A two-step design of 2-D zero-phase IIR filters

In this paper a method is presented to design 2-D IIR filters that approximate the more constrained zero phase condition. The denominator portion of the filter is designed first to meet specified magnitude characteristics and to be in the stable region. The numerator design then achieves the desired frequency response using the magnitude and phase characteristics of the denominator design. Both design stages use the Newton-based, N-step optimization technique presented in [7]. The initial parameter vector is always determined within the design process and is related to the desired magnitude response of the filter. This procedure guarantees the stability of the filter and hence, there is no need for a stability test after each iteration.