| 摘要 |
PURPOSE:To reduce the generation of buzz noise due to the effect of phase modulation of a video carrier by branching and extracting the output phase error voltage of a phase comparator in a video detection circuit using a PLL and operating the result with a detected audio signal. CONSTITUTION:The phase error voltage extracted from the phase comparator 12 in a video detection circuit 4 is branched into two; one is fed to an LPF 13 and the other is given to an LPF 20. The LPF 20 is low pass filter to decide the band of buzz to be cancelled and its cut-off frequency is selected sufficiently higher than that of a locking range setting LPF 13 of the PLL. The output signal of the LPF 20 is matched with the phase with the buzz component in an audio detection signal from an audio detection circuit 26 by a phase adjusting device 21 and the result is amplified by an amplifier 22 and after the amplitude is matched with that of the buzz component by a level adjusting device 23, the result is fed to an operation circuit 24, which adds or subtracts the audio signal extracted from an FM detection circuit 8 and the phase error voltage subjected to phase and amplitude adjustment and outputs an audio signal whose buzz component is cancelled to an output terminal 27.
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