| 摘要 |
PURPOSE:To prevent the occurrence of disorder of colors due to external disturbance by discriminating the state of phase of a color burst signal by a synthesizing signal of a delay signal and phase shifting signal of a carrier chrominance signal and a color burst signal. CONSTITUTION:The chrominance demodulating circuit of a video reproducing device consists of a 1H delay circuit 1, adder circuits 3, 4, a subtracter circuit 5, a burst gate 6, a B-Y demodulator 7, and R-Y demodulator 8, a subcarrier generator 9, a 90 deg. phase shifter 10, a 180 deg. phase shifter 11, a PAL switch 12 and a burst detecting circuit 13. Further, output of the 1H delay circuit is supplied to a 90 deg. phase shifter 14. A carrier chrominance signal and a color burst signal are added and composed to output of the 90 deg. phase shifter in the adder circuit 4. Output of the adder circuit 4 is supplied to the burst detecting 13. Accordingly, even when inversion action of a subcarrier signal by the PAL switch 12 is reversed, the inversion action is restored to normal in 2H. Thus, high speed response is made possible, and occurrence of disorder of colors due to channel changing can be prevented.
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