特征分解型求取离散分数阶傅里叶变换
特征分解算法通过求ＤＦＴ的核矩阵Ｆ（ｋ，ｎ）的特征值
和特征向量构造ＤＦＴ核矩阵的分数幂，以此作为Ｆａ（ｋ，ｎ）
来计算ＤＦｒＦＴ。(The kernel matrix eigenvalue decomposition algorithm for DFT F (k, n) characteristic value And the feature vectors are constructed as the fractional powers of the DFT kernel matrix, which are used as Fa (k, n)
To calculate DFrFT.)