Filter Design Toolbox

System Identification

One common application is to use adaptive filters to identify an unknown system, such as the response of an unknown communications channel or the frequency response of an auditorium, to pick fairly divergent applications. Other applications include echo cancellation and channel identification.

In the figure, the unknown system is placed in parallel with the adaptive filter.

Figure 3-3: Using an Adaptive Filter to Identify an Unknown System

Clearly, when e(k) is very small, the adaptive filter response is close to the response of the unknown system. In this case the same input feeds both the adaptive filter and the unknown. When the unknown system is a modem, the input often represents white noise, and is the sound you hear from your modem when you log in to your Internet service provider.

Choosing an Adaptive Filter

Inverse System Identification