Design of 2-D IIR filters using a new digital spectral transformation

A Digital Spectral Transformation (DST) has been proposed for the design of 2-D IIR digital filters with a circular and an elliptical region for the passband region of the lowpass filter. This method guaranteed stability of the 2-D filter and did not resort to tedious optimization techniques. The same DST can be used to approximate the constant group delay response. In this paper, a new DST is proposed to design these filters using the same design procedure but it yields a significantly smaller value for the error in the approximation to the circular and elliptical contours in the ω₁-ω₂ plane. Some illustrative examples are included