复杂目标极化散射特性建模与仿真模拟

【作者】 张莉莉；

【导师】 肖泽龙； 孙建红；

【作者基本信息】 南京理工大学 ， 通信与信息系统， 2021， 硕士

【摘要】 极化是描述目标散射特性的重要信息,利用极化信息能够有效提高雷达识别和探测目标的能力。本文主要通过建模仿真,从远场、近场、散射中心三个维度,研究典型军事目标的极化散射特性。主要研究内容如下:(1)针对毫米波段复杂目标全极化信息难以准确快速获取问题,采用射线寻迹几何光学法(RL-GO)进行目标散射特性研究,验证了它在计算具有多次反射、尖劈结构的电大尺寸目标散射特性的准确性,仿真结果表明该算法适用于工程应用中目标散射特性的快速分析。通过理论推导和仿真比较确定了二面角反射器是一类较为广泛的产生强交叉极化散射的典型几何结构,复杂目标交叉极化散射有可能大于同极化散射。针对吸波材料在不同极化方式下对目标的隐身性能不同,比较了涂覆和未涂覆情况下典型的无人机和履带式坦克“M1A2”目标在远场全极化雷达散射截面(RCS)分布和差异,分析了强交叉极化产生的原因,结果表明设置的吸波材料对目标的交叉极化分量值降低更为显著,有利于全极化雷达目标探测的隐身。(2)针对毫米波近程探测系统和电大尺寸的复杂目标探测问题,引入广义雷达散射截面(GRCS)概念,在发射天线在远场、接收天线在近场的条件下,对三面角反射器和履带式坦克目标在毫米波段的近场全极化散射特性进行研究。仿真结果表明,目标与天线二者之间的距离越接近,对RCS值的影响就越大。而当距离逐渐增大时,近场GRCS值逐渐趋近于远场RCS值,且交叉极化对距离的敏感程度低于同极化GRCS,证明了可通过改变极化方式来提高对近场复杂目标探测的能力。(3)通过目标的宽带高分辨成像可获得目标更细致的几何特征,提取目标的散射中心,研究目标的宽带全极化散射特性。仿真计算了装甲车全极化高分辨一维距离像(HRRP),结果表明在全极化方式下,通过Pauli分解,能较好地识别强散射点具体的部位、数量、不对称分量、奇偶次散射以及位置等重要特征信息;对由多种反射器构成的组合体“SLICY”目标和“Stryker”装甲车模型目标进行逆合成孔径(ISAR)雷达成像仿真,结果表明同极化像对镜面和多次反射效应显著,而交叉极化像对边缘、尖劈和曲率大的结构等更为敏感和细腻,可作为对同极化ISAR像的有力补充。更多还原

【Abstract】 Polarization information is important to describe the scattering characteristics of targets,which can improve radar performances of target recognition and detection.In this thesis,the polarimetric scattering characteristics of typical military targets by modeling and simulation are studied.The dimensions of research include far-field,near-field and scattering center.The main research contents are as follows:(1)Since it is difficult to obtain fully polarimetric information of complex targets of millimeter wave accurately and quickly,the accuracy of Ray-Launching Geometrical Optics in calculating the scattering characteristics of targets with multiple reflection and wedge structure is verified.The results show that the algorithm is suitable for the rapid analysis of target scattering characteristics in engineering applications.Through theoretical derivation and simulation comparison,it is determined that dihedral corner reflector is a kind of typical geometric structure with strong cross-polarization scattering.The cross-polarization scattering of complex targets may be greater than the co-polarization scattering.In view of the different stealth performance of absorbing materials to targets under different polarization modes,the distribution and difference of far-field fully polarimetric radar cross section(RCS)of typical UAV and M1A2 targets under coated and uncoated conditions are compared.The causes of strong cross-polarization are analyzed.The results show that the cross-polarization component of the target is reduced more significantly by absorbing material,which is conducive to the stealth of fully polarimetric radar target detection.(2)The concept of generalized radar cross section(GRCS)is introduced for millimeter wave short-range detection system and electrically large complex target detection.The nearfield fully polarimetric scattering characteristics of trihedral corner reflector and tracked vehicle target in millimeter wave band are studied with the transmitting antenna in the far-field and the receiving antenna in the near-field.The results show that the closer distance between the target and the antenna,the greater influence of RCS.When the distance increases,the near-field GRCS approaches the far-field RCS gradually.The sensitivity of cross-polarization to distance is lower than that of co-polarization GRCS.It is proved that the ability of detecting near-field complex targets can be improved by changing the polarization mode.(3)The detailed geometric features of the target can be obtained by the wideband highresolution imaging of the target.The scattering center of the target is extracted to analyse wideband polarimetric scattering characteristics.The results show that in the full polarization mode,the Pauli decomposition can better identify the specific parts,the quantity,asymmetric component,odd-even scattering and the location of strong scattering points.The Inverse Synthetic Aperture Radar(ISAR)imaging simulation is carried out for the combined “SLICY”target composed of multiple reflectors and the tank “Stryker”.The results show that the copolarization image has significant mirror and multiple reflection effect,while the crosspolarization image is more sensitive to the structure with edge,wedge and large curvature.The cross-polarization image can be used as a favorable supplement to the co-polarization ISAR image.更多还原