说明：  快速傅里叶变 (Fast Fourier Tranformation，FFT)是将一个大点数N的DFT分解为若干小点的D F T的组合。将用运算工作量明显降低， 从而大大提高离散傅里叶变换(D F T) 的计算速度。因各个科学技术领域广泛的使用了FFT 技术它大大推动了信号处理技术的进步， 现已成为数字信号处理强有力的工具
(Fast Fourier Transform (Fast Fourier Tranformation, FFT) is a large number N of DFT is decomposed into a number of small dots combination of DFT. Arithmetic will significantly reduce the workload, thus greatly improving the Discrete Fourier Transform (DFT) calculation speed. Due to various technical fields of science extensive use of FFT techniques which greatly promoted the progress of signal processing technology, has become a powerful tool for digital signal processing)