Software

Procedure:
Amplitude Modulation:

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1. Select the controls which are used for AM transmitter place it on Block Diagram.
2. Select the carrier message signal from function palette (Right click on Block Diagram ? Signal
Processing ?Wave form Generation ? Simulate signal) drag to block diagram. Select the parameters
such as frequency, amplitude sampling frequency for the Amplitude Modulation as listed in Table: Front
panel configurations for Amplitude Modulation.

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3. Select the required Numeric controls used in the circuit from the block diagram (Right click on Block
Diagram ? Programming ? Numeric) connect as shown in figure: Circuit diagram for Amplitude
Modulation.
4. Select the waveform graphs to display the input output waveforms (Right click on Front Panel ?
Modern ? Graph ? Waveform Graph) place those waveform Graphs on Front panel connect it as shown

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in figure: Circuit diagram for Amplitude Modulation.
5. Run the circuit; observe the output signal for the corresponding Input (Message Carrier) signal.
Configurations on Front panel:
1. Disable the Auto scale option for both X Y axis on each waveform graph(By making right click on
waveform graph) which is used in Front panel.

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2. Select the X axis scale (0 to 0.03) Y axis scale (-1 to +1) as required to view the waveform graph properly
on the Front panel.

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FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?



DEPARTMENT OF

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ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
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DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.

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? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul

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DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING


To impart professional education integrated with human values to the younger generation, so as to

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shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity


? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics

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industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION

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VISION
MISSION
MISSION
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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education

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2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to

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find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context

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5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field

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b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems

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e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility

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i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

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To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms

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? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing
3. AM Modulator and Demodulator

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4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes

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9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

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COURSE OBJECTIVES
COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction

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7
2 Time division multiplexing
13
3 AM modulation demodulation
18

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4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33
6 Delta modulation demodulation

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38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB

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51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB
55

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11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS

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13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS

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Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.

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2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at

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which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.

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Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples

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taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To

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recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit

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works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.

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3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

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Circuit Diagram

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal
Sampled output

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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.

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Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)

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5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate

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4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?

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9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.

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14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.

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19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
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Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:

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To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.

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4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.

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Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .

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3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .

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6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .

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Circuit Diagram

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Time division multiplexing

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TDM Trainer Kit

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Model Graph:

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Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1
2. Message Signal 2

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3. TDM signal

Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:

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After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.


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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network

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2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis

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5. The GSM telephone system


1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?

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3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?

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8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce
17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver

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Apparatus required:
.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.
3 Diode ? 2 No.

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4
AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.
6 Patch cards ? 6 No.

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Theory:

AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the

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instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.

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Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal

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Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index

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Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if
M < 1 Under modulation
M = 1 Critical modulation

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M > 1 over modulation

Procedure:
1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.

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3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

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AM Modulated wave



2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)

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Message

Carrier

Modulated

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Demodulated


Result:

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Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.
Applications:

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1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?

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5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?
9. What are the different types of AM generation?

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10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce
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12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?

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17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?

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21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after

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demodulating using FM receiver
Apparatus required:
.
1. Resistor ? 4 No.
2. Capacitor ? 1 No.

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3. Diode ? 2 No.
4.
AM transmitter Receiver
trainer kit ? 1 No.
5. CRO ? 1 No.

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6. Patch cards ? 6 No.

Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the
instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct

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proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used
in broadcast is generally called wide-FM, or W-FM.

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In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the

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luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of
noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes

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print-through pre-echo.

Procedure:
FM Modulator:
1. Switch ON the Power supply.

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2. Connect the sine wave generator output to frequency modulator input.

3. Select the low frequency carrier (or) high frequency carrier.

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4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

6. Observe the frequency modulator output .

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FM Demodulator:
A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

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2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

4. Observe the Demodulated O/P compare with the original input.

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B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

2. Now set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Quadrature detector output.

4. Observe the Demodulated O/P and compare with the original input.
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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

4. Observe the Demodulated O/P and then compare with the original input.

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D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

2. Set the DPDT switch in high frequency mode.

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3. Connect the CRO input to Ratio detector output.

4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram
FM Modulator

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FM Demodulator

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29 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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FM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency
modulated and demodulated wave.
Applications:

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1. Television sound transmission
2. Two way mobile radio
3. Cellular Radio
4. Microwave
5. Satellite Communication System

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1. Define ? Frequency Modulation
2. How it is different from phase modulation?
3. Write equation of FM wave, explain each parameter in it.

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4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.
6. Define ? Modulation Index
7. Differentiate between Narrow band FM from Wide band FM.
8. Draw message, carrier FM waves .

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9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?
11. Give the practical applications of FM.
12. State advantages and disadvantages of FM.
13. What is the range of speech signals?

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14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation
17. Draw the phasor diagram of FM signal.
18. What are the different types of FM generation?

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Viva - voce

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32 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 5 PCM MODULATION & DEMODULATION

Aim:

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To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator
Apparatus Required:
1. PCM trainer kit ? 1 No.
2. CRO ? 1 No.

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3. Connecting probes ? 4 No.
Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is
first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of
converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization

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can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization
the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel
serially.

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At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword
is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to
Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks

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for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:
1. Power on the PCM kit.
2. Measure the frequency of sampling clock.

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3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.
5. Connect the clock to the timing control circuit.

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6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.
9. Observe the waveform at the output of DAC.
10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the

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codeword graphically for a DC input.
Block diagram of PCM Transmission system

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34 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PCM Modulation and Demodulation Trainer kit

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35 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Model Graph:

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Tabulation

Result:
Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.

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Outcome:
After the completion of this experiment the students will be able to design and construct the pulse code
modulated and demodulated wave.
Applications:
1. Military Applications.

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2. The PCM is used in the satellite transmission system.
SIGNALS AMPLITUDE (V) TIME PERIOD (s)
DC Input
Sampled Signal
Clock Pulse

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PCM Output
DC Output
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3. It is used in space communication.

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4. It is used in telephony.
5. The compact disc (CD) is a recent application of PCM.


1. Define ? Modulation

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2. State sampling theorem
3. Define ? Demodulation
4. Define ? Pulse Code Modulation
5. What is aliasing effect?
6. What is quantization?

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7. Define ? Bit Rate
8. Define ? Baud Rate
9. What are the advantages of PCM?
10. Define ? Signal to Noise Ratio
11. What are the limitations of PCM?

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12. What are the applications of PCM?
13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate
16. What is multiplexing?

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17. What is de-multiplexing?
18. What are the types of pulse modulation?
19. What should be the minimum bandwidth required to transmit a PCM channel?
20. What is the value of signal to noise ratio in PCM?

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Viva - voce
37 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 6 DELTA MODULATION & DEMODULATION

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Aim:
To transmit an analog message signal in its digital form and reconstruct back the original analog message
signal at receiver by using Delta modulator
Apparatus required:
1. DM and ADM Trainer kit ? 1 No.

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2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The
difference signal between two successive samples is encoded into a single bit code. A present sample of the

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analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level
(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.
The comparison of samples is accomplished by converting the digital to analog form then comparing with the
present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to
a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.

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Procedure:
1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.
2. Observe the modulated signal in the CRO.
3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.
4. Also observe the DAC output on the CRO.

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5. Change the amplitude of the modulating signal.
6. Observe the DAC output. Notice the slope overload distortion.
7. Keep the tuning knob to minimize distortion.
8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope
overload distortion.

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9. Calculate the sampling frequency required for no slope overload distortion.
10. Compare the calculated measured values of the sampling frequency.


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Block Diagram Delta modulator and demodulator

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Delta Modulator

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Delta Demodulator

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Block diagram of Adaptive delta modulator and demodulator

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Adaptive Delta Modulator

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Adaptive Delta Demodulator

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Delta Modulation and Adaptive Delta Modulator Trainer kit

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41 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Model Graph:

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Tabulation 1
For Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal

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2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

Tabulation 2

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For Adaptive Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal
2 Carrier Signal
3 Modulated Signal

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4 Demodulated Signal

Result:
Thus the output waveforms of Delta modulation and adaptive delta modulation circuit were observed.
Outcome:

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After the completion of this experiment the students will be able to design and construct the delta modulation
adaptive delta modulation circuit.
Applications:
1. Digital voice storage
2. Voice transmission

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43 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

3. Radio communication devices such TV remotes.
4. Delta Modulation was used by Satellite Business Systems or SBS
5. DM used in high resolution A/D and D/A converters.

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1. What is delta modulation?
2. What is adaptive delta modulation?
3. What are the advantages of adaptive delta modulation over delta modulation?

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4. What is slope over load distortion?
5. What is granular noise effect?
6. What are the two limitations of delta modulation?
7. What is the function of integrator?
8. What is comparator?

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9. What is companding?
10. What is the advantage of delta modulation over pulse modulation?
11. Distinguish between DPCM and DM.
12. What are the different types of digital modulation?
13. What is sampling rate?

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14. Which kind of multiplexing used in digital communication?
15. Why is sample hold circuit used?
16. What are the advantages of digital transmission?
17. How is the performance corrupted in PCM?
18. What are the different types of multiplexing?

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19. What is aliasing effect?
20. How to avoid aliasing effect?

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Viva - voce

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44 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 7 LINE CODING DECODING TECHNIQUES

Aim:

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To study different line coding techniques.
Apparatus required:
1. Line coding and decoding trainer kit ? 1 No.
2. Patch cords ? 6 No.
3. CRO ? 1 No.

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Theory:
Line coding refers to the process of representing the bit stream (1 ?s and 0 ?s) in the form of voltage or current
variations optimally tuned for the specific properties of the physical channel being used. The selection of a proper
line code can help in many ways. One possibility is to aid in clock recovery at the receiver. A clock signal is

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recovered by observing transitions in the received bit sequence, if enough transitions exist, a good recovery of
the clock is guaranteed, the signal is said to be self-clocking. Another advantage is to get rid of DC shifts. The
DC component in a line code is called the bias or the DC coefficient. Unfortunately, most long-distance
communication channels cannot transport a DC component. This is why most line codes try to eliminate the DC
component before being transmitted on the channel. Such codes are called DC balanced, zero-DC, zero-bias, or

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DC equalized. Some common types of line encoding in common-use nowadays are unipolar, polar, bipolar,
Manchester, MLT-3 Duo binary encoding.
Unipolar (Unipolar NRZ and Unipolar RZ):
Unipolar is the simplest line coding scheme. It has the advantage of being compatible with TTL logic. Unipolar
coding uses a positive rectangular pulse p(t) to represent binary 1, the absence of a pulse (i.e., zero voltage) to

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represent a binary 0. Two possibilities for the pulse p(t) exist3: Non-Return-to-Zero (NRZ) rectangular pulse
Return-to-Zero (RZ) rectangular pulse. The difference between Unipolar NRZ Unipolar RZ codes is that the
rectangular pulse in NRZ stays at a positive value (e.g., +5V) for the full duration of the logic 1 bit, while the pule
in RZ drops from +5V to 0V in the middle of the bit time.

