Electromagnetic Scattering Analysis Of Covered Plasma Target Based On High Frequency Algorithm

In this paper,high frequency algorithm is used to study the electromagnetic scattering characteristics of covered plasma targets.The high-frequency algorithm includes physical optics method,bouncing ray method and ray tracing algorithm.The covered plasma target includes covered uniform plasma target,covered non-uniform plasma target and covered plasma sheath target.Physical optics method is very effective in the study of electromagnetic scattering of electrically large targets.Its physical concept is clear,easy to program,and has the advantages of less consumption of computer resources and fast calculation speed.However,for targets with strong cavity target and surface coupling,it is impossible to obtain accurate radar cross section results.Bouncing ray method combines geometric optics method and physical optics method.Firstly,geometric optics method is used to accurately describe the multiple scattering of electromagnetic wave on the target surface.When the electromagnetic wave leaves the target surface after multiple scattering,the electromagnetic field is integrated by physical optics method to obtain the scattered field.The bouncing ray method makes up for the shortcomings of the physical optics method in the calculation of electromagnetic scattering of cavity targets and targets with strong surface coupling.Considering uniform plasma and special non-uniform plasma as special coating media,combined with step-by-step method and impedance boundary condition,physical optics method and bouncing ray tracing method,the electromagnetic scattering of covered plasma targets can be calculated.Ray tracing algorithm is mainly used to cover plasma sheath targets.Based on the layered model,the propagation of electromagnetic wave in plasma is tracked to obtain the propagation attenuation of electromagnetic wave and the electromagnetic scattering of targets.In this paper,the covered plasma target is studied in the following aspects:1.Combined with the equivalent medium theory,the electromagnetic scattering characteristics of targets covered with uniform plasma are calculated by physical optics method.For the target covered with uniform plasma,the uniform plasma is equivalent to the coating medium with the same electromagnetic parameters,and then the coating medium physical optics method is used to calculate it.At the same time,the influence of thickness on the RCS of coated target is discussed.It shows that the reduction of RCS by coating medium does not increase with the increase of thickness.2.A high frequency electromagnetic scattering algorithm covering specially distributed non-uniform plasma targets based on bouncing ray method is proposed.For the special distribution of non-uniform plasma,it is layered.Each layer is approximately regarded as uniform plasma,and each layer of uniform plasma is regarded as coated medium,which can be equivalent to the electromagnetic scattering calculation of multi-layer coated medium targets.Firstly,combined with the impedance boundary condition,the generalized reflection coefficient of the surface of the coated multilayer dielectric target is calculated,and then combined with the bouncing ray method,the electromagnetic scattering characteristics of the coated multilayer dielectric target are calculated.In the bouncing ray method,the octree method is used to accelerate the algorithm and improve the computational efficiency of the algorithm.Finally,the effects of different plasma parameters on target RCS Reduction are analyzed,which provides a theoretical basis for the development of plasma stealth technology.3.Navier Stokes equations are used to simulate the flow field around the target.Combined with computational fluid dynamics,the three-dimensional dimensionless Navier Stokes equations of two temperature 7-component chemical reaction model are used to simulate the flow field around the target,and the effects of height and height on the flow field around the target are analyzed.Through the calculation of the flow field around the target,the plasma characteristic parameters of the plasma sheath around the target can be obtained,which paves the way for the subsequent study of the electromagnetic wave propagation attenuation and electromagnetic scattering characteristics of hypersonic targets.4.A ray tracing algorithm is proposed to calculate the propagation attenuation and scattering characteristics of targets covered with plasma sheath.Solving the non-uniformity of plasma sheath is the difficulty and innovation of this paper.The electromagnetic parameters at different positions are obtained by ray tracing.It is assumed that the plasma near the refraction point is uniform plasma.The improved Monte Carlo method can effectively solve the problems of large memory and time-consuming in ray tracing algorithm due to the massive rays in layers.When calculating the scattering field of rays,the extended equivalent current approximation method can greatly improve the calculation accuracy of the algorithm.Finally,the effects of plasma sheath on the propagation attenuation of electromagnetic wave and the reduction of target RCS under different calculation scenarios are analyzed.