ECHO CANCELLATION SYSTEM AND ITS METHOD, AND MOBILE COMMUNICATION EQUIPMENT

PROBLEM TO BE SOLVED: To provide an echo cancellation method that employs especially two filters used for a telephone system. SOLUTION: This system uses two adaptive filters, that are, a main filter 10 and a background filter 50. The purpose of the background filter 5 is to ensure a model of the main filter 10 to be in a correct state. A main filter coefficient and a background filter coefficient are updated by various conditions and residual signals (L- RES1, LRES2) generated by each filter are compared. A set of filter coefficients used to generate an output signal (S- OUT) of an echo canceller is selected based on the comparison of the residual signals. The set of the filter coefficients is selected by copying a background filter coefficient to the main filter 10 or replacing a function of the background filter 50 with a function of the main filter 10.