RECEIVERS FOR DIGITAL SIGNALS BURIED WITHIN THE TRACE AND RETRACE INTERVALS OF NTSC TV SIGNALS

摘要

An NTSC television signal transmitter also transmits through the same transmission channel a suppressed data carrier having a frequency differing from that of video carrier, having a symbol rate that is a multiple of horizontal scanning rate of video signal, having data frames occurring at a data frame rate that is the same as the video frame rate, and transmitting the symbols transmitted in each of alternate data frames in opposite phase during the next data frame. The data carrier has no image on the other side of the video carrier and preferably its modulation spectrum overlaps the video carrier. A receiver recovers data from such a data carrier buried in an NTSC television signal, using frame-comb filtering to separate data from interfering video signal.