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Procedure:

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1. Connect the PRBS (test point P5) to various line coding formats. Obtain the coded output as per the
requirement.
2. Connect coded signal test point to corresponding decoding test point as inputs.
3. Set the SW1 as per the requirement.
4. Set the potentiometer P1 in minimum position.

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5. Switch ON the power supply. Press the switch SW2 once.
6. Display the encoded signal on one channel of CRO and decoded signal on second channel of CRO.

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46 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Line coding decoding trainer kit

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47 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Model Graph:

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48 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00



Tabulation

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Sl. No. Type of Coding AMPLITUDE (V) Time period (s)
1. Unipolar data(NZ NRZ )

2. Unipolar data (NRZ RZ)
3. Bipolar Data(NRZ AMI)

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4. Manchester


Result:
Thus the different line coding techniques was studied and verified.

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Outcome:
After the completion of this experiment the students will be able to understand implement the different line
coding schemes.
Applications:
1. DC balance

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2. embedded clock applications
3. computing applications
4. Manchester codes are commonly used for local area networks
5. Bipolar codes are commonly used for local area networks

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49 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


1. What is line coding?
2. Define ? Polar Encoding

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3. Define ? Unipolar Encoding
4. Define ? Bipolar Encoding
5. Define ? Manchester Encoding
6. What are the two function of fast frequency hopping?
7. What is return to zero?

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8. What is Non-return to zero?
9. What is the difference between source coding and line coding?
10. What are the properties of line coding?
11. What is the effect of inter symbol interference?
12. How ISI can be reduced?

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13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate
16. Draw the NRZ and RZ code for the digital data 10110001.
17. Define ? Equalization

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18. What is PRBS?
19. Write the Boolean expression for X-NOR gate.
20. Define ? Digital demodulation

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Viva - voce

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50 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

CYCLE 2 ? EXPERIMENTS
Expt. No.8 ERROR CONTROL CODING USING MATLAB
Aim:

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To write a program in MATLAB for error control coding techniques
Software required:
PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.

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2. MATLAB logo will appear after few moments comon prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitiled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the

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program press F5 or go to debug menu select run.
6. After execution output will appear in the common window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the error control coding techniques are executed using MATLAB programs.
Outcome:
After the completion of this experiment the students will be able to simulate the different error control coding
schemes using MATLAB.

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Applications :
1. Deep space communication
2. Satellite communication
3. Data transmission
4. Data storage

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5. Mobile communication
6. File transfer
7. digital audio/video transmission.
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1. What is the need for error control coding?
2. What is meant by linear code?
3. What is meant by cyclic code?
4. Name some error control coding techniques.

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5. Name the code which is used only for error detection.

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Viva - voce
52 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 9 DESIGN OF BPSK, QPSK, QAM USING MATLAB
Aim:
To write a program in MATLAB for design of BPSK, QPSK and QAM
Software required:

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PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper

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icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error

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will appear in red colour.
7. Rectify the error, if any go to debug menu select run.

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53 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Result:
Thus the BPSK, QPSK and QAM were simulated using MATLAB.
Outcome:
After the completion of this experiment the students will be able to simulate the various modulation schemes

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such as BPSK, QPSK and QAM using MATLAB.
Applications:
QPSK
1. Data transmission, mainly radio transmissions.
2. RTTY means radio teletype transmissions from amateur radio up to WiFi transmissions or Zigbees

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QAM
1. Radio communications and data delivery applications.


1. What is a correlator?

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2. Define ? Constellation Diagram
3. What is BPSK ? Mention its significance.
4. Give the expression for bandwidth of BPSK scheme.
5. What is QPSK mention its significance?
6. Give the expression for bandwidth of QPSK scheme.

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7. Draw the constellation diagram of QPSK.
8. What is QAM ?
9. Give the expression for bandwidth of QAM scheme.
10. What are the blocks in BPSK receiver?
11. What is the function of a decision device?

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12. Draw the constellation diagram of QAM.
13. What are the types of QPSK?
14. What is the significance of Q-channel I channel in QPSK modulator?
15. What is the minimum bandwidth requirement of QPSK?
16. Draw the output phase versus time relationship for a QPSK modulator.

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17. Compare OQPSK with QPSK.
18. Identify the error in the matlab command Sin 3.
19. Draw the constellation diagram of QPSK.
20. Give the applications of QPSK modulation scheme.
Viva - voce

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54 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 10 DESIGN OF FSK, PSK, DPSK USING MATLAB
Aim:
To write a program in MATLAB for design of FSK, PSK and DPSK

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Software required:
PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.

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3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.

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6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the FSK, PSK and DPSK were simulated using MATLAB.
Outcome:
After the completion of this experiment the students will be able to simulate the various modulation schemes

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such as FSK, PSK and DPSK using MATLAB.
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Applications:
ASK:

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1. ASK is used to transmit digital data over optical fiber
PSK:
1. over voice lines
2. in high-freq. radio transmissions.

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1. What is FSK? Mention its significance.
2. What is PSK? Mention its significance.
3. What is DPSK? Mention its significance.
4. What are the applications of DPSK?

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5. Give the equation for average probability of symbol error for DPSK.
6. List the operations performed in DPSK transmitter.
7. Compare DPSK with QPSK modulation scheme.
8. What is differential encoding technique?
9. Why do we make 180 degree phase shift in PSK why not 90 or 270?

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10. What is the function of a decision device?
11. What is RZ?
12. What is NRZ?
13. What is Manchester encoding?
14. Sketch the FSK waveform for the input a) 1010110 b) 1100101

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15. Define modulation index.
16. Write a MATLAB program for generating PN sequence.
17. Differentiate coherent with non-coherent FSK.
18. Give the expression for bandwidth of FSK scheme.
19. What is the difference between PSK and FSK?

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20. What is the major advantage of coherent PSK over coherent ASK?

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Viva - voce
56 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

sExpt. No. 11 COMMUNICATION LINK SIMULATION USING
MATLAB

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Aim:
To simulate the basic communication link using mat lab
Software required:
PC with MATLAB version 7.0 software installed
Procedure:

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1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.

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5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the communication link simulation was designed using MATLAB.

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Outcome:
After the completion of this experiment the students will be able to simulate and design the communication link
using MATLAB.

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57 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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1. Give examples for digital modulation techniques.
2. What is meant by pass-b transmission?

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3. What is meant by base-b transmission?
4. What is the meaning for error pattern?
5. Differentiate systematic from non-systematic coding.

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Viva - voce
58 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 12 ZERO FORCING LMS EQUALIZATION
ALGORITHMS USING MATLAB
Aim:
To write a program in MATLAB for design of zero forcing LMS algorithms
Software required:

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PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper

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icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error

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will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the equalization of zero forcing LMS algorithms was simulated using MATLAB.
Outcome:
After the completion of this experiment the students will be able to implement the various algorithms using

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MATLAB.



59 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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1. Define ? Equalization

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2. What is meant by zero forcing algorithms?
3. Define ? LMS Algorithm
4. What is meant by pass-b transmission?
5. What is meant by base-b transmission?
6. What is the meaning for error pattern?

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Viva - voce
60 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS

Expt. No. 13 PULSE AMPLITUDE MODULATION
Aim:
To study the Pulse Amplitude Modulation technique and observe the output waveform

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Apparatus required:
Sl. No. Name of the Apparatus Range Quantity
1 Function generator 0-3 MHz 1
2 Diode 1N4007 2
3 Resistors, 3.3 k? 2

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4 Bread Board 1
5 Power supply (0-30) V 1
6 CRO 30 MHz 1
7 Probe few
8 Connecting Wires few

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Procedure:
1. Measure the amplitude of each pulse, no. of pulses in one cycle, frequency of pulses.
2. Vary the modulating input signal observe its effect on the output.
3. Observe compare the output waveform with input waveform/

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4. See the input and output that are same in frequency, amplitude phase.
5. Draw the waveform of the modulating signal, sampling signal, pulse amplitude a modulated signal.

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Circuit Diagram
Pulse amplitude modulation

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Model Graph:

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62 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Tabulation
Signal Amplitude (V) Time Period (s)
Message

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Carrier

PAM wave

Demodulated

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Result:
Thus the pulse amplitude modulation (PAM) output waveform was generated.
Outcome:

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After the completion of this experiment the students will be able to design and construct the PAM modulated
wave.


1. What is PAM?

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2. Differentiate PAM from PCM.
3. Write the application of PAM.
4. Draw the PAM signal.
5. Compare PAM, PPM and PWM.
6. What are the advantage of PAM and PWM?

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7. What is the advantage of PPM over PWM and PAM?
8. What is Pulse position modulation?
9. Mention the applications of PAM.
10. What are the disadvantages of PAM?
11. What is PWM or Pulse length modulation or pulse duration modulation?

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12. Define ? Pulse Modulation


Viva ? voce
63 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 14 AMPLITUDE MODULATION DEMODULATION
USING Lab VIEW
Aim:
To generate amplitude modulated wave using NI LabVIEW demodulate the AM wave

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using envelope detector
Apparatus required:
1. Windows XP or Later Version
2. LabVIEW Software

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Procedure:
Amplitude Modulation:
1. Select the controls which are used for AM transmitter place it on Block Diagram.
2. Select the carrier message signal from function palette (Right click on Block Diagram ? Signal
Processing ?Wave form Generation ? Simulate signal) drag to block diagram. Select the parameters

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such as frequency, amplitude sampling frequency for the Amplitude Modulation as listed in Table: Front
panel configurations for Amplitude Modulation.
3. Select the required Numeric controls used in the circuit from the block diagram (Right click on Block
Diagram ? Programming ? Numeric) connect as shown in figure: Circuit diagram for Amplitude
Modulation.

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4. Select the waveform graphs to display the input output waveforms (Right click on Front Panel ?
Modern ? Graph ? Waveform Graph) place those waveform Graphs on Front panel connect it as shown
in figure: Circuit diagram for Amplitude Modulation.
5. Run the circuit; observe the output signal for the corresponding Input (Message Carrier) signal.
Configurations on Front panel:

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1. Disable the Auto scale option for both X Y axis on each waveform graph(By making right click on
waveform graph) which is used in Front panel.
2. Select the X axis scale (0 to 0.03) Y axis scale (-1 to +1) as required to view the waveform graph properly
on the Front panel.

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64 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Front panel configurations for Amplitude Modulation
Parameter Message Signal Carrier Signal
Signal Type Sine Sine
Frequency 100 Hz 1000 Hz
Amplitude 1 0.5

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Phase 0 0
Offset 0 0
Sampling Rate 10000 Hz 10000 Hz
Number of Samples 1000(Automatic) 1000(Automatic)
Timing Run as fast as possible Run as fast as possible

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Timestamps Relative Relative



Amplitude modulation using labVIEW

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FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING


V SEMESTER - R 2013

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL
2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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DHANALAKSHMI


College of Engineering is committed to provide highly disciplined, conscientious

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enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry
? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels

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? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

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To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

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? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems
? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical

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practices

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VISION
VISION
MISSION
MISSION
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PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,
enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher

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education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions
3. Breadth

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To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students
to make them multi-faceted personalities develop their ability to relate engineering issues to broader social

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context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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PROGRAMME OUTCOMES (POs)
a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics

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Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics
communication engineering circuits

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d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large
h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness

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of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

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To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM
? To implement FSK, PSK and DPSK schemes

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? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction
2. Time Division Multiplexing

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3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation
7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM

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8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation
12. Equalization ? Zero Forcing and LMS algorithms (simulation)

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Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.
Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise

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performance of communication system.

