Telefonaktiebolaget Lm Ericsson (publ)

Gunnar A Eriksson

Tonu Trump

Johan G Meyer

Tommy E Svensson

Ingemar E Dalqvist

A single two-ended echo canceller is provided that uses an adaptive FIR filter to model the impulse response of the echo path and cancel the echo originating from the PSTN side of the connection, and a non-linear processor controlled by input signal levels to cancel the echo originating from the mobile phone side of the connection. Since the linear processing function is not used for cancelling echoes of the mobile phone side, the algorithms directed to estimating and cancelling echoes on the two sides of the connection can be executed in a single DSP, with all of the attendant advantages.

Method and apparatus for controlling echo on both sides of a connection

An interface circuit between a four wire line and a two wire line includes correlator and control circuit means connected for receiving a longitudinal signal (V.sub.1) and a transversal signal (V.sub.t) corresponding to a differential signal received on the terminals of a two wire interface from the two wire line. The correlator and control circuit includes a circuit for creating a correction signals being a measure of the correlation between the longitudinal signal and the transversal signal. The circuit for creating the correction signal is connected for using this correction signal to adaptively control the amplifications in feed back loops so as to minimize the correlation between the longitudinal and transversal signals.

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Huddinge, Sweden

Gunnar A Eriksson