In the course of filtration, interpolation is the essential step to produce the intrinsic mode functions, and the basis of the Hilbert spectral analysis.
在筛选过程中，插值是产生本征模函数关键的一步，是希尔伯特谱分析的基础。
2
A sine basis function model is introduced, bringing forward an example of Hilbert convertor and differentiator optimal design.