Metamaterial-based Compact and Efficient Wireless Power Transfer System for Biomedical Implants

我们开发了一种低磁损的亚表面，并将其用于设计一种紧凑的生物医学植入物的WPT系统。我们还提出了低电感值的设计理论，以克服频移和不对准问题。我们通过使用在普通杂货店购买的鸡肉进行实验来验证所提出的设计。该系统的性能达到了预期的要求。本文简要介绍了一种结构紧凑、效率高的谐振移位不敏感无线功率传输系统。这可以通过使用小的电气长度缺陷接地结构(DGS)谐振器来实现，该谐振器被发现能够有效地对抗由于组织的高介电常数而引起的共振位移现象。组织对WPT系统有两种不良影响：(I)耦合品质因数降低，以及(Ii)导致失配损失的自谐振位移。因此，WPT系统的效率在组织环境中降低。然后，使用小电长的DGS，我们构建了一个使用三个协同DGS谐振器的WPT发射机(TX)来缓解这两个问题。制造的原型在空气和组织中以49 MHz的频率运行。这表明，当相同的接收器(Rx)保持在空气中或嵌入组织内时，工作频率没有变化，这证明了所提出的协作DGS-WPT系统对抗共振漂移的有效性。当RX嵌入组织内时，测量的效率为62%，而在空气中的测量效率为68%。

We have developed a metasurface of low magnetic losses and employed it to design a a compact WPT system to biomedical implants. We have also proposed the design theory of a low inductance value to overcome the problem of frequency shifting and misalignment. We verified the proposed design by conducting experiments using chicken meat bought at an ordinary grocery shop. The performance of the proposed system was satisfactory as expected.This brief presents a compact and efficient resonance-shift insensitive wireless power transfer (WPT) system. This is possible by using a small electrical length defected ground structure (DGS) resonator, which is found effective against the resonance-shift phenomenon resulted from the higher permittivity of the tissue. Tissue has two undesired effects on a WPT system: (i) reduced coupled quality factor, and (ii) self-resonance shifting that leads to mismatch loss. So, the efficiency of a WPT system degrades in a tissue environment. Then, using the small electrical length DGS, we build a WPT transmitter (TX) using three cooperative DGS resonators to mitigate both issues. The fabricated prototype operates at 49 MHz in the air and tissue. This shows no change in operating frequency when the same receiver (Rx) is kept in the air or embedded inside tissues, which proves the effectiveness of the proposed cooperative DGS-WPT system against the resonance shift. The measured efficiency is 62% when the RX is embedded inside the tissue and is 68% in the air.