On lowpass and highpass IIR filters with an adjustable bandwidth
Håkan Johansson · 2003
Abstract – This paper deals with adjustable-bandwidth digital lowpass and highpass IIR filters obtained from a lowpass prototype filter via frequency transformations. Starting with adjustable-bandwidth filter specifications, including requirements on passband and stopband edges as well as on passband and stopband ripples, it is shown how to select the prototype filter and how to perform the frequency transformations so as to ensure that all specifications can be satisfied. Traditionally, only one cutoff frequency has been controlled when using such transformations. 1