说明：  双线性变换法无限长单位脉冲响应滤波器的设计，用到的模拟原型是切比雪夫和巴特沃斯低通滤波器。能够显示滤波器的幅频特性和相频特性曲线
(bilinear transform infinite impulse response filter units in the design, use of simulation is a prototype and Chebyshev low-pass Butterworth filter. To demonstrate the filter frequency characteristics and phase frequency response curve)