FFT的奈奎斯特频率为 ，（ 为采样间隔）实际上的FFT变换点数要求为2的n次幂，各点所对应的频率是从 到 ，求出 后，可以用 ，这里N为FFT变换的点数。如变换点数为2048，由于对称性，实际有用的点数为1024个。

在该程序中，做完富氏变换后，已经将数据按照频率从0到 到0的顺序排好。

在运行结果中，只需存储左下角的1/4区域的数据即可。

-FFT of the Nyquist frequency, (for the sampling interval) is actually the FFT, the n number of points required for the power of 2, the frequency corresponding to each point is to, find, you can use the FFT, where N points. Such as the transformation point to 2048, due to the symmetry, the actual useful points to 1024. In the process, done after the Fourier transform has the data in accordance with the frequency range from 0 to 0 in order to line up. In the run results, only the lower left corner of the store 1/4 of regional data can be.