Improvements in capacity of analog voice multiplex systems carried by satellite

Techniques in use for frequency division multiplex/frequency modulation (FDM/FM) and single sideband-amplitude modulation (SSB-AM) based satellite telephony systems are described. Both employ syllabic compandors, which consist of a compressor on the transmit side of the channel and an expandor on the receiver end. IC technology provides good matching between the transmit and receive sides. Compandors in FDM/FM double the voice capacity of FM channels on the Satcom satellites. Companded FDM/FM carriers can operate beyond the filtered bandwidths through overdeviation, which raises the transponder capacity to 2900 channels. No performance decrements are experienced during multiple access operations with either speech or data transmissions. SSG-AM companding can raise the transponder capacity to nearly six times the normal volume.