说明：  HHT就是先将信号进行经验模态分解（EMD分解），然后将分解后的每个IMF分量进行Hilbert变换，得到信号的时频属性的一种时频分析方法。
(HHT is the first signal empirical mode decomposition (EMD decomposition), and then each IMF component decomposed Hilbert transform, frequency analysis method of time-frequency properties obtained when a signal.)