インピーダンス整合を考慮した人体通信送信機の電極設計と周辺電界に関する検討

概要

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Human body communication is carried out along the body surface between the wearable equipment, and this technology can be potentially used for Body Area Networks. In this study, transmitter electrodes for human body communication were analyzed at 10MHz by FDTD method. This analysis has shown that the input impedance of the electrodes was dependent on the structure and dimensions of the electrodes. We derived approximation formulas to express these relationships between the input impedance and the design parameters. As an example, the electrodes for the wristwatch-sized (24 × 24mm) device were designed to have a matched input impedance of 50Ω without using impedance transformers or stubs. The electric field around the electrodes on the human arm under the impedance-matched condition was 10∼20 dB stronger than that of the mismatched condition, and the VSWR characteristics were less than 2 when the matched electrodes were used. The electric fields and currents on the body surface and inside the body, and those of the equipment, were less than the safety standards, when the received signal had sufficient strength for practical receivers. The transmission power of the antenna was less than that of Bluetooth devices.
ライフサポート学会の論文