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This paper presents a numerical analysis (FDTD) of the electromagnetic wave propagation mechanism at f = 2.45 GHz around the human trunk. Different body models starting from planar models, to cylindrical models up to realistic trunk models are considered. In addition homogeneous and inhomogeneous model structures are compared with each other. For excitation a half-wavelength dipole in close proximity to the models is used in both tangential and normal orientation to the body. As a result of reflection and diffraction of the model the main propagation mechanism can be shown to be a surface wave which can be more effectively excited by a dipole in normal orientation to the body than in tangential orientation. In case of the curved trunk model the surface wave can be used to illuminate the non line of sight region e.g. in the back of the human body. However, the superposition of the two waves creeping from both sides around the body can lead to a standing wave profile in this region. I. INTRODUCTIONThe analysis of electromagnetic waves propagation in body centric scenarios is quite different from corresponding free space applications due to the complex structure of the human body [1] and the fact that channel and antennas overlap and cannot be separated easily. Therefore numerical evaluation can help to obtain suitable propagation models for a wide class of possible wireless communications for in-, on-and offbody applications.Based on the investigations of Norton dealing with electromagnetic propagation effects along a conducting surface [2] the on-body propagation effects for a short dipole is characterized in [3]. According to these results an EM wave with normal polarization with respect to the surface of the body is found to be more effective in exciting a creeping wave which propagates along the surface compared to tangential polarization.In our investigation a half-wavelength dipole will be used as excitation source. In analogy to the cited publications both, normal and tangential polarization will be investigated using different trunk models. First an infinite homogeneous planar body model will be analysed. To achieve a more realistic model these results will be compared with a layered model which consist of a skin, fat and muscle layer. In the next step a cylindrical model will be used as approximation for an

Within the scope of on-body communications an approach is presented which is capable to describe the radiated on-body field of arbitrarily shaped antenna structures. The method is based on a segmentation of the excited current distribution on the antenna body by a finite number of small electric dipoles. To consider the presence of the human body, which affects the underlying radiation mechanism significantly, the model is implemented by the use of the Norton surface wave theory. Based thereon, a method is presented to model the onbody far field of an antenna by two equivalent electric dipoles, a TM and a TE source. Based on this assumption the directivity and the effective antenna area are defined for on-body propagation scenarios. The radiation characteristic of body worn antennas is discussed in terms of their radiation characteristic using the example of tilted half-wave dipoles and a planar inverted-F antenna. The last part of the study discusses a pathloss model which is calculated from the underlying antenna parameters. Numerical full-wave simulations, based on the FDTD method, and measurements in an anechoic chamber, verify the results. Index Terms-Body area networks, antenna theory, on-body directivity, on-body propagation, wearable antennas0018-926X (c)

This paper presents a structured evaluation of the Norton equations to describe the propagation of electromagnetic waves along the human body surface. In conjunction with this theory an antenna de-embedding of dipole antennas is proposed and a simple pathloss channel model for a vertical and horizontal orientated half-wave dipole in close proximity to a homogeneous phantom is developed. Furthermore the influence of the airphantom boundary is verified to show different physical propagation conditions which should be considered for future antenna design approaches.

This paper presents an antenna concept which is focused on an optimized performance for on-body communications using the 5 GHz ISM band. Primary design parameters are a strong normal polarization and a low effective antenna height. In addition, the antenna concept is capable to use the 2.7 GHz E-UTRA band for off-body uplinks. In this context, the underlying on-body channel properties are discussed to deduce design aspects which result in optimized propagation properties. Based here on, a numerical method is used to calculate the antenna on-body radiation characteristic to determine a model of the on-body path gain. The related results show a good agreement with a numerical calculated path gain along a realistic full human body model.