System and method for echo cancelling and mobile communications device

摘要

The invention relates to echo cancelling methods used in telephone systems, more specifically to echo cancelling methods based on two filters. The echo cancelling method according to the invention employs two adaptive filters, namely, a main filter (10) and a background filter (50). The purpose of the background filter (50) is to make sure that the main filter (10) model stays correct. The main and background filter coefficients are updated on different conditions, and the residual signals (L-RES1, L-RES2) produced by the filters are compared to each other. The set of filter coefficients used for generating the echo canceller's output signal (S-OUT) is selected on the basis of said comparison of the residual signals. The selection of the set of filter coefficients is carried out either by copying the background filter coefficients to the main filter or by interchanging the background and main filter functions. Operation of the echo canceller in a double talk situation is enhanced by comparing the residual signals produced by the two filters frequency band by frequency band, thus avoiding errors caused by echo-resembling correlations caused by random loud sounds in double talk situations.