利用双线性变换法设计一个巴特沃斯数字低通滤波器。根据滤波器的设计思想，通过双线性变换法将模拟低通滤波器变换到数字低通滤波器，利用MATLAB绘制出数字低通滤波器的系统幅频函数曲线。最终利用双线性变换法利用MATLAB函数仿真出了巴特沃斯低通滤波器的对数幅频及相频率曲线。-Bilinear transform design a digital low-pass Butterworth filter. According filter design ideas, through bilinear transform the analog low-pass filter is transformed into a digital low-pass filter, using MATLAB to draw out the digital low-pass filter amplitude-frequency system function curve. End-use bilinear transform simulation using MATLAB function of the logarithm of the amplitude frequency and phase frequency curve Butterworth low-pass filter.