COMPLEX NOTCH FILTER DESIGN USING ALLPASS FILTER

Complex coefficient IIR notch filter design problems are investigated. The specification of a notch filter is first transformed into that of an allpass filter. An effective approach to the design of this desire d allpass filter is developed. The realisation of the proposed notch f ilter is equivalent to the realisation of an allpass filter. Owing to the mirror-image symmetry relation between the numerator and denominat or polynomials of allpass filters, the notch filter can be realised by a computationally efficient lattice structure with very low sensitivi ty.