In §5.1 we defined the general difference equation for IIR filters, and a couple of secondorder examples were diagrammed in Fig.5.1. In this section, we take a more detailed look at the special case of Finite Impulse Response (FIR) digital filters. In addition to introducing various terminology and practical considerations associated with FIR filters, we'll look at a preview of transferfunction analysis (Chapter 6) for this simple special case.

Figure 5.5 gives the signal flow graph for a general causal FIR filter Such a filter is also called a transversal filter, or a tapped delay line. The implementation shown is classified as a directform implementation.