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Question Bank I

The document is a question bank for EC3491 Communication Systems focusing on Amplitude Modulation (AM). It includes questions on modulation concepts, calculations related to AM and FM, principles of signal generation and detection, and comparisons between different modulation techniques. Additionally, it covers spectral characteristics and the workings of a super heterodyne receiver.

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8 views1 page

Question Bank I

The document is a question bank for EC3491 Communication Systems focusing on Amplitude Modulation (AM). It includes questions on modulation concepts, calculations related to AM and FM, principles of signal generation and detection, and comparisons between different modulation techniques. Additionally, it covers spectral characteristics and the workings of a super heterodyne receiver.

Uploaded by

tpgitspotify
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as DOCX, PDF, TXT or read online on Scribd
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EC3491 Communication Systems

Question Bank

Unit I Amplitude modulation

Part A Two marks

1. What is modulation index and percentage modulation in AM?


2. In a amplitude modulation, fc=100KHz, the maximum frequency of the message signal is 5KHz.
Determine the lower and upper sidebands of AM signal.
3. The maximum frequency deviation in a FM is 10 KHz and signal frequency is 10 KHz. Find out
the bandwidth using Carson's rule and the modulation index
4. Define Amplitude modulation, Frequency modulation and Phase modulation.
5. Draw the frequency spectrum and mention the bandwidth of AM signal
6. In an AM transmitter, the carrier power is 10 kW and the modulation index is 0.5. Calculate the
total RF power delivered
7. State Carson’s rule.
8. Draw the waveforms of AM modulated signal.
9. Define frequency deviation and what is the required bandwidth for FM signal, in terms of
frequency deviation.
10. A broadcast radio transmitter radiates 5 KW power when the modulation percentage is 60% How
much is the carrier power.
11. If a modulated wave with an average voltage of 20Vp changes in amplitude ±5V, determine the
maximum and minimum envelope amplitudes and the modulation coefficients.
12. Compare AM, FM, and PM.
13. What is heterodyning. Define image frequency and image frequency rejection ratio.
14. What is pre-envelope and complex-envelope.
15. What is a Hilbert transform
Part B
1. Explain the principles of following AM ,its generation and detection
(i) Ordinary AM (ii) DSBSC (8+8M)
(ii) Explain the principles of SSB and VSB , its generation and detection. (8+8M)
2. Explain the spectral characteristics and angle modulated waves. (16M)
3. In an AM modulator, 500 KHz carrier of amplitude 20 V is modulated by 10 KHz modulating
signal which causes a change in the output wave of ± 7.5 V. (2+2+2+2M)
Determine:
(1) Upper and lower side band frequencies
(2) Modulation Index
(3)Peak amplitude of upper and lower side frequency
(4) Maximum and minimum amplitudes of envelope.

4. With a neat block diagram, explain the working of super heterodyne receiver. (10M)

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