Analog Communication - May 2015

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 the following (any four):

1 (a) Classify and explain the various types of noises affecting communication. (5 marks)

1 (b) Differentiate between narrowband and wideband FM. (5 marks)

1 (c) In AM why IF is selected 455 Khz? (5 marks)

1 (d) What is aliasing? How it can be prevented? (5 marks)

1 (e) Why AGC is required in radio receivers? Explain diode detector circuit with simple AGC. (5 marks)

2 (a) The antenna current of AM broadcast transmitter modulated to depth of modulation index 40% by an audio wae is 11A. Increase to 12A as a result of simultaneous modulation by another audio sine wave. What is modulation index due to this second wave? (5 marks)

2 (b) Compare FM and PM. (5 marks)

2 (c) Explain with neat block diagram the phase shift method for suppression of unwanted sideband. (10 marks)

3 (a) State and Prove sampling theorem for low pass band limited signals. (10 marks)

3 (b) Explain the principle and generation of indirect method of FM generation. (10 marks)

4 (a) What are the drawbacks of delta modulation? Explain with neat block diagram working of Adaptive delta modulator. (5 marks)

4 (b) Explain how PPM is generated from PWM? (5 marks)

4 (c) Explain VSB transmission. (10 marks)

5 (a) Explain the operation of Foster seely discriminator with the help of circuit diagram and phasor diagram. (10 marks)

5 (b) Draw a neat block diagram of super heterodyne radio receiver and explain function of each block with waveforms. (10 marks)

Write short notes on (any four):

6 (a) Independent sideband system. (5 marks)

6 (b) FM noise triangle. (5 marks)

6 (c) μ-law and A-law companding (5 marks)

6 (c) TDM and FDM. (5 marks)

6 (d) Double spotting. (5 marks)