Introduction - If you have any usage issues, please Google them yourself
IIR digital filter is characterized by h (n) for infinitely long sequence. The basic idea of the design are: analog systems and discrete systems there is the theoretical basis of mutual imitation, so you can make the characteristics of a digital filter to imitate the characteristics of an analog filters, digital filters are H (z), H () of the the relationship between the transformation. Design, first to design a simulation of the filter transfer function, s variables and z and then transform the relationship between variables derived digital filter system function H (z).