COURSE OBJECTIVES
COURSE OUTCOMES
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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.
CYCLE 1 - EXPERIMENTS

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1 Signal sampling reconstruction
7
2 Time division multiplexing
13
3 AM modulation demodulation

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18
4 Frequency modulation demodulation
26
5 PCM modulation demodulation
33

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6 Delta modulation demodulation
38
7 Line coding decoding techniques
45
CYCLE 2 ? EXPERIMENTS

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8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB
53
10 Design of FSK, PSK DPSK using MATLAB

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55
11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB
59

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ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit
Apparatus required:

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1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.
Theory:

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Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For
reconstructing the continuous time signal from its discrete time samples without any error, the signal should be

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sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known
as Nyquist sampling theorem.

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A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the
sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is

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accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:
1. Assemble the sample and hold circuit with the desired components.

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2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.
6. Integrate the sampling inputs.

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Circuit Diagram

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9 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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10 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Tabulation

Analog signal sampling and reconstruction trainer kit

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Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer
kit.

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Signal Amplitude (V) Time period (s)
Message signal
Carrier signal

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Sampled output
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Outcome:
After completion of this experiment, the students will be able to understand the discretization process of

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continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)
3. Storage, and transmission

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4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem
2. What is the necessary sufficient condition for sampling reconstruction of a signal?

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3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?
7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.

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8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?
12. Define ? Sample Hold Circuits

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13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal
17. What is the need for converting a continuous signal into a discrete signal?

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18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
12 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 2 TIME DIVISION MULTIPLEXING

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Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.

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3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common
signal path by means of synchronized switches at each end of the transmission line so that each signal appears

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on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.
(a) Set all sine wave voltages to 2V,

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(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this
sine wave in TDM signal note down.

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5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of
Oscilloscope.

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8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .


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Circuit Diagram
Time division multiplexing

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14 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


TDM Trainer Kit

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Model Graph:

Tabulation
Sl. No. Signal Amplitude (V) Time period (s)
1. Message signal 1

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2. Message Signal 2
3. TDM signal

Result:
Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.

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Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital
transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)

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or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital
Network (ISDN).

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4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system


1. What is meant by multiplexing technique ?

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2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?
6. Distinguish between TDM and FDM.

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7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce

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17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 3 AM MODULATION & DEMODULATION
Aim:
To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after

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demodulating using AM receiver
Apparatus required:
.
1 Resistor ? 4 No.
2 Capacitor ? 1 No.

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3 Diode ? 2 No.
4
AM transmitter receiver
trainer kit ? 1 No.
5 CRO ? 1 No.

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6 Patch cards ? 6 No.

Theory:

AMPLITUDE MODULATION

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Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt
VC (t) = VC sin ?Ct

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The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,
VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where
Vm = maximum amplitude of modulating signal

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VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:
M= (Vmax ? Vmin / Vmax + Vmin ) * 100

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Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if
M < 1 Under modulation

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M = 1 Critical modulation
M > 1 over modulation

Procedure:
1. Give the modulating signal input to the Amplitude modulator.

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2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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19 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:
1. AM Waveform (Ring diode Transistor based AM Modulator)

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AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation

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Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated
demodulated wave.

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Applications:
1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.
3. What is the degree of modulation?

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4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?
8. What is depth of modulation?

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9. What are the different types of AM generation?
10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce
24 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation
15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?

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16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.
19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.

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20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.
.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION
Aim:

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To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver
Apparatus required:
.
1. Resistor ? 4 No.

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2. Capacitor ? 1 No.
3. Diode ? 2 No.
4.
AM transmitter Receiver
trainer kit ? 1 No.

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5. CRO ? 1 No.
6. Patch cards ? 6 No.

Theory:
Frequency modulation (FM) is a form of modulation that represents information as variations in the

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instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A
narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used

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in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to
present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of

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noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

Procedure:
FM Modulator:

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1. Switch ON the Power supply.

2. Connect the sine wave generator output to frequency modulator input.

3. Select the low frequency carrier (or) high frequency carrier.

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4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

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6. Observe the frequency modulator output .

FM Demodulator:
A) PLL Detector
1. Connect frequency modulated output to the PLL detector input.

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2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

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4. Observe the Demodulated O/P compare with the original input.

B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

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2. Now set the DPDT switch in high frequency mode.

3. Connect the CRO input to Quadrature detector output.

4. Observe the Demodulated O/P and compare with the original input.

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C) Phase Discriminator (Foster-Seeley detector)
1. Connect the frequency modulated output to Phase discriminator input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

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4. Observe the Demodulated O/P and then compare with the original input.

D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Ratio detector output.

4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram

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FM Modulator

FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

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Carrier

Modulated

Demodulated

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Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency
modulated and demodulated wave.

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Applications:
1. Television sound transmission
2. Two way mobile radio
3. Cellular Radio
4. Microwave

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5. Satellite Communication System


1. Define ? Frequency Modulation
2. How it is different from phase modulation?

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3. Write equation of FM wave, explain each parameter in it.
4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.
6. Define ? Modulation Index
7. Differentiate between Narrow band FM from Wide band FM.

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8. Draw message, carrier FM waves .
9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?
11. Give the practical applications of FM.
12. State advantages and disadvantages of FM.

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13. What is the range of speech signals?
14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation
17. Draw the phasor diagram of FM signal.

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18. What are the different types of FM generation?

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Viva - voce
32 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 5 PCM MODULATION & DEMODULATION

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Aim:
To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator
Apparatus Required:
1. PCM trainer kit ? 1 No.

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2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is
first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of

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converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization
can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization
the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel

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serially.
At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword
is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to

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Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks
for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:
1. Power on the PCM kit.

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2. Measure the frequency of sampling clock.
3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.

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5. Connect the clock to the timing control circuit.
6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.
9. Observe the waveform at the output of DAC.

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10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the
codeword graphically for a DC input.
Block diagram of PCM Transmission system

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PCM Modulation and Demodulation Trainer kit

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35 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Model Graph:

Tabulation

Result:

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Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.
Outcome:
After the completion of this experiment the students will be able to design and construct the pulse code
modulated and demodulated wave.
Applications:

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1. Military Applications.
2. The PCM is used in the satellite transmission system.
SIGNALS AMPLITUDE (V) TIME PERIOD (s)
DC Input
Sampled Signal

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Clock Pulse
PCM Output
DC Output
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3. It is used in space communication.
4. It is used in telephony.
5. The compact disc (CD) is a recent application of PCM.

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1. Define ? Modulation
2. State sampling theorem
3. Define ? Demodulation
4. Define ? Pulse Code Modulation
5. What is aliasing effect?

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6. What is quantization?
7. Define ? Bit Rate
8. Define ? Baud Rate
9. What are the advantages of PCM?
10. Define ? Signal to Noise Ratio

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11. What are the limitations of PCM?
12. What are the applications of PCM?
13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate

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16. What is multiplexing?
17. What is de-multiplexing?
18. What are the types of pulse modulation?
19. What should be the minimum bandwidth required to transmit a PCM channel?
20. What is the value of signal to noise ratio in PCM?

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Viva - voce
37 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 6 DELTA MODULATION & DEMODULATION
Aim:
To transmit an analog message signal in its digital form and reconstruct back the original analog message
signal at receiver by using Delta modulator
Apparatus required:

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1. DM and ADM Trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The

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difference signal between two successive samples is encoded into a single bit code. A present sample of the
analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level
(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.
The comparison of samples is accomplished by converting the digital to analog form then comparing with the
present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to

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a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.
Procedure:
1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.
2. Observe the modulated signal in the CRO.
3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.

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4. Also observe the DAC output on the CRO.
5. Change the amplitude of the modulating signal.
6. Observe the DAC output. Notice the slope overload distortion.
7. Keep the tuning knob to minimize distortion.
8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope

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overload distortion.
9. Calculate the sampling frequency required for no slope overload distortion.
10. Compare the calculated measured values of the sampling frequency.

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Block Diagram Delta modulator and demodulator

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Delta Modulator

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Delta Demodulator

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Block diagram of Adaptive delta modulator and demodulator

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Adaptive Delta Modulator

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Adaptive Delta Demodulator

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Delta Modulation and Adaptive Delta Modulator Trainer kit

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Model Graph:

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Tabulation 1
For Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)

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1 Modulating Signal
2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

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Tabulation 2
For Adaptive Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal
2 Carrier Signal

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3 Modulated Signal
4 Demodulated Signal

Result:
Thus the output waveforms of Delta modulation and adaptive delta modulation circuit were observed.

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Outcome:
After the completion of this experiment the students will be able to design and construct the delta modulation
adaptive delta modulation circuit.
Applications:
1. Digital voice storage

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2. Voice transmission
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3. Radio communication devices such TV remotes.
4. Delta Modulation was used by Satellite Business Systems or SBS

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5. DM used in high resolution A/D and D/A converters.


1. What is delta modulation?
2. What is adaptive delta modulation?

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3. What are the advantages of adaptive delta modulation over delta modulation?
4. What is slope over load distortion?
5. What is granular noise effect?
6. What are the two limitations of delta modulation?
7. What is the function of integrator?

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8. What is comparator?
9. What is companding?
10. What is the advantage of delta modulation over pulse modulation?
11. Distinguish between DPCM and DM.
12. What are the different types of digital modulation?

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13. What is sampling rate?
14. Which kind of multiplexing used in digital communication?
15. Why is sample hold circuit used?
16. What are the advantages of digital transmission?
17. How is the performance corrupted in PCM?

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18. What are the different types of multiplexing?
19. What is aliasing effect?
20. How to avoid aliasing effect?

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Viva - voce
44 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 7 LINE CODING DECODING TECHNIQUES

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Aim:
To study different line coding techniques.
Apparatus required:
1. Line coding and decoding trainer kit ? 1 No.
2. Patch cords ? 6 No.

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3. CRO ? 1 No.

