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JNTU B.Tech II ANALOG COMMUNICATIONS Previous Question Paper (April/May - 2023 - R16)

B.Tech | II | II-II | R16 | April/May - 2023

Answer PaperPaper Code: 134ACMaximum Marks: 75Time: 3 Hours

Question paper consists of Part A and Part B. Part A is compulsory, carrying 25 marks. Answer all questions in Part A. In Part B, answer any one question from each unit. Each question in Part B carries 10 marks.

Part A

1
Answer all questions.
25 marks
a
Define modulation and explain the need of it.
2 marks

Answer

Modulation is the process of varying one or more parameters of a high-frequency carrier signal in accordance with the instantaneous amplitude of a low-frequency baseband message signal. It is necessary to facilitate antenna size reduction, enable frequency division multiplexing, improve signal-to-noise ratio, and allow for long-distance wireless transmission.

b
What is the maximum transmission efficiency of an amplitude modulated system for 100% modulation?
3 marks

Answer

The transmission efficiency of an AM system is given by the ratio of sideband power to total power: η = μ2 / (2 + μ2). For 100% modulation (μ = 1), η = 1 / (2 + 1) = 1/3, which is approximately 33.3%.

c
Draw the spectrum of VSB modulated signal.
2 marks

Answer

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d
What is the threshold effect in envelope detector?
3 marks

Answer

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e
What is the average power of an FM signal?
2 marks

Answer

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f
Explain how PLL is useful in detecting FM signals.
3 marks

Answer

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g
Why Pre-emphasis and de-emphasis are needed?
2 marks

Answer

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h
Write the SNR expression for FM and AM?
3 marks

Answer

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i
Give the drawbacks of PAM.
2 marks

Answer

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j
Describe the factors on which selectivity depends.
3 marks

Answer

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Part B

210 marks
a
Compare Square law detector with envelope detector.
5 marks

Answer

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b
Draw the waveforms and spectrum of Amplitude Modulation (AM) for an arbitrary baseband signal x(t).
5 marks

Answer

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OR
310 marks
a
With a neat Sketch, generate DSB-SC signal with the help of ring modulator using diodes.
5 marks

Answer

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b
Explain the detection of message signal from the amplitude modulated signal using an envelope detector and bring out the significance of RC time constant.
5 marks

Answer

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410 marks
a
Derive an expression for SSB modulated wave for which upper side band is retained.
5 marks

Answer

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b
Draw the block diagram of phase shift discriminator and explain the functionality of each block.
5 marks

Answer

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OR
5
What is vestigial side band? Explain the process of generation and detection of VSB modulated wave using a carrier
ACcos(2πfct)
.
10 marks

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610 marks
a
Explain the operation of the balanced slope detector with a circuit diagram and draw its response characteristics.
6 marks

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b
Give the comparison between FM and AM.
4 marks

Answer

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OR
7
An FM wave with modulation index β = 1 is transmitted through an ideal band pass filter with mid band frequency fc and bandwidth is 5 fm, where fc is the carrier frequency and fm is the frequency of the sinusoidal modulating wave. Determine the amplitude spectrum of the filter output.
10 marks

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810 marks
a
In a cascade connection of two Two-Port devices the noise figure of first and second stages are 5 and 15 respectively. The available power gain of first and second stages are 12dB and 20dB respectively. Find the overall noise figure.
4 marks

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b
Define and explain the following and obtain the relation between them: i) Noise figure, ii) Equivalent noise temperature.
6 marks

Answer

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OR
910 marks
a
Derive the expression for the Figure of Merit for an envelope detector used to detect an AM-DSB-Full Carrier signal, under low noise case.
6 marks

Answer

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b
What is thermal noise? List the properties of thermal noise and briefly explain.
4 marks

Answer

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1010 marks
a
Describe how different signals can be multiplexed using TDM system.
5 marks

Answer

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b
With the help of a neat block diagram, explain the working of tuned radio receiver.
5 marks

Answer

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OR
1110 marks
a
Explain the demodulation procedure for PWM signal demodulation.
5 marks

Answer

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b
List and discuss the factors influencing the choice of the intermediate frequency for a radio receiver.
5 marks

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About this paper

This page contains the question paper of ANALOG COMMUNICATIONS from JNTU for B.Tech ECE II II-II, April/May - 2023, R16.

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