Demo program for teaching the characteristics of low-pass IIR filters

Demo programs that illustrate concepts with visual aids, become the important tools in the field of engineering education. They help students to learn better, remember longer, and better identify the appropriate concepts. Another benefit of the demo programs is, that they can be used as a complementary tool in the traditional classes in the classroom, to visualize and improve understanding of the presented subject. To this end here is presented the demo program for teaching the principal characteristics of digital IIR (Infinite impulse response) filters: Butterwort, Chebyshev I, Chebyshev II, and Elliptic filters. The program was implemented in MATLAB using MATLAB tool makeshow which has different favorable characteristics. First it is demonstrated how the analog filters can be converted into digital IIR filters using impulse invariance and bilinear transforms. The goal is to visualize the advantages of the bilinear transform. Next goal was to visualize the comparison of different above mentioned IIR filters in terms of complexity, magnitude and phase responses. The program can be also used as a self-study tool for the classes on the fundamentals of digital signal processing at the graduate level. The student validation of the program is also included.