Apparatus for processing NTSC TV signals having digital signals on quadrature-phase video carrier

摘要

A vestigial-sideband amplitude-modulation transmitter using a balanced modulator for generating a suppressed carrier that is in quadrature phasing with the video carrier of a television signal receives as modulating signal a binary phase-shift-keying (BPSK) signal encoding digital signals. The quadrature transmission reduces the visibility of the lower-frequency PSK sidebands in the TV signal as viewed on screen. The symbol rate of the PSK is made to be a multiple of the horizontal line scan rate of video signal. To reduce the visibility of the higher-frequency PSK sidebands in the TV signal as viewed on screen, the BPSK is transmitted twice during respective frames of successive pairs of data frames, which data frames recur at the same rate as video frames. To reduce the interference of video with the PSK, the PSK is subjected to partial-response filtering at the transmitter and is highpass line-comb filtered at the digital signal receiver.