说明：  求瞬时频率必不可少，MATLAB系统不自带的，下载后放在MATLAB到toolbox，然后在EMD文件夹下，更新MATLAB路径即可。运行emd即可出现频谱分析图。
(It is necessary to find the instantaneous frequency. The MATLAB system does not come with it. After downloading, it is placed in the MATLAB to toolbox. Then, under the EMD folder, the MATLAB path can be updated. The spectrum analysis diagram can appear when EMD is run.)