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SPPU Electronics and Telecom Engineering (Semester 4)
Analog Communication
December 2015
Total marks: --
Total time: --
INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary

Solve any one question from Q1 and Q2
1 (a) Explain phase shift method of generation of SSB-SC signals.
6 M
1 (b) A frequency modulated signal is given by:
xc(t)=10 cos [2π×108t+5 sin 2π×200t]
Determine:
i) The carrier frequency
ii) Peak frequency deviation
iii) The modulation index.
6 M

2 (a) Explain the ring modulator method to generate DSB-SC signal with waveform.
6 M
2 (b) Give comparison between FM and PM.
6 M

Solve any one question from Q3 and Q4
3 (a) Explain principle of operation of envelope detector. State the conditions to avoid distortion.
6 M
3 (b) Derive Friss formula considering only three amplifiers in cascade.
6 M

4 (a) Explain superheterodyne receiver characteristics: i) Sensitivity
ii) Selectivity
iii) Fidelity.
6 M
4 (b) A low noise amplifier of 30K equivalent noise temperature and 20dB available power gain precedes a microwave receiver which has a noise figure of 25 dB. What is the overall equivalent temperature, if the room temperature is 27°C.
6 M

Solve any one question from Q5 and Q6
5 (a) Derive equation of figure of merit for noise contaminated DSB-SC system.
6 M
5 (b) Critically compare the noise performance of AM, DSB-SC and SSB-SC system.
6 M

6 (a) Show that a SSB-SC system gives the same destination SNR as a base band system.
7 M
6 (b) Explain the need of pre-emphasis and de-emphasis in the case of FM system. How is it implemented?
6 M

Solve any one question from Q7 and Q8
7 (a) Explain how a PAM signal may be generated. How can it be demodulated?
7 M
7 (b) State the low pass sampling theorem and briefly explain its significance.
6 M

8 (a) Describe with the help of neat sketches of waveforms methods of generation of PDM/PWM and PPM.
7 M
8 (b) What is aliasing? How can it be avoided?
3 M
8 (c) Draw and explain a circuit for flat top sampling.
3 M

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