| 摘要 |
Echo canceller for use in a homochronous data transmission system, comprising two-wire and four-wire connections and arranged for suppressing echo signals occurring in the four-wire connection. This echo canceller comprises an adjustable signal processing arrangement to which the data signal to be transmitted is applied and which produces a synthetic echo signal. A signal formed by a received data signal and an echo signal is present in the receive path of the four-wire connection. To generate a residual signal, the synthetic echo signal is subtracted from the signals in the receive path. For the adjustment of the signal processing arrangement there is added to this residual signal, outside the receive path of the four-wire connection, an auxiliary signal which is not correlated to this residual signal. The sum signal thus obtained is sampled with a suitably chosen sampling rate which is harmonically related to the symbol rate. The signal samples obtained are applied to a limiter circuit which converts each signal sample into a positive or a negative pulse, which is indicative of the polarity of the signal sample. The pulses thus obtained are applied as the control signal to an adjusting device for adjusting the signal processing arrangement. |
