User Body Interaction of 5G Switchable Antenna System for Mobile Terminals at 28 GHz

In this paper, a 12-element switchable antenna system for handsets is proposed at 28 GHz. The effect of the head and hand in the impedance matching and radiation pattern is assessed. The electromagnetic field (EMF) exposure in the body is analyzed. The evaluation method of exposure for the previous mobile generations is the specific absorption rate (SAR). Since the penetration depth of the EMFs is lower at the millimeter-wave (mm-wave) band, power density (PD) in free space is employed as evaluation metric instead. The maximum permissible transmitted power to satisfy the proposed limits is calculated, showing a severe discontinuity compared with the maximum power in 4G UE. The exposure of the switchable monopole is compared with a patch phased array, showing a faster decrease in the PD peak than the array at 1.3 cm from the terminal.