摘 要

雷达技术的快速发展扩展了常规雷达的应用领域，合成孔径雷达 (SAR) 及逆合成孔径雷达 (ISAR) 等高分辨率雷达应运而生，对人造目标的准确识别也成为了当前的重点和难点。在军用方面，需要实现对车辆、飞机和舰船等人造目标的侦查与识别。在民用方面，灾害损失评估以及事故搜寻营救等任务对人造目标识别同样需求迫切。人造目标通常由多个典型结构组成。本文基于合成孔径雷达成像原理，通过分析极化散射理论，研究极化分解方法，对比理论模型与仿真数据，进一步研究典型结构及其判别方法。以下为本文主要工作：

本文首先通过介绍研究目的与背景，以及国内外的研究现状，突出目标结构判别的重要作用。进一步分析 SAR 成像原理，讨论基于投影—切片定理的转台成像方法，并通过仿真测试成像效果。随后介绍了常用电磁散射模型，根据人造目标结构特征，研究了多类典型几何结构的极化散射特性，并通过空域极化特性，描述了不同姿态角下典型结构散射特性的变化。最后介绍多种极化分解理论，并针对单一方法难以准确判断结构类型的问题，将属性散射中心模型的频率特性与目标极化散射特性相结合，提出了结合频率和极化分解的几何结构判别方法。并通过建立模型进行仿真测试，成功判别了该模型中包含的几何结构类型。

关键词：合成孔径雷达；人造目标结构；极化散射特性；极化分解；频率特性

Abstract

The rapid development of radar technology has expanded the application field of conventional radar. High-resolution radars have emerged as the times require, such as Synthetic Aperture Radar (SAR) and Inverse Synthetic Aperture Radar (ISAR). Accurate identification of man-made targets has also become the current focus and difficulty. In terms of military use, it is necessary to detect and recognize man-made targets such as vehicles, aircraft and ships. In terms of civilian use, the task of disaster loss assessment and accident search and rescue is also urgent for man-made target recognition. Man-made targets usually consist of several typical structures. Based on the principle of SAR imaging, this paper analyzes the theory of polarization scattering, studies the polarization decomposition method, compares the theoretical model and simulation data, and further studies the typical structure and its discrimination method. The main work of this paper is as follows:

Firstly, this paper introduces the research purpose and background, as well as the research status at home and abroad, which highlights the important role of target structure discrimination. Furthermore, the principle of SAR imaging is analyzed, the method of turntable imaging based on projection slice theorem is discussed, and the imaging effect is tested by simulation. Then, the commonly used electromagnetic scattering model is introduced. According to the structural characteristics of artificial target, the polarization scattering characteristics of many kinds of typical geometric structures are studied, and the variation of the scattering characteristics of typical structures under different attitude angles is described through the polarization characteristics of airspace. At last, several polarization decomposition theories are introduced. Aiming at the problem that a single method is difficult to accurately determine the structure type, the frequency characteristics of the attribute scattering center model are combined with the polarization scattering characteristics of the target, and a geometric structure discrimination method combining frequency and polarization decomposition is proposed. And through the establishment of the model for simulation test, the geometry types included in the model are successfully identified.

Key Words: Synthetic Aperture Radar; man-made target structure; Polarization scattering characteristics; coherent decomposition; frequency characteristic

目录

摘要 I

Abstract II

第1章 绪论 1

1.1研究目的与背景 1

1.2国内外研究现状 1

1.2.1典型几何结构极化特性 2

1.2.2典型结构判别方法 2

1.3本文主要工作 3

第2章 雷达成像特性研究与仿真 5

2.1合成孔径雷达 5

2.1.1成像原理 5

2.1.2 SAR 信号的性质 6

2.2转台成像 9

2.2.1投影—切片定理 9

2.2.2转台成像原理 11

2.2.3成像方法 12

2.2.4仿真测试 12

2.3本章小结 13

第3章 典型结构极化散射特性 15

3.1电磁散射模型 15

3.1.1理想点散射中心模型 15

3.1.2属性散射中心模型 17

3.2典型几何结构散射模型 18

3.2.1散射模型 18

3.2.2极化响应 20

3.2.3模型建立与对比 21

3.3空域极化特性 24

3.4本章小结 27

第4章 目标几何结构判别 28

4.1极化分解方法 28

4.1.1 Pauli 分解 28

4.1.2 Krogager 分解 30

4.1.3 Cameron 分解 32

4.2几何结构判别 34

4.2.1频率依赖因子 34

4.2.2结合频率和 Krogager 分解的几何结构判别 35

4.2.3仿真测试 37

4.3本章小结 39

第5章 结论 40

参考文献 41

致谢 43

第1章 绪论

1.1研究目的与背景

合成孔径雷达 (Synthetic Aperture Radar, SAR) 在近年来受到越来越广泛的关注，其甚至可以对每个照射目标进行高分辨率成像。相比于传统光学图像，其通过微波进行成像，具有全天时、全天候工作以及穿透云雾等光学图像所不具备的特点，甚至一些隐匿于树林和地表浅层下的目标也将被工作在低频段的合成孔径雷达所发现。SAR 是一种主动式的微波成像传感器。自上世纪五十年代开始，从获得第一幅全聚焦 SAR 图像，到成功发射第一颗 SAR 卫星，SAR 已逐渐向成熟性与实用性进步^[1]。发展 SAR 技术已经成为了当今主流趋势之一，其优秀的性能必将为各国所重视。

目前，SAR 对于民用以及军事方面都具有重要意义。在民用方面 SAR 可以用来进行三维成像地图测绘，以及植被观测，例如采集北方针叶林植被区的覆盖面积数据等。在军事方面 SAR 主要用来探测重要军事目标，例如机场、坦克、无人机等，同时也可用来对打击效果进行评估。对各类目标的有效识别可为决策提供可靠的帮助。