首页 >  2021, Vol. 25, Issue (1) : 323-331

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DOI:

10.11834/jrs.20210397

收稿日期:

2020-09-11

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微波目标散射特性全要素测量试验
邵芸1,2,宫华泽1,2,田维1,2,张庆君3,王国军1,2,卞小林1,2,张婷婷1,2,张风丽1,2,李坤1,2,刘致曲2,倪崇3
1.中国科学院空天信息创新研究院, 北京 100101;2.浙江省微波目标特性测量与遥感重点实验室, 湖州 313200;3.中国空间技术研究院遥感卫星总体部, 北京 100094
摘要:

合成孔径雷达SAR(Synthetic Aperture Radar )以其全天时全天候的观测能力在地表目标识别、灾害监测等领域得到了越来越多的重视,高分辨率、全极化等各类先进SAR载荷卫星的发展日新月异。相对而言,微波与地物目标的相互作用机理仍有待深入研究。在可控无电磁干扰的测试环境下开展典型目标微波特性测量实验,可以再现SAR卫星电磁波与地物目标的相互作用过程,有效提升微波电磁波与典型地物目标相互作用机理的认知水平。本文基于“陆地目标微波特性测量与仿真成像科学实验平台”,在可控环境下对两种典型的人工目标(金属球与四旋翼植保无人机)以及典型自然地物(水稻)目标分别开展了全频段微波散射特性测量与多波段、多极化、多入射角、多方位角成像实验。实验结果表明,金属球的雷达散射截面积RCS(Radar Cross Section)测量值精度较高,在2.5 GHz以上与Mie级数模拟值的均方根误差分别为1.09 dBsm(HH极化)与1.00 dBsm(VV极化);同时实验平台能够较好地呈现无干扰环境下目标多入射角、多方位角的散射特性。此外,由于结构特征的不规则性和介电特征的不连续性,水稻的0.8—18 GHz连续微波波谱曲线起伏变化较大,这也是导致对自然地物目标的SAR图像解译困难的主要原因之一。

Experiment of measuring targets' full-parameters microwave properties
Abstract:

Synthetic Aperture Radar (SAR) has gained more and more attention in the field of target identification and disaster monitoring because of its all-weather observation capability. Many more advance SAR satellite developed in the last decade, e.g. high resolution SAR and full polarized SAR. However, the mechanism of interaction between electromagnetic wave and target in microwave band is still limited in the current research. Measurement of microwave characteristics in a controllable and non-interference environment can recur the interaction between electromagnetic wave and target on the ground, and can greatly help improving the cognition of SAR imaging as well. In this paper, the Laboratory of Target Microwave Properties (LAMP) was introduced and a full-parameters microwave properties measurement experiment was demonstrated. The internal size of LAMP is: 24 m (length) ×24 m (width) ×17 m (height). The positioning accuracy of the straight orbit system is 0.1 mm, while 0.01 °for the arc orbit. This guarantees that LAMP could implement the quantitative control of the relative motion between the antenna and the target under measurement, with high-precision. The dynamic range of LAMP is better than 100 dB, and the sensitivity is greater than -60 dBsm. The platform could conduct either imaging in conventional SAR imaging modes such as spotlight, stripmap and ISAR or in complex SAR imaging modes such as POLSAR, InSAR, polInSAR, with the highest spatial resolution is as high as 1cm. In this experiment, two kinds of typical man-made targets (medal ball and four-wind UAV) and natural targets (rice), were measured in LAMP, in conditions of multi-frequencies, multi-polarization, multi-incidence angles and multi-azimuth angles. The test results showed that the measured value of Radar Cross Section (RCS) of the metal ball was acceptable (2.5 —17 GHz): the RMSE is 1.09 dBsm and 1.00 dBsm for HH and VV polarization respectively, relative to the Mie scattering simulation value. For the rest of frequency band (lower than 2.5 GHz or higher than 17 GHz), however, the deviation between the measured and the theoretical RCS value of the medal ball was observed. The reason why it happened is that the surface of the medal ball is not smooth enough, on the other hand, the frequency band, lower than 2.5 GHz, is located at resonance area because of the diameter is of the same order of the length of incidence electromagnetic wave. At the same time, the scattering characteristics of multi-incident Angle and multi-azimuth Angle can be well presented in the experiment. On the other hand, the natural targets show varied microwave spectral graph (0.8—18 GHz), resulting from their irregular structures and discontinuous dialectical properties. This is the reason why it is tough to interpret SAR imageries in terms of objects of the nature.

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