Theory:
Line coding refers to the process of representing the bit stream (1 ?s and 0 ?s) in the form of voltage or current
variations optimally tuned for the specific properties of the physical channel being used. The selection of a proper

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line code can help in many ways. One possibility is to aid in clock recovery at the receiver. A clock signal is
recovered by observing transitions in the received bit sequence, if enough transitions exist, a good recovery of
the clock is guaranteed, the signal is said to be self-clocking. Another advantage is to get rid of DC shifts. The
DC component in a line code is called the bias or the DC coefficient. Unfortunately, most long-distance
communication channels cannot transport a DC component. This is why most line codes try to eliminate the DC

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component before being transmitted on the channel. Such codes are called DC balanced, zero-DC, zero-bias, or
DC equalized. Some common types of line encoding in common-use nowadays are unipolar, polar, bipolar,
Manchester, MLT-3 Duo binary encoding.
Unipolar (Unipolar NRZ and Unipolar RZ):
Unipolar is the simplest line coding scheme. It has the advantage of being compatible with TTL logic. Unipolar

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coding uses a positive rectangular pulse p(t) to represent binary 1, the absence of a pulse (i.e., zero voltage) to
represent a binary 0. Two possibilities for the pulse p(t) exist3: Non-Return-to-Zero (NRZ) rectangular pulse
Return-to-Zero (RZ) rectangular pulse. The difference between Unipolar NRZ Unipolar RZ codes is that the
rectangular pulse in NRZ stays at a positive value (e.g., +5V) for the full duration of the logic 1 bit, while the pule
in RZ drops from +5V to 0V in the middle of the bit time.

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Procedure:
1. Connect the PRBS (test point P5) to various line coding formats. Obtain the coded output as per the
requirement.
2. Connect coded signal test point to corresponding decoding test point as inputs.
3. Set the SW1 as per the requirement.

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4. Set the potentiometer P1 in minimum position.
5. Switch ON the power supply. Press the switch SW2 once.
6. Display the encoded signal on one channel of CRO and decoded signal on second channel of CRO.

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Line coding decoding trainer kit

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Model Graph:

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48 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Tabulation
Sl. No. Type of Coding AMPLITUDE (V) Time period (s)
1. Unipolar data(NZ NRZ )

2. Unipolar data (NRZ RZ)

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3. Bipolar Data(NRZ AMI)
4. Manchester


Result:

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Thus the different line coding techniques was studied and verified.
Outcome:
After the completion of this experiment the students will be able to understand implement the different line
coding schemes.
Applications:

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1. DC balance
2. embedded clock applications
3. computing applications
4. Manchester codes are commonly used for local area networks
5. Bipolar codes are commonly used for local area networks

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1. What is line coding?

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2. Define ? Polar Encoding
3. Define ? Unipolar Encoding
4. Define ? Bipolar Encoding
5. Define ? Manchester Encoding
6. What are the two function of fast frequency hopping?

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7. What is return to zero?
8. What is Non-return to zero?
9. What is the difference between source coding and line coding?
10. What are the properties of line coding?
11. What is the effect of inter symbol interference?

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12. How ISI can be reduced?
13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate
16. Draw the NRZ and RZ code for the digital data 10110001.

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17. Define ? Equalization
18. What is PRBS?
19. Write the Boolean expression for X-NOR gate.
20. Define ? Digital demodulation

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Viva - voce
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CYCLE 2 ? EXPERIMENTS
Expt. No.8 ERROR CONTROL CODING USING MATLAB

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Aim:
To write a program in MATLAB for error control coding techniques
Software required:
PC with MATLAB version 7.0 software installed
Procedure:

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1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments comon prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitiled?.

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5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the common window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the error control coding techniques are executed using MATLAB programs.
Outcome:
After the completion of this experiment the students will be able to simulate the different error control coding

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schemes using MATLAB.
Applications :
1. Deep space communication
2. Satellite communication
3. Data transmission

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4. Data storage
5. Mobile communication
6. File transfer
7. digital audio/video transmission.
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1. What is the need for error control coding?
2. What is meant by linear code?
3. What is meant by cyclic code?

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4. Name some error control coding techniques.
5. Name the code which is used only for error detection.

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Viva - voce

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52 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 9 DESIGN OF BPSK, QPSK, QAM USING MATLAB
Aim:
To write a program in MATLAB for design of BPSK, QPSK and QAM

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Software required:
PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.

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3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.

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6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error, if any go to debug menu select run.

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53 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Result:
Thus the BPSK, QPSK and QAM were simulated using MATLAB.
Outcome:

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After the completion of this experiment the students will be able to simulate the various modulation schemes
such as BPSK, QPSK and QAM using MATLAB.
Applications:
QPSK
1. Data transmission, mainly radio transmissions.

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2. RTTY means radio teletype transmissions from amateur radio up to WiFi transmissions or Zigbees
QAM
1. Radio communications and data delivery applications.

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1. What is a correlator?
2. Define ? Constellation Diagram
3. What is BPSK ? Mention its significance.
4. Give the expression for bandwidth of BPSK scheme.
5. What is QPSK mention its significance?

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6. Give the expression for bandwidth of QPSK scheme.
7. Draw the constellation diagram of QPSK.
8. What is QAM ?
9. Give the expression for bandwidth of QAM scheme.
10. What are the blocks in BPSK receiver?

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11. What is the function of a decision device?
12. Draw the constellation diagram of QAM.
13. What are the types of QPSK?
14. What is the significance of Q-channel I channel in QPSK modulator?
15. What is the minimum bandwidth requirement of QPSK?

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16. Draw the output phase versus time relationship for a QPSK modulator.
17. Compare OQPSK with QPSK.
18. Identify the error in the matlab command Sin 3.
19. Draw the constellation diagram of QPSK.
20. Give the applications of QPSK modulation scheme.

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Viva - voce
54 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 10 DESIGN OF FSK, PSK, DPSK USING MATLAB
Aim:

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To write a program in MATLAB for design of FSK, PSK and DPSK
Software required:
PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.

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2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the

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program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the FSK, PSK and DPSK were simulated using MATLAB.
Outcome:

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After the completion of this experiment the students will be able to simulate the various modulation schemes
such as FSK, PSK and DPSK using MATLAB.
55 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Applications:

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ASK:
1. ASK is used to transmit digital data over optical fiber
PSK:
1. over voice lines
2. in high-freq. radio transmissions.

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1. What is FSK? Mention its significance.
2. What is PSK? Mention its significance.
3. What is DPSK? Mention its significance.

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4. What are the applications of DPSK?
5. Give the equation for average probability of symbol error for DPSK.
6. List the operations performed in DPSK transmitter.
7. Compare DPSK with QPSK modulation scheme.
8. What is differential encoding technique?

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9. Why do we make 180 degree phase shift in PSK why not 90 or 270?
10. What is the function of a decision device?
11. What is RZ?
12. What is NRZ?
13. What is Manchester encoding?

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14. Sketch the FSK waveform for the input a) 1010110 b) 1100101
15. Define modulation index.
16. Write a MATLAB program for generating PN sequence.
17. Differentiate coherent with non-coherent FSK.
18. Give the expression for bandwidth of FSK scheme.

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19. What is the difference between PSK and FSK?
20. What is the major advantage of coherent PSK over coherent ASK?

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Viva - voce
56 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

sExpt. No. 11 COMMUNICATION LINK SIMULATION USING

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MATLAB
Aim:
To simulate the basic communication link using mat lab
Software required:
PC with MATLAB version 7.0 software installed

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Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.

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4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.

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7. Rectify the error if any go to debug menu select run.



Result:

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Thus the communication link simulation was designed using MATLAB.
Outcome:
After the completion of this experiment the students will be able to simulate and design the communication link
using MATLAB.

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57 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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1. Give examples for digital modulation techniques.

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2. What is meant by pass-b transmission?
3. What is meant by base-b transmission?
4. What is the meaning for error pattern?
5. Differentiate systematic from non-systematic coding.

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Viva - voce
58 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 12 ZERO FORCING LMS EQUALIZATION
ALGORITHMS USING MATLAB
Aim:
To write a program in MATLAB for design of zero forcing LMS algorithms

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Software required:
PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.

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3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.

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6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the equalization of zero forcing LMS algorithms was simulated using MATLAB.
Outcome:

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After the completion of this experiment the students will be able to implement the various algorithms using
MATLAB.

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59 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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1. Define ? Equalization
2. What is meant by zero forcing algorithms?
3. Define ? LMS Algorithm
4. What is meant by pass-b transmission?
5. What is meant by base-b transmission?

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6. What is the meaning for error pattern?

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Viva - voce
60 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS

Expt. No. 13 PULSE AMPLITUDE MODULATION
Aim:

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To study the Pulse Amplitude Modulation technique and observe the output waveform
Apparatus required:
Sl. No. Name of the Apparatus Range Quantity
1 Function generator 0-3 MHz 1
2 Diode 1N4007 2

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3 Resistors, 3.3 k? 2
4 Bread Board 1
5 Power supply (0-30) V 1
6 CRO 30 MHz 1
7 Probe few

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8 Connecting Wires few

Procedure:
1. Measure the amplitude of each pulse, no. of pulses in one cycle, frequency of pulses.
2. Vary the modulating input signal observe its effect on the output.

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3. Observe compare the output waveform with input waveform/
4. See the input and output that are same in frequency, amplitude phase.
5. Draw the waveform of the modulating signal, sampling signal, pulse amplitude a modulated signal.

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61 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Circuit Diagram
Pulse amplitude modulation

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Model Graph:

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62 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Tabulation
Signal Amplitude (V) Time Period (s)
Message

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Carrier

PAM wave

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Demodulated


Result:
Thus the pulse amplitude modulation (PAM) output waveform was generated.

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Outcome:
After the completion of this experiment the students will be able to design and construct the PAM modulated
wave.

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1. What is PAM?
2. Differentiate PAM from PCM.
3. Write the application of PAM.
4. Draw the PAM signal.
5. Compare PAM, PPM and PWM.

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6. What are the advantage of PAM and PWM?
7. What is the advantage of PPM over PWM and PAM?
8. What is Pulse position modulation?
9. Mention the applications of PAM.
10. What are the disadvantages of PAM?

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11. What is PWM or Pulse length modulation or pulse duration modulation?
12. Define ? Pulse Modulation


Viva ? voce

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63 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 14 AMPLITUDE MODULATION DEMODULATION
USING Lab VIEW
Aim:

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To generate amplitude modulated wave using NI LabVIEW demodulate the AM wave
using envelope detector
Apparatus required:
1. Windows XP or Later Version
2. LabVIEW Software

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Procedure:
Amplitude Modulation:
1. Select the controls which are used for AM transmitter place it on Block Diagram.
2. Select the carrier message signal from function palette (Right click on Block Diagram ? Signal

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Processing ?Wave form Generation ? Simulate signal) drag to block diagram. Select the parameters
such as frequency, amplitude sampling frequency for the Amplitude Modulation as listed in Table: Front
panel configurations for Amplitude Modulation.
3. Select the required Numeric controls used in the circuit from the block diagram (Right click on Block
Diagram ? Programming ? Numeric) connect as shown in figure: Circuit diagram for Amplitude

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Modulation.
4. Select the waveform graphs to display the input output waveforms (Right click on Front Panel ?
Modern ? Graph ? Waveform Graph) place those waveform Graphs on Front panel connect it as shown
in figure: Circuit diagram for Amplitude Modulation.
5. Run the circuit; observe the output signal for the corresponding Input (Message Carrier) signal.

