In this paper, a synthetic aperture radar (SAR) approach, for imaging internal structures of generally lossy layered dielectric cylindrical objects, is presented. This method which properly accounts for different transmission and refraction paths at each boundary between different layers produces a properly focused image of embedded targets. This approach is also capable of addressing imaging needs for asymmetrical multilayered cylindrical bodies. Consequently, this approach overcomes the limitation associated with the conventional methodology, in which free-space propagation is assumed. The calculation method of angular sampling criterion for circular and cylindrical SARs (i.e., circumferential and in height) is also presented. Electromagnetic simulations are performed on a three-layer cylindrical object, symmetrical and asymmetrical, with embedded targets to validate the approach. In addition, representative measurements are conducted at X-band (8.2–12.4 GHz), demonstrating the effectiveness of the approach for practical nondestructive evaluation applications.

中文翻译：

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用于圆形和圆柱形多层介电结构无损检测的时间反转 SAR 成像

在本文中，提出了一种合成孔径雷达 (SAR) 方法，用于对一般有损分层介电圆柱形物体的内部结构进行成像。这种方法正确地考虑了不同层之间每个边界处的不同传输和折射路径，产生了嵌入目标的正确聚焦图像。这种方法还能够解决非对称多层圆柱体的成像需求。因此，该方法克服了与假设自由空间传播的传统方法相关的限制。还介绍了圆形和圆柱形SAR（即周向和高度）角度采样准则的计算方法。电磁模拟是在三层圆柱物体上进行的，对称和不对称，使用嵌入式目标来验证该方法。此外，在 X 波段 (8.2–12.4 GHz) 上进行了代表性测量，证明了该方法在实际无损评估应用中的有效性。