An Improved Antenna Mounting for Ultra-Wideband On-Body Communications and Channel Characterization

Abstract

The electromagnetic coupling of antennas with the human body is a well-known, but often neglected, problem in body area network (BAN) communications. The resulting distortion of the antenna's free-space characteristics may, in turn, demand more complex terminals to cope with the different conditions encountered as antennas are mounted on different parts of the body and/or varying separations from the skin. Therefore, in this paper, we propose a mounting method to provide a more stable response and to reduce the antenna's coupling to the body for ultra-wideband (UWB) BAN applications. The proposed mounting method is evaluated on two UWB BAN antennas, characterizing the antennas coupling with the body by analyzing variations in the antennas reflection coefficient between 4-9 GHz, when mounted at different distances from the skin and at different locations on the body. The modified mounting method was found to increase the correlation coefficient between the antenna's reflection coefficient when in free space and mounted using 5 mm of spacer, for the two antennas, from 0.22 and 0.13, to 0.66 and 0.90. The free-space characteristics of the modified antennas are also tested, showing a reduction of up to 4.7 dB of radiated power into the body.