Approximation of complex-valued 2-D frequency response specifications by separable-denominator digital filters

In this paper the approximation of a complex-valued specification by the frequency response of a 2-D IIR separable-denominator (SD) digital filter is considered. The approximation problem is transformed into an equivalent one, where a real-valued 2-D IIR SD digital filter with some additional characteristics has to be determined that approximates a given real-valued 2-D FIR digital filter. A theorem is presented that helps to reduce the number of parameters in the FIR-to-IIR approximation problem and a procedure to solve the problem numerically is given