Noninvasive Absorbed Power Density Assessment From 5G Millimeter-Wave Mobile Phones Using Method of Moments

Absorbed power density (APD) is challenging to assess due to antenna–human body interactions since the antenna is close to the human body. This article presents a novel technique for noninvasive APD assessment by considering antenna–human body coupling. The electric field integral equation based on spatial dyadic Green’s functions (DGFs) is solved inversely by the method of moments (MoMs) to reconstruct the equivalent currents (EQCs) using the electric field sampled on the surface of the hemisphere surrounding the antenna. Then, the APD is assessed by the EQCs beneath the air–phantom interface. The reconstruction errors are obtained using two types of placement of the antenna array, at the edge and corner of the handheld device, at frequencies of 15, 30, and 60 GHz. It was found that at 60 GHz, the errors did not exceed 8.75% and 11.1% for the edge- and corner-type antennas, respectively, for the maximum spatially averaged power density. The measurement requirements were investigated for an actual testing scenario, including angular resolution,
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-field measurement uncertainty, and required phantom size. It is shown that the proposed technique paves the way for a new methodology to assess APD, including the antenna–human body coupling, for exposure to handheld devices operating above 6 GHz.