Process and device for adaptive digital cancellation of the echo

Details Process and device for adaptive digital cancellation of the echo Process and device for adaptive digital cancellation of the echo

1993-02-23

1995-05-09

Dwyer, James L.

Telephonic communications

Subscriber line or transmission line interface

Network interface device

379406, 379411, 379345, 370 321, H04M 908

Patent

active

054147662

ABSTRACT:
An echo cancellation device usable in telephone connections affected by phase-roll is described. The canceller calculates the echo path propagation delay and produces an estimate of the echo signal by digitally filtering the signal originated by the far-end talker. The echo estimate is then subtracted from the actual echo to eliminate listening disturbances. The filter used is of the FIR type with adaptive coefficients updated iteratively by adding algebraically, to the values which they had upon the preceding iteration, a correction term proportional to the estimate error. The frequency of the coefficient updating iterations is a multiple of the rate f.sub.c of acquisition of the voice and echo samples by the canceller.

REFERENCES:
patent: 4736414 (1988-04-01), Montagna et al.
patent: 4813073 (1989-03-01), Ling
patent: 4887258 (1989-12-01), Belloc et al.
patent: 4965786 (1990-10-01), Salle
patent: 5132963 (1992-06-01), Ungerboeck
"Digital Signal Processing Theory, Application, And Hardware", by R. A. Haddad et al, pp. 203-212.
"Digital Processing of Signals, Theory and Practice", by M. Bellanger, Book by John Wiley & Sons, pp. 298-300.

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