Analog Communication - Dec 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.

Solve any four:

1 (a) What is modulation? Explain the need of modulation.(5 marks) 1 (b) Explain Pre-emphasis and De-emphasis in FM.(5 marks) 1 (c) Define sensitivity, selectivity, fidelity and image frequency in radio receiver.(5 marks) 1 (d) What are the causes of fold over distortion or aliasing? How can it be prevented or removed.(5 marks) 1 (e) Explain companding in detail.(5 marks) 2 (a) Derive Friss formula for calculation of total noise figure, if two amplifiers are connected in cascade.(10 marks) 2 (b) Draw the block diagram of phase cancellation SSB generator and explain how carrier and unwanted sidebands are suppressed?(10 marks) 3 (a) With the help of a neat block diagram explain the principle and generation of indirect method of FM generation.(10 marks) 3 (b) Draw and explain Adaptive delta modulation transmitter and receiver with its advantages.(10 marks) 4 (a) An AM transmitter radiates 5 MHZ carrier with 80KW power, carrier is modulated by 600HZ and 2KHZ signals.
i) What will be the total modulation index if each signal modulates at 60% of modulation?
ii) Determine the transmitted power.
iii) Draw the frequency spectrum of modulated signal.
iv) What is % of power saving if one of the sidebands and carrier is suppressed?(10 marks) 4 (b) What is signal multiplexing? Explain FDM in detail.(10 marks) 5 (a) Explain the operation of Foster Seeley discriminator with the help of circuit diagram and phasor diagram.(10 marks) 5 (b) Explain with block diagram and waveform of AM Super - heterodyne radio receiver.(10 marks)

Write a short notes on (solve any four):

6 (a) Aliasing error and aperture effect.(5 marks) 6 (b) Applications of pulse communication.(5 marks) 6 (c) Practical diode detector.(5 marks) 6 (d) ISB receiver.(5 marks) 6 (e) Wide band FM and Narrow band FM.(5 marks)