Design of IIR notch filterswith maximally flat or equiripple magnitude characteristics

This paper presents the design of IIR (Infinite Impulse Response) notch filters with desired magnitude characteristic, which can be either maximally flat or equiripple. Butterworth polynomial, used for designing the allpass filter, will result in a maximally flat magnitude. Similarly, an equiripple characteristic is obtained by using Chebyshev I, Chebyshev II and Elliptic polynomials. The parameters of the design are notch frequency, rejection bandwidth and passbands ripple.