A new structure for adaptive echo cancellation

A structure is proposed for adaptive removal of echoes from communications signals. It consists of an FIR adaptive filter which models the echoing channel, and an IIR programmable filter which performs the echo removal. This technique allows the use of a recursive filter without incurring the stability problems normally associated with adaptive fIR filters. The adaptive filter programs the weights of the recursive filter via a simple transform, which may in fact be incorporated in the adaptive process. Results of computer simulations are presented, showing convergence on PRBS sequences corrupted by echoing channels.