基于冲激响应不变法的IIR数字滤波器设计，冲激响应不变法的设计原理是利用数字滤波器的单位抽样响应序列H(z)来逼近模拟滤波器的冲激响应g(t)。

按照冲激响应不变法的原理，通过模拟滤波器的系统传递函数G(s)，可以直接求得数字滤波器的系统函数H(z)，其转换步骤如下：

1) 利用ω=ΩT(可由关系式 推导出)，将 ， 转换成 ，Ω，而 ， 不变；

2) 求解低通模拟滤波器的传递函数G(s)；

3) 将模拟滤波器的传递函数G(s)转换为数字滤波器的传递函数H(z)。

-The same method based on the impulse response of the IIR digital filter design, the same impulse response method is to use the design principles of digital filter unit sample response sequence of H (z) to approximate the impulse response of analog filters g (t). The same impulse response in accordance with the principles of law, through the analog filters of the system transfer function G (s), digital filters can achieve the system function H (z), the conversion steps are as follows: 1) using ω = ΩT (by relationship is derived), will, convert, Ω, and, unchanged　2) low-pass analog filters to solve the transfer function G (s)　3) the analog filter transfer function G (s) is converted to digital filter transfer function H (z).