Echo control system

Abstract

An echo control system for an adaptive echo canceller which cancels an echo signal while successively estimating the transmission characteristic of an echo path by the use of a received signal and the echo signal, comprising means using the received signal of a predetermined duration for obtaining an autoregression coefficient in a case of using the received signal as the output of an autoregressive model, means for obtaining a difference signal between a predicted value of the received signal produced by using the autoregression coefficient and the received signal, means for obtaining a difference signal between a predicted value of the echo signal produced by using the autoregression coefficient and the echo signal, a memory for storing the estimated transmission characteristic of the echo path, and a corrector for correcting the content of the memory following an identification method by learning. The content of the memory is successively corrected by the corrector on the basis of the difference signal of the received signal and the difference signal of the echo signal. An echo replica is produced using the successively corrected estimated transmission characteristic and is used to subtract it from the true echo signal, thereby cancelling the echo signal.