Design of two-dimensional pseudorotated digital filters satisfying prescribed specifications

Two methods for the design of two-dimensional (2-D) rotated digital filters proposed by Costa and Venetsanopoulos and Goodman are modified by performing rotation through a somewhat more general transformation. This modification eliminates nonessential singularities of the second kind, which can lead to an unstable 2-D digital filter when finiteprecision arithmetic is used for the implementation. The paper also describes detailed procedures for the design of 2-D rotated digital filters satisfying prescribed specifications. The procedures can be used for the design of low-pass, high-pass, bandpass, and bandstop filters of the Butterworth, Chebyshev, or elliptic type, and also for the design of wave digital filters. The specifications that can be prescribed are the maximum passband ripple, the minimum stopband attenuation, the passband and stopband edges, and the degree of circularity. Further, zero phase can readily be achieved.