Cochin University of Science and Techology (CUST) 2008-2nd Year B.Tech Electronics and Communications Engineering analog communication - Question Paper

BTECH DEGREE IV SEMESTER exam , APRIL 2008
ANALOG COMMUNICATION

Time : three Hrs



1. a) describe modulation. elaborate the needs for modulation?

b) discuss any one method for SSB generation .

c) elaborate the advantages & dis advantages of FM over AM .

d) discuss the principle of FM generation .Draw & discuss a direct FM generator
ckt.

e) describe thermal agitation noise. An RF amplifier operating at 17 degree celsious
has 200 ohm equivalent noise resistance & 300 i/p resistor. compute the rms
noise voltage at the i/p to this amplifier. The band width of this amplifier is six
MHz.

f) describe ‘selectivity’ & ‘sensitivity’ with regard to a receiver.

g) discuss Pulse signaling & DTMF signaling used to telephony.

h) discuss the terms “grade of service” & blocking – probability in telephony.


2. a) Draw an AM wave with regard to a sinusoidal i/p signal & derive the expression
for modulation index ‘m’ from an AM wave diagram.

b) Derive the mathematical expression for an AM wave & draw its frequency
spectrum. explain about band width needed for AM.


OR

3. a) discuss the working of a super heterodyne receiver with the help of a block
diagram.

b) What is the principle of a double super heterodyne receiver? explain its
advantages.

4. a) discuss the indirect method for FM generation with relevant diagrams.

b) explain about band width requirement of an FM system
OR

5. discuss the principle of a slope detector . discuss a balanced slope detector with
ckt & necessary diagrams.

6. discuss in detail , different kinds of noises that are affected upon a receiver.


OR

7. a) describe (i) SNR
(ii) Noise factor & noise figure
(iii) Effective noise temperature

b) describe AGC in a receiver. explain how it affects the performance of a receiver.
Compare simple AGC & delayed AGC.

8. a) discuss the mechanism of a Strowger Switch with neat diagram.Compare b/w a
“uniselector”& a “two motion selector” .

OR

9. a) describe the terms “busy hour”,BHCA”& “CCR” with regard to telephone
traffic engineering.

b) An exchange serves 2000 subscribers. If avg BHCA is 10,000 & CCR is 60%,
compute busy hour calling rate.

c) Write short notes on “Time Division Switching”

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Earning:   Approval pending.