Holographic Phase Retrieval of RF-EMFs for Human Exposure Assessment Using Fine 3D Electric Field Measurements in a Real Environment from a Beamforming 28 GHz Antenna

With the increasing frequencies for 5G and 6G technology, accurate assessment of Radio-Frequency Electromagnetic Fields (RF-EMFs) on humans is crucial for compliance with safety guidelines. Matching measurement results with simulations is challenging due to the loss of phase information and the need for high-fidelity digital twins of complex environments. In this paper, we propose a novel holographic phase retrieval method based on fundamental electromagnetics, utilizing the Gerchberg-Saxton algorithm, to reconstruct the full electric and magnetic vector fields in real environments from phaseless measurements. The exposure can be computed using a Huygens' box method. We conducted fine-grained 3D electric field measurements using a calibrated probe in a real environment illuminated by a beamforming 28 GHz antenna. Although the algorithm did not converge in the complex real-world environment, we validated the feasibility of our method with a proof-of-concept at 3.5 GHz. The results demonstrate interference patterns and suggest that, with further refinement, the proposed approach can be effective for human exposure assessment in realistic scenarios.