说明：  频域滤波器器的一些相关实验和滤波器的实现（包括理想低通，Butterworth低通，高斯低通，理想高通，Butterworth高通，高斯高通滤波器）
(Some related experiments of frequency-domain filter and Realization of filter (including ideal low-pass, Butterworth low-pass, Gauss low-pass, ideal high pass, Butterworth high pass, Gauss high pass filter))