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 雷达学报  2018, Vol. 7 Issue (1): 97-107  DOI: 10.12000/JR17086 0

### 引用本文

Gao Jingkun, Deng Bin, Qin Yuliang, et al. Radar echo scattering modeling and image simulations of full-scale convex rough targets at terahertz frequencies[J]. Journal of Radars, 2018, 7(1): 97-107. DOI: 10.12000/JR17086.

### 文章历史

THz全尺寸凸体粗糙目标雷达回波散射建模与成像仿真

(国防科技大学电子科学学院   长沙   410073)

Radar Echo Scattering Modeling and Image Simulations of Full-scale Convex Rough Targets at Terahertz Frequencies
Gao Jingkun, Deng Bin, Qin Yuliang, Wang Hongqiang, Li Xiang
(College of Electronic Science and Engineering, National University of Defense Technology, Changsha 410073, China)
Foundation Item: The National Natural Science Foundation of China (61701513, 61571011)
Abstract: Echo simulation is a precondition for developing radar imaging systems, algorithms, and subsequent applications. Electromagnetic scattering modeling of the target is key to echo simulation. At terahertz (THz) frequencies, targets are usually of ultra-large electrical size that makes applying classical electromagnetic calculation methods unpractical. In contrast, the short wavelength makes the surface roughness of targets a factor that cannot be ignored, and this makes the traditional echo simulation methods based on point scattering hypothesis in applicable. Modeling the scattering characteristics of targets and efficiently generating its radar echoes in THz bands has become a problem that must be solved. In this paper, a hierarchical semi-deterministic modeling method is proposed. A full-wave algorithm of rough surfaces is used to calculate the scattered field of facets. Then, the scattered fields of all facets are transformed into the target coordinate system and coherently summed. Finally, the radar echo containing phase information can be obtained. Using small-scale rough models, our method is compared with the standard high-frequency numerical method, which verifies the effectiveness of the proposed method. Imaging results of a full-scale cone-shape target is presented, and the scattering model and echo generation problem of the full-scale convex targets with rough surfaces in THz bands are preliminary solved; this lays the foundation for future research on imaging regimes and algorithms.
Key words: Terahertz waves    Echo simulation    Rough surface    Electric-Large
1 引言

2 回波散射建模方法 2.1 面片分级建模

 图 1 全尺寸目标一级面片建模示意图 Fig.1 Illustration of the first-level-facets modeling of full-scale targets

 图 2 二级面片建模过程示意图 Fig.2 Illustration of the second-level-facets modeling

2.2 粗糙面散射场计算

 图 3 一级面片坐标系定义 Fig.3 Definition of the first-level-facet coordinate system

 (1)

$C_n\,\!\!^{\rm{i}}$ , $S_n^{\rm{i}}$ , $C_n\,\!\!^{\rm{s}}$ , $S_n^{\rm{s}}$ 分别代表入射与散射角的余弦与正弦，上标0或1用以区分介质0和介质1，两种介质中入射与散射角的关系可以通过折射定律确定。式(6)中 $\cos \left( {\phi _n^{\rm{s}} - \phi _n^{\rm{i}}} \right)$ , $\sin \left( {\phi _n^{\rm{s}} - \phi _n^{\rm{i}}} \right)$ 分别代表入射与散射平面间夹角的余弦与正弦。

2.3 全尺寸凸体粗糙目标回波仿真

 (11)

 图 4 THz全尺寸凸体粗糙目标回波仿真流程 Fig.4 Flowchart of radar echo simulation for THz full-scale convex rough targets
3 回波生成与成像仿真结果分析

3.1 小尺寸粗糙矩形板

 图 5 粗糙矩形板RCS随俯仰角变化曲线 Fig.5 Calculated RCS vs. elevation angle of the rough rectangular plate

 图 6 粗糙平板成像结果，粗糙度250 μm( $\lambda /4$ ) Fig.6 Imaging results of the rough plate with 250 μm surface roughness

3.2 全尺寸粗糙锥体

 图 7 粗糙锥体成像结果，粗糙度125 μm( $\lambda /8$ ) Fig.7 Imaging results of the full-scale cone with 125 μm surface roughness
 图 8 粗糙锥体成像结果，粗糙度250 μm( $\lambda /4$ ) Fig.8 Imaging results of the full-scale cone with 250 μm surface roughness
4 结论