Research On Near-field Scattering Modeling Of Ship On The Sea And GPU Parallel Technology

The research on the electromagnetic scattering from the composite target of seasurface ships can provide strong theoretical support for the fields of radar guidance,target recognition,invisibility and anti-invisibility.Modeling the electromagnetic scattering of sea-surface ships in real radar scenes is always a very important application topic.Based on the physical optics method-bounce ray method,this thesis studies the target ultra-near field scattering problem,the lossy medium sea surface problem and the ultra-large target problem respectively.The main research contents of this thesis are as follows:1.In view of the electromagnetic scattering from the composite target of a sea-based vessel,the basic theory of the related problems is elaborated in detail.Starting from the radiation equation,the criteria for the division of different fields in the case of electrically large size problems are analyzed.The calculation principles of physical optics and bounce ray methods in different fields are introduced.The geometric modeling technique of wind driven sea surface,i.e.the construction method of wind driven sea surface based on Pierson-Moskowitz spectrum,is given.Debye formula is used to describe the relationship between hydroelectric characteristics and frequency,temperature and salinity.2.Two methods,array antenna radiation model and antenna equivalent radiation model,are presented to characterize the radiation characteristics of ultra-near field antenna.The ideal point source and dipole radiation expression are introduced to calculate the target scattering field of each element in the array antenna.The total scattering field of ultra-near field array antenna is derived by superimposing the above scattering field.To characterize the radiation characteristics of general antennas,an equivalent radiation model consisting of dipole arrays is constructed.Based on spherical wave function,the radiation field of the antenna and the equivalent radiation model is expanded.The radiation field expansion coefficients of the equivalent radiation model are derived by matching the radiation field.The dipole moment in the model is solved by using the expansion coefficients.The above methods can effectively simplify the antenna electromagnetic model and improve the calculation efficiency.An example shows that the average error of this method is 2 d BV/m when calculating the near-field electromagnetic scattering of surface ships compared with the numerical method,which meets the actual simulation needs.3.The application of Volume Shooting and Bouncing Ray(VSBR)in surface scattering of lossy media is studied.The propagation theory of electromagnetic wave in medium is introduced.Based on this theory,the solution of wave vector,reflection coefficient and transmission coefficient of electromagnetic wave at the boundary of medium is corrected.The parallel acceleration of the image processing unit(GPU)of the algorithm is demonstrated from two aspects: the computational model and the memory model of the algorithm.The main technologies used include the iterative ray tracing strategy,data compression and dump.By comparing the results with those of the numerical method,it is proved that the average error of this method for the lossy surface ship scene is 1.9d BV/m.4.The application of Multi-GPU technology in high frequency method is studied.The multi-GPU parallel acceleration framework is introduced,that is,each device is managed by a unique control thread,and the task dispatching thread subdivides and assigns tracking tasks to each control thread based on the principle of subdomain ray.To avoid access conflicts of shared resources between threads,an atomic operation is used to achieve synchronization mechanism to ensure efficient transfer of data between threads.The example shows that the acceleration ratio of the double GPU can be about 200% compared with that of the single device.Based on the high frequency method,this thesis studies and analyses several key issues in the real surface warship scene,further expands the application scope of the algorithm,optimizes the calculation efficiency,and provides theoretical and technical support for the explanation of the electromagnetic scattering mechanism of the composite target of the surface warship and its engineering application.