Research On The Electromagnetic Scattering Characteristics Of The Target With Periodic Structure And Complex Medium By The Method Of Moment

Periodic structures,such as frequency selective surfaces(FSSs)and photonic band-gap structures,are widely used in the field of microwave millimeter waves and antennas.With the extensive application of periodic structures,the analysis and design of periodic electromagnetic structures have become more and more complicated.Therefore,it is of great theoretical value and practical significance to carry out further theoretical analysis of periodic structures and to develop accurate and reliable periodic structural analysis and calculation methods.As a high-precision method to electromagnetic simulation,the method of moment has been widely used.In this paper,by using the method of moment and the periodic Green function,we do some research on the analysis the electromagnetic characteristics of two-dimensional periodic structures with complex media.First of all,according to the physical meaning of periodic Green functions,we derive the spatial and spectral expressions of periodic Green functions.And then,the Ewald method is introduced to accelerate the convergence of periodic Green functions.The periodic Green's function is applied to the surface integral equation(SIE),and the specific formula of the PMCHWT equation combined with the periodic Green's function is deduced.The current continuity is also considered when the boundary the unit cell is continuous.Apparently,the singularity of periodic Green's function will appear in the moment method.Thus,the method to eliminate its singularity is given in this paper.To further accelerating the calculation of periodic Green's function in matrix filling,a linear interpolation method is introduced.So,the scattering field of two-dimensional infinite periodic metallic or homogeneous dielectric structure can be obtained by witting the program.Considering the periodic structures with more complex media,such as anisotropic media,the periodic volume-surface integral equation is deduced.Firstly,the periodic structures with isotropic medium can be simulated.And then the periodic volume-surface integral equation is extended to analyze the periodic structures with anisotropic medium.The dielectric parameter is in a tensor form,which needs to be handled carefully.Similarly,the linear interpolation method is also introduced.The reflection coefficient for the periodic structures is deduced.Finally,the accuracy of the proposed method is verified by several examples.