Phase reversal signal generator in TV set - is synchronised by phase reversal of burst signal in chrominance signal

摘要

A chrominance signal has two colour signals modulated on an auxiliary colour carrier, and the burst signal is modulated on the auxiliary colour carrier. Phase one of the two colour signals is reversed at each scanning period, and the burst signal phase is shifted by (+-) 45 deg. relative to the mean phase. A phase discriminator (64) detects the phase difference between the burst signal and the auxiliary carrier. It has a Schmitt trigger (66) triggered by the phase discriminator (64) output signal, thus generating the phase reversal signal with two different output levels, changed at each scanning period. It is used for phase reversal of the auxiliary carrier for one colour signal demodulation.