Fundamentals of Communication Engg - Dec 2014

Electronics Engineering (Semester 4)

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. 1 (a) Compare AM and FM.(5 marks) 1 (b) In a broadcast superheterodyne receiver having no RF amplifier, the loaded Q of the antenna coupling circuit is 150. If the IF is 455 Khz, calculate the image frequency and its rejection ratio at 1400 kHz.(5 marks) 1 (c) Explain noise triangle in FM.(5 marks) 1 (d) Explain the following terms:-
i) Signal-to-noise ratio
ii) Noise figure
iii) Noise factor
iv) Equivalent noise temperature(5 marks) 1 (e) Explain ISB transmission(5 marks) 2 (a) Explain Armstrong method of FM generation with the help of a neat block diagram and phasor diagrams.(10 marks) 2 (b) Draw the block diagram of Delta modulation technique and explain each block.(10 marks) 3 (a) State sampling theorem. Explain flat-top sampling. Draw its spectrum and explain aperture effect.(10 marks) 3 (b) Explain generation and demodulation of PAM, PPM and PWM with waveforms.(10 marks) 4 (a) Explain TDM and FDM(10 marks) 4 (b) Explain the following with reference to ratio receivers:
i) Selectivity
ii) Fidelity
iii) Sensitivity
iv) Double spotting(10 marks) 5 (a) Draw the schematic diagram of simplified medium-power transistor AM DSBFC modulator and explain the operation with the help of collector waveforms with no modulating signal and collector waveforms with a modulating signal.(10 marks) 5 (b) Draw the block diagram of Super heterodyne radio receiver and explain the same.(10 marks)

Write short notes on.

6 (a) ISB transmission(5 marks) 6 (b) Pre-emphasis and De-emphasis(5 marks) 6 (c) Companding(5 marks) 6 (d) AGC(5 marks)