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Configurations on Front panel:
1. Disable the Auto scale option for both X Y axis on each waveform graph(By making right click on
waveform graph) which is used in Front panel.
2. Select the X axis scale (0 to 0.03) Y axis scale (-1 to +1) as required to view the waveform graph properly
on the Front panel.

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64 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Front panel configurations for Amplitude Modulation
Parameter Message Signal Carrier Signal
Signal Type Sine Sine
Frequency 100 Hz 1000 Hz

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Amplitude 1 0.5
Phase 0 0
Offset 0 0
Sampling Rate 10000 Hz 10000 Hz
Number of Samples 1000(Automatic) 1000(Automatic)

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Timing Run as fast as possible Run as fast as possible
Timestamps Relative Relative

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Amplitude modulation using labVIEW


65 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Amplitude Demodulation:
1. Connect the circuit in external kit as shown in Figure Demodulator of AM wave with Envelope Detector.
2. Apply the modulated signal input from LabVIEW software to external hardware kit.
3. Verify the message signal after demodulating using the envelope detector circuit.

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D1
1N4007
R1
1k?

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C1
1uF
XSC1
A B
Ext Trig

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+
+
_
_
+

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_
Amplitude
Modulated wave

Demodulator of AM wave with Envelope Detector using labVIEW

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Result:
Thus the simulation of amplitude modulation and demodulation using NI LabVIEW was performed.
Outcome:
After the completion of this experiment the students will be able to simulate the AM modulated wave and

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demodulated wave using LabVIEW.



1. What is LabVIEW?

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2. Define ? Amplitude Modulation
3. Draw the phasor diagram of AM signal.
4. What is depth of modulation?
5. Draw the frequency spectrum of amplitude modulation.

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Viva - voce
FirstRanker.com - FirstRanker's Choice
1 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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?

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DEPARTMENT OF
ELECTRONICS COMMUNICATION ENGINEERING

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V SEMESTER - R 2013

EC6512 ? COMMUNICATION SYSTEMS LABORATORY

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Name : _______________________________________
Register No. : _______________________________________
Section : _______________________________________

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LABORATORY MANUAL

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2 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

DHANALAKSHMI

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College of Engineering is committed to provide highly disciplined, conscientious
enterprising professionals conforming to global stards through value based quality education training.


? To provide competent technical manpower capable of meeting requirements of the industry

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? To contribute to the promotion of Academic Excellence in pursuit of Technical Education at different levels
? To train the students to sell his brawn brain to the highest bidder but to never put a price tag on heart soul
DEPARTMENT OF ELECTRONICS AND COMMUNICATION
ENGINEERING

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To impart professional education integrated with human values to the younger generation, so as to
shape them as proficient dedicated engineers, capable of providing comprehensive solutions to the challenges
in deploying technology for the service of humanity

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? To educate the students with the state-of-art technologies to meet the growing challenges of the electronics
industry
? To carry out research through continuous interaction with research institutes industry, on advances in
communication systems

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? To provide the students with strong ground rules to facilitate them for systematic learning, innovation ethical
practices

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VISION
VISION
MISSION
MISSION

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3 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

PROGRAMME EDUCATIONAL OBJECTIVES (PEOs)
1. Fundamentals
To provide students with a solid foundation in Mathematics, Science fundamentals of engineering,

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enabling them to apply, to find solutions for engineering problems use this knowledge to acquire higher
education
2. Core Competence
To train the students in Electronics Communication technologies so that they apply their knowledge
training to compare, to analyze various engineering industrial problems to find solutions

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3. Breadth
To provide relevant training experience to bridge the gap between theory practice this enables them to
find solutions for the real time problems in industry, to design products
4. Professionalism
To inculcate professional effective communication skills, leadership qualities team spirit in the students

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to make them multi-faceted personalities develop their ability to relate engineering issues to broader social
context
5. Lifelong Learning/Ethics
To demonstrate practice ethical professional responsibilities in the industry society in the large,
through commitment lifelong learning needed for successful professional career

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4 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00



PROGRAMME OUTCOMES (POs)

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a) To demonstrate apply knowledge of Mathematics, Science engineering fundamentals in Electronics
Communication Engineering field
b) To design a component, a system or a process to meet the specific needs within the realistic constraints
such as economics, environment, ethics, health, safety manufacturability
c) To demonstrate the competency to use software tools for computation, simulation testing of electronics

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communication engineering circuits
d) To identify, formulate solve electronic communication engineering problems
e) To demonstrate an ability to visualize work on laboratory multidisciplinary tasks
f) To function as a member or a leader in multidisciplinary activities
g) To communicate in verbal written form with fellow engineers society at large

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h) To understand the impact of Electronics Communication Engineering in the society demonstrate awareness
of contemporary issues commitment to give solutions exhibiting social responsibility
i) To demonstrate professional and ethical responsibilities
j) To exhibit confidence in self-education ability for lifelong learning
k) To participate succeed in competitive exams

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5 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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EC6512 - COMMUNICATION SYSTEMS LABORATORY

To visualize the effects of sampling and TDM
? To Implement AM and FM modulation and demodulation
? To implement PCM and DM

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? To implement FSK, PSK and DPSK schemes
? To implement Equalization algorithms
? To implement Error control coding schemes
LIST OF EXPERIMENTS
1. Signal Sampling and reconstruction

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2. Time Division Multiplexing
3. AM Modulator and Demodulator
4. FM Modulator and Demodulator
5. Pulse Code Modulation and Demodulation
6. Delta Modulation and Demodulation

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7. Observation (simulation) of signal constellations of BPSK, QPSK and QAM
8. Line coding schemes
9. FSK, PSK and DPSK schemes (Simulation)
10. Error control coding schemes ? Linear Block Codes (Simulation)
11. Communication link simulation

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12. Equalization ? Zero Forcing and LMS algorithms (simulation)


Simulate end-to-end Communication Link
Demonstrate their knowledge in base b signaling schemes through implementation of FSK, PSK DPSK.

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Apply various channel coding schemes and demonstrate their capabilities towards the improvement of the noise
performance of communication system.

COURSE OBJECTIVES
COURSE OUTCOMES

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EC6512 ? COMMUNICATION SYSTEMS LABORATORY
CONTENTS
Sl. No. Name of the Experiment Page No.

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CYCLE 1 - EXPERIMENTS
1 Signal sampling reconstruction
7
2 Time division multiplexing
13

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3 AM modulation demodulation
18
4 Frequency modulation demodulation
26
5 PCM modulation demodulation

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33
6 Delta modulation demodulation
38
7 Line coding decoding techniques
45

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CYCLE 2 ? EXPERIMENTS
8 Error control coding using MATLAB
51
9 Design of BPSK, QPSK, QAM using MATLAB
53

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10 Design of FSK, PSK DPSK using MATLAB
55
11 Communication link simulation using MATLAB
57
12 Zero forcing LMS equalization algorithms using MATLAB

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59
ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS
13 Pulse amplitude modulation 61
14 Amplitude modulation demodulation using LabVIEW 64

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7 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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CYCLE 1 - EXPERIMENTS
Expt. No. 1 SIGNAL SAMPLING AND RECONSTRUCTION
Aim:
To study the process of sampling and reconstruction of signals using analog sampling trainer kit

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Apparatus required:
1. Analog signal sampling and reconstruction trainer kit ? 1 No.
2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 Nos.
4. CRO (30 MHz) ? 1 No.

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Theory:
Sampling is defined as measuring the value of an information signal at predetermined time interval. The rate at
which the signal is sampled is known as the sampling rate or sampling frequency. The types of sampling are
natural sampling and flat top sampling.
A continuous time signal can be processed by processing its samples through a discrete time system. For

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reconstructing the continuous time signal from its discrete time samples without any error, the signal should be
sampled at a sufficient rate that is determined by the sampling theorem.
Sampling theorem
If a signal is band limited and its samples are taken at sufficient rate than those samples uniquely specify the
signal and the signal can be reconstructed from those samples. The condition in which this is possible is known

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as Nyquist sampling theorem.
A signal whose spectrum is band limited to D Hz [X(f) = 0 for | f | >D] can be reconstructed from its samples
taken uniformly at a rate fs > 2D samples/sec. The minimum sampling frequency is fs = 2D Hz.
Reconstruction of Signals
The process of reconstructing a continuous time signal x(t) from its samples is known as interpolation. In the

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sampling theorem a signal x(t) band limited to D Hz can be reconstructed from its samples. This reconstruction is
accomplished by passing the sampled signal through an ideal low pass filter of bandwidth D Hz.To
recover x(t) or X(f), the sampled signal must be passed through an ideal low pass filter having bandwidth D Hz
and gain T.
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Sample and hold circuit is used to operate on analog information in a time frame which is expedient. This circuit
works by sampling a segment of the information holding it and then converts it into some readout or a form of
control signal.
Procedure:

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1. Assemble the sample and hold circuit with the desired components.
2. Give the input signal from the function generator.
3. Do not exceed the input signal above 10 volt.
4. Set the frequency of the input signal to 600 Hz.
5. Set the frequency of the sample signal to 5600 Hz.

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6. Integrate the sampling inputs.

Circuit Diagram

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9 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Natural Sampling and Flat Top Sampling Circuit Diagram

Model Graph:

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Tabulation

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Analog signal sampling and reconstruction trainer kit


Result:
Thus the sampling and reconstruction of signal was studied and verified using sampling reconstruction trainer

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kit.


Signal Amplitude (V) Time period (s)
Message signal

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Carrier signal
Sampled output
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Outcome:

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After completion of this experiment, the students will be able to understand the discretization process of
continuous time signal.
Applications:
1. Analog-to-digital conversion (ADC)
2. Digital-to-analog conversion (DAC)

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3. Storage, and transmission
4. Telephone and encrypted walkie-talkie (8000 Hz sample rate)
5. Wireless intercom and wireless microphone transmission (Audio Sampling)

1. Define ? Sampling Theorem

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2. What is the necessary sufficient condition for sampling reconstruction of a signal?
3. Define ? Nyquist rate
4. Define ? Nyquist interval
5. What are the different types of sampling techniques?
6. What is the effect on sampled signal if fs< 2 fm?

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7. Draw the amplitude spectrum of sampled signal if fs< 2 fm, fs =2 fm, fs > 2 fm.
8. What is aliasing effect in sampling? How to avoid it?
9. Why do we use pre-filtering in sampling?
10. What is reconstruction of sampling theorem?
11. What are the types of filters used in reconstruction?

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12. Define ? Sample Hold Circuits
13. Differentiate second order; fourth order and sixth order low pass filters in reconstruction process.
14. Explain the sampling reconstruction process.
15. What is the difference between discrete and digital signals?
16. Define ? Digital Signal

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17. What is the need for converting a continuous signal into a discrete signal?
18. Explain zero-order hold circuit.
19. How to convert an analog signal into a digital signal?
20. Differentiate flat top sampling from natural sampling.
21. Define ? Natural Sampling

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Viva - voce
12 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Expt. No. 2 TIME DIVISION MULTIPLEXING
Aim:
To study the process of time division multiplexing of four signals using sampling trainer kit
Apparatus required:
1. TDM trainer kit ? 1 No.

