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Seat No.: Enrolment
GUJARAT TECHNOLOGICAL UNIVERSITY
PDDC SEMESTER-IV EXAMINATION WINTER 2018
Subject Code:X41101 Date: 17/11/2018
Subject Name: Electronic Communication
Time: 02:30 PM TO 05:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Q.1
Classify Noise. Define the terms SNR, Noise figure, and Noise temperature.
07
Explain the communication system with block diagram.
07
Q.2
What is modulation? Explain the need of modulation.
07
A certain transmitter radiates 9KW with the carrier unmodulated, and 10.125KW when the carrier is sinusoidally modulated. Calculate the modulation index. If another sine wave is simultaneously transmitted with modulation index 0.4, determine the total radiated power.
07
OR
What is the modulation index of an FM signal having a carrier frequency 80 MHz and carrier swing of 100 KHz when the modulating signal has a frequency of 8 KHz? What will be the new modulation index when the modulating signal amplitude is doubled and halved?
07
Q.3
Explain the Superhetrodyne receiver with block diagram.
07
Explain envelop detector for AM demodulation.
07
OR
Q.3
What is AGC? Explain simple AGC and delayed AGC with proper graph.
07
Explain Adjacent channel selectivity and image frequency rejection.
07
Q.4
Compare pre-emphasis and De-emphasis
07
List all the properties of Fourier transform. State and prove time Shifting property.
07
OR
Q.4
Find the Fourier transform of the signal:
07
Q.4
Define Frequency Modulation. Derive the expression for frequency modulated wave.
07
Q.5
Give difference between SSB and VSB. Explain filter method with necessary block diagram.
07
Explain parallel tuned circuit and derive equation for resonant frequency and Q-factor.
07
OR
Q.5
Explain Series tuned circuit and derive equation for resonant frequency and Q-factor.
07
Explain phase shift method of SSB generation with necessary block diagram.
07