System for synchronizing the phase of color synchronization signals in the receiver to the phase of the color subcarrier in the received signal in a pal receiver

Abstract

Abstract A RECEIVED COLOR TELEVISION SIGNAL HAS A SINGLE COLOR SUBCARRIER AND A COLOR SYNCHRONIZATION SIGNAL (BURST) WHOSE PHASE ALTERNATES BETWEEN PLUS AND MINUS 45* FOR SEQUENTIAL LINES. SWITCHING SIGNALS FOR SYNCHRONIZING THE PHASE OF SAID COLOR SUBCARRIER IN THE RECEIVER TO THE PHASE OF SAID COLOR SYNCHRONIZATION SIGNAL ARE SUPPLIED BY FREQUENCY DIVIDING CIRCUIT WHICH RECEIVES A SINGLE LINE SYNCHRONIZATION SIGNAL FOR EACH LINE AND FURNISHES SIGNALS OF HALF-LINE FREQUENCY. PHASE SELECTOR SIGNALS FOR SELECTING THE PHASE OF THE FREQUENCY DIVIDING CIRCUIT ARE GENERATED BY FIRST SEPARATING THE BURSTS AND SERVE TO IDENTIFY THE COLOR SUBCARRIER PHASE FROM THE RECEIVED TELEVISION SIGNAL. THE BURSTS ARE THEN DELAYED FOR A TIME CORRESPONDING TO A LINE INTERVAL AND PHASE SHIFTED BY 90*. THE PHASE SHIFTED BURSTS ARE COMPARED TO THE BURSTS WITHOUT DELAY IN A PHASE COMPARATOR THE OUTPUT SIGNALS OF WHICH HAVE A POLARITY CORRESPONDING TO THE PRODUCT OF HE POLARITIES OF THE INPUT SIGNALS. AFTER FILTERING, SIGNALS OF ONE POLARITY ARE SELECTED TO CONSTITUTE THE SIGNALS DETERMINING THE PHASE OF THE FREQUENCY DIVIDING CIRCUIT.

Inventors

• 👤 Gerhard Krause

Bibliographic Details