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2. Dual Power Supply ? 1 No.
3. Patch cords ? 6 No.
4. CRO (30 MHz) ? 1 No.
Theory:
Time Division Multiplexing (TDM) is a method of transmitting and receiving independent signals over a common

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signal path by means of synchronized switches at each end of the transmission line so that each signal appears
on the line only a fraction of time in an alternating pattern.
Procedure:
1. Switch ON the power supply.
2. Make initial settings on TDM Trainer kit as follows.

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(a) Set all sine wave voltages to 2V,
(b) Make the wiring connections as in wiring diagram .
3. Display the multiplexed signal at test point T14 on channel 1 and 250Hz sine wave at test point T2 on
channel 2 of oscilloscope.
4. Display the 500Hz sine wave at test point T3 on channel 2 in place of 250Hz, identify sampled version of this

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sine wave in TDM signal note down.
5. Observe 1 KHz 2 KHz waveforms at test point T4 T5 respectively on oscilloscope .
6. Display the TDM waveform (test point T14) on channel 1 channel synchronization signal (test point T13)
on channel 2 of oscilloscope .
7. Display 250Hz sine wave at test point T2 on channel 1 and output sine wave at test point T16 on channel 2 of

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Oscilloscope.
8. Similarly, observe input output 500Hz, 1 KHz and 2 KHz sine waves on oscilloscope .


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Circuit Diagram
Time division multiplexing

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TDM Trainer Kit

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Model Graph:

Tabulation
Sl. No. Signal Amplitude (V) Time period (s)

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1. Message signal 1
2. Message Signal 2
3. TDM signal

Result:

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Thus the TDM was studied the different types of signals are multiplexed using TDM Technique.
Outcomes:
After completion of this experiment the students will be able to understand the concept of multiplexing the
signals.

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Applications:
1. The plesiochronous digital hierarchy (PDH) system, also known as the PCM system, for digital

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transmission of several telephone calls over the same four-wire copper cable (T-carrier or E-carrier)
or fiber cable in the circuit switched digital telephone network
2. The synchronous digital hierarchy (SDH)/synchronous optical networking (SONET) network
transmission standards that have replaced PDH.
3. The Basic Rate Interface and Primary Rate Interface for the Integrated Services Digital

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Network (ISDN).
4. The RIFF (WAV) audio standard interleaves left and right stereo signals on a per-sample basis
5. The GSM telephone system

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1. What is meant by multiplexing technique ?
2. What are the different types of multiplexers?
3. What is the transmission band width of a PAM/TDM signal?
4. What is the crosstalk effect in PAM/TDM system?
5. What are the advantages of TDM system?

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6. Distinguish between TDM and FDM.
7. What is the value of Ts in TDM system?
8. What are the applications of TDM system? Give some example.
9. What is meant by signal overlapping?
10. Which type of modulation technique will be used in TDM?

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Viva - voce
17 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 3 AM MODULATION & DEMODULATION
Aim:

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To transmit a modulating signal after amplitude modulation using AM transmitter receives the signal back after
demodulating using AM receiver
Apparatus required:
.
1 Resistor ? 4 No.

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2 Capacitor ? 1 No.
3 Diode ? 2 No.
4
AM transmitter receiver
trainer kit ? 1 No.

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5 CRO ? 1 No.
6 Patch cards ? 6 No.

Theory:

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AMPLITUDE MODULATION
Amplitude Modulation is a process by which amplitude of the carrier signal is varied in accordance with the
instantaneous value of the modulating signal, but frequency and phase of carrier wave remains constant.
The modulating carrier signal are given by
Vm(t) = Vm sin ?mt

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VC (t) = VC sin ?Ct
The modulation index is given by, ma = Vm/ VC.
Vm = Vmax ? Vmin VC = Vmax + Vmin

The amplitude of the modulated signal is given by,

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VAM(t) = VC (1+ma sin ?mt) sin ?Ct

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Where

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Vm = maximum amplitude of modulating signal
VC = maximum amplitude of carrier signal
Vmax = maximum variation of AM signal
Vmin = minimum variation of AM signal
Formula Used:

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M= (Vmax ? Vmin / Vmax + Vmin ) * 100
Where, M = Modulation index
Vmax = Maximum peak amplitude
Vmin = Minimum peak amplitude
if

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M < 1 Under modulation
M = 1 Critical modulation
M > 1 over modulation

Procedure:

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1. Give the modulating signal input to the Amplitude modulator.
2. Increase the amplitude of the modulating signal to the required level.
3. Observe the amplitude and the time duration of the modulating signal using CRO.
4. Observe the amplitude modulated output from the output of amplitude modulator stage .
5. Calculate the modulation index

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Circuit Diagram
AM Modulation

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AM Demodulation

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Model Graph:

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1. AM Waveform (Ring diode Transistor based AM Modulator)

AM Modulated wave

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2. Envelope Detector Waveform (Modulating and Demodulated Signal)

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AM Modulation demodulation trainer kit

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AM Modulation and Demodulation trainer kit

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

Carrier

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Modulated

Demodulated

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Result:
Thus the AM signal was transmitted using AM trainer kit the AM signal detected using AM detector kit.
Outcome:
After the completion of this experiment the students will be able to design construct the amplitude modulated

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demodulated wave.
Applications:
1. Commercial broadcasting of both audio and video signals
2. Two way mobile radio communication such as citizen band (CB) radio.
3. Facsimile transmission

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1. What is modulation and demodulation?
2. Draw the phasor diagram of AM signal.

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3. What is the degree of modulation?
4. Explain the need of modulation and demodulation?
5. What is analog modulation? State the various techniques.
6. Why frequency modulation is better than amplitude modulation?
7. Which type of modulation is used in TV transmission?

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8. What is depth of modulation?
9. What are the different types of AM generation?
10. Define ? Modulation Index
11. What are different types of analog modulation techniques?
Viva - voce

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24 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

12. What are the other names of message signal? What are the other names of carrier signal?
13. Write the equation of AM signal .Explain each parameter of the equation.
14. Define ? Amplitude modulation

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15. What is the range of Audio frequency signals? What is the range of Radio frequency signal?
16. What are the applications of Amplitude modulators?
17. How many generation methods are there to generate an AM wave? What are the methods of
demodulation of an AM wave?
18. Explain the operation of diode detector circuit.

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19. Write the formula for modulation index. Differentiate under, over perfect modulation in AM.
20. As the amplitude of message signal increases, modulation index increases or decreases?
21. Define ? Single tone modulation
22. Draw the frequency spectrum of AM wave.
23. If modulation index is 100%, calculate the ratio of total power to carrier power of an AM wave.

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.

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Expt. No. 4 FREQUENCY MODULATION & DEMODULATION

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Aim:
To transmit a modulating signal after frequency modulation using FM transmitter receive the signal back after
demodulating using FM receiver
Apparatus required:
.

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1. Resistor ? 4 No.
2. Capacitor ? 1 No.
3. Diode ? 2 No.
4.
AM transmitter Receiver

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trainer kit ? 1 No.
5. CRO ? 1 No.
6. Patch cards ? 6 No.

Theory:

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Frequency modulation (FM) is a form of modulation that represents information as variations in the
instantaneous frequency of a carrier wave. In analog applications, the carrier frequency is varied in direct
proportion to changes in the amplitude of an input signal. Shifting the carrier frequency among a set of discrete
values can represent digital data, a technique known as frequency-shift keying. FM is commonly used at VHF
radio frequencies for high-fidelity broadcasts of music speech Normal TV sound is also broadcast using FM. A

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narrowband form is used for voice communications in commercial amateur radio settings. The type of FM used
in broadcast is generally called wide-FM, or W-FM.
In two-way radio, narrow-fm (N-FM) is used to conserve bandwidth. In addition, it is used to send signals into
space.
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FM is also used at intermediate frequencies by most analog VCR systems, including VHS, to record the
luminance (black,white) portion of the video signal. FM is the only feasible method of recording video and
retrieving video from magnetic tape without extreme distortion, as video signals have a very large range of
frequency components ? from a few hertz to several megahertz, it is too wide for equalizers to work with due to

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present of electronic noise below -60 dB. FM also keeps the tape at saturation level, therefore acts as a form of
noise reduction, a simple limiter can mask variations in the playback output.The FM capture effect removes
print-through pre-echo.

Procedure:

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FM Modulator:
1. Switch ON the Power supply.

2. Connect the sine wave generator output to frequency modulator input.

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3. Select the low frequency carrier (or) high frequency carrier.

4. Connect the CRO input to the frequency modulator output.

5. Vary the amplitude pot meter from minimum to maximum to find out the frequency deviation for FM.

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6. Observe the frequency modulator output .

FM Demodulator:
A) PLL Detector

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1. Connect frequency modulated output to the PLL detector input.

2. Now set the DPDT switch in low frequency mode.

3. Connect CRO input to PLL detector output.

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4. Observe the Demodulated O/P compare with the original input.

B) Quadrature Detector
1. Connect the frequency modulated output to Quadrature detector input.

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2. Now set the DPDT switch in high frequency mode.

3. Connect the CRO input to Quadrature detector output.

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4. Observe the Demodulated O/P and compare with the original input.
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C) Phase Discriminator (Foster-Seeley detector)

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1. Connect the frequency modulated output to Phase discriminator input.

2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Phase discriminator output.

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4. Observe the Demodulated O/P and then compare with the original input.

D) Ratio Detector
1. Connect the frequency modulated output to Ratio detector input.

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2. Set the DPDT switch in high frequency mode.

3. Connect the CRO input to Ratio detector output.

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4. Observe the Demodulated O/P and then compare with the original input.

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Circuit Diagram
FM Modulator

FM Demodulator

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FM Modulation and Demodulation Trainer kit

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Model Graph:

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Tabulation
Signal Amplitude (V) Time Period (s) Frequency (Hz)
Message

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Carrier

Modulated

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Demodulated


Result:
Thus the FM Modulation and Demodulation is performed for the given message signal.

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Outcome:
After the completion of this experiment the students will be able to design and construct the frequency

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modulated and demodulated wave.
Applications:
1. Television sound transmission
2. Two way mobile radio
3. Cellular Radio

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4. Microwave
5. Satellite Communication System


1. Define ? Frequency Modulation

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2. How it is different from phase modulation?
3. Write equation of FM wave, explain each parameter in it.
4. Draw the amplitude spectrum of FM wave.
5. Give the Carson?s rule in FM.
6. Define ? Modulation Index

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7. Differentiate between Narrow band FM from Wide band FM.
8. Draw message, carrier FM waves .
9. Explain the methods for generation of FM its demodulation.
10. How FM wave is different from PM wave?
11. Give the practical applications of FM.

