| 摘要 |
<p>A serial data local area network system comprising a serial data highway (10) interconnecting a plurality of transmitting/receiving nodes having transmitters and/or receivers (12) connected thereto characterised in that each transmitter includes means (22), (23) to spread-spectrum modulate digital data signals (21) and address said data signals and means (24) to connect the baseband modulated signal to the highway and each receiver includes means (26)-(29) to selectively demodulate the respective addressed signals from the received signal to reconstitute the data signals, the arrangement being such that multiple simultaneous data signals can be connected to the highway. Direct sequence spread spectrum modulation is preferably employed using a selected code from a family of orthogonal codes. Each code then forms a node or area address, enabling a variety of communications to be achieved eg point-to-point, broadcast, selected area, priority etc. The received signal is oversampled (110), (113) and converted to a binary signal to derive the received sequence and synchronise receiver clocks. Each receiver may include a stack (53) of address codes which are sequentially placed in a sliding polarity correlator (114) through which the received sequence is passed. Means may be provided to change the length of the code sequences in dependence on the number of current users.</p> |
