Skin Temperature Elevation for Incident Power Densities From Dipole Arrays at 28 Ghz

The relationship between skin temperature elevation and incident power density (IPD) from radio-frequency near-field exposure at 28 GHz for different angles of incidence is evaluated computationally in this study. The averaging scheme of the IPD is crucial for determining the maximum allowable exposure levels of wireless equipment to comply with certain standards/regulations. However, it is still unclear which component of the IPD (i.e., the norm or normal component to the human body) is more related the temperature elevation. In the case of four-element dipole arrays, the distances between the model and the antenna were 15 and 30 mm in transverse-electric-and transverse-magnetic-like polarized waves, respectively, and in the case of eight-element dipole arrays, the distances were 45 mm from the center of the array. From our computational results for four-and eight-element dipole arrays, we confirmed that the normal component of the IPD provides better correlation with the surface skin temperature, regardless of angle of incidence, particularly for smaller angles of incidence (<30 degrees). The enhancement of the ratio of the temperature increase to IPD was observed around the Brewster's angle, which is mainly attributable to the difference in transmittance at the body surface. This exposure scenario may not occur as the antennafi human distance was too large to consider compliance at the closest distance. In terms of output power, the most restrictive condition for compliance is shown to be normal incidence, suggesting the importance of compliance for such exposure scenarios. Furthermore, the absorbed power density proved to be an appropriate metric to monitor in relation to skin temperature elevation.