Digital linear phase notch filter design based on IIR all-pass filter application

A new procedure for design of linear phase IIR notch filters is presented in this paper. Resulted filter is realized using parallel connection of two IIR all-pass filters with approximately linear phase. Adequate amplitude characteristic is obtained by approximation of all-pass filter phase. Amplitude characteristic satisfies all prescribed demands but it is not equiripple no matter both all-pass filters have equiripple phase. Algorithm exhibits fast convergence and easy initial values determination.

► We proposed method for design of notch filter with linear phase in the pass-band. ► Two IIR all-pass filters in parallel branches are used for realization instead of delay line. ► Design of multiple notch filters is possible using this method.