Scattering Structure Recognition of Space Target in Polarimetric Rotation Domain
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摘要: 极化逆合成孔径雷达(ISAR)具备全极化测量和高分辨成像能力,已成为空间态势感知的重要传感器。作为典型的人造目标,空间目标散射特性敏感于目标姿态和雷达视线方向的相对夹角。这种散射多样性给极化ISAR数据解译带来困难,也蕴藏着丰富的极化散射信息。为提高空间目标散射结构辨识性能,该文深入挖掘绕雷达视线的极化旋转域信息,提出一种空间目标散射结构极化旋转域辨识方法,共包含3个步骤。首先,对极化ISAR数据开展绕雷达视线的极化旋转域分析,导出极化相关方向图特征。其次,分析基本散射体的极化相关方向图特性,构造极化特征编码矢量。最后,基于极化特征编码矢量距离度量实现散射结构极化辨识。围绕太阳能帆板、反射面天线等空间目标典型部件开展仿真实验研究,所提方法相较于传统的Cameron分解方法性能更优,鲁棒性更高。Abstract: Polarimetric Inverse Synthetic Aperture Radar (ISAR), which has the ability of full polarization measurement and high-resolution imaging, has become an important sensor for space awareness. As a typical man-made target, space target has various scattering characteristic, which is sensitive to the relative angle between the target orientation and the radar’s line of sight. This scattering diversity makes it difficult for polarimetric ISAR data interpretation. Besides, enrich polarimetric scattering information is hidden within it. In order to promote the interpretation performance of space target, a scattering structure recognition method in polarimetric rotation domain is proposed by mining the polarimetric rotation domain information along the radar’s line of sight, which mainly contains three steps. Firstly, polarimetric rotation domain analysis along the radar’s line of sight is conducted on the polarimetric ISAR data and a set of polarimetric correlation pattern features are derived. Secondly, the polarimetric correlation pattern characteristics of canonical structures are analyzed and the polarimetric feature coding vectors are given. Finally, the target scattering structure can be recognized by the distance of polarimetric feature coding vectors. Simulation experimental studies are carried out with the typical space target components of solar panel and reflector antenna. Compared with the traditional Cameron decomposition, the proposed method has superior and robust performance.
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表 1 极化相关方向图特征表达式及物理意义
极化相关方向图特征 表达式 物理意义 原始极化相关特征值 ${\tilde \gamma _{ \text{-}{\text{org} } } } = \left| {\tilde \gamma \left( 0 \right)} \right|$ 原始成像几何下的去相关效应 极化相关度 ${\tilde \gamma _{ \text{-}{\text{mean} } } } = {\text{mean} }\left\{ {\left| {\tilde \gamma \left( \theta \right)} \right|} \right\}$ 极化旋转域的平均去相关效应 极化相关起伏度 ${\tilde \gamma _{ \text{-}{\text{std} } } } = {\text{std} }\left\{ {\left| {\tilde \gamma \left( \theta \right)} \right|} \right\}$ 极化相关值在极化旋转域中的起伏程度 