# Mumbai University Previous year question papers

## Principles of Communication

N.S.: (1) Question No.1 is compulsory.

(2) Solve any three from the remaining.

(4) Assume suitable data whereever  required.

1. (a) Find Fourier transform of unit impulse signal o(t). 5

(b) Draw and explain the basic block diagram of Communication system.

(c) Explain A-law and W1awcompanding.

(d) Comp-are Frequency modulation and Phase modulation. 5

2.(a) De~ineAmplitude Modulation. Derive the equation of AM wave. Draw envelope of AM for m

(b) A 400 W carrier is modulated to depth of 75% . Calculate total power in,followirig forms of AM : .

(i) DSB – Fe

(ii) DSB – SC

(iii) SSB – FC

(iv) SSB – SC.

3.a) Explain working of Foster Seely discriminator with phasor diagram. 10

(b) In an FM syster:n,when the Audio Frequency (AF) is 500 Hz and the At:

voltage is 2·4 V, the deviation is 4·8 kHz. If the AF, voltage is now increased to 7·2 V, what is new deviation ? If the AF voltage  is raised to 10V while the AF is dropped to 200 Hz, what is new deviation? Find modulation index in each case.

4. (a) Explain the sideband generation in SSB using phase shift method. 10

(b) Explain satellite communication system. List applications in various fields.

5.

(a) Draw and explain block diagram of four channel FDM system. 10

(b) Explain double conversion  superhetrodyne receiver with neat block diagram. 10

6.(a) Explain the terms sensitivity, image frequency, double spotting, automatic gain control and three point tracking in radio receivers.

(b) How adaptive  DM is improvement of linear DM ? Draw block diagram of adaptive DM and explain its working.

7. (a) State sampling theorem for low pass signals. What in Nyquist rate?

(b) Explain working of balanced modulator.

(c) Define Noise temperature and Noise Bandwidt.h.

(d) Find Fourier transform of x(t) = e-