Human Body as Antenna and Its Effect on Human Body Communications

Abstract

Abstract-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-field of the high frequency (HF) band and in the lower frequencies of the very high frequency (VHF) band, where the electromagnetic field has the tendency to be confined 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 effect. Nevertheless, there is a gap in knowledge on the mechanism of HBC interference that is prompted when the human body is exposed to electromagnetic fields as well as the effect of the human body as an antenna on HBC. This paper narrows the gap by introducing the mechanisms of HBC interference caused by electromagnetic field exposure of human body. We derived analytic expressions for induced total axial current in the body and associated fields 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 1-200 MHz frequency range. Also, fields 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 50 MHz is due to whole-body resonance, and the maximum at 80 MHz 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 field exposure of human body is higher near 50 MHz.

Characterizing the Human Body as a Monopole Antenna

“…Applying the boundary conditions of the axial electric fields on the surface of the cylinder, the scattered axial electric field on the surface of the cylinder is related to A 2z (a, z) using the onedimensional wave equation [8], [16], [17] as…”

“…In a related study, Poljak et al implemented the method-of-moments (MoM) approach to calculate the axial current inside the thick-wire model of the human body [7]. Recently, we have applied the cylindrical antenna model of the human body using the threeterm approximation to investigate the antenna effect of the human body on intrabody communication [8] and to analyse the whole-body averaged specific absorption rate [9].…”

Analysis of the Whole-Body Averaged Specific Absorption Rate (Sar) for Far-Field Exposure of an Isolated Human Body Using Cylindrical Antenna Theory

“…In the literature, it has been largely reported that the height to wavelength ratio (H/λ res ) at the resonance frequency approaches 0.4 [4,6,7,21]; but, an adequate rationale has not been reported that sheds light on the phenomenon. Since the accurate formulation of the resonance frequency (26) proposed in this paper is a function of anatomical parameters and the dielectric properties of the body, it points to the possible explanation of the phenomenon observed.…”

“…The comparison of the resonance frequencies calculated from (26) to the FDTD based resonance frequencies calculated for the six voxel models is shown in Table 1. It is to be noted that the value of T is different for little children and adults with large BMI.…”

“…One of the reasons for the deviation could be King's oversimplified assumption of using a single-term sinusoidal current in order to solve the two integral expressions inside the Hallén's type equation involved. Moreover, recently, the study of the human body antenna effect based on the cylindrical antenna model of the human body is reported by the authors of this paper [26]. In general, the ongoing acceptable trend of computing electromagnetic fields inside the human body makes use of the FDTD algorithm on realistic voxel-based models of the human body.…”