Traceable Absorbed Power Density Assessment System in the 28 GHz Band

Authors: Ninad Chitnis, Fariba Karimi, Arya Fallahi, Sven Kühn, and Niels Kuster;
Presentation by Ninad Chitnis

BioEM 2023, 18-23/06/2023, Oxford, United Kingdom



ICNIRP and IEEE closed a critical gap in the safety guidelines by introducing a basic dosimetric restriction above 6 GHz. These are the absorbed power density (APD) and the spatial averaged power density. In previous work by our group, a phantom and a compatible probe were developed to measure the APD in the 5G new radio frequency range 2 (NR FR2; 24–30 GHz). Here, an experimental validation procedure for the proposed phantom is detailed. The reflection coefficient was measured with sources at different distances from the phantom. Target values were obtained using the finite-difference time-domain solver in Sim4Life (ZMT Zurich MedTech AG, Switzerland). The measurements and simulations were compared on the basis of cosine similarity.
A setup based on the multi-mode solution for a rectangular waveguide radiating into a dielectric half-space was developed for calibrating the novel APD probe. The field profile of the propagating mode is  obtained analytically by formulating the fields in both, the rectangular waveguide and the dielectric medium, and matching them at the intersection. The calibrated electric field is obtained by scaling the uncalibrated probe response to match the computed field profile. The results of this research validate the first APD measurement system designed for the 5G NR FR2 band (24–30 GHz).