Local communication system and apparatus for use therein

摘要

A local area network is based on a ring of twisted pair cable links (UTP), each carrying at least 1.4 Mbps gross data rate. Each station on the network includes an encoder and a following station includes a decoder for PSK (phase shift keying) modulated serial data. The encoder uses an analog sine wave oscillator and inverter for generating antiphase analog sine wave signals at a carrier frequency and a switching circuit for selecting between the carrier signals according to the data signal to be transmitted. The decoder may use a simple integrator and comparator arrangement. The encoder and decoder may be provided in the form of an adapter circuit, such that a network based on optical fibre can be replaced by a network based on twisted pair cable using the same digital circuits. Generation of the PSK waveform by analog circuitry rather than digital synthesis reduces radio frequency emissions to a level suitable for use in an automotive audio/video communications network.