We describe the observation of a previously unreported resonance phenomenon in UWB SAR imaging, and its application in a novel scheme for the retrieval of dielectric properties of scene features. The resonance was observed in a 14-50GHz laboratory study of very high-resolution SAR imagery. It presented as a periodic fluctuation in the backscatter of a scene feature in response to changes in the radar measurement frequency. Complimentary static reflectivity measurements of a range of dielectric materials showed the phenomenon could be understood as a material behaving as a resonant microwave cavity. Modeling simulations were able to accurately reproduce the observed nulling characteristics for visually homogeneous materials (acrylic, MDF, plasterboard), and which dis-played a regular frequency spacing between nulls. Those with inhomogeneous structures (chipboard, plywood) showed much more irregular nulling patterns. The spacing of the backscatter nulls is set by the product of the permittivity and thickness of the material. By exploiting diversity in viewing geometry, the two terms can be separated and measured. The scheme offers a valuable new opportunity in SAR surveillance and monitoring of man-made structures

中文翻译：

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在 UWB 14-50GHz SAR 中观察到的新共振现象及其在场景特征的厚​​度和介电特性检索中的应用

我们描述了对 UWB SAR 成像中以前未报告的共振现象的观察，及其在检索场景特征介电特性的新方案中的应用。在 14-50GHz 的超高分辨率 SAR 图像实验室研究中观察到了共振。它表现为场景特征反向散射的周期性波动，以响应雷达测量频率的变化。一系列介电材料的免费静态反射率测量表明，这种现象可以理解为一种材料表现为谐振微波腔。建模模拟能够准确地重现观察到的视觉均质材料（丙烯酸、MDF、石膏板）的归零特性，并显示零点之间的规则频率间隔。那些结构不均匀的（刨花板、胶合板）表现出更不规则的归零模式。反向散射零点的间距由材料的介电常数和厚度的乘积设置。通过利用观察几何的多样性，可以分离和测量这两个术语。该计划为 SAR 监视和人造结构监测提供了宝贵的新机会