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Seat No.: Enrolment
GUJARAT TECHNOLOGICAL UNIVERSITY
PDDC- SEMESTER-IV EXAMINATION SUMMER 2017
Subject Code: X41101 Date:25/05/2017
Subject Name: Electronic Communication
Time: 10:30 AM TO 01:00 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

Draw the communication system block diagram and explain each block briefly
07

Explain briefly: 1. Skin effect 2.Mutual inductance
07
Q.2

Draw series tuned circuit and derive equation for resonant frequency and Q-factor.
07

Draw the circuit diagram of low frequency transformer and derive the equation for reflected load.
07
OR

A receiver tunes signals from 550 to 1600 KHz with an IF of 455KHz. Find the frequency tuning ranges and capacitor tuning ranges for oscillator section and for the RF section.
07
Q.3

In measurement of noise temperature, an avalanche diode source is used, the ENR (excess noise ratio) being 14 dB. The measured Y factor is 9 dB. Calculate the equivalent noise temperature of the amplifier under test.
07

Draw and explain block diagram of Electronically Tuned Receiver(ETR) for AM.
07
OR
Q.3

Derive expression of noise factor and noise temperature for Amplifiers in cascade.
07

Explain Phasing method for SSBSC generation.
07
Q.4

For amplitude modulation, derive the following parameters: modulation index, Frequency spectrum and average power.
07

Write a short note on foster-Seeley Discriminator.
07
OR
Q.4

With circuit diagram and waveform, explain amplitude demodulator. Also explain diagonal peak clipping.
07

Describe FM generation with clapp oscillator utilizing varactor diode.
07
Q.5

Enlist all the properties of Fourier transform. Prove the time shifting property.
07

Describe double conversion super heterodyne receiver.
07
OR
Q.5

Find the Fourier transform of the signal:
07

Write short note on Automatic Gain Control.
07