极化相关特征最大值 ${\tilde \gamma _{ \text{-} \max } } = \max \left\{ {\left| {\tilde \gamma \left( \theta \right)} \right|} \right\}$ 极化相关值上界 极化相关特征最小值 ${\tilde \gamma _{ \text{-} \min } } = \min \left\{ {\left| {\tilde \gamma \left( \theta \right)} \right|} \right\}$ 极化相关值下界 极化相关对比度 ${\tilde \gamma _{\text{-}{\text{contrast} } } } = {\tilde \gamma _{ \text{-} \max } } - {\tilde \gamma _{ \text{-} \min } }$ 极化相关值极差 极化相关特征反熵 ${\tilde \gamma _{ \text{-}{\text{A} } } } = \left( { { {\tilde \gamma }_{ \text{-} \max } } - { {\tilde \gamma }_{ \text{-} \min } } } \right)/\left( { { {\tilde \gamma }_{\text{-} \max } } + { {\tilde \gamma }_{\text{-} \min } } } \right)$ 极化相关值相对极差 最小化旋转角 ${\theta _{\tilde \gamma \text{-} \min } } = \arg {\text{ } }\min \left\{ {\left| {\tilde \gamma \left( \theta \right)} \right|} \right\}$ 极化相关值最小时对应旋转角 最大化旋转角 ${\theta _{\tilde \gamma \text{-} \min } } = \arg {\text{ } }\max \left\{ {\left| {\tilde \gamma \left( \theta \right)} \right|} \right\}$ 极化相关值最大时对应旋转角 极化相关宽度 $\left\{ \begin{aligned}& { { {\tilde \gamma }_{ \text{-}{\text{bw0} }{\text{.95} } } } = {\theta _1} - {\theta _2} } \\ & {\tilde \gamma \left( { {\theta _1} } \right) = \tilde \gamma \left( { {\theta _2} } \right) = 0.95 \cdot { {\tilde \gamma }_{ {\text{-max} } } } } \end{aligned} \right.$ 目标对取向依赖性效应的敏感程度 表 2 7种典型散射体极化散射矩阵及极化相关方向图
平板 二面角 偶极子 圆柱 窄二面角 1/4波器件 螺旋散射体 极化散射矩阵 $\left[ {\begin{array}{*{20}{c}} 1&0 \\ 0&1 \end{array}} \right]$ $\left[ {\begin{array}{*{20}{c}} 1&0 \\ 0&{ - 1} \end{array}} \right]$ $\left[ {\begin{array}{*{20}{c}} 1&0 \\ 0&0 \end{array}} \right]$ $\left[ {\begin{array}{*{20}{c} } 1&0 \\ 0&{\dfrac{1}{2} } \end{array} } \right]$ $\left[ {\begin{array}{*{20}{c} } 1&0 \\ 0&{ - \dfrac{1}{2} } \end{array} } \right]$ $\left[ {\begin{array}{*{20}{c}} 1&0 \\ 0&{\text{j}} \end{array}} \right]$ $\dfrac{1}{2}\left[ {\begin{array}{*{20}{c} } 1&{\text{j} } \\ {\text{j} }&{ - 1} \end{array} } \right]$ $\left| { { {\tilde \gamma }_{ {\text{HH-HV} } } }\left( \theta \right)} \right|$ $\left| { { {\tilde \gamma }_{ {\text{HH-VV} } } }\left( \theta \right)} \right|$ $\left| { { {\tilde \gamma }_{({\text{HH+VV} }){\text{-(HH-VV)} } } }\left( \theta \right)} \right|$ $\left| { { {\tilde \gamma }_{({\text{HH-VV} }){\text{-(HV)} } } }\left( \theta \right)} \right|$ 表 3 电磁仿真参数
波段 载频(GHz) 距离向分辨率(m) 成像孔径(°) 方位向分辨率(m) 方位角(°) 俯仰角(°) X 9.5~10.5 0.150 5.73 0.150 [0:15:90] [30 40] Ku 15.5~17.5 0.075 6.94 0.075 [0:15:90] [30 40] 表 4 X波段太阳能帆板结构辨识结果中各散射结构占比(%)
