2D IIR filters with square-shaped frequency response

This paper proposes an analytical design method for 2D IIR filters with square-shaped frequency response. The design relies on an analog 1D maximally-flat low-pass prototype filter. To this filter a frequency transformation is applied, which yields a 2D filter with a square shape in the frequency plane. The proposed method combines the analytical approach with numerical approximations. Since the prototype transfer function is factored into biquad functions, the 2D filter will also result with a factored transfer function, which is an advantage in implementation.