lecture slides auxiliary materials reference books study guide
TRANSCRIPT
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LectureSlides
Auxiliary materials
Reference Books
Study Guide
Study Guide
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• Grasp essential concepts from lecture slide
• Get further details from auxilliary materials
• Use study guide to assist learning
• Study reference books on specific topics
• Clarify problems in tutorials
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(A1) Why is interlaced video scanning adopted in Television system?
Hint:Consider bandwidth and human perception
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(A1.1) The resolution of a video signal is 320(H)X240(V). The number of pictures per second is 25. Determine the difference in bandwidth of the video signal with (i) interlaced scanning, and(ii) interlaced scanning.
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(A2) What are the purposes of separating RGB video signals to Luminance and Chrominance in TV transmission?
Hint:Consider bandwidth, human perception and compatibility problems
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(A2.1) Consider a line of RGB signal with 256 pixels
R = [0,1,2,3,...........,255]G = [0,1,2,3,...........,255]B = [0,1,2,3,...........,255]
Determine the entropy between of the video signal in the form of(i) RGB , and(ii) YUV representation.
Note: Entropy reflects the amount of redundancy in a signalWhat can you tell about the redundancies of the two representations from their entropies?
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(A3) What is meant by vestigial sideband? Why is it better than double sideband modulation in TV system
Hint:Based your discussion on bandwidth, filter response, and importance of low frequency components in video signal
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(A4) Describe how luminance and chrominance signals are interleaved in the frequency domain
Hint:Determine the repetitive frequency of Y, U and V. Applied Fourier Transform to illustrate the interleaving mechanism
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(A4.1) Given the frequency of the color subcarrier is N times the line frequency. Calculate, with respect to the luminance signal, the locations in the frequency spectrum at which the chrominance components exist with N = 4.
(A4.2) Repeat the above calculations with N = 2 and 1.
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(A5) How can luminance be extracted in the receiver?
Hint:Remember: human visual response is less sensitive to high frequency video contents
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(A6) Describe how chrominance components are extracted in the receiver?
Hint:How does ‘Comb Filter’ works?
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(A6.1) Sketch the structure of a comb filter and express its transfer function in the ‘z’ domain.
(A6.2) Determine the transfer function of a comb filter in the Fourier domain.
Try this: construct the time expression for the input and output signals of a comb filter. Next, transform the time expression.
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(A7) Describe how are the baseband of U and V extracted in the receiver?
Hint:Derive the steps involved in quadrature modulation and demodulation?
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Note: It is the baseband component to be extracted, i.e. free from the color sub-carriers.
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(A8) How is phase error in quadrature demodulation be compensated in the PAL system.
Hint:•Sketch the phasor diagram for U and V.•How does ‘U+V’ changes with error?
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(A9) What is the difference between PAL-S and PAL-I systems. Which is better?
Hint:How is the compensation mechanism in PAL implemented in practice?
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(A10) Why is it necessary to convert RF to IF in TV receiver?
Hint:Try to think of it in the frequency domain. Make a few sketches is often helpful.
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(A11) Sketch the IF response of a TV receiver? How can it be implemented in practice?
Hint:The IF response is shaped to adapt to the spectral characteristics of the composite video signal.
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(A12) What are the function of the color burst?
Hint:•What is needed in quadrature demodulation?•How can correct chrominance level be maintained in the receiver?
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(A13) Why is DC restoration necessary?
Hint:• Sketch a few arbitrary video waveforms
with different levels.• Align these waveform with their
estimated DC levels. What do you observed?
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(A14) What is meant by ‘swinging burst’?
Hint:Sketch the phasor diagram for the color burst.
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(A15) Describe the principles of operation of a PAL decoder?
Hint:•How are the 2 LOs generated?•How to demodulate U and V? •How to compensate the phase error
using alternate line information
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(A16) Why is it necessary to include the ‘color killer’ in a TV?
Hint:Study the color video signal spectrum and the PAL decoder, imagine what would happen if the signal is black and white.
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