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The complex permittivity of the human skin has been measured in vivo in the 10-60 GHz range using a recently developed coaxial slim probe. The results are compared with the literature data at millimetre waves, and a broad-band Cole-Cole model is proposed for several locations on the arm, namely at the palm, wrist, and forearm. This reported study provides relevant data required for studying interactions between emerging body-centric wireless millimetre-wave technologies and the human body.
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Introduction: The millimetre-wave (MMW) band has been recently identified as a highly promising solution for various body-centric applications, including wireless communications within local and personal area networks, and more recently in body area networks (BAN). For the accurate analysis and optimisation of the electromagnetic interactions of on- and off-body radiating structures with the human body, a precise characterisation of skin permittivity in the MMW band is crucial [1]. In contrast to frequencies below 20 GHz, there are very few data available on the human skin permittivity values at MMW. The skin permittivity data reported in the 10-60 GHz band are summarised in Fig. 1. Gabriel et al. [2] and Gandhi and Riazi [3] proposed complex permittivity models for theMMWrange based on extrapolation of experimental data collected at microwaves. Alabaster [4], Hwang et al. [5], and Alekseev and Ziskin [6] performed direct measurements of the human skin permittivity at MMW. Alekseev's data (in vivo study) are very similar to those published by Gabriel and Gandhi. However, Hwang (in vivo study) and Alabaster (in vitro study) reported much lower permittivity values. These discrepancies are related to the intrinsic differences of measurement techniques, but also to variabilities depending on the part of the body and sample types (in vivo or in vitro, skin temperature, thickness of different skin layers, etc.). Therefore, detailed measurements on different body...