# RGPV Exam Previous Question Papers CSE 4th Semester

# Analog and Digital Communication june 2002

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**Note: Attempt any five question. **

**All question carry equal marks.**

(a) Find the Fourier transforms of following function and sketch them:

(i) sgn (ii) rect (tT) (iii) cos Ω_{0} t u(t)

(b) Define PSD of a signal and list the properties of it.

(a) Describe the operation of a switching modulator , for generating DSB-SC waves with the help of

diagram and wavefourms .

(b) Distuingsh between AM signal and PM signal .

(a) Prove the sampling theorem for a signal band limited to BHz. How the sampled signal is recovered

Using LPF ?

(b) Draw the black diagram of a PCM system

(a) Briefly explain BFSK technique . specify the bandwidth requirement and probability of error.

(b) What are the problems associated with deta modulator? How they overcome ?

(a) Define CDF,PDF, average value , variance concerned with a random variable.

(b) Prove that ESD is the Fourier transform of autocorrelation function ( of energy signal) .

Define following terms-

(i) Unit of information and information

(ii) Entropy

(iii) Channel capacity

(iv) Rate of information

(a) Encode (1011) using (7,4) cyclic code.

(b) A television transmission requires 30 frames of 3,00,000 picture element each to be transmitted

Per second. Estimate theoretical BW if SNR required is 50 dB . assume missing data .

8. Write short on any two of the following :

(i) Superheaterodyne Radio Receiver

(ii) Companding Technique

(iii) VSB Modulation and demodulation

(iv) Time division and frequency division multiplexing