Abstract：When implantable biomedical devices are in operation, electromagnetic field leakage is inevitable. It is necessary to mitigate the impact of magnetic field leakage from wireless power transfer (WPT) systems on the human body, ensure that implantable medical devices meet human safety standards, and maintain high transmission efficiency in the system. This paper proposes a resonant wireless power transfer system for cardiac pacemakers based on an LCC-LCC compensation circuit model, which operates at a frequency of 120 kHz and features a four-capacitor matching reactive shielding structure. The theoretical circuit model is analyzed, and the inductance ratio is computed to determine the circuit parameters under conditions relevant to human body models. The optimal primary-coil dimension of the WPT system is analyzed to account for biocompatibility factors, which include selecting an appropriate implantation depth and coil size. Subsequently, the principles of the resonant reactive shielding structure are analyzed. COMSOL simulations are employed to establish five distinct reactive shielding structures. Based on the designed electrical parameters, topological structures are constructed, and joint simulations are conducted. The magnetic field distribution and transmission efficiency results are comprehensively analyzed to select the optimal shielding structure. The WPT reactive shielding structure is integrated into an upper-body model to assess the compatibility of the shielding structure with the human body. Simulations are conducted to evaluate various factors, including system temperature rise, induced electric field, magnetic field strength, and specific absorption rate. Finally, WPT reactive shielding experiments are conducted within an isolation chamber at an implantation depth of 8 mm. Exvivo pig tissues are used to simulate the working environment of an implantable medical device. The five different reactive shielding structures are measured and compared with simulations. The experimental results align with the simulation results, meeting the system design requirements. With the four-capacitor reactive shielding structure in the WPT system, the magnetic flux density measured at a distance of 45 mm from the coil center is reduced by 28.5%. Additionally, the WPT system’s transmission efficiency is increased by 3%. The temperature rise of the implantable device is only 0.87℃, which adheres to the ICNIRP 2020 guidelines. The proposed method improves transmission efficiency, ensures effective shielding, and avoids using high magnetic permeability or temperature-sensitive materials, demonstrating excellent biocompatibility. In the design of performance testing for the WPT reactive shielding system, potential deviations due to implantation or other factors are not considered. However, the four-capacitor reactive shielding structure slightly mitigates the impact of such deviations. Future research will explore the effects of deviations on performance to provide new insights into the design of wireless power systems for biomedical implants. This paper offers a novel approach for the efficiency enhancement and safety of wireless power transfer systems used in implantable biomedical devices.
陈伟华, 刘岳鹏, 闫孝姮, 曹鹤译, 黄志石. 心脏起搏器谐振式无线供能四匹配电容无功屏蔽[J]. 电工技术学报, 2025, 40(14): 4382-4394.
Chen Weihua, Liu Yuepeng, Yan Xiaoheng, Cao Heyi, Huang Zhishi. Reactive Shielding of Four Matching Capacitors for Resonant Wireless Power Transfer in Cardiac Pacemakers. Transactions of China Electrotechnical Society, 2025, 40(14): 4382-4394.
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