Design of digital recursive notch filter with linear phase characteristic

A new method for design of recursive digital notch filter with linear phase is described in this paper. Obtained filter is realized using parallel connection of delay line and IIR all-pass filter. The resulted amplitude characteristic in all pass-bands is equiripple. Coefficients of the obtained filter are calculated by approximation of all-pass ideal linear phase characteristic. The efficiency of the proposed algorithm is demonstrated on a few examples. The algorithm exhibits a fast convergence and an easy determination of initial values.