Comb filter separating video spectra in PCM TV system - uses digital delay cct. and adder and subtractor

摘要

The comb filter, for separating video spectra in PCM television transmission systems, has the FBAS input signal passed to a delay circuit in digital form as a parallel or serial code. The delay circuit consists of a shift register, monostable flip-flop or similar. The output of the delay circuit is added and subtracted from the original input signal to obtain the luminance and the chrominance signals. The signal may be applied to the delay circuit before A/D conversion in which case the delay circuit is constructed from analog components. The filter avoids the problems inherent in delay circuit's that use analog techniques.