说明：  FFT，即为快速傅氏变换，是离散傅氏变换的快速算法，它是根据离散傅氏变换的奇、偶、虚、实等特性，对离散傅立叶变换的算法进行改进获得的。它对傅氏变换的理论并没有新的发现，但是对于在计算机系统或者说数字系统中应用离散傅立叶变换，可以说是进了一大步。 设x(n)为N项的复数序列，由DFT变换，任一X（m）的计算都需要N次复数乘法和N-1次复数加法，而一次复数乘法等于四次实数乘法和两次实数加法，
(FFT, fast Fourier transform which is a discrete fast Fourier transform algorithm, which is the discrete Fourier transform of the odd and even, true, false, such as characteristics of the Discrete Fourier Transform algorithm obtained. Fourier transform theory it is not a new discovery, but in the computer system or the application of digital systems Discrete Fourier Transform, can be said to be a big step. Set x (n) for N sequences of the plural, by the DFT transform, either X (m) requires the calculation of complex multiplication and N times N-1 times the plural adder, and a complex multiplication is equivalent to four times the number of multiplication and two real addition,)