M.Sc. (Semester III) (CBCS) Examination Mar/Apr-2018
Physics (Applied Electronics)
COMMUNICATION SYSTEM
Time: 2½ Hours
Max. Marks: 70
Instructions: All questions carry equal marks. Q.1 and Q.2 are compulsory. Attempt any three questions from Q. 3 to 7.
Q.1

Select the correct alternative:
06
The process of impressing information on carrier signal is called
mixing
impressing
modulation
detection
The modulation index of an AM wave is changed from 0 to 1. The transmitter power is
unchanged
halved
doubled
increased by 50%
The demodulator circuit of the frequency modulated signal is called
decoder
AFC
discriminator
envelop detector
ASK is rarely used in modems because,
it shifts only between ON and OFF
it takes care of amplitude only
it is highly susceptible to noise
it shifts between amplitude and phase
Two binary values are represented by two different frequencies in
ASK
FSK
PSK
None of the above
A carrier signal has
a constant amplitude
a varying amplitude
a frequency above 20 GHz
the information content
Q.1

Fill in the blanks:
04
ASK, PSK and FSK are the examples of to encoding.
is the category of data transmission, if the binary pulse is maintained for the entire bit time.
A PAM signal is demodulated with filter.
VCO is a part
Q.1
C)State true and false:
04
TDM system is more immune to inter-channel cross talk as compared to FDM system.
PPM can be generated from PWM signals.
Pulse modulation is often used in telegraphy.
In full duplex communication system, the flow of information takes place in both directions simultaneously.

Q.2Answer the following:
14
A)Write a brief note on Class B modulated power amplifiers.
B)Discuss low and high level modulation.
C)Write a brief note on data formats.
Q.3
A)Discuss the construction and operation of AM receiver and detector circuits.
10
B)Write the advantages of FM over AM.
04
Q.4
A)With relevant diagram, discuss in detail, the construction and working of pulse position modulator and demodulators circuits.
10

Explain the Sampling theorem.
04
Q.5
A)With relevant diagram, discuss in detail, the process of PSK and DPSK.
10
B)Explain the cross talk in TDM.
04
Q.6
A)Describe the generation and demodulation PTM signals.
10
B)What is a transponder? Explain.
04
Q.7
A)With relevant diagram and waveforms, explain the functioning of PDMA systems.
10
B)Write a brief note on multiplexing.
04