| In modern high-tech warfare,electromagnetic detection is an essential and important part.To improve the detection capability of military targets,it is necessary to solve the problems of separating target echoes from clutter signals and correlating target echoes with the measured targets.This has been a long-standing focus and difficulty in the radar field.Therefore,the theoretical modeling research on the scattering mechanism of electromagnetic wave detection signals and target interaction is the theoretical basis and prerequisite for military target reconnaissance,warning,detection,tracking,identification,guidance,and interception in actual battlefield environments.The simulation of target radar scattering characteristics is to model the interaction process between radar and target as a Maxwell’s equations with specific boundary conditions,and use electromagnetic calculation algorithms to solve the equations to obtain the target radar scattering characteristics.Developing efficient and accurate simulation methods for target radar scattering characteristics can not only replace some difficult-toconduct actual experiments but also provide a theoretical basis and data support for the study of electromagnetic scattering mechanisms.Simulation calculation has become an indispensable and important part of the research on target’s radar scattering characteristics.The finite-difference time-domain(FDTD)method,as a numerical electromagnetic simulation method,not only has the advantages of high accuracy and an unrestricted frequency range but also has unique advantages in calculating wide-band radar response and targets with complex mixed media.Due to these advantages,the FDTD method has been widely used in the modeling and simulation of target radar scattering characteristics in recent years.However,the FDTD method is affected by numerical dispersion and restraint by stability conditions,and it occupies a large amount of system resources and consumes a long simulation time when simulating large-scale targets.This problem greatly limits the application scope of the FDTD method in the study of target radar scattering characteristics.In response to the above-mentioned timeliness issue,this project takes numerical simulation of target radar scattering characteristics as the application background and improves the computational efficiency of the traditional FDTD method for simulating largescale targets from the perspectives of computational complexity and execution efficiency.Additionally,research is conducted on the radar scattering characteristics of targets and backgrounds based on FDTD for natural scenes.The research content of the paper is summarized as follows:1.This paper studies the target radar scattering characteristics computation method based on the unconditionally stable leapfrog complying-divergence implicit-FDTD(leapfrog CDI-FDTD)method.This method is free from the stability condition limitation when calculating target radar scattering characteristics,thereby increasing the time step and reducing the number of iterations in the simulation,significantly improving the efficiency of traditional explicit FDTD in simulating the scattering characteristics of largescale targets.Firstly,a leapfrog CDI-FDTD calculation method for lossy media is proposed,which can be applied to the simulation of targets with lossy materials such as metals.Secondly,a high-order CPML absorption boundary for leapfrog CDI-FDTD is proposed,which truncates the calculation area and infinite space to accurately simulate the scattering problem in open space.Finally,an incident plane wave introduction method is proposed for leapfrog CDI-FDTD,which can accurately and efficiently introduce the radar incident wave into the computation domain.2.This paper studies the parallel execution methods of the FDTD method and leapfrog CDI-FDTD in heterogeneous computing systems.Firstly,a parallel FDTD method based on GPU+CPU collaborative computing is proposed.This method uses domain decomposition technology to distribute FDTD computing tasks to different processors of the heterogeneous system.The adjacent processor data communication based on‘kernel-split method’ensures the efficient and correct operation of FDTD iterations.The dynamic load balancing technology is used to dynamically adjust the processor load distribution and enhance parallelism between processors,improving the efficiency and adaptability of the method.Secondly,a multi-processor parallel method for leapfrog CDIFDTD based on the SPIKE method is proposed.The SPIKE algorithm models the tridiagonal equations in the leapfrog CDI-FDTD update as a multi-processor block parallel solving form.By introducing intermediate storage variables,the iterative calculation amount of leapfrog CDI-FDTD updates is reduced.The thread organization and data communication methods are proposed to ensure the efficient implementation of multi-processor parallelism.3.This paper investigates the simulation method for radar scattering characteristics of targets and backgrounds based on FDTD method.Firstly,an modified FDTD model is proposed for the calculation of composite scattering and difference scattering of targets and backgrounds.The model adopts the double output boundary and partitioned incident field introduction method,which greatly improves the problem of traditional FDTD scattering calculation models that overly rely on the truncation rough surface size when calculating difference scattering fields for targets and rough backgrounds.Based on the modified FDTD model,the near-field to far-field transformation formulation for composite scattering and difference scattering of targets and backgrounds in two-dimensional and three-dimensional cases is derived,and detailed implementation methods are provided.Secondly,combining the Monte-Carlo method with the modified FDTD model,the FDTD and leapfrog CDI-FDTD methods are applied to the radar scattering characteristic calculation of typical targets above the PM(Pierson-Moskowitz)wave spectrum sea surface,and the simulation results are analyzed.The research presented in this paper provides a fast and effective theoretical and computational method for simulating the radar scattering characteristics of targets,which has significant implications for the fields of target detection,identification,and radar system design. |
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