Download PTU (I.K. Gujral Punjab Technical University Jalandhar (IKGPTU) ) BE/BTech EEE (Electrical And Electronics Engineering) 2020 March 6th Sem Elements Of Communication System Previous Question Paper
Roll No. Total No. of Pages : 02
Total No. of Questions : 09
B.Tech.(Electrical & Electronics Engg.) (OE 2013 Onwards Batch)
(Sem.?6)
ELEMENTS OF COMMUNICATION SYSTEM
Subject Code : BTEEE-OPB
M.Code : 72839
Time : 3 Hrs. Max. Marks : 60
INSTRUCTIONS TO CANDIDATES :
1. SECTION-A is COMPULSORY consisting of TEN questions carrying TWO marks
each.
2. SECTION-B contains FIVE questions carrying FIVE marks each and students
have to attempt any FOUR questions.
3. SECTION-C contains THREE questions carrying TEN marks each and students
have to attempt any TWO questions.
SECTION-A
1. Answer briefly :
a. What is the need of modulation ?
b. A single side band contains 1 kW power. How much power is contained in the side
bands and how much in the carrier?
c. Write basic difference between low level and high level modulation.
d. Define angle modulation.
e. The maximum frequency deviation in an FM is 10kHz and signal frequency is 10kHz.
Find out the bandwidth using Carson's rule and the modulation index.
f. What is FM Capture effect?
g. Define Sensitivity and Fidelity of radio receiver.
h. Define noise triangle.
i. For an 8-PSK system, operating with an information bit rate of 24 kbps, determine
bandwidth efficiency.
j. Define pulse width modulation.
SECTION-B
2. What is Freqency Shift Keying (FSK) ? Explain FSK bit rate, Baud rate, Bandwidth and
frequency spectra of FSK.
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1 | M-72839 (S2)-2206
Roll No. Total No. of Pages : 02
Total No. of Questions : 09
B.Tech.(Electrical & Electronics Engg.) (OE 2013 Onwards Batch)
(Sem.?6)
ELEMENTS OF COMMUNICATION SYSTEM
Subject Code : BTEEE-OPB
M.Code : 72839
Time : 3 Hrs. Max. Marks : 60
INSTRUCTIONS TO CANDIDATES :
1. SECTION-A is COMPULSORY consisting of TEN questions carrying TWO marks
each.
2. SECTION-B contains FIVE questions carrying FIVE marks each and students
have to attempt any FOUR questions.
3. SECTION-C contains THREE questions carrying TEN marks each and students
have to attempt any TWO questions.
SECTION-A
1. Answer briefly :
a. What is the need of modulation ?
b. A single side band contains 1 kW power. How much power is contained in the side
bands and how much in the carrier?
c. Write basic difference between low level and high level modulation.
d. Define angle modulation.
e. The maximum frequency deviation in an FM is 10kHz and signal frequency is 10kHz.
Find out the bandwidth using Carson's rule and the modulation index.
f. What is FM Capture effect?
g. Define Sensitivity and Fidelity of radio receiver.
h. Define noise triangle.
i. For an 8-PSK system, operating with an information bit rate of 24 kbps, determine
bandwidth efficiency.
j. Define pulse width modulation.
SECTION-B
2. What is Freqency Shift Keying (FSK) ? Explain FSK bit rate, Baud rate, Bandwidth and
frequency spectra of FSK.
2 | M-72839 (S2)-2206
3. Consider a message signal m(t) with a spectrum shown below. The message bandwidth
w = 1 kHz. This signal is applied to a product modulator, together with a carrier wave
A
c
Cos(2 ?f
c
t)producing the DSBSC modulated signal S(t). The modulated signal is next
applied to a coherent detector. Assuming perfect synchronism between carrier wave in
the modulator and detector. Determine the spectrum of the detector output when (i) =1.25
kHz, (ii) = 0.75 kHz. What is the lowest carrier frequency for which each component of
the modulated signal S(t) is uniquely determined by m(t).
FIG.1
4. Discuss the advantage of Pulse Code Modulation (PCM) over the other modulation
techniques.
5. Draw circuit diagram and suitable waveform of square law detector used for
demodulation of amplitude modulation (AM) wave.
6. What do you mean by multiplexing? With the help of schematic block explain the time
division multiplexing (TDM).
SECTION-C
7. Design an Armstrong indirect FM modulator to generate an FM signal with carrier
frequency 98.1 MHz and ?f =75 KHz. A NBFM generator of f
c1
= 100 kHz and ?f = 10
Hz is available. Additionally, a local oscillator (LO) with adjustable frequency between
10 to 11 MHz is readily available for frequency mixing. There are also plenty of
frequency doubler, tripler and quintuplers.
8. With the help of the suitable block diagrams and waveforms, explain pulse code
modulation (PCM). Explain the coding and decoding techniques used in PCM.
9. Write short notes on :
a. Superheterodyne receiver
b. Optical fiber modulation techniques
NOTE : Disclosure of Identity by writing Mobile No. or Making of passing request on any
page of Answer Sheet will lead to UMC against the Student.
M(f)
?w 0 w
Spectrum of the message signal m(t).
f
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This post was last modified on 21 March 2020