Jawaharlal Nehru Technological University Hyderabad
Jawaharlal Nehru Technological University Hyderabad B.Tech II PRINCIPLES OF COMMUNICATIONS Previous Question Paper (December - 2018 - R15)
Note: This question paper contains two parts A and B. Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit. Each question carries 10 marks.
Part A
(25 Marks)
Define Noise figure.
Answer
Noise figure (F) is defined as the ratio of the signal-to-noise ratio at the input of a system to the signal-to-noise ratio at the output of the system. It is a measure of the degradation of signal quality caused by components in a radio frequency system.
Define information, messages and signals.
Answer
Information is the abstract measure of the uncertainty or surprise associated with a message. Messages are the physical manifestations of information, such as voice, text, or images. Signals are the electrical or electromagnetic representations of messages, typically expressed as time-varying voltage or current waveforms.
State Carson rule.
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Define Modulation index and percent modulation for an AM wave.
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Define multiplexing.
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Define under sampling; critical sampling and over sampling.
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Write short notes on Granular Noise.
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What are the advantages and disadvantages of Digital Communication?
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Define Rate of Information and entropy.
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Define and State the properties of mutual information.
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Part B
(50 Marks)
With the help of block diagram explain the elements of communication system.
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Explain different types of noise and noise calculation in linear systems.
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What are the applications of Modulation? Explain in detail.
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Explain Square law modulators.
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Explain how FM can be generated from PM?
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Explain about the Pre-Emphasis and De-Emphasis Filtering.
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What is the need for pulse modulation systems? Compare it with analog Modulation.
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With help of the circuits, explain about PAM modulator and demodulator.
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Explain about sampling theorem for band limited signals.
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Compare Time Division Multiplexing and Frequency Division Multiplexing.
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Explain with a neat block diagram the PCM system.
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Derive the relation for signaling rate and transmission bandwidth in a PCM system.
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Explain with a block diagram and derive an expression for error probability of differentially coherent PSK system.
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An information source produces sequences of independent symbols having the following probabilities: A=1/3, B=1/27, C=1/3, D=1/9, E=1/9, F=1/27, G=1/27. Using Shannon-Fano procedure:
Construct a binary code.
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Determine the efficiency and redundancy.
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Consider a (6, 3) generator matrix. Find:
All the code vectors of this data.
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The parity check matrix for this code.
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The minimum weight of this code.
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