| 摘要 |
PURPOSE:To suppress influence due to disturbance such as noise, etc., and to obtain a stable detecting characteristic at the time of inputting a weak electric field signal or an overmodulation signal, by increasing a difference between a mean potential and a reference potential at the time of locking and unlocking a loop circuit. CONSTITUTION:A video intermediate frequency signal is supplied to a first input of each of a video detector 1 and a phase detector 2, and the detector 2 constitutes a PLL circuit with a loop filter 3, a voltage controlled oscillator 4 and a phase shifter 5. And when a PLL signal is unlocked, the detector 1 outputs a video signal OUT. The signal OUT, the lower side of which being clipped by a clipping circuit 10, becomes a clip waveform (a), and its mean potential VAV is set higher than the mean potential of the signal OUT. Therefore, a potential difference between the mean potential of the signal OUT outputted from the detector 1 at the time of locking the PLL signal and the clip waveform is expanded, thereby, a loop filter switching characteristic can be stabilized.
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