面向植入式医疗设备的无线能量传输系统研究

Implantable medical devices (IMDs) are playing growing roles in advancing medical diagnosis and therapeutic methods. This is not only due to their abilities to monitor vital signs and critical health information,but also their functionalities to stimulate and regulate human internal organs through its internal micro-electro-mechanical systems, leading to therapeutic effects..However, the operation of most IMDs still heavily relies on continuous power supply from batteries, which limits their applications due to battery sizes and lifespan. Considering the infeasibility of connection to external power source through wire for continuous power supply and the medical risks from repeated surgeries to replace the internal batteries, the application of high-volume rechargeable batteries to IMDs and the implementation of wireless power Transfer (WPT) technique for wireless charging or continuous power supply become more than necessary. This not only eliminates the need for repeated surgeries, but also avoids transcutaneous wiring for charging batteries; furthermore, it can significantly reduce the size of IMDs due to feasibility of using smaller rechargeable batteries with shorter recharging cycles. .There are many technical hurdles in the design of WPT systems for efficient wireless power transfer to IMDs. One difficulty lies in the derivation of an effective equivalent circuit model to facilitate the hardware design; another difficulty is to miniaturize the receiver coils of the WPT system with little sacrifice in transmission efficiency and distance. Furthermore, accurate, effective and efficient electromagnetic numerical modeling and simulation are essential, especially to the optimization of the design, the analysis of the interference to existing wireless communication systems and networks, and quantitation of potential harms to human and other biological objects. Although similarities exist between the transceiver coils of a WPT system and the loop antenna in resonating behavior, non-radiative near-fields and evanescent modes, commercial EM tools widely used for the CAD of antennas still suffer substantially in numerical modeling accuracy and simulation efficiency..To overcome above technical difficulties, this research proposed a systematic approach to the design of WPT systems that are fully competent for IMDs, where effective equivalent circuit models are applied as the design guidance, the time-domain RPIM meshless method is deployed as the numerical framework, and the design concepts of radio-frequency identification tags and near-field antenna arrays are adopted for miniaturization and efficiency enhancement. Furthermore, through numerical analysis on the interference of the WPT system to existing wireless communication systems and networks, and investigation of specific absorption rate using computational human phantom, the safety, reliability and consistency of the design can be fully ensured.

植入式医疗设备可实时监控人体生命体征及关键健康信息，并能通过内部微机电系统来刺激和调节人体内部器官，以达到治疗效果，在现代医学中正扮演越来越重要的角色。但大多数可植入医疗设备依赖于电池供电，电池的体积、容量和寿命很大程度上限制了其在生物医疗领域中的应用范围。考虑到对其采用电源线供电的不可行性以及通过手术更换电池的医疗风险，应用无线能量传输技术对其进行无线充电或持续供电势在必行。针对无线能量传输系统在设计上尚无法兼顾小型化、传输距离、传输效率和稳定性，以及传统数值方法在对系统的辅助设计上精度不够且效率低下等技术难题，本项目提出了以等效电路理论为设计指引，以无网格方法为数值模拟框架，并结合射频识别标签、近场天线阵的设计理念的系统化研究方案,以研发可用于植入式医疗设备的无线能量传输系统；并拟通过量化人体对系统的辐射能量的特定吸收率以及系统对周边电子设备的电磁干扰，来保证系统的安全性和高效性。

无线充电技术主要分为磁感应耦合，磁共振耦合和电磁辐射三种方式。相比于磁感应技术，磁共振耦合技术在充电距离、空间自由度、一对多充和功率扩展上有明显优势；而相比于电磁辐射式无线输能技术，磁共振耦合技术在能量转化效率、传输功率和电磁安全方面更具备实际应用价值。.而将磁共振无线充电技术用于医疗领域，对小型医疗设备进行无线充电和供电，除了需要满足传输距离、传输效率、传输稳定性等性能指标之外，在设计上还必须满足医疗设备小型化要求和应用场景要求；另外还应符合国际上相关频段的辐射安全标准。为了实现以上目标，在本项目执行期内，项目团队围绕磁共振无线充电的等效电路分析、收发天线设计、中继耦合技术、磁场赋形技术、自适应匹配技术、磁场多输入多输出技术和接收端整流稳压集成电路设计开展了一系列科学研究工作，取得的主要技术突破如下：.1.采用阵列天线设计和磁场波束赋形技术，有效提高了收发线圈之间的耦合强度，降低了边缘效应。.2.采用交叉绕线设计，在发射线圈的过耦合区域中引入反向谐振磁场，有效降低了收发天线之间的过耦合区，解决了奇偶模式不统一而导致的频率分裂。.3.采用磁场多输入多输出(Mag-MIMO)技术和自动增益调配技术，实现了多路输入和多路输出之间的动态磁谐振耦合。.4.设计开发了磁共振无线充电收发链路的自适应匹配方案，保证了能量转换效率的稳定性。 .5.应用带CPML吸波条件时域无条件稳定RPIM法，对无线充电系统中的瞬态热效应进行了仿真和分析。.6.采用磁反射技术和中继耦合技术，有效扩展了接收端的横向接收范围，实现对多个小功耗电子设备的同步无线充电。.7.应用功放源增益自动调配技术，并基于F类功放设计方案，设计开发了6.78MHz 100w动态功率调配的射频功放源。.8.在磁共振无线电能收发链路中引入了带外通信及相关集成电路，实现了收发端之间的双向通信。.除完成技术攻关之外，项目团队还形成了发明及实用新型专利27项，发表论文9篇，参加国内外无线充电领域的技术交流活动和相关会议8次，培养电源工程师、射频工程师、EMI工程师及通信软件工程师数十名，并以定制化项目开发和标准化模组输出两种商业模式实现了相关技术的成果转化，已与国内数十家消费电子厂商和医疗设备厂商达成项目开发合作，2019年已实现销售额200余万，2020年预计销售额可达3000万。

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