McClellan transformation for two-dimensional IIR digital filter design

The McClellan transformation is extended to the design of two-dimensional zero-phase and causal IIR (infinite impulse response) digital filters. In the case of a circularly symmetric contour, explicit conditions for a certain globally type preserving property are given, where the corresponding extended McClellan transformation is consequently of the so-called scaling-free form. Examples for circularly symmetric and elliptical contours are presented. A comparison with other McClellan transformations shows the advantages of the extended transformation for the approximation of a given contour.<>