Optimal Design of Wireless Power Transmission Links for Millimeter-Sized Biomedical Implants
Optimal Design of Wireless Power Transmission Links for Millimeter-Sized Biomedical Implants
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DOI：
10.1109/tbcas.2014.2370794
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发表时间：
2016-02-01
影响因子：
5.1
通讯作者：
Ghovanloo, Maysam
中科院分区：
文献类型：
--
作者：
Ahn, Dukju;Ghovanloo, Maysam
本文提出了一种射频功率传输到毫米级植入式生物医学设备的设计方法。找到了最佳工作频率和线圈几何形状，使功率传输效率（PTE）和组织损耗约束允许功率最大化。我们定义了接收机功率接收磁化率（Rx- prs）和发射机品质系数（Tx- fom），使它们的乘积产生PTE。Rx- prs和Tx- fom分别定义了Rx和Tx在PTE中的作用。首先，确定最佳的Rx线圈几何形状和工作频率范围，以便在给定的植入物约束下最大化Rx- prs。由于Rx非常小，设计自由度比Tx小，因此总体工作频率主要受Rx的限制。Rx- prs识别由Rx施加的这种工作频率约束。其次，选择Tx线圈的几何形状，使Tx- fom在Rx-PRS饱和的频率约束下最大化。这使Tx优化的目标频率范围与Rx性能较高的频率范围保持一致，从而获得最大的PTE。最后，我们发现，即使在PTE相对平坦的频率范围内，每个频率的单位输出功率的组织损失也可能存在显著差异。Rx-PRS可以预测在保持高PTE的同时，将单位输出功率的组织损失降至最低的频率范围。这样，通过表征Rx-PRS实现了PTE和组织损耗约束允许功率的频率调节。通过全波电磁场仿真和去嵌入法测量验证了设计过程。一个直径为1mm的原型种植体，在组织环境中，PTE为0.56% (22.5 dB)，负载传递功率（PDL）为224 μ W，频率为200 MHz， tx - rx分离为12 mm。
This paper presents a design methodology for RF power transmission to millimeter-sized implantable biomedical devices. The optimal operating frequency and coil geometries are found such that power transfer efficiency (PTE) and tissue-loss-constrained allowed power are maximized. We define receiver power reception susceptibility (Rx-PRS) and transmitter figure of merit (Tx-FoM) such that their multiplication yields the PTE. Rx-PRS and Tx-FoM define the roles of the Rx and Tx in the PTE, respectively. First, the optimal Rx coil geometry and operating frequency range are identified such that the Rx-PRS is maximized for given implant constraints. Since the Rx is very small and has lesser design freedom than the Tx, the overall operating frequency is restricted mainly by the Rx. Rx-PRS identifies such operating frequency constraint imposed by the Rx. Secondly, the Tx coil geometry is selected such that the Tx-FoM is maximized under the frequency constraint at which the Rx-PRS was saturated. This aligns the target frequency range of Tx optimization with the frequency range at which Rx performance is high, resulting in the maximum PTE. Finally, we have found that even in the frequency range at which the PTE is relatively flat, the tissue loss per unit delivered power can be significantly different for each frequency. The Rx-PRS can predict the frequency range at which the tissue loss per unit delivered power is minimized while PTE is maintained high. In this way, frequency adjustment for the PTE and tissue-loss-constrained allowed power is realized by characterizing the Rx-PRS. The design procedure was verified through full-wave electromagnetic field simulations and measurements using de-embedding method. A prototype implant, 1 mm in diameter, achieved PTE of 0.56% (22.5 dB) and power delivered to load (PDL) was 224 mu W at 200 MHz with 12 mm Tx-to-Rx separation in the tissue environment.