Human Body as Antenna and its Effect on Human Body Communications

Human body communication (HBC) is a promising wireless technology that uses the human body as part of the communication channel. HBC operates in the near-fleld of the high frequency (HF) band and in the lower frequencies of the very high frequency (VHF) band, where the electromagnetic fleld has the tendency to be conflned inside the human body. Electromagnetic interference poses a serious reliability issue in HBC; consequently, it has been given increasing attention in regard to adapting techniques to curtail its degrading efiect. Nevertheless, there is a gap in knowledge on the mechanism of HBC interference that is prompted when the human body is exposed to electromagnetic flelds as well as the efiect of the human body as an antenna on HBC. This paper narrows the gap by introducing the mechanisms of HBC interference caused by electromagnetic fleld exposure of human body. We derived analytic expressions for induced total axial current in the body and associated flelds in the vicinity of the body when an imperfectly conducting cylindrical antenna model of the human body is illuminated by a vertically polarized plane wave within the 1{200MHz frequency range. Also, flelds in the vicinity of the human body model from an on-body HBC transmitter are calculated. Furthermore, conducted electromagnetic interference on externally embedded HBC receivers is also addressed. The results show that the maximum HBC gain near 50MHz is due to whole-body resonance, and the maximum at 80MHz is due to the resonance of the arm. Similarly, the results also suggest that the magnitude of induced axial current in the body due to electromagnetic fleld exposure of human body is higher near 50MHz.

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