Echo canceller utilizing correlation

摘要

An echo canceller for cancelling echoes reflected from the receiving path of a long-distance telephone circuit to the sending path through a four-wire to two-wire coupling circuit, in which cross-correlation between the instantaneous level of a receiving signal in the receiving path and the instantaneous level of a sending path in the sending path is established in regular intervals in addition to the autocorrelation of the instantaneous level of the receiving signal. The impulse response of an echo return path from the receiving path to the sending path through the four-wire to two-wire coupling circuit is calculated by the use of the cross-correlation and the autocorrelation and then integrated to provide a convolution integral output. The convolution integral output is subtracted from the sending signal to cancel the echoes.