Analog Filter Design (AFD) Toolbox allows the user to design, analyze, and simulate active analog filters easily in a graphical (GUI) environment. It was developed at MIT and is currently used in several universities to teach signal processing concepts. It can be used to build Butterworth, Bessel, Chebychev I and II, and elliptic filters. It can display time and frequency responses, pole/zero plots, transfer functions, circuit diagrams, and provides the ability to simulate filtering of user-supplied and standard data types (e.g. sinusoidal, squarewaves, EKG data).
To use, type AFD from the command prompt. The toolbox includes a comprehensive user's manual.
It has been tested to work up to Matlab R2011b, and likely will work beyond that.