S变换

代码说明：

  S 变换是 Stockwell（1996）等提出的一个时-频分析方法，它结合了短时 Fourier 变换和小波变换的特点，能够完全无损地实现逆变换。(S-transform is a time-frequency analysis method proposed by Stockwell (1996). It combines the characteristics of short-time Fourier transform and wavelet transform, and can realize inverse transform completely without loss.)