Time-frequency multiplexing (TFM) of two NTSC color TV signals — simulation results

Simple frequency-division multiplexing (FDM) of two television signals onto a microwave radio channel is frequently unsatisfactory because of nonlinearity-induced crosstalk from one picture into the other. With time-frequency multiplexing (TFM), two successive scan lines (or fields) of one picture are frequency multiplexed so that they can be sent in one line (or field) period. During the next time interval, two successive lines (or fields) from the other picture are transmitted, thus avoiding crosstalk between pictures. To reduce the bandwidth required, one of the two simultaneously transmitted lines (or fields) is sent as an analog differential signal. In this paper, we discuss computer simulations of these techniques with application to a 20-MHz-bandwidth microwave radio channel. Effects of filtering and nonlinearities are included insofar as possible.