Loop gain processing system for speakerphone applications

Abstract

A loop gain processing scheme for a speakerphone arrangement determines system loop gain according to two echo feedback paths within the speakerphone system. Gain values for each half-loop are calculated separately to ensure that both the local and far end telephone or speakerphone system are stable. A first half-loop includes gain contributions from a feedback path extending from a local speakerphone microphone to a hybrid line interface, which couples the speakerphone to the telephone network line, and subsequently to a local loudspeaker. A second half-loop defines a feedback path from a line receive channel to a transmit channel. Gain contributions are input into a system controller which determines gain values for each of the half-loops to accurately set the proper gain switching mode.