UWB Signal Propagation at the Human Head
AuthorsThomas Zasowski, Gabriel Meyer, Frank Althaus, and Armin Wittneben
ReferenceIEEE Transactions on Microwave Theory and Techniques, Apr. 2006.
AbstractAmong different wireless solutions ultra wideband (UWB) communication is one promising transmission technology for wireless body area networks (WBANs). To optimize receiver structures and antennas for UWB WBANs with respect to energy efficiency and complexity the distinct features of the BAN channel have to be considered. Thus, it is necessary to know the propagation mechanisms in the proximity of the human body. In this paper, we limit ourselves on transmission at the head since the most important human communication organs, such as mouth, eyes, and ears are located there. We especially focus on the link between both ears and consider direct transmission, surface waves, reflections, and diffraction as possible propagation mechanisms. We show theoretically and by measurements, which were performed in the frequency range between 1.5-8 GHz, that direct transmission through the head is negligible due to the strong attenuation. We conclude by process of elimination that diffraction is the main propagation mechanism around the human body and verify these conclusions using a finite difference time domain (FDTD) simulation. Based on a second measurement campaign we derive an approximation of the average power delay profile for the ear-to-ear link and calculate values for mean excess delay and delay spread. Finally, we briefly discuss the impact of the distinct ear-to-ear channel characteristic on the design of a WBAN communication system.
KeywordsBody Area Network, Ultra Wideband, Propagation Mechanisms
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