JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II ANALOG COMMUNICATIONS Previous Question Paper (September/October - 2023 - R16)
Note: i) Question paper consists of Part A, Part B. ii) Part A is compulsory, which carries 25 marks. In Part A, answer all questions. iii) In Part B, Answer any one question from each unit. Each question carries 10 marks and may have a, b as sub questions.
Part A
What is Amplitude modulation? Define the modulation index of an AM.
Answer
Amplitude Modulation (AM) is a process where the amplitude of a high-frequency carrier signal is varied in accordance with the instantaneous amplitude of the message signal. The modulation index (μ) is defined as the ratio of the peak amplitude of the message signal (A_m) to the peak amplitude of the carrier signal (A_c), expressed as μ = A_m / A_c.
Regarding AM, what is over modulation, under modulation and 100% modulation?
Answer
These terms describe the relationship between message and carrier amplitudes:
- Under modulation (μ < 1): The carrier amplitude is greater than the message amplitude, resulting in no distortion of the envelope.
- 100% modulation (μ = 1): The message amplitude equals the carrier amplitude, providing the maximum possible power efficiency without distortion.
- Over modulation (μ > 1): The message amplitude exceeds the carrier amplitude, causing phase reversals and envelope distortion, which leads to signal degradation.
What are the advantages of SSBSC over DSBSC, AM?
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What is Hilbert transform and what are its applications?
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Give the comparisons between AM and FM.
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Draw the Phasor diagram of narrow band FM.
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What is thermal noise?
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Write the properties of narrow band noise.
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List the different types of receivers.
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Explain the need for an amplitude limiter in the FM receiver.
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Part B
Explain the generation of the DSB-SC signal with the help of a balanced modulator using diodes.
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Develop the equation of a single-tone modulation of the AM system and explain the power relations.
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Describe the VSB in the time domain and then explain any one method of generating VSB modulated wave.
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Explain the Frequency discrimination method for generating SSB signal.
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A 20 MHz carrier is frequency modulated by a sinusoidal signal such that the peak frequency deviation is 100 kHz. Determine the modulation index and the approximate bandwidth of the FM signal if the frequency of the modulating signal is: (i) 1 kHz (ii) 15 kHz.
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Explain the spectrum analysis of sinusoidal FM wave with neat diagrams.
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What are the different types of generation of FM? Explain any two methods.
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Derive the expression of the figure of merit for the frequency-modulated system.
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Explain the threshold effect in the angle modulation system.
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Derive equation for Average Noise figure of cascaded networks.
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Explain the operation of a Tuned Radio Frequency (TRF) receiver with the block diagram and mention its advantages and disadvantages.
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What is AGC? Why it is needed in receivers.
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Explain the generation and demodulation of PAM signals.
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