区别去传统的傅里叶变换，对于非平稳信号而言，分数傅里叶变换是一个较好的方法，本程序实现了分数傅里叶变化对LPF类信号的估计。具有较高的学习价值(Different from the traditional Fourier transform, for non-stationary signals, fractional Fourier transform is a better method, this program implements the fractional Fourier transform to estimate the class LPF signal. It has higher learning value)