Telephonic communications – Subscriber line or transmission line interface – Network interface device
Patent
1991-04-04
1994-01-11
Dwyer, James L.
Telephonic communications
Subscriber line or transmission line interface
Network interface device
379411, 379406, 379390, 370 321, H04M 908
Patent
active
052789004
ABSTRACT:
A digital echo canceller has a receive path (2) and a send path (3) and comprises combining apparatus (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 [e(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 apparatus (13, 15) for transforming the receive input signal [x(k)] and the send output signal [r(k)]; transforming apparatus (14) for transforming the replica signal [e(k)]; a digital adaptive filter (9) which has a number of filter coefficients for generating the replica signal [e(t)] in response to the receive input signal [x(k)] and the send output signal [r(k)], adaptation apparatus (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 apparatus (25-28, 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 apparatus (17) in response to the levels thus determined, which control signals depend in a predetermined manner on the difference between the levels concerned.
REFERENCES:
patent: 4894820 (1990-01-01), Miyamoto et al.
patent: 4903247 (1990-02-01), Van Gerwen et al.
patent: 4951269 (1990-08-01), Amano et al.
Mansour et al., "Unconstrained Frequency-Domain Adaptive Filter" IEEE Trans., Acoustics, Speed & Signal, vol. ASSP-30, No. 5 Oct. 1982, pp. 726-734.
Kellerman, "Kompensation akustischer Echos in Frequenzteilbandern", Frequenz 39 (1985) 7/8 pp. 209-215.
Clark et al, "Unified Approach to Time-and Frequency-Domain Realization of FIR Adaptive Digital Filters", IEEE Trans Acoustics, Speech . . . , Oct. 1983 pp. 1073-1083 ASSP.31, No. 5.
Kotmans Hendrik J.
van de Laar Franciscus A. M.
van Gerwen Petrus J.
Barschall Anne E.
Dwyer James L.
Fournier Paul A.
U.S. Philips Corporation
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