观测视角 Cameron分解 极化旋转域辨识 俯仰角 方位角 平板 圆柱 1/4波器件 其它 平板 圆柱 1/4波器件 其它 30° 0° 73.33 26.67 0 0 73.33 26.67 0 0 15° 0 86.67 13.33 0 0 100.00 0 0 30° 23.33 76.67 0 0 76.67 13.33 10.00 0 45° 100.00 0 0 0 96.67 0 0 3.33 60° 100.00 0 0 0 100.00 0 0 0 75° 23.33 73.33 3.33 0 73.33 3.33 23.33 0 90° 0 30.00 70.00 0 0 83.33 6.67 10.00 40° 0° 90.00 10.00 0 0 90.00 10.00 0 0 15° 100.00 0 0 0 100.00 0 0 0 30° 0 100.00 0 0 0 100.00 0 0 45° 73.33 26.67 0 0 46.67 53.33 0 0 60° 0 100.00 0 0 0 100.00 0 0 75° 0 100.00 0 0 0 100.00 0 0 90° 63.33 20.00 13.33 3.33 63.33 10.00 23.33 3.33 表 5 Ku波段太阳能帆板结构辨识结果中各散射结构占比(%)
观测视角 Cameron分解 极化旋转域辨识 俯仰角 方位角 平板 圆柱 1/4波器件 其它 平板 圆柱 偶极子 其它 30° 0° 0 28.00 72.00 0 0 30.00 70.00 0 15° 0 18.00 82.00 0 0 18.00 82.00 0 30° 0 94.00 6.00 0 0 100.00 0 0 45° 0 14.00 62.00 24.00 0 24.00 22.00 54.00 60° 2.00 50.00 46.00 2.00 2.00 66.00 18.00 14.00 75° 0 28.00 72.00 0 0 50.00 50.00 0 90° 40.00 60.00 0 0 98.00 0 0 2.00 40° 0° 54.00 40.00 6.00 0 56.00 42.00 0 2.00 15° 0 48.00 52.00 0 0 66.00 34.00 0 30° 8.00 92.00 0 0 62.00 38.00 0 0 45° 2.00 12.00 64.00 22.00 2.00 8.00 34.00 56.00 60° 26.00 52.00 22.00 0 20.00 24.00 2.00 54.00 75° 0 100.00 0 0 0 100.00 0 0 90° 58.00 42.00 0 0 58.00 42.00 0 0 表 6 X波段反射面天线结构辨识结果中各散射结构占比(%)
观测视角 Cameron分解 极化旋转域辨识 俯仰角 方位角 平板 圆柱 1/4波器件 其它 平板 圆柱 1/4波器件 其它 30° 0° 85.00 10.00 0 5.00 85.00 10.00 5.00 0 15° 80.00 20.00 0 0 80.00 20.00 0 0 30° 95.00 5.00 0 0 95.00 5.00 0 0 45° 100.00 0 0 0 100.00 0 0 0 60° 80.00 20.00 0 0 85.00 15.00 0 0 75° 90.00 10.00 0 0 90.00 10.00 0 0 90° 85.00 10.00 0 5.00 85.00 10.00 5.00 0 40° 0° 35.00 40.00 20.00 5.00 50.00 15.00 30.00 5.00 15° 75.00 25.00 0 0 90.00 10.00 0 0 30° 65.00 25.00 5.00 5.00 80.00 0 15.00 5.00 45° 45.00 50.00 5.00 0 80.00 20.00 0 0 60° 80.00 15.00 5.00 0 90.00 0 5.00 5.00 75° 75.00 25.00 0 0 90.00 10.00 0 0 90° 35.00 40.00 15.00 10.00 50.00 15.00 30.00 5.00 表 7 Ku波段反射面天线结构辨识结果中各散射结构占比(%)
观测视角 Cameron分解 极化旋转域辨识 俯仰角 方位角 平板 圆柱 1/4波器件 其它 平板 圆柱 1/4波器件 其它 30° 0° 56.67 36.67 6.67 0 66.67 20.00 13.33 0 15° 56.67 36.67 6.67 0 66.67 26.67 6.67 0 30° 70.00 23.33 3.33 3.33 73.33 16.67 6.67 3.33 45° 56.67 36.67 3.33 3.33 70.00 20.00 3.33 6.67 60° 66.67 30.00 0 3.33 70.00 26.67 0 3.33 75° 63.33 33.33 3.33 0 73.33 23.33 3.33 0 90° 56.67 33.33 10.00 0 66.67 20.00 13.33 0 40° 0° 46.67 40.00 13.33 0 40.00 56.67 0 3.33 15° 56.67 40.00 3.33 0 60.00 36.67 3.33 0 30° 60.00 40.00 0 0 66.67 33.33 0 0 45° 56.67 40.00 3.33 0 56.67 36.67 3.33 3.33 60° 46.67 50.00 3.33 0 63.33 33.33 3.33 0 75° 60.00 36.67 3.33 0 60.00 40.00 0 0 90° 46.67 40.00 13.33 0 40.00 56.67 0 3.33 -
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