DIGITAL FILTER DESIGNING METHOD AND DESIGNING DEVICE

摘要

A digital filter having desired frequency characteristics can be designed through an extremely simple processing. A basic filter has a passing bandwidth equal to a sampling frequency divided by an integer. Frequency shift operation is performed on the basic filter so as to generate a plurality of filters where the frequency/amplitude characteristics of the basic filter are shifted by a predetermined frequency so that adjacent filter banks are overlapped at the part of a one half amplitude. One or more filters are selected arbitrarily among the basic filter and the plurality of frequency-shifted filters and the filter coefficients thereof are added to obtain the final filter coefficient. What is required is only to select one or more desired filters among the basic filter and the plurality of frequenc-shifted filters generated therefrom and add the filter coefficients thereof.