GTU Electronic Communication - June 2015 Exam Question Paper

GTU Electrical and Electronic Engineering (Semester 6)
Electronic Communication
June 2015

Total marks: --
Total time: --

INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary

1 (a) What do you mean by "Communication"? Describe in detail Communication system with the help of block-diagram.

7 M

1 (b) State and prove following properties of Fourier Transform
1. Duality
2.Frequency Shifting
3.Convolution in time domain.

7 M

2 (a) Explain the signal to noise ratio [SNR] of an amplifier and effect of amplification on the SNR.

7 M

Answer any two question from Q2 (b) or Q2 (c)

2 (b) Explain the following:
Shot noise, Partition noise, Flicker noise, Burst noise, Avalanche noise, Bipolar transistor Noise, Field effect transistor noise.

7 M

2 (c) Draw the circuit diagram of high frequency transformer and derive the equation for transfer impedances.

7 M

Answer any two question from Q3 (a), (b) or Q3 (c), (d)

3 (a) Draw the AM wave forms for less than 100%, with 100%, more than 100% and with 0% modulation. Assume that the modulating signal is a pure sine wave. And compare the wave forms. How to achieve this?

7 M

3 (b) Explain electronically tuned radio receivers. The carrier amplitude after AM varies between 4 volts and 1 volt. Calculate depth of modulation.

7 M

3 (c) Explain operation of an envelope detector circuit. Explain the importance of RC time constants for the envelope detector circuit. Also state and explain various distortions encountered in the envelope detector.

7 M

3 (d) A coil has a series resistance of 10Ω, a self-capacitance of 28 pF and an inductance of 2μH. Determine the effective inductance and effective Q-factor when coil forms part of series tuned circuits resonant at 12 Mhz.

7 M

Answer any two question from Q4 (a), (b) or Q4 (c), (d)

4 (a) Define and explain energy spectral density (ESD).Obtain the Fourier transform of a unit step function.

7 M

4 (b) Explain: "Skin effect."

7 M

4 (c) Write a short note on: A.G.C. (Automatic Gain Control).

7 M

4 (d) A 20 MHz carrier is modulated by a 300 Hz audio sine wave, If the carrier voltage is 5 volt and the maximum deviation is 12 kHz, Write the equation of this modulated wave for :(A) F. M. (B) P.M.

7 M

Answer any two question from Q5 (a), (b) or Q5 (c), (d)

5 (a) State and explain Kepler's laws in relation to artificial satellites orbiting the earth. Differentiate between geosynchronous and geostationary satellite orbits.

7 M

5 (b) What do you mean by "tracking" in a super heterodyne receiver? What is "tracking error"? Explain the "three point tracking" in MW band receiver.

7 M

5 (c) What is Transponder? Explain various Transponders.

7 M

5 (d) What do you mean by altitude control? Explain Multiple-access methods with diagram.

7 M

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