Two-dimensional half-plane recursive filter design

This paper describes a technique for designing two-di mensional (2-D) recursive digital filters with an infinite impulse response which is a "one-sided" array, according to the most general form for a recursive system. If we confine the impulse response to a triangular sector of the half-plane, it is possible to design such filters (?) by using a simple variable transformation starting from a classical one-quadrant recursive interpolated filter. With a slightly increased number of coefficients it is possible to get very good frequency responses in terms of amplitude and phase specifications. Several examples are presented in order to illustrate the method and to compare it with existing techniques.