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Chrominance signal processing circuit in color television receiver
| Details |
Inventors: Hosoya, Nobukazu;
Assignee: Sanyo Electric Co., Ltd. (Osaka, JP)
Primary Examiner: Murray; Richard
Assistant Examiner:
Attorney, Agent or Firm: Armstrong, Nikaido, Marmelstein & Kubovcik
A chrominance signal processing circuit in a color television receiver which comprises a bandpass amplifier, a burst gate pulse source, a subcarrier generator, a 90.degree. phase shifter for phase shifting the generated subcarrier, a B - Y demodulator and an R - Y demodulator both coupled to the bandpass amplifier and separately coupled to the subcarrier generator and the 90.degree. phase shifter, respectively, characterized in that a flip-flop is provided responsive to the burst gate pulse to alternately provide a first and second selected burst gate pulses, the B - Y and R - Y demodulators are structured to provide a burst magnitude representing signal and a subcarrier phase drift representing signal, respectively, in the line blanking period and to be disabled responsive to the first and second selected burst gate pulses, respectively, an automatic color control sample and hold circuit is provided to be enabled to the second burst gate pulse to hold the burst magnitude representing output of the B - Y demodulator to supply the held level signal to the bandpass amplifier as a gain control signal, and an automatic phase control sample and hold circuit is provided to be enabled responsive to the first selected burst gate pulse to hold the subcarrier phase drift representing output of the R - Y demodulator to supply the held level signal to the subcarrier generator as a frequency control signal. Preferably a color gain control and tint control are provided, which are structured to be responsive to the burst gate pulse to be disassociated with the bandpass amplifier and the subcarrier generator. |
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DETAILED DESCRIPTION Briefly described, the present invention comprises a chrominance signal processing circuit in a color television receiver, comprising bandpass amplifying means of a voltage controlled variable gain type for amplifying a chrominance signal, burst gate pulse source means, subcarrier generating means of a voltage controlled variable frequency oscillator type, and color demodulating means coupled to the bandpass amplifying means and the subcarrier generating means, characterized in that first chrominance demodulating means is provided responsive to the chrominance signal and subcarrier signal for providing a first chrominance demodulated signal in the line scanning period and for providing a first signal representing the magnitude of the chrominance signal in the blanking period, second chrominance demodulating means is provided responsive to the chrominance signal and the subcarrier signal for providing a second chrominance demodulated signal in the line scanning period and for providing a second signal representing the phase drift of the subcarrier signal in the blanking period, first sample and hold means is provided responsive to the burst gate pulse to be enabled and responsive to the first chrominance demodulating means for sampling the first magnitude representing signal and holding a first level signal representing the first magnitude representing signal, the first level signal being applied to the bandpass amplifying means as a voltage control signal, and second sample and hold means is provided responsive to the burst gate pulse to be enabled and responsive to the second chrominance demodulating means for sampling the second phase drift representing signal and holding a second level signal representing the second phase drift representing signal, the second level signal being provided to the subcarrier generating means as a voltage control signal.
According to the present invention, an automatic color control signal and an automatic phase control signal are obtained by the use of the chrominance demodulating means
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TV Signal 
