Ave - TV receiver (PAL - D circiut main)


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Ave - TV receiver (PAL - D circiut main)

  1. 1. Chroma signal amplifier circuit and Yagi-uda antenna<br />By <br /><ul><li>Ashton
  2. 2. Pooja
  3. 3. Prathik</li></li></ul><li>AVE Colour TV<br /><ul><li>Circuit diagram of Chroma signal amplifier
  4. 4. 5 different stages
  5. 5. Stage 1(Q1) and 2(Q2 and Q3), colour saturation, colour killer bias and burst blanking pulse stage.
  6. 6. Yagi – uda antenna and radiation pattern.</li></li></ul><li>
  7. 7. Pal – D colour receiver<br /><ul><li>Video detector suppies composite video signal to colour decoder (pal) and y channel decoder.
  8. 8. o/p pal d = V and U ( scaled down colour difference signals U=0.493(B-Y) and V=0.877(R-Y)
  9. 9. o/p y channel = luminance (brightness)signal (y)
  10. 10. Given to matrix ckt for RGB colour signal generation.</li></li></ul><li>
  11. 11. Why separation of chroma signal and colour burst signal?<br /><ul><li>The chroma signal separation circuit used.
  12. 12. Encoding= process of combining the 2 colour difference signals by translating them to a higher freq. domain.
  13. 13. Since the 2 carrier freq. are suppressed in the balanced mod. of the encoder, it is necessary to regenerate them at the receiver for demod. of the chroma signal.
  14. 14. So,8-10 cycles of colour sub-carrier oss. o/p are transm. with sync pulses in short bursts called colour burst.</li></li></ul><li>
  15. 15.
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  17. 17. Stage 1 (Q1)<br />Input to Q1 via C1<br />Gain controlled by XL1<br />Magnitude of ACC voltage fed to base Q1 via R1 R2<br />C2 avoids undesirable feedback between Q1 and ACC.<br />Ie of Q1 = 0.5Vpp<br />o/p to stage 2 via C6<br />o/p to burst stage via C5<br />Function of ACC amp. = o/p Voltage used to control gain of 1st stage of chroma amp. for constant chroma signal amplitude.<br />
  18. 18.
  19. 19. Stage 2 (Q2 and Q3)<br />Consists of transistors Q2 and Q3<br />Q2 acts as emitter follower<br />Q3 acts as phase splitting amplifier i.e. to provide anti-phase chroma signal for chroma delay line circuit that separates U and V signals.<br />
  20. 20.
  21. 21. Colour saturation control section<br />Saturation<br />Determines the pureness of the colour.<br />Level of saturation indicates amounts of other colours present in received light.<br />Saturation control section - function is as a variable attenuator to change mag. of the chroma signal led to U and V demodulator.<br />Consists of D1,D2 with R7,R9.<br />
  22. 22.
  23. 23. Burst pulse blanking<br />D3,D4 and R18 prevent the colour burst pulses from getting through the second stage.<br />Blanking level > to avoid visibility during fly back time.<br />
  24. 24.
  25. 25. Colour killer control<br />Function – rectifies burst pulses to produce steady dc V. and keeps the 2nd stage amp operative allowing the chroma signal to reach the demodulators.<br />In case B&W, no burst pulses, no dc V, and 2nd amp blocked, no colour.<br />
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  28. 28. Thank you !<br />