Nonlinear Echo Cancellation Based on Polyphase Filter Bank

Abstract

In hands-free telephone systems and mobile communication devices, it is often desirable for the devices to operate at large sound volume, which can result in obvious nonlinear acoustic echoes due to overload of small loudspeaker. These nonlinear echoes can't be fully eliminated by linear AEC (Acoustic Echo Cancellation) algorithm, so the conversation quality is affected seriously. Since the nonlinear echoes contain additional harmonics in high frequency, which breaks the linear relation required for fullband linear AEC, these harmonics, however, becomes additive noise in subband system. Therefore, in this paper, a subband AEC method based on polyphase filter bank is proposed. It is found that ERLE (Echo Return Loss Enhancement) of the proposed method outperforms the fullband counterpart constantly in nonlinear situation, especially with tone-like signals, where ERLE improves more than 15 dB. The results are validated through both simulation and real signals.