Carrier signal generating circuit in video signal recording/reproducing

Abstract

In a video signal apparatus, a carrier signal generating circuit includes a VCO for generating a signal having a frequency at least twice that of a carrier signal necessary for conversion to a lower band with a sub-carrier in an NTSC system, a one-half divider circuit for dividing the VCO frequency signal by two, a delayed flip-flop circuit for receiving the divided signal and the sub-carrier signal to generate a difference frequency signal, a 1/40 divider circuit for dividing the Q output, a phase comparator circuit for comparing the phases of the 1/40 divided signal and the horizontal synchronizing signal to output a phase difference, a frequency discriminator circuit for comparing the phase of the flip-flop output with the frequency-divided output of the horizontal synchronizing signal to output a frequency error, and a circuit for converting the output of the phase comparator circuit and the frequency error into DC voltages and applying their sum as a control voltage for the VCO. A CR constant control circuit controls the CR constant of a four-phase signal generator for converting the output of the one-half divider circuit into a four-phase signal.