Method and device for designing digital filter,program for designing digital filter,digital filter,method and device for generating numerical sequence of des

摘要

A standard function is inputted and an interpolation function of finite length is calculated therefrom. Then, the frequency characteristics of the interpolation function is shifted by a desired amount in the frequency axial direction, thereby determining input frequency characteristics based on specification. Filter coefficients are determined by performing inverse FFT of a numerical sequence representative of the input frequency characteristics and rounding is performed according to the coefficient values in order to obtain a smaller number of filter coefficients. Thus, it is possible to eliminate the need for windowing as an operation for decreasing the number of filter coefficients and easily design an FIR filter having desired frequency characteristics.