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12. State advantages and disadvantages of FM.
13. What is the range of speech signals?
14. What type of modulation is used in radios?
15. What type of modulation is used in voice signals?
16. Define ? Phase Modulation

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17. Draw the phasor diagram of FM signal.
18. What are the different types of FM generation?

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Viva - voce
32 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 5 PCM MODULATION & DEMODULATION

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Aim:
To generate a PCM signal using PCM modulator detect the message signal from PCM signal by using PCM
demodulator
Apparatus Required:

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1. PCM trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:
Pulse code modulation is a process of converting an analog signal into digital. The voice or any data input is

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first sampled using a sampler (which is a simple switch) then quantized. Quantization is the process of
converting a given signal amplitude to an equivalent binary number with fixed number of bits. This quantization
can be either mid tread or mid raise it can be uniform or non-uniform based on the requirements. For example in
speech signals, the higher amplitudes will be less frequent than the low amplitudes. So higher amplitudes are
given less step size than the lower amplitudes thus quantization is performed non-uniformly. After quantization

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the signal is digital the bits are passed through a parallel to serial converter and then launched into the channel
serially.
At the demodulator the received bits are first converted into parallel frames .Each frame is de-quantized to an
equivalent analog value. This analog value is thus equivalent to a sampler output. This is the demodulated signal.
In the kit the analog signal is passed through a ADC (Analog to Digital Converter) and then the digital codeword

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is passed through a parallel to serial converter block. This is modulated PCM. This is taken by the Serial to
Parallel converter and then through a DAC to get the demodulated signal. The clock is given to all these blocks
for synchronization. The input signal can be either DC or AC according to the kit. The waveforms can be
observed on a CRO for DC without problem. AC also can be observed but with poor resolution.
Procedure:

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1. Power on the PCM kit.
2. Measure the frequency of sampling clock.
3. Apply the DC voltage as modulating signal.
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4. Connect the DC input to the ADC measure the voltage.
5. Connect the clock to the timing control circuit.
6. Note the binary work from LED display. The serial data through the channel can be observed in the CRO.
7. Also observe the binary word at the receiver end.
8. Now apply the AC modulating signal at the input.

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9. Observe the waveform at the output of DAC.
10. Note the amplitude of the input voltage the codeword. Also note the value of the output voltage. Show the
codeword graphically for a DC input.
Block diagram of PCM Transmission system

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34 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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PCM Modulation and Demodulation Trainer kit

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Model Graph:

Tabulation

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Result:
Thus the PCM wave generated for the given DC or sinusoidal signals using Trainer.
Outcome:
After the completion of this experiment the students will be able to design and construct the pulse code
modulated and demodulated wave.

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Applications:
1. Military Applications.
2. The PCM is used in the satellite transmission system.
SIGNALS AMPLITUDE (V) TIME PERIOD (s)
DC Input

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Sampled Signal
Clock Pulse
PCM Output
DC Output
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3. It is used in space communication.
4. It is used in telephony.
5. The compact disc (CD) is a recent application of PCM.

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1. Define ? Modulation
2. State sampling theorem
3. Define ? Demodulation
4. Define ? Pulse Code Modulation

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5. What is aliasing effect?
6. What is quantization?
7. Define ? Bit Rate
8. Define ? Baud Rate
9. What are the advantages of PCM?

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10. Define ? Signal to Noise Ratio
11. What are the limitations of PCM?
12. What are the applications of PCM?
13. Define ? Encoding
14. Define ? Decoding

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15. Define ? Nyquist Rate
16. What is multiplexing?
17. What is de-multiplexing?
18. What are the types of pulse modulation?
19. What should be the minimum bandwidth required to transmit a PCM channel?

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20. What is the value of signal to noise ratio in PCM?

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Viva - voce
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Expt. No. 6 DELTA MODULATION & DEMODULATION
Aim:
To transmit an analog message signal in its digital form and reconstruct back the original analog message
signal at receiver by using Delta modulator

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Apparatus required:
1. DM and ADM Trainer kit ? 1 No.
2. CRO ? 1 No.
3. Connecting probes ? 4 No.
Theory:

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Delta modulation is the DPCM technique of converting an analog message signal to a digital sequence. The
difference signal between two successive samples is encoded into a single bit code. A present sample of the
analog signal m(t) is compared with a previous sample , the difference output is level shifted, i.e. a positive level
(corresponding to bit 1) is given if difference is positive and negative level (corresponding to bit 0) if it is negative.
The comparison of samples is accomplished by converting the digital to analog form then comparing with the

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present sample. This is done using an Up counter DAC. The delta modulated signal is given to up counter then to
a DAC. The analog input is given to OPAMP and LPF to obtain the demodulated output.
Procedure:
1. Switch on the kit. Connect the clock signal and the modulating input signal to the modulator block.
2. Observe the modulated signal in the CRO.

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3. Connect the DM output to the demodulator circuit. Observe the demodulator output on the CRO.
4. Also observe the DAC output on the CRO.
5. Change the amplitude of the modulating signal.
6. Observe the DAC output. Notice the slope overload distortion.
7. Keep the tuning knob to minimize distortion.

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8. Note this value of the amplitude. This is the minimum required value of the amplitude to overcome slope
overload distortion.
9. Calculate the sampling frequency required for no slope overload distortion.
10. Compare the calculated measured values of the sampling frequency.

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Block Diagram Delta modulator and demodulator

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Delta Modulator

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Delta Demodulator



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Block diagram of Adaptive delta modulator and demodulator

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Adaptive Delta Modulator

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Adaptive Delta Demodulator

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40 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Delta Modulation and Adaptive Delta Modulator Trainer kit

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Model Graph:

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42 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Tabulation 1
For Delta Modulation

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Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal
2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

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Tabulation 2
For Adaptive Delta Modulation
Sl. No. Signal Amplitude (V) Time period (s) Frequency (Hz)
1 Modulating Signal

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2 Carrier Signal
3 Modulated Signal
4 Demodulated Signal

Result:

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Thus the output waveforms of Delta modulation and adaptive delta modulation circuit were observed.
Outcome:
After the completion of this experiment the students will be able to design and construct the delta modulation
adaptive delta modulation circuit.
Applications:

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1. Digital voice storage
2. Voice transmission
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3. Radio communication devices such TV remotes.

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4. Delta Modulation was used by Satellite Business Systems or SBS
5. DM used in high resolution A/D and D/A converters.


1. What is delta modulation?

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2. What is adaptive delta modulation?
3. What are the advantages of adaptive delta modulation over delta modulation?
4. What is slope over load distortion?
5. What is granular noise effect?
6. What are the two limitations of delta modulation?

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7. What is the function of integrator?
8. What is comparator?
9. What is companding?
10. What is the advantage of delta modulation over pulse modulation?
11. Distinguish between DPCM and DM.

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12. What are the different types of digital modulation?
13. What is sampling rate?
14. Which kind of multiplexing used in digital communication?
15. Why is sample hold circuit used?
16. What are the advantages of digital transmission?

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17. How is the performance corrupted in PCM?
18. What are the different types of multiplexing?
19. What is aliasing effect?
20. How to avoid aliasing effect?

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Viva - voce
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Expt. No. 7 LINE CODING DECODING TECHNIQUES

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Aim:
To study different line coding techniques.
Apparatus required:
1. Line coding and decoding trainer kit ? 1 No.

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2. Patch cords ? 6 No.
3. CRO ? 1 No.

Theory:
Line coding refers to the process of representing the bit stream (1 ?s and 0 ?s) in the form of voltage or current

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variations optimally tuned for the specific properties of the physical channel being used. The selection of a proper
line code can help in many ways. One possibility is to aid in clock recovery at the receiver. A clock signal is
recovered by observing transitions in the received bit sequence, if enough transitions exist, a good recovery of
the clock is guaranteed, the signal is said to be self-clocking. Another advantage is to get rid of DC shifts. The
DC component in a line code is called the bias or the DC coefficient. Unfortunately, most long-distance

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communication channels cannot transport a DC component. This is why most line codes try to eliminate the DC
component before being transmitted on the channel. Such codes are called DC balanced, zero-DC, zero-bias, or
DC equalized. Some common types of line encoding in common-use nowadays are unipolar, polar, bipolar,
Manchester, MLT-3 Duo binary encoding.
Unipolar (Unipolar NRZ and Unipolar RZ):

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Unipolar is the simplest line coding scheme. It has the advantage of being compatible with TTL logic. Unipolar
coding uses a positive rectangular pulse p(t) to represent binary 1, the absence of a pulse (i.e., zero voltage) to
represent a binary 0. Two possibilities for the pulse p(t) exist3: Non-Return-to-Zero (NRZ) rectangular pulse
Return-to-Zero (RZ) rectangular pulse. The difference between Unipolar NRZ Unipolar RZ codes is that the
rectangular pulse in NRZ stays at a positive value (e.g., +5V) for the full duration of the logic 1 bit, while the pule

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in RZ drops from +5V to 0V in the middle of the bit time.



45 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Procedure:
1. Connect the PRBS (test point P5) to various line coding formats. Obtain the coded output as per the
requirement.
2. Connect coded signal test point to corresponding decoding test point as inputs.

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3. Set the SW1 as per the requirement.
4. Set the potentiometer P1 in minimum position.
5. Switch ON the power supply. Press the switch SW2 once.
6. Display the encoded signal on one channel of CRO and decoded signal on second channel of CRO.

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46 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


Line coding decoding trainer kit

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47 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


Model Graph:

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48 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Tabulation
Sl. No. Type of Coding AMPLITUDE (V) Time period (s)
1. Unipolar data(NZ NRZ )

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2. Unipolar data (NRZ RZ)
3. Bipolar Data(NRZ AMI)
4. Manchester

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Result:
Thus the different line coding techniques was studied and verified.
Outcome:
After the completion of this experiment the students will be able to understand implement the different line
coding schemes.

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Applications:
1. DC balance
2. embedded clock applications
3. computing applications
4. Manchester codes are commonly used for local area networks

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5. Bipolar codes are commonly used for local area networks

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49 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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1. What is line coding?
2. Define ? Polar Encoding
3. Define ? Unipolar Encoding
4. Define ? Bipolar Encoding
5. Define ? Manchester Encoding

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6. What are the two function of fast frequency hopping?
7. What is return to zero?
8. What is Non-return to zero?
9. What is the difference between source coding and line coding?
10. What are the properties of line coding?

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11. What is the effect of inter symbol interference?
12. How ISI can be reduced?
13. Define ? Encoding
14. Define ? Decoding
15. Define ? Nyquist Rate

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16. Draw the NRZ and RZ code for the digital data 10110001.
17. Define ? Equalization
18. What is PRBS?
19. Write the Boolean expression for X-NOR gate.
20. Define ? Digital demodulation

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Viva - voce
50 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

CYCLE 2 ? EXPERIMENTS

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Expt. No.8 ERROR CONTROL CODING USING MATLAB
Aim:
To write a program in MATLAB for error control coding techniques
Software required:
PC with MATLAB version 7.0 software installed

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Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments comon prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.

