对于非平稳信号的分析不能依靠傅里叶变换，但可以采用时频分析的方法，其中加窗傅里叶变换是最简单的一种。但是，它有很大的局限性：当基本窗函数一旦取定，窗口的时窗宽度和频窗宽度就固定了，不会随时域和频域的位移而变化。-For non-stationary signal analysis can not rely on Fourier transform, but you can use time-frequency analysis method, in which the windowed Fourier transform is the simplest one. However, it has many limitations: once when the window function to take the basic set, the window width and frequency window when the window width is fixed and will not at any time and frequency domain displacement change.