用数值拟合法代替数字滤波法，实现了对不同频率误差信息的分离。通过推导证明两种方法在本质上是相同的。当将前者按后者的形成理论进行推导时，得出了一种与传统窗函数形状迥然不同的新型窗函数。给出了全部推导过程，并介绍了实用效果 Using numerical fitting method instead of digital filtering method, the separation of error information with different frequency is realized. Prove that the two methods are essentially the same. When the former is deduced according to the formation theory of the latter, a new type of window function that is quite different from the shape of the traditional window function is obtained. All the derivation process is given, and the practical effect is introduced