Echo canceller

Details Echo canceller Echo canceller

1994-02-14

1996-03-19

Hofsass, Jeffery A.

Telephonic communications

Repeater

Component processes bidirectional signals

379402, 379406, 379410, H04B 323

Patent

active

055008925

ABSTRACT:
Analog signals representing individual digital values (+3, +1, -1, -3) of data pass through a telephone line to a receiver. These signals may first be provided in a pseudo random sequence. A linear echo canceller and a first adder at the receiver simultaneously eliminate, to some extent, echo signals resulting from second analog signals transmitted through the telephone line by the receiver. A non-linear echo canceller and a second adder further significantly reduce the echo signals and specifically reduce non-linear components in the echo signals. Adjustable signal delays achieve optimal performance of the linear and non-linear echo cancellers. In one inventive embodiment, each echo canceller includes a memory which stores, for each terminal in such echo canceller, data representing (a) the pseudo random sequence and (b) coefficients for adjusting the signals in such sequence. Such data for each terminal in such echo canceller is recorded in the memory for introduction to the next terminal in the memory. For each terminal in such echo canceller, the signals representing the data for the coefficient and the output from the associated adder are processed to determine an adjusted value of such coefficient for storage in the memory and for use in the next cycle of processing. The adjusted coefficient value and the data stored in the memory for such terminal are processed to produce signals for introduction to the associated adder. The signals from the second adder are processed to restore the data transmitted through the telephone line to the receiver.

REFERENCES:
patent: 4677668 (1987-06-01), Ardalan et al.
patent: 4686703 (1987-08-01), Bruno et al.
patent: 4771463 (1988-09-01), Beeman
patent: 4782525 (1988-11-01), Sylvain et al.
patent: 5148427 (1992-09-01), Buttle et al.
patent: 5272695 (1993-12-01), Makino et al.
patent: 5371789 (1994-12-01), Hirano

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