Color television receiver for use in pal system

Claim 2

A color television receiver for receiving television signal including a chrominance signal formed by quadrature amplitude modulation of a carrier wave with two color signals, one of the modulations axes being changed by 180* for alternate line periods of the video signal, the receiver comprising a circuit means for phase-detecting a chrominance signal with a first output of a reference oscillator to produce a first color signal, gate means for gating a second output of said reference oscillator with said first color signal, said second output for producing a second color signal, means for phase-detecting said chrominance signal with a gated oscillation delivered from said gate means, means for converting the outpUt of the second-mentioned phase-detecting means into a corresponding D. C. signal and means for phasecontrolling said reference oscillator with respect to said chrominance signal by means of the output of said converting means, said output of said converting means being representative of a difference in amplitude between the demodulated chrominance signal when a 180* change of the phase of the chrominance signal is effected and the demodulated chrominance signal when no 180* change of the phase of the chrominance signal is effected.

Claim 3

The color television receiver as claimed in claim 1, wherein said gate means includes means for phase-shifting said second output of said reference oscillator to produce as said second color signal two signals at output electrodes 180* out of phase to each other, diodes each having one end connected with different one of said output electrodes of said phase-shifting means, and other ends of said diodes being connected with each other, means for supplying said first color signal as a gate signal to the connection point between said diodes and means for applying bias voltages to said diodes so that said diodes are not conductive when said supplied gate signal is small.

Claim 4

A color television receiver for receiving a television signal including a chrominance signal formed by guadrature amplitude modulation of a carrier wave with two color signals, one of the modulation axes being changed by 180* for alternate line periods of the video signal, the receiver comprising circuit means for phase-detecting a chrominance signal with a first output of a reference oscillator to produce a first color signal, gate means for gating a second output of said reference oscillator with said first color signal, means for phase-detecting said chrominance signal with the output of said gate means to produce a first detected signal; another circuit means for phase-detecting said chrominance signal with a third output of said reference oscillator to produce a second color signal, said third output being derived from said second output, another gate means for gating said first output of said reference oscillator with said second color signal, another means for phase-detecting said chrominance signal with the output of said other gate means to produce a second detected signal, means for combining said first and second detected signals into a single detected signal and means for phase-controlling said reference oscillator with respect to said chrominance signal by means of the output of said combining means.

Claim 5

A color television receiver for receiving a television signal including a chrominance signal formed by guadrature amplitude modulation of a carrier wave with two color signals, one of the modulation axes being changed by 180* for alternate line periods of the video signal, the receiver comprising circuit means for phase-detecting a chrominance signal with a first output of a reference oscillator to produce a first color signal, gate means for gating a second output of said reference oscillator with said first color signal, means for phase-detecting said chrominance signal with the output of said gate means to produce a first detected signal; another circuit means for phase-detecting said chrominance signal with a third output of said reference oscillator to produce a second color signal, said third output being derived from said second output, another gate means for gating said first output of said reference oscillator with said second color signal, another means for phase-detecting said chrominance signal with the output of said other gate means to produce a second detected signal, means for combining said first and second detected signals into a single detected signal and means for phase-controlling said reference oscillator with respect to said chrominance signal by means of the output of said combining means.

Claim 6

A color television receiver for receiving a television signal including a chrominance signal formed by guadrature amplitude modulation of a carrier wave with two color signals, one of the modulation axes being changed by 180* for alternate line periods of the video signal, the receiver comprising a pair of demodulators for alternatively demodulating a chrominance signal phase- shifted by 180* at every horizontal scanning reference oscillator means, the output of said reference oscillator means being fed to said demodulators, a pair of integrators for integrating the outputs of said pair of demodulators, means for combining the outputs of said pair of integrators into a single detected signal representative of a difference in amplitude between the demodulated chrominance signal when a 180* change of the phase of the chrominance signal is effected and the demodulated chrominance signal when no 180*-change of the phase of the chrominance signal is effected, and means for phase controlling said reference oscillator with respect to said chrominance signal by means of the output of said combining means.

Claim 7

A color television receiver for receiving a television signal including a chrominance signal formed by guadrature amplitude modulation of a carrier wave with two color signals, one of the modulation axes being changed by 180* for alternate line periods of the video signal, the receiver comprising a pair of demodulators for alternatively demodulating a chrominance signal phase- shifted by 180* at every horizontal scanning reference oscillator means, the output of said reference oscillator means being fed to said demodulators, a pair of integrators for integrating the outputs of said pair of demodulators, means for combining the outputs of said pair of integrators into a single detected signal representative of a difference in amplitude between the demodulated chrominance signal when a 180* change of the phase of the chrominance signal is effected and the demodulated chrominance signal when no 180*-change of the phase of the chrominance signal is effected, and means for phase controlling said reference oscillator with respect to said chrominance signal by means of the output of said combining means.

Claim 8

The color television receiver as claimed in claim 1, wherein said converting means comprises an integrator having a time constant equal to a time period of about 3 - 7 fields.

Claim 9

A color television receiver for receiving a television signal including a chrOminance signal formed by quadrature amplitude modulation of a carrier wave with two color signals, one of the modulation axes being changed by 180* for alternate line periods of the video signal, the receiver comprising a demodulator for demodulating a (B-Y) signal from said chrominance signal; a demodulator for demodulating an (R-Y) signal from said chrominance signal; a reference oscillator for demodulation; a phase controller interconnected between said reference oscillator and said (B-Y) demodulator; a 90*-phase shifter interconnected between said reference oscillator and another phase controller, said other controller being connected with said (R-Y) demodulator; a pair of gates to both of which the output of said (R-Y) demodulator is fed, said gates being driven by said (B-Y) demodulator so that their times of conduction are different from each other; a differential amplifier connected with said gates; and an integrator for integrating the output of said differential amplifier, said integrator being connected with said both phase controllers.

Claim 10

A color television receiver for receiving a television signal including a chrOminance signal formed by quadrature amplitude modulation of a carrier wave with two color signals, one of the modulation axes being changed by 180* for alternate line periods of the video signal, the receiver comprising a demodulator for demodulating a (B-Y) signal from said chrominance signal; a demodulator for demodulating an (R-Y) signal from said chrominance signal; a reference oscillator for demodulation; a phase controller interconnected between said reference oscillator and said (B-Y) demodulator; a 90*-phase shifter interconnected between said reference oscillator and another phase controller, said other controller being connected with said (R-Y) demodulator; a pair of gates to both of which the output of said (R-Y) demodulator is fed, said gates being driven by said (B-Y) demodulator so that their times of conduction are different from each other; a differential amplifier connected with said gates; and an integrator for integrating the output of said differential amplifier, said integrator being connected with said both phase controllers.