# ANU B.Tech Analog and Digital Communication April 2014 Question Paper

University Board: Acharya Nagarjuna University  ANU
College: Bapatla Engineering College
III/IV B.Tech Degree Examinations, April 2014
Second Semester
Analog and Digital Communication
Time : 3 hours
Maximum Marks : 60
Answer ONE question from each Unit

1. Briefly explain following [12 x 1 = 12M]
a) What is the need for modulation?
b) What do you mean by Information capacity?
c) What is modulation coefficient?
d) What are the disadvantages of angle modulation?
e) Draw the circuit of slope detector.
f) What is the bandwidth of FM signal?
g) What is meant by phase locked loop?
h) What is Delta modulation?
i) What do you mean by companding?
j) Define Sampling theorem.
k) What is meant by TDM?
l) Draw the block diagram of QPSK modulator.

UNIT - I [1 x 12 = 12M]

2. a) Show the block diagram for phase shift method of SSB generation and explain its working.
2. b) An SSB transmission contains 10 K W. This transmission is to be replaced by a standard AM signal with same power content. Determine the power content of the carrier and each of the side bands when present modulation is 80%. (OR)
3. a) If the percentage modulation is 100% how much percentage of the total power is present in the signal when DSB-SC is used?
3. b) How AM is generated using square law modulator? Derive relevant expressions.

UNIT - II [1 x 12 = 12M]

4. a) Explain the principle of operation of Envelope detector used for AM detection.
4. b) Compare TRF and super heterodyne receiver. (OR)
5. a) Explain the principle of operation of SSB BFO receiver.
5. b) With a neat block diagram, explain super heterodyne receiver and the function of each block.

UNIT - III [1 x 12 = 12M]

6. a) Explain in detail about PM. Compare it with FM.
6. b) Explain the method of indirect generation of FM using Armstrong's method and explain how the final carrier frequency and frequency deviation are fixed. (OR)
7. a) What is frequency deviation? Derive expression for frequency deviation of FM and hence define Carson's rule.
7. b) With a neat block diagram explain the direct method of FM generation.

UNIT - IV [1 x 12 = 12M]

8. a) Explain clearly about the generation of Pulse code Modulation and bring out the advantages of DPCM over PCM.
8. b) What is Multiplexing? Explain clearly the TDM and FDM systems and compare them. (OR)
9. a) Explain the procedure for pulse width modulation and demodulation with the help of block diagram.