| 摘要 |
PURPOSE:To reduce modulation distortion nearly without any adjustment by providing a video tape recorder with a demodulator which is supplied with the output of a frequency converter, using a voltage-controlled oscillator as an oscillator, and feeding the output of a demodulator back negatively to the voltage-controlled oscillator. CONSTITUTION:The output of the demodulator 21 becomes higher by a modulation distortion component than when it has no distortion corresponding to a frequency shift corresponding to the modulation distortion. A subtracter 23 subtracts the output of the demodulator 21 from an original video signal to invert and separate the modulation distortion component, which is supplied to the VCO 25, whose oscillation frequency becomes lower than when there is no distortion. The modulation distortion is less and less as the control sensitivity of the VCO 25 is higher and higher, namely, as the gain of a negative feedback loop is larger and larger. In this case, a negative feedback signal is supplied to the VCO 25 for heterodyne and a modulator 21 is not included in the negative feedback loop, so the gain of the negative feedback loop is easily adjusted independently of the adjustment of modulation gain to the video signal.
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