设计IIR数字滤波器一般采用间接法（脉冲响应不变法和双线性变换法），应用最广泛的是双线性变换法。基本设计过程是：①先将给定的数字滤波器的指标转换成过渡模拟滤波器的指标； ②设计过渡模拟滤波器；③将过渡模拟滤波器系统函数转换成数字滤波器的系统函数。MATLAB信号处理工具箱中的各种IIR数字滤波器设计函数都是采用双线性变换法。-IIR digital filter design commonly used indirect method (impulse response method and the bilinear transform), the most widely used is the bilinear transformation method. Basic design process are: ① the first digital filter given transition indicators into analog filter indicator　② transition analog filter design　③ analog filter system function will transition into a digital filter system function. MATLAB Signal Processing Toolbox in a variety of IIR digital filter design functions are based on the bilinear transform.