A Self-Tuned Method for Impedance-Matching of Planar-Loop Resonators in Conformable Wearables
A Self-Tuned Method for Impedance-Matching of Planar-Loop Resonators in Conformable Wearables
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DOI：
10.3390/electronics11172784
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发表时间：
2022-09-01
期刊：
影响因子：
2.9
通讯作者：
Chiao, J-C
中科院分区：
文献类型：
--
作者：
Bing, Sen;Chawang, Khengdauliu;Chiao, J-C
环形结构已被用作单个谐振器和超材料。诸如开口环谐振器的回路结构的变型已经被用作用于可穿戴应用的集成设备中的感测元件或用于自由空间谐振的阵列配置中的感测元件。以前，阻抗公式和等效电路模型已经开发了一个单一的回路制成的导体线与一个可以忽略不计的线直径在自由空间。然而，尽管具有平面和小的特征，但单环谐振器或天线的品质因数还没有足够高以将它们有效地用于感测或功率传输。为了研究这种局限性，我们首先通过实验研究了由平面金属片制成的单个回路的公式和等效电路，沿着进行有限元模拟。改变环路性能因子以验证公式和等效电路。然后，在平面环路中利用调谐元件，通过向环路提供分布阻抗匹配来改善谐振。所提出的调谐方法进行了证明与仿真和测量。建立了调谐环路谐振器的等效电路模型。谐振时的品质因数显示出显著的改善，并且可以在不改变环路半径的情况下针对特定谐振阶数进行调谐。研究还表明，调谐方法为谐振器提供了更鲁棒的性能。该调谐机构适用于传感应用中的微型平面器件架构，特别是适用于尺寸和形状因子有限制的植入物和可穿戴设备。等效电路模型也可以应用于阵列配置的超材料。
Loop structure has been used as a single resonator and in meta-materials. Variations from the loop structures such as split-ring resonators have been utilized as sensing elements in integrated devices for wearable applications or in array configurations for free-space resonance. Previously, impedance formula and equivalent circuit models have been developed for a single loop made of a conductor wire with a negligible wire diameter in the free space. Despite the features of being planar and small, however, the quality factors of single-loop resonators or antennas have not been sufficiently high to use them efficiently for sensing or power transfer. To investigate the limitation, we first experimentally examined the formula and equivalent circuits for a single loop made of planar metal sheets, along with finite element simulations. The loop performance factor was varied to validate the formula and equivalent circuits. Then a tuning element was utilized in the planar loop to improve resonance by providing distributed impedance-matching to the loop. The proposed tuning method was demonstrated with simulations and measurements. A new equivalent circuit model for the tuned loop resonator was established. Quality factors at resonance show significant improvement and the tuning can be done for a specific resonance order without changing the loop radius. It was also shown that the tuning method provided more robust performance for the resonator. The tuning mechanism is suitable for miniature planar device architectures in sensing applications, particularly for implants and wearables that have constraints in dimensions and form factors. The equivalent circuit model can also be applied for meta-materials in arrayed configurations.