DESIGN OF 2-D IIR DIGITAL-FILTERS WITH SYMMETRY AND CONSTANT GROUP DELAYS

A computationally efficient technique is developed for the design of t wo-dimensional (2-D) recursive digital filters that meet simultaneousl y magnitude and phase specifications. A quadrantal symmetry which exis ts in the 2-D frequency response is incorporated into the 2-D filter d esign. The denominator and the numerator of a 2-D transfer function ar e designed individually: the former is used to approximate the constan t group delays and then the latter is used to approximate the overall magnitude response. The filter design is analytically feasible by solv ing linear equations only. These serve to reduce the amount of calcula tions drastically. The stability of the resulting filters is always gu aranteed. Finally two examples are given to illustrate the utility of the proposed technique.