An efficient technique for the design of 2-D IIR digital filters with symmetry and constant group delay

A computationally efficient technique is developed for the design of two-dimensional (2D) recursive digital filters that meet simultaneously magnitude and phase specifications. A quadrantal symmetry which exists in the 2D frequency response is incorporated into the 2D filter structure. The denominator and the numerator of a 2D transfer function are designed individually: the former is used to approximate the constant group delays and then the latter is used to approximate the overall magnitude response. The filter design is analytically feasible by solving linear equations. These serve to reduce the amount of calculations drastically. The stability of the resulting filters is always guaranteed. Two examples are given to illustrate the utility of the proposed technique