An analog-digital adaptive echo canceller for hybrids

Adaptive hybrids can cancel the echoes in telephone systems. Since the ratio of the far-end and the local speaker´s signal level can be very high, the quantization effects of the analog-digital converters can diminish the speech signal´s quality additional to the echo. A new analog-digital solution is proposed to overcome the problem. Since the error path transfer function can mainly be constructed as a pure delay, a least mean-square algorithm with delayed update (DLMS) is used to find the optimal echo estimator