A Hybrid Time And Frequency Domain Electromagnetic Simulation Method Of High-order Variable Mesh For Typical Targets

The electromagnetic scattering characteristics of target include the inherent information such as size,structure,and material of target.They have important roles in radar detection,SAR image interpretation,and remote sensing.Therefore,how to obtain the target's electromagnetic scattering characteristics more quickly and accurately becomes the focus of study.With the development of technology,using computer to establish the target model and simulate is a very important way to obtain the scattering characteristics.For large electric size targets,the commonly simulation method is high-frequency approximation method,however,which has low simulation accuracy,and it is difficult to meet the needs of high-precision target recognition.If the numerical method with high simulation accuracy is used,a large amount of computing resources and time will be consumed.For this reason,the time and frequency hybrid electromagnetic simulation method with high-order variable grid is proposed.The method studied in this paper combines the high-frequency approximation method with high efficiency but poor accuracy,and the time-domain numerical method with high simulation ac curacy but slow calculation.According to the characteristics of the two methods and the structure of target,the numerical method is applied to the complex structure area of target,for the simple structure,a high frequency approximation method is used.Meanwhile the two parts are coupled and calculated to give full play of the advantages of different methods to realize the electromagnetic simulation of large electric size targets precisely and quickly.This algorithm uses the advantages of the two metho ds to achieve high-precision and fast electromagnetic simulation.The FDTD algorithm is a time-domain numerical method to solve the discrete forms of Maxwell's differential equations in time and space.Physical Optics(PO)is a high-frequency approximation that approximates the scattering properties of each differential element on the target surface.Physical Optics(PO)is a high-frequency approximation method that approximates the scattering properties of each differential element on the target surface.The time-frequency hybrid electromagnetic simulation method divides the target into two calculation areas,named the time area and the frequency area,according to the complexity and the size of the structure firstly.Then,on the one hand,the target are simulated independently in the respective areas by the FDTD and PO method to obtain the far-field scattering data of the target.On the other hand,through the near-to-field extrapolation technique,the “secondary excitation source” between time and frequency regions is derived,and based on this,the coupled electromagnetic field between the two regions is calculated.In order to give full play of the advantages in different calculation methods,this paper designs a high-order variable grid computing scheme.In the FDTD calculation,different lengths of grids are divided according to the complexity of the target,and the variable facets are used to reached a higher precision in PO simulation.Finally,a simulation experiment is performed for a simple target to verify the correctness of the method,and the electromagnetic scattering characteristics of a typical target has been simulated.Analysing the experimental results,the quantitative comparison of the scattering results verifies the accuracy of the metho d studied in this paper.Comparing with the simulation time,a faster calculation of the target electromagnetic scattering characteristics has been achieved.Therefore,the method studied in this paper has practical significance and value in obtaining electromagnetic scattering characteristics of large electric size targets.