Telephonic communications – Subscriber line or transmission line interface – Network interface device
Patent
1993-06-09
1994-10-25
Dwyer, James L.
Telephonic communications
Subscriber line or transmission line interface
Network interface device
379406, 379407, 379411, 379390, 379402, 379391, 379392, H04M 900
Patent
active
053596560
ABSTRACT:
An adaptive echo cancellation apparatus disclosed herein has three channels and a channel selection circuit. The first channel serves to block an outgoing digital signal from flowing to a transceiver. The second channel is used to directly couple the outgoing digital signal to the transceiver. The third channel serves to subtract a predicted echo signal, estimated by using the incoming digital signal, from the outgoing digital signal and to couple an error signal, representative of the difference therebetween, to the transceiver. The adaptive channel selection circuit is used to select one of the channels depending on the presence of the valid outgoing and incoming digital signals in order to effectively reduce the estimation operation. Further, the third channel is provided with a filter wherein the filter coefficients are adaptively updated by using the signs of a predetermined number of samples, thereby achieving a considerable reduction in the computational complexity.
REFERENCES:
patent: 4007341 (1977-02-01), Sourgens et al.
patent: 4633046 (1986-12-01), Kitayama et al.
patent: 5042026 (1991-08-01), Koike et al.
patent: 5131032 (1992-07-01), Esaki et al.
Daewoo Electronics Co. Ltd.
Dwyer James L.
Pinsak William F.
Saint-Surin Jacques M.
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