Near-Field Electromagnetic Scattering Of Large-Size Targets Based On Parallel SBR

At present,the far-field electromagnetic scattering research has been relatively mature,but in practical applications(such as missiles and target rendezvous),the far-field approximation conditions are often not satisfied between the target and the radar,so the research of target's near-field electromagnetic scattering has more practical significance.The near-field and far-field electromagnetic scattering of the target are different in the scattering mechanism,model method,echo characteristics,etc.However,the theoretical basis of both is based on Maxwell's equations,so the far-field electromagnetic scattering calculation method can be extended to the near field.In this thesis,the far-field electromagnetic scattering algorithm is extended to the near-field electromagnetic scattering calculation to achieve the purpose of quickly solving the near-field radar cross-section and angular glint of complex targets.The main work of the thesis is as follows:1,The commonly used high-frequency algorithms: Physical Optics,Geometric Optics and Shooting and Bouncing Ray are introduced,analyzing the advantages and disadvantages of the various algorithms and the scope of application,due to sovle the electromagnetic scattering problem of the complex and large targets,so this thesis is mainly using Shooting and Bouncing Ray method.Focusing on the implementation process of the Shooting and Bouncing Ray method: ray tube generation,ray tracing,field-strength tracking and field strength solving.The algorithm for generating the ray tube is improved.The Kd-Tree algorithm is applied to the Shooting and bouncing Ray algorithm to improve the efficiency of the algorithm.The correctness and accuracy of the program are verified by comparing the simulation results with the results of the commercial software FEKO simulation.2.The far-field electromagnetic solution algorithm is generalized to the near-field electromagnetic scattering calculation.Firstly,the basis for the far-field and near-field scattering is presented.Next the near-field radar cross-section definition is showed.The way to calculate near-field radar cross-section definition is given,followed by the complete flow calculation process of the near-field radar cross section,and the correctness of the algorithm is verified by an example.In addition,local illumination is studied and the cause of local illumination is explain,and a narrow beam antenna is irradiated to illuminate the flat panel.3.The physical mechanism of the target's angular glint is analyzed.It is proved theoretically that the angular glint line deviation is independent of the distance and the angular glint line deviation is negatively correlated with the radar cross section.It is more practical to study the near field angular glint,especially when there is local illumination,the distribution of the target scattering center will be changed,resulting the difference between the characteristics of the near field angular glint and the characteristics of the far field angular glint.In addition,this paper presents a variety of methods for suppressing angular glint.The advantages and disadvantages of various inhibitory methods are analyzed through examples.Finally,the near-field angle suppression algorithm used in this thesis is presented.The effectiveness of the algorithm is verified by an example.4.This thesis will use multiple threads for ray tracing to improve the efficiency of ray tracing.An open source Open MP parallel programming framework is used to accelerate the program and improve the utilization of computer computing resources.In parallel programs,an important factor that restricts program efficiency is load balancing.This thesis optimizes(near-field electromagnetic scattering calculation)procedures from the perspective of load balancing,and improves the operating efficiency of the program.