IIR multiple notch filter design based on allpass filter

A real coefficient IIR notch filter design problem is investigated. The notch filter specification is first transformed into that of an allpass filter. Then, we develop an effective approach to design this desired allpass filter. The realization of the proposed notch filter is equivalent to the realization of an allpass filter. Due to the mirror-image symmetry relation between the numerator and denominator polynomials of the allpass filter, the notch filter can be realized by a computationally efficient lattice structure with very low sensitivity. Moreover, some design and application examples are presented to examine the effectiveness of proposed method