Impact of Antenna Topology and Feeding Technique on Coupling With Human Body: Application to 60-GHz Antenna Arrays

The 60-GHz band has been identified as an attractive solution for the next-generation mobile networks (5G) as well as for body-centric applications. This paper provides a quantitative comparative analysis of electromagnetic exposure and heating induced by 60-GHz body-mounted antennas. Near-field interaction between representative antenna arrays for off-body communications with three feeding topologies and human body is compared in terms of matching and radiation, as well as in terms of user exposure. The presence of a ground plane results in exposure reduction by more than 70 and 8 times in terms of peak and averaged levels, respectively. Designs allowing to avoid grating lobes allow further reduction of exposure. For considered antenna arrays operating at the maximum allowable power, International Commission on Non-Ionizing Radiation Protection occupational exposure limits are not exceeded. However, only the antennas with a ground plane comply with general public limits. Resulting heating is quantified for on-body millimeter-wave antennas. Detailed analysis is performed for acute and disperse exposures. Numerical results are validated by measurements. Effect of averaging is also investigated. For antennas with a ground plane, heating (typically of several tenths of degrees C) remains within environmental temperature fluctuations. However, the antennas without a ground plane can induce heating locally exceeding 10 degrees C.