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4. A blank M ?file will appear with a title ?untitiled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the common window. If there is an error then with an alarm, type of error
will appear in red colour.

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7. Rectify the error if any go to debug menu select run.

Result:
Thus the error control coding techniques are executed using MATLAB programs.
Outcome:

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After the completion of this experiment the students will be able to simulate the different error control coding
schemes using MATLAB.
Applications :
1. Deep space communication
2. Satellite communication

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3. Data transmission
4. Data storage
5. Mobile communication
6. File transfer
7. digital audio/video transmission.

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51 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


1. What is the need for error control coding?
2. What is meant by linear code?

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3. What is meant by cyclic code?
4. Name some error control coding techniques.
5. Name the code which is used only for error detection.

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Viva - voce
52 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 9 DESIGN OF BPSK, QPSK, QAM USING MATLAB
Aim:

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To write a program in MATLAB for design of BPSK, QPSK and QAM
Software required:
PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.

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2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the

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program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error, if any go to debug menu select run.

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53 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Result:
Thus the BPSK, QPSK and QAM were simulated using MATLAB.

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Outcome:
After the completion of this experiment the students will be able to simulate the various modulation schemes
such as BPSK, QPSK and QAM using MATLAB.
Applications:
QPSK

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1. Data transmission, mainly radio transmissions.
2. RTTY means radio teletype transmissions from amateur radio up to WiFi transmissions or Zigbees
QAM
1. Radio communications and data delivery applications.

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1. What is a correlator?
2. Define ? Constellation Diagram
3. What is BPSK ? Mention its significance.
4. Give the expression for bandwidth of BPSK scheme.

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5. What is QPSK mention its significance?
6. Give the expression for bandwidth of QPSK scheme.
7. Draw the constellation diagram of QPSK.
8. What is QAM ?
9. Give the expression for bandwidth of QAM scheme.

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10. What are the blocks in BPSK receiver?
11. What is the function of a decision device?
12. Draw the constellation diagram of QAM.
13. What are the types of QPSK?
14. What is the significance of Q-channel I channel in QPSK modulator?

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15. What is the minimum bandwidth requirement of QPSK?
16. Draw the output phase versus time relationship for a QPSK modulator.
17. Compare OQPSK with QPSK.
18. Identify the error in the matlab command Sin 3.
19. Draw the constellation diagram of QPSK.

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20. Give the applications of QPSK modulation scheme.
Viva - voce
54 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 10 DESIGN OF FSK, PSK, DPSK USING MATLAB

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Aim:
To write a program in MATLAB for design of FSK, PSK and DPSK
Software required:
PC with MATLAB version 7.0 software installed
Procedure:

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1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.

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5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the FSK, PSK and DPSK were simulated using MATLAB.

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Outcome:
After the completion of this experiment the students will be able to simulate the various modulation schemes
such as FSK, PSK and DPSK using MATLAB.
55 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Applications:
ASK:
1. ASK is used to transmit digital data over optical fiber
PSK:
1. over voice lines

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2. in high-freq. radio transmissions.


1. What is FSK? Mention its significance.
2. What is PSK? Mention its significance.

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3. What is DPSK? Mention its significance.
4. What are the applications of DPSK?
5. Give the equation for average probability of symbol error for DPSK.
6. List the operations performed in DPSK transmitter.
7. Compare DPSK with QPSK modulation scheme.

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8. What is differential encoding technique?
9. Why do we make 180 degree phase shift in PSK why not 90 or 270?
10. What is the function of a decision device?
11. What is RZ?
12. What is NRZ?

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13. What is Manchester encoding?
14. Sketch the FSK waveform for the input a) 1010110 b) 1100101
15. Define modulation index.
16. Write a MATLAB program for generating PN sequence.
17. Differentiate coherent with non-coherent FSK.

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18. Give the expression for bandwidth of FSK scheme.
19. What is the difference between PSK and FSK?
20. What is the major advantage of coherent PSK over coherent ASK?

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Viva - voce
56 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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sExpt. No. 11 COMMUNICATION LINK SIMULATION USING
MATLAB
Aim:
To simulate the basic communication link using mat lab
Software required:

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PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.
2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper

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icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the
program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error

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will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the communication link simulation was designed using MATLAB.
Outcome:
After the completion of this experiment the students will be able to simulate and design the communication link
using MATLAB.

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57 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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1. Give examples for digital modulation techniques.
2. What is meant by pass-b transmission?
3. What is meant by base-b transmission?
4. What is the meaning for error pattern?
5. Differentiate systematic from non-systematic coding.

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Viva - voce

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58 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 12 ZERO FORCING LMS EQUALIZATION
ALGORITHMS USING MATLAB
Aim:

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To write a program in MATLAB for design of zero forcing LMS algorithms
Software required:
PC with MATLAB version 7.0 software installed
Procedure:
1. Open the MATLAB software by double clicking its icon.

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2. MATLAB logo will appear after few moments command prompt will appear.
3. Go to the file menu select a new M ? file.( File _New_M-file) 0r in the left h corner a blank white paper
icon will be there. Click it once.
4. A blank M ?file will appear with a title ?untitled?.
5. Now start typing your program. After completing, save the M-file with appropriate name. To execute the

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program press F5 or go to debug menu select run.
6. After execution output will appear in the command window. If there is an error then with an alarm, type of error
will appear in red colour.
7. Rectify the error if any go to debug menu select run.

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Result:
Thus the equalization of zero forcing LMS algorithms was simulated using MATLAB.

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Outcome:
After the completion of this experiment the students will be able to implement the various algorithms using
MATLAB.

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59 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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1. Define ? Equalization
2. What is meant by zero forcing algorithms?
3. Define ? LMS Algorithm
4. What is meant by pass-b transmission?

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5. What is meant by base-b transmission?
6. What is the meaning for error pattern?

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Viva - voce

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60 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

ADDITIONAL EXPERIMENTS BEYOND THE SYLLABUS

Expt. No. 13 PULSE AMPLITUDE MODULATION

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Aim:
To study the Pulse Amplitude Modulation technique and observe the output waveform
Apparatus required:
Sl. No. Name of the Apparatus Range Quantity
1 Function generator 0-3 MHz 1

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2 Diode 1N4007 2
3 Resistors, 3.3 k? 2
4 Bread Board 1
5 Power supply (0-30) V 1
6 CRO 30 MHz 1

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7 Probe few
8 Connecting Wires few

Procedure:
1. Measure the amplitude of each pulse, no. of pulses in one cycle, frequency of pulses.

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2. Vary the modulating input signal observe its effect on the output.
3. Observe compare the output waveform with input waveform/
4. See the input and output that are same in frequency, amplitude phase.
5. Draw the waveform of the modulating signal, sampling signal, pulse amplitude a modulated signal.

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61 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00


Circuit Diagram
Pulse amplitude modulation

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Model Graph:

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62 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Tabulation
Signal Amplitude (V) Time Period (s)

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Message

Carrier

PAM wave

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Demodulated


Result:

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Thus the pulse amplitude modulation (PAM) output waveform was generated.
Outcome:
After the completion of this experiment the students will be able to design and construct the PAM modulated
wave.

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1. What is PAM?
2. Differentiate PAM from PCM.
3. Write the application of PAM.
4. Draw the PAM signal.

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5. Compare PAM, PPM and PWM.
6. What are the advantage of PAM and PWM?
7. What is the advantage of PPM over PWM and PAM?
8. What is Pulse position modulation?
9. Mention the applications of PAM.

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10. What are the disadvantages of PAM?
11. What is PWM or Pulse length modulation or pulse duration modulation?
12. Define ? Pulse Modulation

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Viva ? voce
63 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Expt. No. 14 AMPLITUDE MODULATION DEMODULATION
USING Lab VIEW

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Aim:
To generate amplitude modulated wave using NI LabVIEW demodulate the AM wave
using envelope detector
Apparatus required:
1. Windows XP or Later Version

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2. LabVIEW Software

Procedure:
Amplitude Modulation:
1. Select the controls which are used for AM transmitter place it on Block Diagram.

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2. Select the carrier message signal from function palette (Right click on Block Diagram ? Signal
Processing ?Wave form Generation ? Simulate signal) drag to block diagram. Select the parameters
such as frequency, amplitude sampling frequency for the Amplitude Modulation as listed in Table: Front
panel configurations for Amplitude Modulation.
3. Select the required Numeric controls used in the circuit from the block diagram (Right click on Block

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Diagram ? Programming ? Numeric) connect as shown in figure: Circuit diagram for Amplitude
Modulation.
4. Select the waveform graphs to display the input output waveforms (Right click on Front Panel ?
Modern ? Graph ? Waveform Graph) place those waveform Graphs on Front panel connect it as shown
in figure: Circuit diagram for Amplitude Modulation.

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5. Run the circuit; observe the output signal for the corresponding Input (Message Carrier) signal.
Configurations on Front panel:
1. Disable the Auto scale option for both X Y axis on each waveform graph(By making right click on
waveform graph) which is used in Front panel.
2. Select the X axis scale (0 to 0.03) Y axis scale (-1 to +1) as required to view the waveform graph properly

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on the Front panel.

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64 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

Front panel configurations for Amplitude Modulation
Parameter Message Signal Carrier Signal
Signal Type Sine Sine

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Frequency 100 Hz 1000 Hz
Amplitude 1 0.5
Phase 0 0
Offset 0 0
Sampling Rate 10000 Hz 10000 Hz

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Number of Samples 1000(Automatic) 1000(Automatic)
Timing Run as fast as possible Run as fast as possible
Timestamps Relative Relative

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Amplitude modulation using labVIEW


65 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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Amplitude Demodulation:
1. Connect the circuit in external kit as shown in Figure Demodulator of AM wave with Envelope Detector.
2. Apply the modulated signal input from LabVIEW software to external hardware kit.
3. Verify the message signal after demodulating using the envelope detector circuit.

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D1
1N4007
R1

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1k?
C1
1uF
XSC1
A B

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Ext Trig
+
+
_
_

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+
_
Amplitude
Modulated wave

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Demodulator of AM wave with Envelope Detector using labVIEW

Result:
Thus the simulation of amplitude modulation and demodulation using NI LabVIEW was performed.
Outcome:

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After the completion of this experiment the students will be able to simulate the AM modulated wave and
demodulated wave using LabVIEW.

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1. What is LabVIEW?
2. Define ? Amplitude Modulation
3. Draw the phasor diagram of AM signal.
4. What is depth of modulation?
5. Draw the frequency spectrum of amplitude modulation.

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Viva - voce
66 Format No.: FirstRanker/Stud/LM/34/Issue: 00/Revision: 00

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List of Projects
1. Vehicle Tracking System
2. Accident Identification System
3. Wireless Camera Position System

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4. Remote Home Security System
5. Wireless Voting Machine
6. Wireless Security System
7. Video Signal Transmitter
8. Audio Signal Transmitter

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9. Remote Controlled Dish Antenna
10. Wireless Home Appliances Controller

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