Research On Full Polarization Electromagnetic Scattering Analysis And Fast Radar Imaging Method Of Large Electrical Target

In recent years,many cutting-edge technologies have been used in military confrontations.Ships,tanks and other weapons with new technologies often determine the outcome of a war.For both sides in the war,it is particularly important to find important weapons and strike them first.Therefore,the detection of electric large size targets has become a research hotspot.In this field,the key research focuses on electromagnetic scattering calculation and imaging of the target which is a common military detection method.In this thesis,we study the full polarization electromagnetic scattering analysis and radar imaging method of electrically large targets based on high and low frequency mixing method.Firstly,we study the full polarization scattering analysis of electrically large target based on high and low frequency mixing method.The edge diffraction field is calculated by Truncated Wedge Incremental Length Diffraction Coefficients method(TW-ILDCs)to reduce the influence of the edge diffraction field on cross polarization,and the full polarization electromagnetic scattering of the target is calculated by adding the scattering field calculated by the Shooting and Bouncing Ray(SBR).In order to further improve the calculation accuracy,a simple and efficient high and low frequency mixing method was proposed.By mixing the SBR for adding edge diffraction fields with the Method of Moment(Mo M)for Multi-Level Fast Multipole Algorithm(MLFMA)acceleration,the full polarization electromagnetic scattering of electrically large targets can be calculated quickly.A fast calculation of full polarization electromagnetic scattering from coated targets is realized based on the mixture of generalized reflection coefficient and Thin Dielectric Sheet(TDS)algorithm.Numerical results prove that the proposed high and low frequency mixing method can quickly calculate the full polarized RCS of the target under the condition of satisfactory calculation accuracy.As for imaging,the fast generation method of radar image is studied for electrically large mental targets.In order to quickly generate full polarization radar images of electrically large metal targets,a method of fast full polarization imaging is proposed by adding the effect of edge diffraction field calculated by TW-ILDCS to the principle of SBR imaging.Cross-polarized images with more information of target edge can be generated in a very short time by using this method,and these images can display the shape characteristics of target more intuitively.The proposed method is proved to be correct by comparing with the frequency and angle scanning imaging method.Then the pitch direction is added to the 2D fast imaging to achieve 3D fast imaging,and the 3D imaging acceleration method is given.The effect of edge diffraction field calculated by TW-ILDCS is also added to 3D SBR imaging to achieve 3D fast full polarization imaging.More target information is also displayed in the 3D cross-polarized images generated by this method.The proposed method can quickly build a target recognition database for automatic target recognition.