IIR digital filter design via orthogonal projection of singular perturbational model reduction

In this paper, a novel state-space approach for model reduction of FIR digital filters is proposed. The method is based on the initial IIR filter obtained by the singular perturbational model reduction, and then utilizes the iterative algorithm via orthogonal projection under a different stop criterion to search a better result in L₂ norm sense. A lowpass filter example is designed to compare the performance of the proposed method and the singular perturbational model reduction in terms of frequency response and approximation error under the same reduced order. Results indicate that the proposed technique achieves comparable performance with much lower L₂ norm error than the singular perturbational model reduction.