This paper proposes cavity resonators under parity-time- ($PT$) symmetric conditions for robust wireless power transfer (WPT) with minimal exposure to electromagnetic (EM) fields. Transceiver cavities with the same resonant frequencies as that of the fundamental mode are coupled through very small evanescent waves leaking out of the lattices on the top surface of the cavities. This reduces the magnitude of the EM fields near the power-delivery system by $10$ to $10000$ times compared with conventional coil systems. Regardless of the small coupling factors between the cavities, the power-transfer efficiency is maintained at a high level due to the high quality factors of the cavities. According to coupled-mode theory, the resonant frequency of the coupled system changes sensitively with respect to the receiver position, making power delivery unstable. In this work, a feedback loop at the transmit cavity along with the saturated gain of the power amplifier achieves the $PT$-symmetric condition. The power-transfer efficiency is robust because the operating frequency is automatically locked to the resonant frequency, regardless of the operation conditions. The proposed cavity system is promising for supplementing the conventional coil system for WPT applications in which minimal field exposure is crucial. The paper is accompanied by videos demonstrating experiments.

中文翻译：

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使用奇偶时间对称微波腔具有最小场暴露的稳健无线电力传输

本文提出了奇偶时间下的腔谐振器-（$磷吨$) 对称条件，以实现对电磁 (EM) 场的最小暴露的稳健无线电力传输 (WPT)。具有与基模相同谐振频率的收发器腔通过从腔顶表面上的晶格泄漏的非常小的倏逝波耦合。这将供电系统附近的电磁场的幅度降低了$10$ 至 $10000$与传统线圈系统相比。不管腔体之间的小耦合因子如何，由于腔体的高品质因子，功率传输效率保持在高水平。根据耦合模式理论，耦合系统的谐振频率相对于接收器的位置会发生敏感变化，从而导致功率传输不稳定。在这项工作中，发射腔的反馈回路以及功率放大器的饱和增益实现了$磷吨$-对称条件。无论工作条件如何，工作频率都会自动锁定到谐振频率，因此功率传输效率很高。所提出的腔体系统有望补充用于 WPT 应用的传统线圈系统，其中最小的场暴露至关重要。该论文附有演示实验的视频。