M.Sc. (Semester III) (CBCS) Examination Oct/Nov-2017
Electronic Science
COMMUNICATION DIGITAL ELECTRONICS
Day Date: Saturday, 25-11-2017 Max. Marks: 70
Time: 02.30 PM to 05.00 PM
Instructions: Q.1 and Q. 2 are compulsory.
Answer 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 alternative: 06
The amplitude of a frequency modulated wave remains
Constant all the time Varies all the time
Constant and varies None of the these
The bandwidth required for amplitude modulation is
Twice the frequency of modulation signal
Half the frequency of modulation signal
Three times the frequency of modulation signal
None of these
The flat top samples in PCM system are converted to digital form
through
ADC DAC
Instrumentation amplifier Audio amplifier
The satellite follows an orbit that is close to the earth and passes over
the inclination is close to 900. This orbit is called
Polar Lunar
Elliptical Circular
The Long form of Wi-Max is
Worldwide interoperability for microwave access
Worldwide interoperability for maximum access
World interoperability for microwave access
Wide interoperability for maximum access
The universal gates are
NAND and NOR NAND and AND
NOR and OR NOR and AND
State true or False: 04
The power gadget of digital communication is less than analog
communication.
Satellite communication uses multiplexing technique.
Bluetooth is normally used for short range data communication
Boolean algebra is useful to simplify the gates.
Page 2 of 2
SLR-E-2
Fill in the blanks: 04
If the modulating signal is 15 KHz at a certain amplitude and the carrier
shift is 75 KHz, the transmitter will produce number of side
bands.
In a modulation two signals are opposite polarity with each other. The
digital modulation is
The height of the geostationary orbit above the earth is
this the output equation of two input gate.
Q.2 Write short notes:
With a suitable block diagram explain the communication system. 05
Need of modulation 05
Hand-off process in cellular communication 04
Q.3 Draw a block diagram of AM transmitter and explain the working of each
unit.
10
Define QPSK and list its advantages. 04
Q.4 With a neat block diagram explain the working of FM receiver. 10
Simplify following expression using Boolean laws. 04

Q.5 Define TDM and with a neat diagram illustrate the mechanism of TDMA
access.
10
Write a note on types of satellite orbits. 04
Q.6 With a neat diagram explain the architecture of GSM technology. 10
Convert the decimal numbers to hexadecimal. 04
369
4720
Q.7 Write the symbol, truth table and output expression for 08
OR
NAND
Ex-OR
NOT, gates
State and prove De Morgan's theorem for two variables. 06