With continuous filters that have discrete components, the filter structure is an electric schema that includes condensers, coils and resistances, as well as other elements. These filters are active if they contain amplifiers.
In the case of digital filters, the structure of the filter corresponds to the synoptic schema that connects input and output, into which delay elements and weighting values are introduced. This is a way of visualizing the flow of samplings when it undergoes delays or when it is weighted. This structure is directly deduced from the transfer function or the difference equation. It is very simple and for this reason is called a direct structure. For an FIR filter characterized by equation (5.3) in Chapter 5, with input x and output y, we obtain Figure 7.1.