The Filter Design Demo is a program that designs simple IIR (and FIR) digital filters, along with tutorial visualizations of the filter design process.

Features:

A short tutorial on first- and second-order IIR (infinite-length impulse response) filters. This demo shows plots in the three domains for a variety of IIR filters with different filter coefficients.

PeZ (pezdemo) is a MATLAB tool for pole/zero manipulation. Poles and zeros can be placed anywhere on a map of the \(z\)-plane. The corresponding time domain (\(n\)) and frequency domain (\(\hat\omega\)) plots will be displayed. When a zero pair (or pole pair) is dragged, the impulse response and frequency response plots will be updated in real time.

The connection between the \(z\)-transform domain of poles and zeros and the time domain, and also the frequency domain is illustrated with several movies where individual poles, or zeros or pole pairs of IIR filters are moved continuously.

A demo that illustrates the connection between the complex \(z\)-plane and the frequency response of a system. The frequency response is obtained by evaluating \(H(z)\) on the unit circle in the complex \(z\)-plane.