Design and Realization of Variable IIR Digital Filters as a Cascade of Identical Subfilters

摘要

A new approach to design variable IIR digi- tal filters by using a cascade of N identical individual filters of any order n is proposed in this paper. First, the approxi- mation method for lowpass filter specifications is outlined, then the general limitations of the new method are investigated and a compact formula is derived. Next, the limitations for the main canonic approximations (Butterworth, Chebyshev and Elliptic) are investigated and compared and convenient expressions for design and evaluation are obtained.