Time-Compression Multiplexing (TCM) of three broadcast-quality TV signals on a satellite transponder

Abstract

We describe how Time-Compression Multiplexing (TCM) might enable the transmission of three National Television System Committee (NTSC) color TV signals through a satellite transponder of 36-MHz bandwidth. The input TV signals are processed such that three fields from each TV source are compressed into an ordinary field period. This is accomplished by sending one field as is but time compressed; the other two fields are sent as differential signals, also time compressed such that all three fit into a single field period. The resultant compressed waveforms are then time multiplexed between the three sources and have a combined baseband bandwidth of 7.52 MHz for an optimal case, or 8.4 MHz for a practical version. In either case, both the transmitter-multiplexer and the receiver-demultiplexer require only three field memories for (digital) signal processing. Performance is expected to be of network broadcast quality (i.e., weighted signal-to-noise ratio, s/n ≥ 56 dB) for the optimal case of 7.52-MHz baseband if 12-meter receive earth stations are employed in a system such as COMSTAR. The practical version, on the other hand, would yield an s/n ≈ 54 dB.