PTU B.Tech ECE 5th Semester May 2019 70545 DIGITAL COMMUNICATION SYSTEM Question Papers

PTU Punjab Technical University B-Tech May 2019 Question Papers 5th Semester Electronic and Communication Engineering (ECE-EIE)

Roll No.
Total No. of Pages : 02
Total No. of Questions : 09
B.Tech.(ECE)/(ETE) (2011 Onwards)
B.Tech.(Electronics Engg.) (2012 Onwards) (Sem.?5)
DIGITAL COMMUNICATION SYSTEM
Subject Code : BTEC-501
M.Code : 70545
Time : 3 Hrs. Max. Marks : 60
INSTRUCTION TO CANDIDATES :
1.
SECTION-A is COMPULSORY consisting of TEN questions carrying T WO marks
each.
2.
SECTION-B contains FIVE questions carrying FIVE marks each and students
has to attempt ANY FOUR questions.
3.
SECTION-C contains T HREE questions carrying T EN marks each and students
has to attempt ANY T WO questions.

SECTION-A
Q1. Write briefly :

a. What do you mean by Additive White Gaussian Noise?

b. Write the basic difference between delta modulation and Adaptive delta modulation.

c. What is Entropy and Information rate?

d. What is HDB signaling?

e. Draw block diagram of Coherent ASK detector.

f. Discuss noise effect in PCM.

g. What do you mean by EYE diagram?

h. Write advantages of MSK as compared to QPSK.

i. What is Schwarz's inequality?

j. Write Nyquist first criterions for Zero ISI.
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SECTION-B
Q2.
Write a note on Statistical TDM, Codecs and Combo chips.
Q3.
Prove that in BPSK receiver Phase shift increases with increase in probability of Error
and for the same signal energy and noise spectral density, which of BPSK and BFSK
have better error probability, comment on it.
Q4.
Write a note on Slope over load distortion and Granular noise.
Q5.
A communication signal having a band width of 6.2MHz is transmitted using binary
PCM system. Quantization levels are given as 512. Determine:

a) Code Word length

b) Transmission band width

c) Final bit rate

d) Output signal to quantization noise ratio.
Q6.
Calculate probability of error for ASK, PSK and FSK schemes.

SECTION-C
Q7.
Explain BPSK demodulator circuit. Give Geometrical representation of BPSK signal,
Calculate Band Width from frequency Spectrum, write advantages, disadvantages and
probability of error of BPSK signal.
10
Q8.
Apply the Huffman coding procedure for the following message ensemble

(X) = (X1
X2
X3
X4
X5
X6
X7)

(P) = (0.2
0.4
0.12
0.08
0.06
0.08
0.04)


10
Q9.
a) What is power spectral density? State its properties with formula.
6

b) Draw the line code formats for the bit stream 10101101 using 1) Bipolar NRZ
2) Split Phase Manchester 3) Polar RZ 4) Unipolar RZ.
4


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.
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