Chebyshev approximations for the direct design of 2-D quarter-plane IIR filters

The development of various direct design techniques for inherently stable, causal, recursive, two-dimensional (2-D) digital filters is described and illustrated by examples. These techniques center around the development of 2-D z-domain functions for use as arguments in the Chebyshev function, and provide for the design of low-pass, bandpass, and high-pass filters. The specifications that can be prescribed are passband ripple, filter order, and normalized passband position parameters. In addition to being inherently stable, the filters possess an approximately flat group delay in most of the filter´s passband, a feature necessary for most applications