Patent ID: 6697486
Filing Date: 2004-02-24
Classification: H04B

Abstract:
An echo canceler for canceling an echo resulting in a telephone line when part of a reception signal output from sending party end circles back to said sending party end through an echo path on receiving party end, comprising:an adaptive filter modulus computing system for estimating impulse response of said echo path by least mean square method, and outputting said estimated impulse response as an adaptive filter modulus; an adaptive filter for producing, and outputting, a pseudo-echo signal for said echo by convoluting said adaptive filter modulus and said reception signal; and an adder for canceling said echo by subtracting said pseudo-echo signal from said echo; wherein: said adaptive filter modulus computing system comprises: a duplex detector; a block length determinator; and an adaptive filter modulus computer; said duplex detector determines whether call status is simplex status, duplex status, call-transmission status, or non-calling status, when difference between said echo and said pseudo-echo signal is made echo remainder, logarithmic ratio between power of said reception signal and power of said echo remainder is made echo attenuation amount, and any predetermined target value for said echo attenuation amount is made desired echo attenuation amount; said block length determinator determines and outputs block length in said least mean square method so that said echo attenuation amount is ultimately made equal to or greater than said desired echo attenuation amount; and said adaptive filter modulus computer computes said adaptive filter modulus using said block length, said echo remainder, and said reception signal, and outputs said adaptive filter modulus to said adaptive filter.