Complex Digital Filters Using Isolated Poles and Zeroes” www.waltzballs.org/ other/ engr/ fltr2.pdf

The simplest possible explanation is given of how to construct soft-ware digital filters with arbitrary pole-zero configuration and specified gain or loss. These filters simulate the simple behavior of analog filters. This kind of digital filter is the most appropriate for computer pro-grams that simulate the behavior of lumped physical systems, whether electrical, mechanical, or acoustical. It is also the most appropriate for some kinds of audio signal processing. Digital filters commonly accept a stream of real numbers as input and produce a stream of real numbers as output. In the case of simulation of electrical filters, this stream of real numbers represents samples of voltage going into and coming out of a hardware filter. Real linear lumped element analog hardware filters containing no dis-tributed elements like delay lines respond to signals in a way that can be described completely by an assortment of poles and zeroes and a scalar mul