Design of IIR digital filters using all-pass networks

This paper presents a new method of designing the generalized IIR digital filter in the form of a parallel connection of two all-pass filters. It is shown that the numerator of the overall transfer function of this form can be expressed as real function of the all-pass coefficients. Then Remez algorithm is applied to the numerator and the rational approximation problem is transformed into a linear problem. IIR digital filters with the desired specification can be directly designed in the z-domain by this method. The proposed algorithm converges through a few iterations, and the amplitude property of IIR digital filter has equiripple.<
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