# Mumbai University Sample Paper Principles of Communication Engineering

## IT 4th Sem Principles of Communication Engineering

(1) Question no. 1 is compulsory
(2) Attempt any four out of remaining six questions.
(3) Assume suitable data if required.
(4) Figures to the right indicate full marks.

1. (a) Calculate total power and power in each sideband for standard AM transmission 20
that is sinusoidally modulated to depth of 80% if the unmodulated carrier power is
50kW.
(b) The carrierfrequencyof FMbroadcasttransmitteris 100MHzand maximumfrequency
deviation is 75 KHz. If the highest audio frequency modulating the carrier is
15 KHz, what is the approximate bandwidth of the signal.
(c) Compare narrow band and wideband FM.
(d) Compare PCM and OM.
2. (a)
(b)
Define Amplitude Modulation and derive the equation for Amplitude Modulated wave.
A certain transmitter radiates 9 kW with the carrier unmodulated and 10.125 kW
when the carrier is sinusoidally modulated.
Calculate the modulation index.
If another sinewave, corresponding to 40 percent modulation, is transmitted
simultaneously, determine the total radiated power.
.
3. (a) With the help of neat circuit diagram and phasor diagram explain the working of
Foster – Seeley discriminator.
(b) Find the carrier and modulating frequencies the modulation index and 10
the maximum deviation of the FM wave represented by the voltage equation
e = 12 Sin ( 6 x 108t + 5 Sin 1250 t). What power will this FM wave dissipate in
a 10 Q resistor?
4. (a) What is a ‘Balanced Modulator’ ? Sketch a Balanced Modulator circuit and explain
its working.
(b) Find the Fourier Transform of the following:
(i) 8(t)
(ii) Coswot.

5. (a) Draw the block diagram of superheterodyne receive and describe the function of
each block.
(i) Fidelity
(ii) Image Frequency and its rejection
(iii) Tracking
(iv) Selectivity.

6. (a) Compare
(i) FOM and TOM