微波逆散射成像中的若干问题研究

发布时间：2018-02-20 16:49

本文关键词： 逆散射问题子空间优化算法斜入射隔墙成像微波成像系统　出处：《浙江大学》2017年博士论文　论文类型：学位论文

【摘要】：电磁逆散射问题是逆问题研究的一个重要分支,拥有广泛的应用前景。本文主要研究电磁逆散射成像问题。首先,本文针对较少有人研究的斜入射情况下的二维电磁逆散射问题,通过建立TM与TE模式相耦合的电磁散射模型,提出了一种实现任意入射极化、任意斜入射角度下的二维逆散射成像算法。通过数值仿真,分析了斜入射角度和极化对成像质量的影响。研究结果指出,尽管斜入射情况下TM与TE模式之间存在耦合,但斜入射角度较小时交叉极化分量对成像质量影响较小,因而通过合理选择入射波与所测量的散射场的极化,可以在不明显恶化成像质量的前提下简化成像系统的设计。本文设计并实现了斜入射条件下进行逆散射成像的实验系统,并通过基于实测数据的逆散射成像验证了上述算法的有效性。其次,本文针对缺乏实验研究的非均匀背景下的逆散射成像问题,考虑实际系统中可能存在的各种因素的影响,进行了成像方法的优化,提出了多种隔墙成像的策略,并实现了对位于四面墙体围成的封闭区域内的目标进行逆散射隔墙成像的实验。本文在改进校准方法的基础上,通过对多种目标进行测量,得到了逆散射隔墙成像的实验数据。通过比较不同策略的成像结果,可以得出结论:在使用实测数据时,基于非均匀背景格林函数的算法成像效果较好。最后,本文研究了实际应用中普遍存在的观察视角受限时的逆散射成像问题,提出了一种在成像目标背后设置反射平面提升成像质量的方法,可有效弥补观察视角缺失导致的成像信息丢失。本文首先通过镜像原理推导并建立了导体平面附近物体的电磁散射模型,实现了对导体平面附近目标的逆散射成像。其后进一步研究了观察视角受限对成像质量的影响,以及在成像目标背后设置导体平面对成像质量的改善。研究表明,当观察视角受限时,在成像目标背后设置导体平面可以改善成像质量。相关研究结果可用于微波成像系统设计。
[Abstract]:Electromagnetic inverse scattering problem is an important branch of inverse problem research, which has a wide application prospect. This paper mainly studies electromagnetic inverse scattering imaging problem. In this paper, a new electromagnetic scattering model coupled TM with te mode is proposed to realize arbitrary incident polarization in the case of oblique incidence, which is seldom studied. The effect of angle of oblique incidence and polarization on imaging quality is analyzed by numerical simulation. The results show that there is a coupling between TM and te mode in oblique incidence. However, the cross-polarization component has little effect on the imaging quality when the angle of incidence is small, so the polarization of the incident wave and the measured scattering field can be reasonably selected. The design of the imaging system can be simplified without obviously deteriorating the imaging quality. In this paper, an experimental system for inverse scattering imaging under oblique incidence is designed and implemented. The effectiveness of the algorithm is verified by the inverse scattering imaging based on the measured data. Secondly, in this paper, the influence of various factors in the actual system is considered for the inverse scattering imaging in the non-uniform background, which is not studied experimentally. In this paper, the imaging method is optimized, a variety of partition imaging strategies are put forward, and the experiment of inverse scattering partition imaging of a target located in a closed area surrounded by four walls is carried out. In this paper, the calibration method is improved. The experimental data of inverse scattering partition imaging are obtained by measuring various targets. By comparing the imaging results of different strategies, it can be concluded that, when using the measured data, The algorithm based on non-uniform background Green's function has good imaging effect. Finally, the problem of inverse scattering imaging with limited viewing angle is studied in practical applications. In this paper, a method to improve the imaging quality by setting a reflection plane behind the imaging target is presented. It can effectively compensate for the loss of imaging information caused by the absence of viewing angle. Firstly, the electromagnetic scattering model of an object near the conductor plane is derived and established by the mirror image principle. The inverse scattering imaging of the target near the conductor plane is realized. The influence of the limited viewing angle on the imaging quality and the improvement of the imaging quality by setting the conductor plane behind the imaging target are further studied. When the viewing angle is limited, the imaging quality can be improved by setting the conductor plane behind the imaging target. The related results can be used in the design of microwave imaging system.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TN015

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