RF exposure analysis for multiple Wi-Fi devices in enclosed environment

Abstract

Wi-Fi devices operated inside a metallic enclosure have been investigation in the recent years. A motivation for this study is to investigate wave propagation inside an enclosed environment such as elevator, car, aircraft, and spacecraft. There are performances and safety concerns when RF transmitters are used inside a metallic enclosed environment. In this paper, the field distributions inside a closed metallic room were investigated with multiple portable Wi-Fi devices. Computer simulations were performed using rigorous computational electromagnetics (CEM). The method of moments (MoM) was used to model the mutual coupling among antennas. The geometrical theory of diffraction (GTD) was applied for the multiple reflections off the floor and walls. The prediction of the field distribution inside such an environment is useful for the planning and deployment of a wireless radio and sensor system. Factors that affect the field strengths and distributions of radio waves in confined space were analyzed. The results could be used to evaluate the RF exposure safety in confined environment. By comparing the field distributions for various scenarios, it was observed that the Wi-Fi device count, spacing between the devices and relative locations in the room are important factors in the deployment of these devices. The RF Keep Out Zone (KOZ), where the electric field strengths exceed the permissible RF exposure limit, could be used to assess the RF human exposure compliance. This study shows, it's possible to maximize or minimize field intensity in specific area by arranging the Wi-Fi devices as a function of the relative location and spacing.