Research On Composite Scattering Algorithm Of Rough Surface And Target Based On High Frequency Method

The research on composite scattering of rough surfaces and targets is an important hot topic in the field of computational electromagnetics,which has been widely applied in radar imaging,satellite remote sensing,military confrontation and other fields.For the complex electromagnetic scattering problem of rough surfaces and targets of electrically large size,traditional numerical methods require massive computing resource,so the high-frequency method based on the shooting and bouncing ray(SBR)has been widely studied by scholars due to its high precision and fast speed.However,the traditional SBR has many disadvantages.Firstly,the same search strategy is used for each ray in ray tracing,which causes unnecessary time overhead;Secondly,SBR can only be used to solve the scattering problem of pure metal targets,it cannot be applied to rough surfaces and target composite scenes.Aiming at the above problems,based on the framework of SBR,the thesis conducts in-depth research and analysis on ray tracing acceleration algorithm,rough surface and target compound scattering algorithm and electromagnetic imaging algorithm respectively.(1)In order to speed up the computation of shooting and bouncing ray(SBR)with space partitioning data structure such as kd-tree,a modified ray tracing method is proposed based on sparse node.Firstly,the node of kd-tree is modified by sparsely distributing bounding boxes that are linked from bottom to top.Secondly,continues rays are treated as ray cluster instead of a couple of different rays in traditional SBR.Finally,the traversal algorithm for both ends of the ray cluster is same as traditional method,and then the traversal for the ray inside the cluster is beginning with a common interior node determined by end ray.Examples show that the improved method is about 20% faster than the traditional method without reducing the accuracy.(2)In order to solve the scattering problem composited of metal targets embedded in rough dielectric bodies,the volume equivalent shooting and bouncing ray method is introduced.Aiming at the problem of computational distortion under large incident angles,a launch plane generation algorithm based on reverse tracking of launch points is proposed.To explore the composite scattering mechanism of sea surface targets,this thesis proposes an efficient method to calculate the coupling field according to the process of ray tracing,which expands the single total field into a coherent superposition of different scattering fields.Finally,the impact of a series of factors such as incident angle,wind speed,wind direction,and motion attitude on composite scattering is shown,and the mechanism of composite scattering is analyzed.(3)In order to explore the imaging mechanism of rough surface scattering composed of target.From the perspective of time-domain echo,combined with the ray tracing process of the volume equivalent shooting and bouncing ray method,an electromagnetic imaging algorithm for generating one-dimensional range image and ISAR through the frequency domain response function is proposed.The correctness of the imaging algorithm is verified by simulation examples.Finally,the thesis extends the coupling field calculation method to the imaging algorithm framework,and deeply analyzes the imaging mechanism of each part of the scattered field of the sea surface ship target under different incident angles.