JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II ANALOG COMMUNICATIONS Previous Question Paper (May - 2019 - R16)
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.
Part A
A modulating signal consists of a symmetrical triangular wave, which has zero dc component and peak-to-peak voltage 11v. It is used to amplitude modulate a carrier of peak voltage 10v. Find the modulation index?
Answer
The peak amplitude of the modulating signal Am is half the peak-to-peak voltage: Am = 11V / 2 = 5.5V. The carrier peak voltage Ac = 10V. The modulation index μ is given by:
The antenna current of an AM transmitter is 8 Amps, when only the carrier is sent, but it increases to 8.93A, when the carrier is modulated by a single sine wave. Find percentage modulation. Determine the antenna current when the percent modulation changes to 0.8.
Answer
Given carrier current Ic = 8A and modulated current It = 8.93A. Using the formula It = Ic√(1 + μ2/2):
For μ = 0.8:
List the properties of Hilbert Transform.
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Illustrate the block diagram for the detection of SSB-SC signal using phase discrimination method.
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Define modulation index and bandwidth of FM.
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Compare NBFM and WBFM.
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What is meant by Noise? State the different types of Noise.
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Explain how noise can be calculated in a communication system.
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Define sensitivity and selectivity.
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Explain the image frequency rejection of a radio receiver.
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Part B
Develop the equation of a single tone modulation of AM system and Also power relations.
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Explain the principle of operation of Envelope detector used for AM detection, with necessary equations.
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Explain the phase discrimination method for generating SSB signal.
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Why VSB modulation is used in TV broad casting? Give the VSB filter characteristics with spectrum.
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What are the different demodulation techniques of FM? Explain the demodulation of F.M signal with the help of PLL.
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Formulate the equation for FM wave. Define modulation index, maximum deviation and band width of a FM signal.
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Explain about the noise performance of an FM receiver.
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Explain the noise performance of SSB-SC receiver and prove its S/N ratio is unity.
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Draw the block diagram of Superhetrodyne receiver and explain the function of each block.
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Explain, how a PPM signal can be generated from PWM signal?
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Compare PAM, PWM and PPM pulse modulation techniques.
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