说明：  接法又称周期图法，它是把随机序列x(n)的N个观测数据视为一能量有限的序列，直接计算x(n)的离散傅立叶变换，得X(k)，然后再取其幅值的平方，并除以N，作为序列x(n)真实功率谱的估计。
(Connection also known as cycle map, it is random sequence x (n) N observational data as a sequence of limited energy, direct calculation x (n) the discrete Fourier transform, in X (k), then the lesser of the square of the amplitude and divided by N, as the sequence x (n) real power spectrum estimation.)