Research On Efficient Electromagnetic Scattering Algorithm For Thin Medium/medium Hybrid Targets Based On Integral Equations

The electromagnetic scattering from vegetation plays an important role in remote sensing,detection,anti-stealth and other fields.Due to its various types and the distribution shows diversity with the difference of environment.The numerical model will become more and more complex and the calculation is insufferable with the scenario increasing.Therefore,the electromagnetic scattering characteristics can not be predicted with high accuracy under limited computing platforms and modeling capabilities.As a result,there is a big difference between the numerical and experimental results.Therefore,it is urgent to establish an efficient electromagnetic full-wave analysis method to obtain the electromagnetic scattering characteristics of typical vegetation.In this paper,an efficient PMCHWT/TDS-based integral equation algorithm is proposed to calculate the radar cross-sectional area(RCS)of typical vegetation.Moreover,the periodic Green's function is introduced to accelerate the calculation.In the first part of this paper,The TDS(thin dielectric sheet)model is proposed to analyze thin medium targets.The application of tangential equivalent and full wave equivalent is compared respectively.Finally,the full wave equivalent is selected as the approximate analysis method in this paper.Then,based on the theory of the surface integral equation,the PMCHWT/TDS mixed integral equation is derived to solve the electromagnetic scattering characteristics of the thin medium/medium mixed target.Finally,the expansion form of the Green's function in free space is derived,and the fast multipole method is introduced to solve the thin medium target and PMCHWT/TDS mixed integral equation to solve the thin medium/medium mixed target in the paper,electromagnetic scattering characteristics of various dielectric targets can be calculated efficiently.In the second part of this paper,the fast method is used to solve the electromagnetic scattering characteristics of infinite periodic structure.Firstly,the spectral domain and spatial form of periodic Green's function are derived.The infinite summation term of periodic Green's function is solved by Poisson summation formula and Ewald identity respectively,which greatly accelerates the convergence speed of periodic Green's function.Then the spherical harmonic function expansion theory is used to deduce the expansion form of the periodic Green's function,and the gradient term of the far-field expansion of the periodic Green's function is derived by using the difference numerical method innovatively,which makes the periodic fast multipole method suitable for solving infinite medium targets.The accuracy and efficiency of the periodic fast multipole method are verified by numerical simulation.