An Insight into Creeping Electromagnetic Waves around the Human Body

Branimir Ivsic,Zvonimir Sipus,Juraj Bartolic,Davor Bonefacic

doi:10.1155/2017/2510196

Branimir Ivsic, Zvonimir Sipus + Show 2 more

Open Access

https://doi.org/10.1155/2017/2510196

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Abstract

The electromagnetic wave propagation around human body torso is modelled by considering elementary electric and magnetic dipoles over an infinite muscle-equivalent cylinder. The poles in the spectral domain Green’s function with smallest imaginary part are found to correspond to creeping wave propagation coefficients which predict the general trend in propagation around human body. In addition, it was found that axial magnetic field component is crucial for communication via creeping waves since it generates modes with smaller field decay compared to axial electric field. The developed model may thus serve as a practical guideline in design of on-body wearable antennas. The theoretical considerations are verified with simulations and measurements on the prototype of PIFA antenna placed on the human body.

Highlights

As the inherent presence of the human body in body-centric communication systems [1] affects radiation properties of antennas and radio channel, there is considerable interest in characterization of electromagnetic wave propagation in vicinity of the human body with the goal to predict and enhance link budget and optimize the position of antennas on the body
In this paper the creeping wave propagation around human torso is modelled by considering radiation of elementary sources over an infinite muscle-equivalent cylinder
The inverse Fourier transformation is calculated by two-step approximation (Watson’s transformation and taking into account the most contributing spectral variable) in order to obtain a simple expression for the dominant wave propagation part

Summary

Introduction

As the inherent presence of the human body in body-centric communication systems [1] affects radiation properties of antennas and radio channel, there is considerable interest in characterization of electromagnetic wave propagation in vicinity of the human body with the goal to predict and enhance link budget and optimize the position of antennas on the body. Wireless links where the body surface takes the role in transmission channel are generally considered to allow for deterministic modelling to some extent, which gives rise to research in Norton and creeping waves (see, e.g., [2,3,4,5,6,7]). We develop a simple model of propagation for on-body communication link by focusing on the most dominant effect which predicts general behaviour and attenuation of the electric field around the human body. The problem is formulated as a canonical boundary-value problem in the spectral domain where the poles of Green’s function for the two fundamental (TMz and TEz) field configurations are calculated and shown to correspond to creeping wave propagation coefficients around the human body giving rise to the general trend of field attenuation around the body. In the part of the paper we exploit the example of practical application of the model by analyzing wearable PIFA antenna from [7] with respect to the developed theoretical model and discuss the limitations of the model by performing measurements on realistic on-body link

Theoretical Model

Practical Verification

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Conclusion