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Two-dimensional IIR filter design using prototype biquad transformation

In this work an analytical design method for two types of 2D recursive filters is proposed. One class of filters approached here are orientation-selective filters with a narrow frequency response along a direction in the frequency plane specified by a given angle. The other type refers to circularly-symmetric filters. The design is based on 1D IIR digital prototype filters with a given transfer function factorized into biquad functions. Applying specific frequency transformations to the biquad sections, the desired 2D filters are obtained, which are very efficient and preserve the selectivity properties of their 1D counterparts.