A Study On The Mode Matching Method For Electromagnetic Scattering From Periodic Structures

As a typical artificial electromagnetic material,periodic structure is widely used in the fields of antenna,RF circuit and electromagnetic scattering,which the frequency selective surface is the most representative one.The basic idea of analyzing the frequency selective surface is deriving the Floquet mode from the wave equation which satisfying the periodic boundary conditions,and constructing the integral equation by using the boundary conditions.The mode analysis method in the mode matching method and the spectral domain method is summarized,and the frequency response characteristics of various frequency selective structures can be analyzed and calculated by improving the method to strictly conform to all the boundary conditions.In this thesis,based on the principle of mode analysis,the scattering field of the target regions is expanded by vector Floquet modes,and the vector mode matching method is proposed by using the corresponding boundary conditions and point matching techniques.The algorithm is applied to the analysis of single-layer frequency selective surface and compared with the traditional method of moments.The results show that the vector mode matching method has good calculation precision and speed,and can improve the stability of analyzing the frequency selective surfaces with complex elements by reasonably dividing the sub-regions of the unit.On the basis of vector mode analyzing method for single layer frequency selective surface,based on the characteristics of multi-layer structure and three-dimensional structure,the vector mode analyzing method for multi-layer frequency selective surface and three-dimensional frequency selective structure is proposed by the combination of matrix equation and three-dimensional vector mode matching,and is used to analyze the frequency response characteristics of these two different frequency selective structures.The results show that the calculation precision is high and the speed of calculating the multi-layer structure is superior to the simulation software.The validity of the algorithm is verified,and it provides a theoretical basis for analyzing the composite frequency selective structure in the future.