| 摘要 |
<p>A digital echo canceller has a receive path (2) and a send path (3) and comprises combining means (10) for forming a send output signal [r(k)] as the difference between the signal [z(k)] applied to the send input (SI) and a replica signal [ê(t)] used for cancelling an additive echo signal [e(k)] at the send input (SI) that has developed in response to a receive input signal [x(k)] applied to the receive input (RI), which echo canceller at least includes transforming means (13,15) for transforming the receive input signal [x(k)] and the send output signal [r(k)]; transforming means (14) for transforming the replica signal [ê(k)]; a digital adaptive filter (9) which has a number of filter coefficients for generating the replica signal [ê(t)] in response to the receive input signal [x(k)] and the send output signal [r(k)], adaptation means (12) for determining for each block m, adaptation components [A(p;m)] for each of the filter coefficients [W(p;m)] in response to the receive input signal [x(k)] and the send output signal [r(k)]; controllable gate means (17) for selectively passing the adaptation components [A(p;m)] to the adaptive digital filter (9); control means (25-18, 21-24, 16) for determining respective levels of the send output signal [r(k)] and the receive input signal [x(k)] and for generating a control signal for the gate means (17) in response to the levels thus determined, which control signals depend in a predetermined manner on the difference between the levels concerned. The control means (21-28, 16) and gate means (17) operate in the frequency-domain if the transforming means (13, 15, 14) perform an N'-point DOT or N'-point IDOT of each block m of N' points and determine for each of the N' frequency-domain points a separate control signal in dependence on the respective levels of the receive input signal [x(k)] and the send output signal [r(k)] for the frequency-domain point concerned. <IMAGE></p> |
