GB1390081A - Colour television receiver - Google Patents

Abstract

1390081 Colour television GENERAL CORP 5 April 1972 [5 April 1971] 15703/72 Heading H4F In a colour television receiver for a PAL signal having "swinging" bursts, the bursts for every second line are phase-inverted, the resulting bursts controlling a reference oscillator 20 for R-Y demodulation, the phase of the oscillator being the mean of the phases of the bursts fed to it in two successive line periods. A reference oscillation for B-Y demodulation is produced in response to the received bursts in a separate oscillator 5. The phase inversion is achieved by a 180 degree phase shifter 16 and a switch 17 operated at half line frequency. In the embodiment shown the chrominance signal is fed to the R-Y demodulator 3 via 16 and 17 to provide the R-Y component always of the same polarity. In another embodiment (Fig. 4, not shown) the chrominance signal is fed to demodulators 2 and 3 via a one-line delay line and switch to provide to the demodulators every second line of information repeated twice. In a further embodiment (Fig. 3, not shown) the chrominance signal is fed directly to demodulators 2 and 3, the output of reference oscillator 20 being switched at half line frequency.