PURPOSE: To enable the quick convergence of a seeking filter coefficient by restricting the updating of the filter coefficient to an erroneous direction.
CONSTITUTION: An adaptive digital signal processor is provided with an adaptive system 14 estimating an unknown system, a difference calculating means 16 calculating the difference of the adaptive system as against the unknown system and a coefficient updating means 13 updating the filter coefficient of the adaptive system through the use of difference calculated by the difference calculating means and set step gain. The processor is provided with a step gain setting means 17 which sets a step gain value to be the one with which the filter coefficient is not substantially updated when the absolute value of the output of the adaptive system is more than a threshold value and sets the step gain value to be the value with which the filter coefficient is updated when the absolute value is less than the threshold value. When the absolute value of the output of the adaptive system is more than the threshold value and difference which causes the erroneous updating of the filter coefficient seems to be added in the output, the step gain setting means sets step gain to be zero, stops the updating of the filter coefficient and evades the updating of the filter coefficient to the erroneous direction.
UESUGI MITSURU
IGAI KAZUNORI
