Analog Communication - Dec 2013

Electronics & Telecomm. (Semester 5)

TOTAL MARKS: 80
TOTAL TIME: 3 HOURS (1) Question 1 is compulsory.
(2) Attempt any three from the remaining questions.
(3) Assume data if required.
(4) Figures to the right indicate full marks.

Answer any four of the following :-

1 (a) Explain why FM is immune to noise(5 marks) 1 (b) Explain how PPM is generated from PWM(5 marks) 1 (c) Explain Tracking in AM receiver(5 marks) 1 (d) Why AGC (Control) is needed in receivers. Explain its working in brief(5 marks) 1 (e) What is aliasing error and how can it be eliminated?(5 marks) 2 (a) With neat block diagram and waveforms explain working of adaptive delta modulation. Explain its advantages(10 marks) 2 (b) Explain with a neat block diagram and phasor diagram, working of phase discriminator(10 marks) 3 (a) Explain high power AM-DSBFC modulator with schematic diagram(10 marks) 3 (b) Derive expression for mathametical representation of FM and its modulation index(10 marks) 4 (a) Draw block diagram and pulse code modulation technique and explain every block.(10 marks) 4 (b) Derive expression for total trasmitted power, totalside band power and signal side band power for AM wave and draw frequency spectrum for DSBFC(10 marks) 5 (a) Draw block diagram of superhet receiver. Write frequency component present at the output of each block if modulation frequency is 1 KHz, carrier frequency 535 KHz & IF 455 KHz also sketch waveforms of output & IF and derector stage(10 marks) 5 (b) State and prove sampling theorem for low pass band limited signal(10 marks) 6 (a) Draw following data wave forms for bit stream 110101101
(i) Bipolar RZ
(ii) Bipolar RZ AMI
(iii) Unipolar NRZ
(iv) Bipolar NRZ (8 marks) 6 (b) Draw and explain Delta modulation transmitter and receiver. What is slop overload distortion?(12 marks)

Write short notes on any four :-

7 (a) Preemphasis and deemphasis (5 marks) 7 (b) Ratio Detector(5 marks) 7 (c) μ Law and A law of Companding(5 marks) 7 (d) FM noise triangle(5 marks) 7 (e) Compare AM with FM(5 marks)