8 - Digital filter realizations

Abstract

Realization or implementation of the filter is the next stage of the filter design process after the coefficients of a digital filter have been determined. Realization is generally achieved through a structure that relates the input and output of the filter, illustrated by block diagrams. They are called filter structures. The blocks within these block diagrams can be implemented either as a piece of digital hardware or as a program to be executed by a digital signal processing (DSP) chip. There are several structures and forms by which FIR and IIR filters can be implemented, such as direct form, cascade form, parallel form, lattice structure, and frequency sampling structure. Considerations for the choice of a filter structure include ease of programming on a particular DSP chip, and the regularity of the very large scale integrated (VLSI) design. Some structures are more sensitive to (quantization) errors in the coefficients. In some cases, such as IIR filters, the stability of the filter may depend on an appropriate realization.