PARAMETRIC IIR FILTER DESIGN METHOD BASED ON ARBITRARY MAGNITUDE SPECIFICATION
Original Publication Date: 1996-Nov-01
Included in the Prior Art Database: 2002-Apr-30
The purpose of the algorithm described in this paper is to design an IIR filter network which matches an arbitrary tiequency response, based on a user spec- ification, with minimal number of IIR sections. Since the goal is to use a minimum number of second order IIR sections, while maintaining a minimum error between the actual response and specification, the result approximates a minimum cost implemen- tation. Use of the IIR parametric filter [l] avoids stability and coefftcient scaling problems. Step 1 is an iterative error minimization process for obtaining an initial magnitude lit which agrees with the user specification. Reduction of the IIR filter network horn N fixed bands to M parametric bands, where M c N, makes up Step 2. Finally, Step 3 utilizes the Steepest Descent Method to minimize the error between actual response and the user specification. This procedure optimizes the complex frequency response (magnitude and phase) by finding the approximate location of the minimum on a multi- dimensional error surface. Minimiition is performed using the parametric IIR form (with respect to each section's center frequency, gain level and Q-factor). An example application of this would be to reduce the number of bands in a N section, lixed band equal- izer to an M section, parametric band equalizer, where again M < N.