Abstract: An echo canceller includes receive and send paths each having an input and output port, a first non-adaptive filter with first filter coefficients for generating a first replica signal in response to a receive input signal, a second adaptive filter with second filter coefficients for generating a second replica signal in response to the receive input signal, a first subtracter for generating a send output signal representing a difference between a send input signal and the first replica signal, a second subtracter for generating an error signal representing a difference between the send output signal and the second replica signal, and a controller for replacing the first filter coefficients by the sum of the first and second filter coefficients and for resetting the second filter coefficients in response to a calculation that includes a first quantity associated with the send output signal and a second quantity associated with the error signal.

Abstract: An echo canceller system includes first and second echo cancellers. Each echo canceller includes a foreground filter and an adaptive background filter, with the foreground filter providing the actual echo cancellation and the background filter updating the foreground filter. The echo canceller system also includes send and receive paths, a shared coefficient memory, and a controller for switching the shared coefficient memory between background filters in response to signals along the send and receive paths. The switching includes resetting the shared coefficient memory to prevent any transfer of filter coefficients between the background filters. The background filters operate one at a time, depending on which background filter has access to the shared coefficient memory, while the foreground filters operate simultaneously.