PURPOSE: To simplify the hardware configuration of a complete re-configuration filter bank by using an FIR filter whose filter coefficient is the unity so as to form the complete re-configuration filter bank so as to reduce number of multipliers required for filter processing.

CONSTITUTION: An input signal X(n) is inputted from a signal input terminal 30 in a division section 1 and given respectively to a low pass filter 11 and a high pass filter 21 through signal lines 31, 41, in which the signal is subject to filter processing. The processing is executed based on the convolution arithmetic operation of equation shown in figure, where h(n) indicates a filter coefficient and N is number of coefficients. Since most of coefficients of the designed filter are the unity, it is not required to round a coefficient word length and then the complete re-configuration filter is obtained in which a stable characteristic is less susceptive to a round error of the coefficient word length. Since the filter is formed with less number of multipliers, the hardware configuration is simplified.