DIT-FFT算法子程序

FFT长度为2m，m为正整数。FFT输出结果放在输入复数数组中。其中xr存放信号序列实部，xi存放信号序列虚部。如果信号长度小于N，需要给xr和xi后面补足0，计算结果x(k)的实部和虚部仍然分别存放在数组xr和xi中。-DIT - FFT subroutine FFT length of 2m, m is a positive integer. FFT output on the importation of complex array. Xr which kept real signal sequence, the signal sequence xi kept the imaginary part. If the signal is less than the length of N, and the need to xr xi behind complement 0, The results of x (k) the real and imaginary parts were still stored in the array xr and xi China.