VIDEO SYNCHRONIZATION DETECTING DEVICE

PURPOSE:To execute a phase detecting operation correctly and exactly, by utilizing a video carrier signal obtained by making a video intermediate frequency signal pass through a narrow band BPF. CONSTITUTION:A TV signal received by an antenna 1 is supplied to a tuner 2, and a video intermediate frequency signal outputted from the tuner 2 is supplied to a mixing circuit 7 through an intermediate frequency amplifying stage 6. On the other hand, an output of the tuner 2 is supplied to a carrier amplifying and AGC circuit 8, too, is amplified, and after that, is frequency-converted by a mixing circuit 9, and is supplied to a narrow band BPF 11. In the BPF 11, only a video carrier signal is extracted from an output signal of the circuit 9, and this carrier signal is shaped as to its waveform by a limiting circuit 12, and is supplied to the circuit 7. In the circuit 7, a video carrier signal outputted from the circuit 12 is mixed with an output of the amplifying stage 6, and an output of this circuit 7 is provided to a synchronization detecting circuit 13. In the circuit 13, the synchronization is detected by utilizing the output of the circuit 7 directly or indirectly, and a video signal is reproduced in its output side.