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Posted Date: 20 May 2008 Posted By:: nithyajana Member Level: Silver Points: 5 (Rs. 1)
2007 Anna University Chennai B.E Electronics & Tele-Communication Engineering TELEVISION AND VIDEO ENGINEERING Question paper
B.E./B.Tech. DEGREE EXAMINATION,NOVEMBER/DECEMBER 2007.
Electronics and Communication Engineering
EC 1011-TELEVISION AND VIDEO ENGINEERING
Time:Three hours Maximum:100 marks
Answer ALL questions
PART A-(10x2=20 marks)
1.What is the significance of choosing the number of lines as 625 and not 623 or 627 and the frame reception rate as 25 and not 24 as in pictures?
2.Why is a portion of the lower sideband of the AM picture signal transmitted along with the carrier and full VSB?
3.What are the merits of using an RF amplifier before the frequency converter?
4.Why is it necessary to employ an L-C instead of R-C filter to remove IF ripple from the detected output?
5.Why is the colour signal bandwidth requirement much less than that of Y signal?
6.Why is the colour signal transmitted after each scanning line and why PAL colour burst is often called the swinging burst?
7.Justify the choice of 3.579545MHz as the subcarrier frequency in the NTSC system.
8.List the functions of following stages of a PAL-D colour receiver mentioning their input and output.(a)Burst-phase didcriminator (b)Colour killier.
9.Why are up-link and down-link frequencies chosen to be in the GHz range and kept fairly apart from each other?
10.List the merits of digital TV receivers that are not achievable in a analog receiver.
PART B-(5x16=80 marks)
11.(a) (i)Show that the highest modulating frequency that needs to be handled in the 625 TV system is 5MHz.Discuss the effect of number of lines,
interlaced scanning and field frequency on bandwidth. (9)
(ii)For the composite video signal explain the following:
(1)Why are the horizontal pulses not used as sync. pulses. (3)
(2)Why is it necesssary to seperate the broad vertical sync.pulse and why are they notched at 32microsec interval and not at 64microsec interval. (4)
(b) (i)Discuss the merits and demerits of positive and negative amplitude modulation and justify the choice of negative modulation in most TV systems. (8)
(ii)Explain how the inhernet smear effect in a vidicon is overcome in a plumbicon.Explain with a suitable sketch the mechanism by which the video signal
is developed from the P-I-N structure of its target. (8)
12.(a) (i)Describe briefly the factors that influenced the choice of picture IF=38.9MHz in the 625-B monochrome television system. (8)
(ii)What is electronic tuning? Explain with circuit diagram how different channels can be selected by this method. (8)
(b) (i)Give the costructional details of a turnstile antenna and explain by drawing radiation pattern its suitability for television transmission. (8)
(ii)Explain with a circuit diagram how the high voltage pulses,induced in the output transformer windings,are used to generate EHT supply. (8)
13.(a) (i)Explain how by frequency inter leaving the colour information is accommodated within the same channel bandwidth of 7MHz. (8)
(ii)Explain the need for pincushion distortion correction and the method employed to obtain a distortion free raster? (8)
(b) (i)What are weighting factors and why are these applied yo colour difference signals before quadrature modulation.Draw chrominance signal wave shape for
a colour bar pattern and justify the scaling down of (R-Y) and (B-Y) signals. (10)
(ii)Describe the gun structure and focussing details of trinitron picture tube. (6)
14.(a) (i)Explain how the differential phase-error is continuously corrected in the PAL system while affecting QAM of the colour difference signals. (8)
(ii)Show the colour kill circuit and explain how the chrominance signal remains interrupted during monochrome trasmission and how Indent signal is generated? (8)
(b) (i)Explain the delay line method of separating U and V signals in a PAL receiver. (6)
(ii)Describe the circuit of colour burst blanking and first stage of the chroma band-pass amplifier.Explain the circuit of the saturation control in the chroma
bandpass amplifier. (10)
15.(a) (i)Draw the block diagram of a TVRO earth station receiver and explain how the converted down-link IF signal of a TV channel is processed to obtain both
Video and Audio signals. (8)
(ii)Describe how the associated signals of 3-D pictures can possibly be transmitted,received and viewed on present-day receivers. (8)
(b) (i)Describe the new TV standards for HDTV service. (6)
(ii)Draw the functional block diagram of a digital colour receiver and explain how the audio signal is separated and processed to obtain analog sound output. (10)
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