IIR Variable Fractional Delay Digital Filter Design

In this paper, two methods for the design of IIR variable fractional delay (VFD) digital filters are presented. The two methods differ in the approaches to design an initial set of fixed IIR digital filters with different fractional delays. The first method formulates the design as a quadratic programming (QP) problem under the weighted least-squares (WLS) criterion. The stability constraints of IIR filters are based on argument principle. The second method utilizes the model reduction technique to design a set of fixed IIR filters. After fixed IIR digital filters are obtained, IIR filter coefficients are then approximated by polynomial functions. The main design steps of these two methods are described. Through two VFD digital filter examples, we present their design and comparison results with two recent methods