Adaptive echo canceller for full-duplex transmission of data

Details Adaptive echo canceller for full-duplex transmission of data Adaptive echo canceller for full-duplex transmission of data

1980-06-23

1982-10-19

Popek, Joseph A.

H04B 324

Patent

active

043552145

ABSTRACT:
An echo canceller for a full-duplex carrier modulation transmission system terminal. The echo canceller includes a digital time-domain complex transversal filter with controlled weighting coefficients and an offset equal to a submultiple l of a Baud period .DELTA. related to a rate at which a stream of complex symbols is received at the input of the filter. These complex symbols include complex symbols outputted by a coder of a transmitter of the terminal at the rate l/.DELTA. interleaved with l-1 null symbols. The transversal filter output is connected to a digital modulator operated at the transmitter carrier frequency with instantaneous values updated at intervals equal to the Baud period to generate a passband echo copy signal. The invention is of particular benefit in transmission systems in which the product of the transmission carrier frequency and the Baud period is an integral multiple of l/4, as digital implementation of the modulator is then extremely simple.

REFERENCES:
patent: 4087654 (1978-05-01), Mueller
patent: 4117277 (1978-09-01), van den Elzen et al.
patent: 4162378 (1979-07-01), Baudoux et al.
Stephen B. Weinstein, "A Passband Data-Driven Echo Canceller for Full-Duplex Transmission on Two-Wire Circuits", IEEE Transaction on Communications, vol. COM-25, No. 7, Jul. 1977, pp. 654-666.
L. E. Zegers et al., "Digital Signal Processing and LSI in Modems for Data Transmisson", Philips Journal of Research, vol. 33, No. 5/6, 1978, pp. 226-247.
A. Tannhauser et al., "Aspects of Digital Signal Processing in Voice Band Modems", IEEE Conference Record 1978, National Telecommunications Conference, vol. 3, Dec. 3-6, 1978, pp. 46-6-1 to 46-6-4.
J. R. Berland et al., "Choix et Definition d'un Egaliseur automatique adaptatif pour Modem a 9600 bits/sec", Proceedings of the International Seminar on Digital Communications, Mar. 12-15, 1974, pp. H.sub.5 (1) to H.sub.5 (6).

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