Investigation of Correlation Between Absorbed Power Density and Incident Power Density For User Equipment Antennas at Sub-THz Frequencies

In the international guidelines, absorbed power density and incident power density have been proposed as local exposure limits above 6 GHz to protect humans from electromagnetic field exposure. Incident power density has attracted more interest because of easier assessment compared to absorbed power density. However, the correlation between incident power density and absorbed power density should be examined in the near field before using incident power density for the electromagnetic field compliance assessment. The reason is that incident power density is derived from the absorbed power density in the far field. Currently, there is no relevant study focusing on practical antennas used for user equipment at sub-THz frequencies. In this paper, the correlation between incident power density and absorbed power density is studied using an antenna at sub-THz frequencies. The results show that incident power density has a good correlation when they are averaged over four square centimeters, except for 100 GHz.