Echo canceller employing dual-h architecture having improved non-linear echo path detection

Abstract

An echo canceller circuit for use in an echo canceller system is set forth that provides sensitive non-linear echo path response detection. The echo canceller circuit comprises a first digital filter having non-adaptive tap coefficients to simulate an echo response occurring during a call. A second digital filter having adaptive tap coefficients to simulate an echo response occurring during the call is also used. The adaptive tap coefficients of the second digital filter are updated over the duration of the call. A coefficient transfer controller is disposed in the echo canceller circuit to transfer the adaptive tap coefficients of the second digital filter to replace the tap coefficients of the first digital filter when a set of one or more transfer conditions is met. A non-linear echo path response detector is provided. The non-linear echo path detector is responsive to one or more parameters of the first and second digital filters to detect a non-linear echo path condition. In accordance with one embodiment of the present invention, the non-linear echo path detector is responsive to a transfer density value corresponding to a number of transfers executed by the coefficient transfer controller. In accordance with a further embodiment of the present invention, the non-linear echo path detector is responsive to a coefficient time dispersion characteristic of the second digital filter for detecting a non-linear echo path condition.