M.Sc. (Semester III) (CBCS) Examination Nov/Dec-2018
Electronic Science
COMMUNICATION DIGITAL ELECTRONICS
Time: 2½ Hours Max. Marks: 70
Instructions: All questions are compulsory.
All questions carry equal marks.
Q.1 Multiple choice questions. 14
The ideal bandwidth of the FM wave is
200kHZ 150kHz
Infinite 250 kHZ
Amplitude modulation is
Change in amplitude of the carrier according to modulating signal.
Change in frequency of the carrier according to modulating signal.
Change in amplitude of the modulating signal according to carrier signal.
Change in amplitude of the carrier according to modulating signal
frequency.
Types of analog pulse modulation systems are
Pulse amplitude modulation
Pulse time modulation
Frequency modulation
Both a and b
The sampling technique having the minimum noise interference is
Instantaneous sampling Natural sampling
Flat top sampling All of the above
The quantization will be finer when
Smaller the number of discrete amplitudes
Larger the number of discrete amplitudes
Does not depend on amplitudes
None of the mentioned
The function of multiplexing is
To reduce the bandwidth of the signal to be transmitted
To combine multiple data streams over a single data channel
To match the frequencies of the signal at the transmitter as well as the
receiver
To allow multiple data streams over multiple channels in a prescribed
format
The coherent modulation techniques are
PSK FSK
ASK All of the mentioned
Aliasing refers to
Sampling of signals less than at Nyquist rate
Sampling of signals greater than at Nyquist rate
Sampling of signals at Nyquist rate
None of the above
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An AM broadcast station transmits modulating frequencies up to 6 kHz. If the
AM station is transmitting on a frequency of 894 kHz, the values for maximum
and minimum upper and lower sidebands and the total bandwidth occupied by
the AM station are:
894 KHz, 884 KHz, 12 KHz 894 KHz, 888 KHz, 6 KHz
900 KHz, 888 KHz, 12 KHz 900 KHz, 888 KHz, 6 KHz
10) Calculate the total modulation Index when a carrier wave is being modulated
by two modulating signals with modulation indices 0.8 and 0.3.
0.6788 0.9999
0.5545 0.8544
11) If we correlate the received signal with both orthogonal function the inner
product will be
In phase Quadrature
In phase and quadrature Unity
12) The BPSK signal has V volts and V volts respectively to represent
1 and 0 logic levels 11 and 00 logic levels
10 and 01 logic levels 00 and 11 logic levels
13) ASK, PSK and QPSK are example of following encoding
Digital to Digital Digital to Analogue
Analogue to Digital Analogue to Analogue
14) QPSK system uses a phase shift of


Q.2 Attempt the following. (Any Four) 08
Determine the HEX value of the -3.
Prove A+BC
What is final output expression of Q of following logic diagram?
What is LTE?
What is CDMA? Which type of modulation is used in CDMA cellular
communication?
Write note on. (Any Two) 06
Wi-Max
Satellite transponder
Base Station
Q.3 Answer the following. (Any Two) 08
State and explain Demorgan's theorem.
How generate the PPM using PWM?
Draw a logic circuit of Boolean expression.
F X YZ X YZ XZ
Answer the following. (Any One) 06
Explain in detail architecture of GSM cellular communication.
Explain PCM system in detail.
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Q.4 Answer the following. (Any Two) 10
Apply suitable Boolean laws and theorems to modify the expression for a
two-input EX-OR gate in such a way as to implement a two-input EX-OR
gate by using the minimum number of two-input NAND gates only.
Explain the orbits of satellites.
Explain the PSK system.
Answer the following. (Any One) 04
Explain the Bluetooth.
Explain the QPSK system.
Q.5 Answer the following. (Any Two) 14
Derive the Expression of FM.
State and explain the Sampling theorem, reconstruction and Aliasing of
signals with the useful mathematical expressions.
Explain the TDMA, FDMA and OFDMA with suitable waveforms.