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Ave - TV receiver (PAL - D circiut main)
 

Ave - TV receiver (PAL - D circiut main)

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AVE ppt on TV receiver (PAL - D circiut main)

AVE ppt on TV receiver (PAL - D circiut main)

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    Ave - TV receiver (PAL - D circiut main) Ave - TV receiver (PAL - D circiut main) Presentation Transcript

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