JNTU
JNTU B.Tech II ANALOG COMMUNICATIONS Previous Question Paper (December - 2018 - R16)
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
Define analog Modulation and also, list different types of analog modulations.
Answer
Analog modulation is the process of varying one or more parameters of a high-frequency carrier signal (amplitude, frequency, or phase) in accordance with the instantaneous values of a low-frequency baseband (modulating) signal. The primary types are Amplitude Modulation (AM), Frequency Modulation (FM), and Phase Modulation (PM).
Define Modulating Signal, Carrier and Modulated Signals.
Answer
The Modulating signal is the baseband information signal containing the intelligence to be transmitted. The Carrier signal is a high-frequency sinusoidal wave used to transport the information over the communication channel. The Modulated signal is the resultant waveform produced after the carrier's parameters have been modified by the modulating signal.
What is Guard band?
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Compare SSB and VSB.
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List the disadvantages of FM over AM.
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In an FM system, if mf is doubled by halving the modulating frequency, what will be the effect on the maximum deviation?
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What is threshold effect?
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What is pre-emphasis? Why is it used?
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Illustrate Single and double polarity PAM wave.
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Define Sensitivity, Selectivity and image frequency.
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PART - B
With the help of waveforms and spectrum, describe the concept of Amplitude modulation both in time domain and frequency domain.
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Describe the coherent detection of DSB-SB modulated waves.
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With necessary circuit diagram and waveforms, explain how DSB-SC wave is generated using: i) Balance Modulators and ii) Ring Modulator.
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When a broadcast AM transmitter is 50 percent modulated, its antenna current is 12 A. What will be current when the modulation depth is increased to 0.9?
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Describe the SSB in frequency domain and then explain how to generate SSB modulated wave using frequency discrimination method. Also, list the advantages of SSB.
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Describe the VSB in time domain and then explain any one method of generating VSB modulated wave.
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Give the applications of AM-FC and VSB modulation schemes.
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Discuss the detection of FM wave using zero crossing detector.
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Discuss the generation of FM wave using direct method.
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Analyze Sinusoidal FM wave with the help of its spectrum.
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Explain how FM signal is detected with the help of PLLs.
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Derive the Noise Figure for cascade stages.
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What is thermal noise? Derive the expression for the thermal noise voltage across a resistor.
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Discuss the noise performance of AM system using envelope detection.
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Draw the Phasor representation of FM noise.
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Of all the frequencies that must be rejected by a superheterodyne receiver, why is the image frequency so important? What is the image frequency and how does it arise? If the image-frequency rejection of a receiver is insufficient, what steps could be taken to improve it?
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Define and distinguish between PTM and PAM schemes.
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Describe the generation and demodulation of PPM with the help of block diagram.
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Draw the block diagram of FM receiver and explain each block, briefly.
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