| 摘要 |
Carrierless signals of first and second channels pass via filters having quadrature responses and are then added for transmission. A receiver uses adaptive filters (4, 5) which also need quadrature responses to separate the channels effectively. To accommodate misconvergence of the filters giving rise to (a) inverted responses, (b) differential delays, (c) similar or identical responses and/or (d) transposed responses, and hence incorrect decoding: (a) the transmitter and receiver may employ differential coding (25-32) in each channel, (b) the receiver may calculate (33) the group delay of its filters and correct any error, (c) the receiver may compare (34) the filtered signals and if similar replace one filter response with a quadrature response calculated (39) from the other and/or (d) the receiver may respond to a failure to recognize (43, 44) expected synchronization words by transposing (45, 46) the responses of the filters. |
