IIR multiple notch filter design based on allpass filter

In this paper, real coefficient IIR notch filter design problem is investigated. The specification of notch filter is first transformed into that of allpass filter. Then, we develop an effective approach to design this desired allpass filter. The realization of 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 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.