Design of 2-D linear phase IIR filters by using all-pass building blocks

Complementary filters are driven by using two 1-D all-pass functions. A structure of this kind employs a low sensitivity property. This structure is also computationally efficient. An extension of the 1-D structure to the 2-D structure is presented. It consists of the cascade sum of two 2-D all-pass building blocks with appropriate delay elements. Filters with the various cut-off boundaries can be designed by changing the parameters of the proposed structure. These parameters can be adapted from the table given. The coefficients of the all-pass blocks are obtained via an iterative nonlinear optimization technique. The objective function of the optimization program consists of the magnitude and the group delay error functions, resulting in a fairly linear phase filter in the passband with a specified magnitude shape.