相关函数法该方法先由序列估计出自相关函数R，然后对其进行傅立叶变换，得到功率谱估计。当延时和数据长度相比很小的时候可以有良好的估计精度。 -Correlation function method that the method is estimated by the sequence from a correlation function R, then its Fourier transform, the power spectrum estimation. When the length