层状半空间及上方目标复合散射的快速算法研究

发布时间：2018-08-23 14:49

【摘要】：半空间及上方目标复合散射特性的研究在微波遥感、雷达成像、隐身与反隐身、目标探测与识别等方面具有十分重要的理论意义和实际应用价值。在天基雷达观测的情形,由于目标和背景的相互作用,其复合散射特性与目标单独存在时差别很大。本文系统地研究了天基雷达观测情形层状半空间及其上方目标复合电磁散射计算的快速算法。本文在层状半空间上方目标散射计算的入射波引入、背景对反射波极化特性的影响、观察点远离界面时半空间上方任意取向电磁偶极子远场辐射特性的快速计算等方面都做出了创新性的工作。论文主要工作和创新点如下:1.层状半空间上方任意取向电、磁偶极子远区辐射场的快速计算。针对层状半空间情形格林函数包含复杂的Sommerfeld积分,计算困难的问题,本文利用互易定理得到观察点远离界面时(天基雷达观测情形)层状半空间上方任意取向电、磁偶极子频域辐射场的解析表达式。进一步,给出了各向异性层状半空间上方任意取向电、磁偶极子频域辐射场的解析表达式。为半空间上方目标电磁特性的快速计算打下了良好的基础。2.线性极化波入射到半空间时反射波极化特性分析。以往分析计算中,层状半空间反射波的极化特性相比于入射波极化特性的变化常常被忽略。本文系统研究了线性极化波入射到介质界面时反射波极化状态的变化情况。分析了入射波极化角、半空间介质参数等对反射波极化状态的影响。给出在不同入射条件下,反射波极化状态点在Poincare球上的分布情况并对其进行详细分析。这一部分工作为采用半解析的方法计算半空间上方目标电磁散射时入射波的加入提供了保障。3.层状半空间及其上方目标电磁特性计算的半解析方法。本文采用半解析方法计算层状半空间及其上方目标的电磁散射问题,提出了一种仅包含目标本身的半空间上方目标电磁特性研究方法。层状半空间的影响通过双向入射波(直达波和界面反射波)的引入而实现。考虑到反射波相比入射波极化状态、电场幅值、相位上的差别,通过等效原理,将界面反射波引入到计算区域中。在瞬态场计算中,结合傅里叶变换将入射波、反射波时域波形引入到FDTD(Finite Difference Time Domain,时域有限差分方法)计算区域中。4.高功率微波照射下半空间上方目标耦合特性研究。利用上述方法分析了考虑半空间情形下高功率微波入射到目标时,目标内部的近场特征,同时分析并讨论了当改变入射条件时,目标内部能量耦合变化情况。
[Abstract]:The study of composite scattering characteristics of half-space and upper targets has important theoretical significance and practical application value in microwave remote sensing radar imaging stealth and anti-stealth target detection and recognition. In the case of space-based radar observation, due to the interaction between the target and the background, the complex scattering characteristics of the target are very different from that of the target when it exists alone. In this paper, a fast algorithm for the calculation of composite electromagnetic scattering from layered half-space and above targets observed by space-based radar is studied systematically. In this paper, the influence of the background on the polarization characteristics of the reflected wave is introduced into the incident wave of the target scattering calculation over the layered half-space. When the observation point is far from the interface, the fast calculation of far-field radiation characteristics of arbitrarily oriented electromagnetic dipole over the half-space has been done. The main work and innovation of this paper are as follows: 1. Fast calculation of the radiation field in the far region of the electric and magnetic dipole with arbitrary orientation over the layered half-space. In view of the problem that the Green's function contains complex Sommerfeld integrals and is difficult to calculate in layered half-space, in this paper, when the observation point is far from the interface (in the case of space-based radar observation), the arbitrary electric orientation above the layered half-space is obtained by using reciprocity theorem. Analytical expression of radiation field in frequency domain of magnetic dipole. Furthermore, an analytical expression of the radiation field in frequency domain of an anisotropic layered half-space with arbitrary orientation is given. It lays a good foundation for the fast calculation of the electromagnetic characteristics of the target over half space. Analysis of polarization characteristics of reflected waves when linear polarized waves are incident into half space. In the previous analysis and calculation, the polarization characteristics of layered half-space reflected waves are often neglected compared with the polarization characteristics of incident waves. In this paper, the change of the polarization state of the reflected wave when the linear polarized wave is incident to the dielectric interface is systematically studied. The effects of the polarization angle of incident wave and the parameters of half-space medium on the polarization state of reflected wave are analyzed. The distribution of polarization state of reflected wave on Poincare sphere under different incident conditions is given and analyzed in detail. This part of the work provides a guarantee for the addition of incident wave in the calculation of electromagnetic scattering from a target over half space by using the semi-analytical method. A semi-analytical method for the calculation of electromagnetic properties of layered half-space and its upper target. In this paper, the semi-analytical method is used to calculate the electromagnetic scattering problem of layered half-space and its upper target, and a method to study the electromagnetic characteristics of the target above the half-space containing only the target itself is proposed. The effect of layered half-space is realized by the introduction of bi-directional incident wave (direct wave and interfacial reflection wave). Considering the difference in polarization state, electric field amplitude and phase between the reflected wave and the incident wave, the interfacial reflection wave is introduced into the calculation region by the principle of equivalence. In the transient field calculation, the incident wave and the reflected wave are introduced into the FDTD (Finite Difference Time Domain, finite-difference time-domain method with Fourier transform. Study on the coupling characteristics of target over half space under high power microwave irradiation. Using the above method, the near-field characteristics of the target when the high-power microwave is incident into the target under the condition of half-space are analyzed and discussed. When the incident condition is changed, the change of the energy coupling inside the target is analyzed and discussed.
【学位授予单位】：西安电子科技大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TN011

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