傅里叶变换功能的实现，虽然是非常见得的频率成分，但是还是实现了基本的傅里叶变换功能，并不是matlab自带的fft函数。实现了频谱分析可视化。-Fourier transform function, although it is very frequency components appear, but still achieve the basic function of the Fourier transform, comes not matlab fft function. Achieve