Master of Science I (Electronic Science)
Examination: Oct Nov 2016 Semester I (New CBCS)
SLR No. Day
Date Time Subject Name Paper
No. Seat No.
SLR SJ- 334 Monday
21/11/2016
10:30 AM
to
01.00 PM
Communication
Systems
C
HCT 1.3
Instructions: All questions carry equal marks.
Q.1 and Q.2 are compulsory.
Attempt any THREE questions from Q.3 to Q.7
Use of non programmable calculator is allowed.
Total Marks: 70
Q.1 Choose correct alternative 08
A FM signal with a modulation index mf is passed through a frequency
tripler. The wave in the output of the tripler will have a modulation index
of
mf 3mf
mf mf
A 400 W carrier is amplitude modulated with m 0.75. The total power
in AM is
400 W 512 W
588 W 650 W
Non-coherently detection is not possible for
PSK ASK
FSK Both a and c
Which of the following is the indirect way of FM generation?
Reactance bipolar transistor modulator
Armstrong modulator
Varactor diode modulator
Reactance FM modulator
If C is capacity of noisy channel, bandwidth in Hz and S/N
is signal to noise ratio, then
If transmission bandwidth is doubled in FM, Signal to Noise Ratio is

Doubled Raised four times
Decreased four times Halved
Quantizing error occurs in
TDM FDM
PCM PWM
Page 1 of 2
In a two tone AM system the two modulating frequencies are 2000 and
4000 rad/sec. If carrier frequency is 2 X 106 rad/sec, the frequencies of
upper sidebands are
1.002 MHz and 1.004 MHz 1.001 MHz and 1.002 MHz
1.001 MHz and 1.004 MHz 1.002 MHz and 1.008 MHz
State whether following statements are true or false: 06
For an ideal 3000 Hz channel, S/N ratio is 4.
In a single tone AM modulation, the transmission efficiency for m 1 is
33.3%.
In a superheterodyne receiver, having no RF amplifier, the IF is 455 kHz.
The image frequency at 1000 kHz is 545 KHz.
E and H field are perpendicular to each other.
A video monitor is exactly similar to TV receiver.
Audio tapes have two tracks each 2.5 mm wide.
Q.2 Attempt the following: 14
Differentiate between class class B and class C modulated power
amplifiers.
Draw the block diagram of VCO and explain its operation.
With a neat diagram explain the operation of balanced modulator.
04
05
05
Q.3 Draw the block diagram of a high level modulated AM transmitter and
explain each block.
08
Explain how an amplitude modulated signal be detected. 06
Q.4 Explain the process of multiplication of frequency with a neat circuit
diagram.
08
How PLL can be employed as FM detector? Explain. 06
Q.5 Explain briefly about Delta modulation. 08
With a neat circuit diagram, explain how a PTM signal be generated? 06
Q.6 Differentiate between ASK, FSK and PSK. 08
Discuss the characteristics of PN sequences. 06
Q.7 What is frequency hopping spread spectrum? Explain in detail. 08
Explain how a DS signal can be tracked? 06