| 摘要 |
<p>A method and apparatus cancels an echo by using an echo replica generated such that a tap coefficient of an adaptive filter is sequentially updated, the echo being received from a transmitting end to a four-wire side through a two'four wire converter and being obtained such that a pulse signal having positive and negative polarities is fed into a receiving end, wherein a difference signal (error signal) between the echo replica and a reception signal is calculated: a correlation value between a signal representing a polarity of the error signal and a signal representing a polarity of the echo replica is calculated: when the correlation value is smaller than a predetermined value, a first of two types of tap coefficients which belong to each of a plurality of taps is updated based on at least the error signal and is set as the tap coefficient of the adaptive filter during a period in which the pulse signal is set in the positive polarity, and a second type of tap coefficient is updated based on at least the error signal and is set as the tap coefficient of the adaptive filter during a period in which the pulse signal is set in the negative polarity; and when the correlation value is larger than the predetermined value, the first and second types of tap coefficients are updated irrespective of the polarity of the transmission pulse on the basis of the error signal.</p> |
