Arrangement for full-duplex data transmission over two-wire circuits

Claim 1

An arrangement for full-duplex data transmission over a two-wire circuit, said arrangement comprising: a. a one-way transmit channel having an input for coupling with a baseband data transmitter and including a smearing filter; b. a one-way receive channel having an output for coupling with a baseband data receiver; c. a hybrid junction for interconnecting the transmit and receive channels and the two-wire circuit; d. an echo canceller comprising i. an adaptive filter with adjustable filter coefficients for generating an approximated echo signal from signals in the transmit channel; and ii. an adjusting circuit for adjusting the filter coefficients, in response to signals in the transmit channel and in response to a residual signal in the receive channel, so as to minimize a predetermined function of the residual signal, said adjusting circuit being coupled with a tapping point in said receive channel so as to receive the residual signal; and e. a combining circuit in the receive channel for differentially combining the approximated echo signal with incoming signals from the receive channel to generate the residual signal; f. first delay means in a first signal path which extends from an output of the data transmitter to the adjusting circuit; g. a complementary smearing filter disposed within the receive channel between the hybrid junction and said tapping point; h. second delay means in a second signal path which extends from the output of the data transmitter via the adaptive filter and the combining circuit to said tapping point, the first and second delay means creating a delay in the approximated echo signal so as to substantially compensate for a signal delay resulting from the cascade of the smearing filter and the complementary smearing filter; and whereby the complexity of the echo canceller is not affected by the presence of the smearing and complementary smearing filters.