Approximation of 2-D separable denominator recursive filters

After introducing a two-dimensional (2-D) model for the class of quarter-plane-causal, recursive and separable in denominator (CRSD) filters, a technique for approximating a given 2-D filter by a CRSD one is presented which also yields a model reduction procedure. Both the stability and minimality properties of the approximate model are explored. An example is also given to illustrate the proposed technique.