**1. Introduction**

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*on Wireless Communications Technologies and Software Defined Radio (SDR-WInnComm*

The ultra-wideband technology seems very attractive to be transferred to the challenging field of body centric communications. This technology involves the potential to establish robust communication links or high resolution localization systems. All these applications require a characterization of the propagation channel and the influence of the corresponding user to the system performance. Due to the inevitable interaction between the antenna and the related propagation channel a separation of both characteristics via traditional antenna theory methods is hardly applicable. The scope of this study is to establish a so called antenna de-embedding i.e. to separate the antenna form the underlying channel.

Traditional antenna parameters (e.g. directivity, gain, effective area) are based on free space propagation conditions. Underlying is the well known model of an isotropic radiator which enables the separation of channel, transmitter and receiver. It will be shown that this theory can be adapted to deduce approximations of equivalent antenna parameters for body centric communications. Key factor of this approach is the development of equivalent far field models of the corresponding in- and on-body scenarios. For off-body scenarios the propagation direction points away from the human body. The matching and the radiation pattern of the respective antennas may change due to the interaction with the human body but in general no modifications of the far field model are necessary. Therefore, the traditional theory is applicable with just minor restrictions and will not be discussed in further detail here.

The study is structured in two sections. The first part focuses on an in-body link i.e. the main propagation path of the electromagnetic wave leads through the tissue of the human body. Typical applications for this scenario are medical implants like wireless endoscopy or the RF breast cancer detection systems. The second part characterizes an on-body link. This means that the propagation path is defined along the body surface and the antenna is located in close proximity of the human body. The universality of this theory will be shown for the characterization of an UWB teardrop antenna.

©2013 Grimm and Manteuffel, licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. ©2013 Grimm and Manteuffel, licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

2 Will-be-set-by-IN-TECH 154 Ultra-Wideband Radio Technologies for Communications, Localization and Sensor Applications Antennas and Propagation for On-, Off- and In-Body Communications <sup>3</sup>

**Figure 1.** Distribution of the electric field of an implant located within the human abdomen; Left: On-body scenario showing surface waves guided by the body curvature; Right: In-body scenario characterized by circular shaped attenuation within the body.
