体域网生物医学用植入式天线及无线传播信道建模研究

To improve the quality of wireless communications between implanted microsystem and exterior base station/ on-body sensor for medical telemetry in body area network, the project will be focus on the research about design, characteristics and modeling of implanted antennas and propagation channel: (1) To insulate the implanted antennas from tissue and prevent them oxidation, thin film will be coated around the antennas in order to decrease the near-field radiation around the live tissue, enhance the impedance match and solve the long-term biocompatibility. The characteristics of thickness, ingredient and uniform density will be studied on the effect of radiation performance. (2) Within the medical implant communication service frequency band, the antenna design techniques of miniaturization, multiple resonance frequency, wideband will be studied with the consideration of high radiation efficient. Simulation and measurement will go on in the inhomogeneous physical and numerical phantoms. Combined with optimization algorithm, electromagnetic simulation software, experiment, implanted antennas will be designed, fabricated and measured. The maximum allowable input power will be enhanced with the limit of specific absorption ration and effective isotropic radiated power. The radiation will not harm health and interfere with other wireless communication systems. The radiation performance will be evaluated through In-Vitro and In-Vivo experiments, respectively. (3) to construct radio linkage effectively and efficiently, statistical channel based on measurement and deterministic one derived from electromagnetic wave theory and numerical calculation will both be modeled. In different scenarios, the path loss will be analyzed according to geometrical shape, movement gesture, specific tissue ingredient. Wireless communication link budget will be calculated. The electromagnetic modelling can provide a reliable prediction of BAN wireless performce. The proposal is the extension of team's former research. More than twenty pieces of paper indexed by SCI will be published. The results of the project will be useful in telemedicine and mobile-health and potential to improve the patient freedom space and living quality.

为提高体域网医学遥测用植入微系统与外界的无线通信质量，本项目将进行植入式天线及传播信道数值建模等关键问题的理论和实验研究：（1）通过薄膜镀制工艺在天线表面制备介质层，研究薄膜特性对天线性能的影响，减少对生物组织近场电磁辐射，加强天线与人体间的阻抗匹配；（2）在医疗通信服务频段内兼顾辐射效率，对植入式天线宽带多频小型化技术进行研究。根据具体应用，通过算法优化、电磁计算及数值分析研制多款符合安全标准和无线通信要求的天线，在建立非均匀物理和数字人体模型中，进行体外和体内实验测量，评估辐射性能；（3）分析在不同场景下静态或动态环境以及天线性能对无线传播特性的影响，分别建立基于测量数据、电磁波理论的统计学和确定性数值传播信道模型，计算链路预算，预测体域网无线性能。这些内容是项目组成员研究工作的拓展，预计在SCI索引期刊发表论文二十多篇，研究成果对推进远程医疗和移动健康，提高患者生活质量具有重要意义。

本项目针对传统医疗设备有线检测会给患者带来不适、交叉感染等问题，致力于用于生物医学遥测的人体中心通信天线研究，以实现生物医疗传感设备与体外诊断设备的无线通信，增加患者的活动自由空间，提高生活质量。主要研究了：（1）应用于体域网的加载人工磁导体结构的穿戴式天线。集成AMC的双频单极子天线，降低了天线高度，剖面尺寸仅为2 mm，实现了双频单极子天线（2.4-2.48 GHz和5.725-5.85 GHz，增益为11.8 dBi和8 dBi）和宽带风车型天线（5.7-11.0 GHz，增益为8 dBi左右，前后比高于15 dB）；（2）小型植入式差分分形天线。采用分馈电技术使得天线能够直接与植入式医疗器械中差分电路链接，提高了集成度和对共模噪声的抑制能力。通过采用Hilbert分形曲线实现天线的小型化（9.3 mm × 9.3 mm × 0.635 mm）。设计的双频（MICS和ISM频段）分形天线，延长了植入传感器的使用周期；（3）植入式小型宽频圆极化天线。通过刻蚀互补开口环谐振器实现了小型化。通过调节开口环谐振器的开口大小和位置实现天线的圆极化特性，3 dB轴比带宽为2.42 GHz– 2.48 GHz（2.4%），使植入式天线与体外测量设备的朝向无需校准，无线通信性能不会受人体姿势和运动姿态的影响；（4）胶囊内窥镜系统的差分圆极化天线。通过采用高介电常数介质基板、辐射贴片及地板开槽实现小型化（9.8 mm × 9.8 mm × 1.27 mm），差分馈电端口在方形贴片对角线上激励起TM01和TM10两种辐射模式，引入几何微扰调节实现圆极化，3-dB轴比带宽为2.37–2.50 GHz；（5）差分馈电双频双圆极化植入式天线：通过在双环内部加载三角形贴片产生了慢波效应，使低频段谐振频率极大降低，同时这种双环内部的加载产生了高频谐振，实现了双频特性，最终覆盖了915-MHz ISM频段（用于数据通信）和2.45-GHz ISM频段（用于状态控制）。通过调节双环和加载单元的形状和尺寸，实现双频段的圆极化特性，3-dB轴比带宽在低频段为859–960 MHz，在高频段为2.29–2.5 GHz。每一款人体天线都分别研究了生物相容性、电磁辐射对人体健康影响、链路预算等，研究成果对推进植入式天线在生物医疗设备中的应用，实现无线生物医学遥测具有理论指导意义和参考价值。