Absorbed/Epithelial Power Density Assessment Using Plane-Wave Spectrum Method From Inside the Skin Tissue Above 6 GHz

In this article, the idea of measurement inside the human skin liquid-filled phantom for fifth-generation (5G) technologies is examined. Measurement inside the skin tissue phantom is almost off the table due to the shallow penetration depth of fields at millimeter and quasi-millimeter waves. Antenna–body interactions should be considered for absorbed power density (APD) assessment when the device is close to the human body. These effects can be considered to a large extent by measuring within the liquid phantom. The reconstruction technique is used to determine APD at the human skin surface using the backward plane-wave spectrum method through sampling the
$E$
-field at a specific distance within the phantom. The reconstruction errors were obtained using a planar array antenna at 10–60-GHz frequencies. These errors were no larger than 9.4%, 7.35%, and 7.8% at 10, 24, and 60 GHz for assessing the maximum spatially averaged power density for a separation distance between the device and tissue phantom larger than 1 mm. Finally, the measuring requirement for the electric field was also investigated. The results suggest that the coupling/multiple-reflection effects are negligible when the separation distance between antenna and body is larger than
$\lambda $
.