说明：  基2－FFT算法的Matlab代码的实现。其中有一个子程序可以用Matlab内部的程序来实现，以提高程序的运算速度。
(2-FFT-based algorithm for the realization of Matlab code. There is a subroutine can use Matlab s internal procedures are in place to realize in order to improve procedures for computational speed.)