利用MATLAB计算傅里叶变换并作出频谱图像的代码和图像，涉及FFT算法，看代码可以理解一下~为北京理工大学信号与系统实验实验三的答案(Fourier transform using MATLAB calculation and make spectral image code and images, involving the FFT algorithm, look at the code can understand ~ Beijing Institute of Technology signal and system experiment experiment three answe)