DEMODULATION SYSTEM FOR PM COLOR SIGNAL MULTIPLEXED IN ORTHOGONAL TWO-PHASE BASIS

摘要

PURPOSE:To reproduce faithfully a color video signal which is recorded with high picture quality by demodulating alternate inverted PM color signals with a phase-inverted phase reference signal, and the other PM color signal with a phase reference signal having constant-phase. CONSTITUTION:Only signals + or -C'Rt in horizontal blanking periods are extracted by a gate circuit 40 from alternate inverted PM color signals + or -CRt, and PM demodulation 39 is imposed upon the extracted signals with the constant-phase signal, e.g. phase reference signal cosomegact for CBt demodulation to obtain a signal 39a. This signal 39a is inputted to a comparator 42 to obtain a pulse signal 38 of 1/2fH which has level transition at every 1H, and the signal is inputted to an inverting circuit 36. A phase device 35, on the other hand, generates signals sinomegact and cosomegact, and the signal cosomegact is supplied to a modulator 30 for B-Y demodulation as it is. The signal sinomegact is passed through a circuit 36 to obtain signals + or -sinomegact, which are supplied to a modulator for B-Y demodulation. The outputs of the modulators 29 and 30 are passed through low-pass filters 31 and 32 to remove carriers and high-order components, obtaining color signals ER-Yt and EB-Yt.