DESIGN OF VARIABLE DIGITAL FILTERS BASED ON STATE-SPACE REALIZATIONS

This paper proposes a design method of variable IIR digital filters based on balanced realizations and minimum round-off noise realizations of digital filters. Highly accurate vari-able digital filters are easily derived by the proposed method. The coefficient matrices of both realizations of second-order digital filters are obtained directly from prototype realiza-tions. The filter coefficients of variable digital filters can be obtained by frequency transformations to the realizations. The filter coefficients are presented as truncated Taylor se-ries for the purpose of reducing a number of calculations to tune the coefficients. However the proposed filters have highly accurate variable characteristics against the coeffi-cient truncation since balanced realizations and minimum round-off noise realizations have very low coefficient sen-sitivities, which are invariant under the frequency transfor-mations. Numerical examples show the effectiveness of the variable digital filters designed by the proposed method. 1