说明：  本实验首先按照给定技术指标采用模拟低通滤波器（巴特沃思低通滤波器）去逼近理想模拟低通滤波器，然后通过双线性变换法对模拟滤波器进行数字化，得到数字滤波器。
(In this study, first of all technical specifications in accordance with a given analog low-pass filter (Butterworth low-pass filter) to approximate the ideal analog low-pass filter, and then through the bilinear transformation method of the digitization of analog filters, digital filters are .)