Bio-Physical Modeling, Characterization, and Optimization of Electro-Quasistatic Human Body Communication
Bio-Physical Modeling, Characterization, and Optimization of Electro-Quasistatic Human Body Communication
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DOI：
10.1109/tbme.2018.2879462
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发表时间：
2019-06-01
影响因子：
4.6
通讯作者：
Sen, Shreyas
中科院分区：
文献类型：
--
作者：
Maity, Shovan;He, Mingxuan;Sen, Shreyas
人体通信（HBC）已经成为无线电波通信的替代方案，用于连接人体内、人体上和人体周围的低功耗、小型化可穿戴和可植入设备。HBC使用人体作为身体上设备之间的通信信道。先前表征人体通道的研究已经报道了广泛变化的通道响应，其中大部分归因于测量设置的变化。这就要求建立一个统一的HBC生物物理模型，并对HBC测量的激励、终止方式的影响进行深入分析和理解。本文描述了人体信道高达1 MHz的频率，以评估它作为宽带通信的介质。通信主要发生在电准静态（EQS）制度在这些频率通过皮下组织。一个集总的生物物理模型的HBC的开发，实验验证，提供了一些在以前的研究中发现的关键差异的洞察力的支持。电压损失测量是用示波器和微型可穿戴原型来进行的，以捕捉非公共接地的影响。结果表明，信道损耗强烈依赖于接收端的终端阻抗，示波器中不同终端的平均损耗变化高达4 dB，与示波器测量相比，可穿戴原型的信道损耗增加了9 dB。测量的电容终端通道响应降低了低频损耗，并允许低至13 KHz的平带传递函数，将人体建立为宽带通信通道。对测量结果和仿真模型的分析表明，具有50 Ω输入阻抗的仪器（矢量网络分析仪、频谱分析仪）提供了对低频信道损耗的悲观估计。相反，应在接收器端使用高阻抗和容性端接，以便在低频下准确测量HBC通道的电压模式损耗。实验验证的生物物理模型表明，电容电压模式终端可以改善低频损耗高达50 dB，这有助于宽带通信显着。
Human body communication (HBC) has emerged as an alternative to radio wave communication for connecting low power, miniaturized wearable, and implantable devices in, on, and around the human body. HBC uses the human body as the communication channel between on-body devices. Previous studies characterizing the human body channel has reported widely varying channel response much of which has been attributed to the variation in measurement setup. This calls for the development of a unifying bio-physical model of HBC, supported by in-depth analysis and an understanding of the effect of excitation, termination modality on HBC measurements. This paper characterizes the human body channel up to 1 MHz frequency to evaluate it as a medium for the broadband communication. The communication occurs primarily in the electro-quasistatic (EQS) regime at these frequencies through the subcutaneous tissues. A lumped bio-physical model of HBC is developed, supported by experimental validations that provide insight into some of the key discrepancies found in previous studies. Voltage loss measurements are carried out both with an oscilloscope and a miniaturized wearable prototype to capture the effects of non-common ground. Results show that the channel loss is strongly dependent on the termination impedance at the receiver end, with up to 4 dB variation in average loss for different termination in an oscilloscope and an additional 9 dB channel loss with wearable prototype compared to an oscilloscope measurement. The measured channel response with capacitive termination reduces low-frequency loss and allows flat-band transfer function down to 13 KHz, establishing the human body as a broadband communication channel. Analysis of the measured results and the simulation model shows that instruments with 50 Omega input impedance (Vector Network Analyzer, Spectrum Analyzer) provides pessimistic estimation of channel loss at low frequencies. Instead, high impedance and capacitive termination should be used at the receiver end for accurate voltage mode loss measurements of the HBC channel at low frequencies. The experimentally validated bio-physical model shows that capacitive voltage mode termination can improve the low frequency loss by up to 50 dB, which helps broadband communication significantly.