A Novel Method for Evaluating 5G Handset Array Antenna Exposure Applied to Irregular Human Body Models

This communication presents a novel method for assessing spatially averaged absorbed power density (sAPD) in irregular human body parts that are exposed to electromagnetic fields (EMFs) at millimeter wave (MMW) bands. To ensure high precision in sAPD assessment, different surface area weights are assigned to surface voxel blocks based on a defined step size to determine the integral area. In addition, four average methods from two integration shapes of the exposed body surface are discussed to assess the errors caused by splitting the voxel blocks. A realistic ear model and 5G handset antenna arrays at 28 GHz are used for dosimetry analysis. We simulate a real call scenario and discuss the effects of different exposure positions, integration shapes, and antenna rotation angles on the calculation results, and analyze the weights of these potential influence factors. The results demonstrate that in irregular body models, such as the ear, the distribution of EMF energy absorption by human skin is more dispersed and complex. Compared to other factors, the selection of exposure position for absorbed power density (APD) averaging has a greater impact on the sAPD. The proposed algorithm is beneficial for future compliance tests of 5G MMW handset devices for various body parts.

I. Introduction

With the development of wireless technology, user equipment has become an essential part of people’s lives. In the generation (5G) system, the radio wave spectrum is divided into two frequency ranges (FRs), including the FR1 range (Sub-6 GHz) [1] and the FR2 range (from 24.25 to 71 GHz) [2]. As the number of RF devices increases and they are used more frequently in proximity to humans, concerns about adverse effects on the human body have increased. Due to excessive localized millimeter wave (MMW) exposure, the primary effect is the superficial heating of human skin tissue [3]. The IEEE International Committee on Electromagnetic Safety (ICES) and the International Commission on Non-Ionizing Radiation Protection (ICNIRP) have revised standards and guidelines in 2019 and 2020 [4], [5], respectively. Basic restrictions are derived with large safety margins to prevent whole-body and localized tissue heating [5]. Below 6 GHz, the basic restriction for local exposure is the specific absorption rate (SAR), which averaged over 10 g of body tissue. Above 6 GHz, the counterpart is the absorbed power density (APD). According to [5], APD should be averaged over 4 cm² from 6 to 300 GHz and over 1 cm² from 30 to 300 GHz.