Download GTU BE/B.Tech 2019 Summer 5th Sem New 2151004 Electronic And Communication Question Paper

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Subject Code: 2151004

GUJARAT TECHNOLOGICAL UNIVERSITY

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BE - SEMESTER-V (NEW) EXAMINATION - SUMMER 2019
Subject Name: Electronic and Communication
Time: 02:30 PM TO 05:00 PM

Instructions:

1. Attempt all questions.

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2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.

Q.1 (a) Explain how bandwidth of a signal (information) affects its transmission. MARKS 03
(b) Explain need of modulation. MARKS 04
(c) Explain Automatic Gain Control (AGC) and discuss difference between AGC and Delayed AGC. MARKS 07

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Q.2 (a) What is the difference between SSB and VSB wave? MARKS 03
(b) Compare : Frequency modulation and Amplitude Modulation MARKS 04
(c) The frequency span to be received by a receiver is from 525KHz to 1650KHz. If Cmin of tuning circuit is limited to 50pF by a trimmer of 25pF, calculate the value of padder capacitor, if the maximum value of variable capacitor is 450pF. The If is 465KHz. MARKS 07

OR

(c) A FM voltage is represented by erm=12sin(6 x 10^8t + 5cos 1250t) Find Carrier Frequency, Modulating Frequency, Modulation Index, Maximum Deviation, Power dissipation across 10O. MARKS 07

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Q.3 (a) Two resistors 10 KO and 25 KO are at room temperature (300K) for a bandwidth of 150KHz. Calculate thermal noise, if two resistors are in series and if two resistors are in parallel. MARKS 03
(b) Explain the interferences in angle modulated systems. MARKS 04
(c) Explain basic principal of dual slope detector type FM demodulators. MARKS 07

OR

Q.3 (a) Define : 1) Signal to noise ratio 2) Image Frequency Rejection Ratio 3) Phase modulation MARKS 03

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(b) An amplifier with 10dB noise figure and 4dB power gain is cascaded with a second amplifier which has a 10dB power gain. What is the overall noise figure? MARKS 04
(c) Explain the Armstrong method of Frequency modulated signal generation. MARKS 07

Q.4 (a) For superheterodyne receiver, Define : Sensitivity , Selectivity and Image frequency MARKS 03
(b) Explain reason and remedy for Diagonal clipping and Negative peak clipping. MARKS 04
(c) What is bandwidth efficient AM? Explain Phase shift method to generate a bandwidth efficient AM signals. MARKS 07

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OR

Q.4 (a) Describe the problems in TRF receiver. MARKS 03
(b) Explain the working of superheterodyne receiver with help of block diagram. MARKS 04
(c) Derive the mathematical expression of Amplitude Modulated signal and identify the spectrum of AM wave. MARKS 07

Date: 17/06/2019

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Total Marks: 70

Q.5 (a) Explain technology used in amateur radio. MARKS 04
(b) Derive equation for resonant frequency and Q factor for parallel tuned circuit. MARKS 07

OR

(a) Explain Skin effect. MARKS 03

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(b) Explain the importance of HAM radio during natural calamities. MARKS 04
(c) State and prove time scaling property of Fourier transform. Explain the effect of time scaling on bandwidth of the signal. MARKS 07