| 摘要 |
An apparatus is disclosed for use as a first station in a network for transmitting and receiving digital data signals. The apparatus comprises a physical layer interface (PLC) for using twisted pair cable in place of optical fibre. The interface comprises a phase shift keying (PSK) encoder (310) and decoder (306) for transmitting and receiving data (TXD/RXD) to and from at least one other station each station including a similar encoder and decoder. The encoder comprises: means for receiving said digital data in the form of an encoded serial data signal together with at least one binary clock signal, the clock signal frequency being a small integer multiple of the data rate; means (402) for synchronising said digital serial data and said binary clock signal such that transitions in the one are aligned with transitions in the other; an encoding logic circuit (404) responsive to said digital serial data signal for selectively outputting one of said binary and the inverse thereof dependent on said serial data signal, so as to generate a PSK encoded binary waveform (Z); and driver means (406-416) for smoothing said encoded binary waveform and imposing the smoothed waveform (Z') on said conductors in the form of an analogue differential signal pair (TX/nTX). The decoder comprises a differential integrator circuit (504+/504-), to decode such a PSK waveform so as to recover the digital serial data waveform. Various slew rates and decoder time constants are adjustable to suit different data rates. Decoder and encoder can operate synchronised but at different data rates. |
