Calculation of filter factors for digital filter.

摘要

An apparatus for calculating a filter factor for a digital filter which can be made with a simple construction and in which the time period for calculation can be shortened as compared with conventional techniques. The apparatus comprises an inputting circuit (1) for inputting a desirable frequency property, a division circuit (2) for dividing the inputted frequency property into a plurality of frequency bands, and a calculating circuit for obtaining filter factors for realizing a frequency property of each of the divided frequency bands. The inputting circuit inputs the frequency property with a frequency resolution corresponding to the number of the filter factors. The division circuit performs a correction for a division so that the frequency property becomes zero from a frequency over the high cut-off frequency of a band-pass filter toward the Nyquist frequency of the frequency band corresponding to the transversal filter, the Nyquist frequency being 1/2 of the sampling frequency. The calculating circuit has a transformation unit (3) for performing a Hilbert transformation or a linear phase transformation with respect to the respective frequency properties divided by said division means.