M.Sc. (Semester (CBCS) Examination Mar/Apr-2018
Electronic Science
COMMUNICATION SYSTEMS
Time: 2½ Hours
Max. Marks: 70
Instructions: Q.1 and Q.2 are compulsory. Attempt any three questions from Q. 3 to Q.7. All questions carry equal marks. Use of nonprogrammable calculator is allowed.
Q.1

Select the correct alternatives:-
08
BPSK stands for
Binary Phase Shifting Key
Broad Phase Shifting Key
Bit Phase Shifting Key
Binary Pulse Shifting Key
Probability of error in DPSK is less than PSK
true
false
equal
depend upon noise
Two sine waves of amplitude A1 and A2 are multiplied. The amplitude of the spectral component is
A1A22
A1A2
A1A24
(A1A2)12
The phase of colour subcarrier burst in PAL is along the axis at
+1800
-1800
±1800
±450
The resonant frequency of an RF amplifier is 1 MHz and its bandwidth is 10 KHz. The Q factor will be
10
100
0.01
0.1
An AM signal is detected using an envelope detector, the carrier frequency and modulating single frequency are 1 MHz and 2 KHz respectively. An appropriate value for the time constant of the envelope detector is
500 sec
20 sec
0.2 sec
1 sec
If transmitted power is 10 kW, the field strength at a distance d is 50 mV/m. If transmitted power is reduced to 2.5 kW, the field strength at the same point will be
25 mV/m
12.5 mV/m
6.25 mV/m
3.125 mV/m
The carrier frequency will be if L 50 and C 1 nF.
512
612 kHz
712 kHz
812 kHz
Q.1
B)State true and false:
06
A digital signal is a smoothly and continuously varying voltage or current.
Examples of transceivers include televisions, fax machines, cellular telephones, and computer modems.
All electronic communication systems have a transmitter, a communication channel or medium, and an antenna.
A receiver is a collection of electronic components and circuits that accepts the transmitted message from the channel and converts it to a form understandable to humans.
Optical media communication channels are used for audio or video analog signals.
The communication channel is the medium by which the electronic signal is sent from place to place.
Q.2
Attempt the following:-
a)Explain the block diagram of F.M. transmitter.
05
b)Differentiate between Class A and Class C power amplifiers.
05
c)Write a note on FSK.
04
Q.3
a)Explain the effect of cross talk in TDM.
08
b)How PTM signals are demodulated? Explain.
06
Q.4
a)Differentiate between Bipolar, RZ and NRZ transmission modes.
08
b)Explain the modulation process of ASK with a block diagram.
06
Q.5
a)What is signal tracking? Explain in detail.
08
b)List the characteristics of PN sequences.
06
Q.6
a)What is CDMA? Explain in detail.
08
b)Discuss the course synchronization of FM signal.
06
Q.7
a)Explain Sampling theorem.
08
b)Explain the demodulation of PPM signals.
06