Patent ID: 6404832
Filing Date: 2002-06-11
Classification: H03H

Abstract:
A filter device comprising:first means for receiving data of a desired cutoff frequency; second means for deciding whether the desired cutoff frequency is in a predetermined low frequency band or a predetermined high frequency band, the predetermined low frequency band being lower in frequency than the predetermined high frequency band; third means for storing data of filter coefficients corresponding to different cutoff frequencies in the predetermined low frequency band; fourth means for storing data of precalculated basic coefficients corresponding to different cutoff frequencies in the predetermined high frequency band, the precalculated basic coefficients being equal to values resulting from a part of calculation to provide final filter coefficients; fifth means for calculating final filter coefficients from precalculated basic coefficients through a coefficient expanding process; a filtering section; sixth means for, in cases where the second means decides that the desired cutoff frequency is in the predetermined low frequency band, reading out data of filter coefficients corresponding to the desired cutoff frequency from the third means, and setting the data of the filter coefficients corresponding to the desired cutoff frequency in the filtering section; and seventh means for, in cases where the second means decides that the desired cutoff frequency is in the predetermined high frequency band, reading out data of precalculated basic coefficients corresponding to the desired cutoff frequency from the fourth means, causing the fifth means to calculate final filter coefficients from the read-out precalculated basic coefficients, and setting data of the calculated final filter coefficients in the filtering section.