During usage, printed electronic components are often stretched, bent, folded, and/or twisted to conform to underlying structure. In this article, tests have been developed for characterizing the mechanical and high-frequency electrical behavior of inkjet-printed patch antennas on flexible polyethylene terephthalate (PET) substrates under uniaxial and biaxial bending. A patch antenna is designed to have a single resonant frequency of 5 GHz in free space. Polycarbonate cylindrical mandrels of 1.25” diameter and special sculptured surfaces have been used as uniaxial and biaxial bending fixtures, respectively. Up to 2000 bending cycles have been performed in both uniaxial and biaxial bending tests. During bending tests, $S_{11}$ (return loss) has been measured by a vector network analyzer (VNA) in both bent and flat configurations. Mechanical simulations have also been performed to determine the strain distribution in the printed elements which will lead to changes in electrical behavior. Scanning electron microscope (SEM) images have been taken to examine the physical damage in the printed structure and to correlate with the strain values obtained through mechanical simulation. High-frequency electrical simulations have also been performed to correlate with the bending experimental data. It is seen that the conductivity of the printed structure changes differently in different zones, due to various values of strain they undergo. Although the cracks are observed in the printed structures, the maximum relative shift in the measured resonant frequency is less than 1.66% in both uniaxial and biaxial bend tests.

中文翻译：

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变形下印刷柔性天线的机械和高频电气研究


在使用过程中，印刷电子元件经常被拉伸、弯曲、折叠和/或扭曲以符合底层结构。本文开发了一些测试，用于表征柔性聚对苯二甲酸乙二醇酯 (PET) 基板上的喷墨印刷贴片天线在单轴和双轴弯曲下的机械和高频电气行为。贴片天线设计为在自由空间中具有 5 GHz 的单一谐振频率。直径为 1.25 英寸的聚碳酸酯圆柱形心轴和特殊雕刻表面已分别用作单轴和双轴弯曲夹具。单轴和双轴弯曲测试均进行了多达 2000 次弯曲循环。在弯曲测试期间，通过矢量网络分析仪 (VNA) 在弯曲和平坦配置下测量了 $S_{11}$（回波损耗）。还进行了机械模拟以确定印刷元件中的应变分布，这将导致电气行为的变化。拍摄扫描电子显微镜（SEM）图像来检查印刷结构中的物理损伤，并与通过机械模拟获得的应变值相关联。还进行了高频电气模拟以与弯曲实验数据相关联。可以看出，由于所承受的应变值不同，印刷结构的电导率在不同区域的变化也不同。尽管在印刷结构中观察到裂纹，但在单轴和双轴弯曲测试中测得的谐振频率的最大相对偏移均小于1.66%。