Optically-Transparent FSS for Outdoor-to-Indoor Transmission Improvement featuring Electromagnetic-Thermal Co-Analysis

This paper proposes a novel method for mitigating transmission loss in window glass using a frequency selective surface (FSS), featuring angular stability, optical transparency, and insulation performance. The unit cell period is reduced to 0.05
$\lambda_{0}$
, where λ0 is the free-space wavelength at the operating frequency of 3.45 GHz. This enables stable bandpass characteristics, effectively mitigating transmission loss in the window glass under oblique incidence scenarios. In addition, this proposed FSS consists of a metal mesh electrode on a transparent dielectric substrate for achieving optical transparency. Electromagnetic (EM)-coupled multiphysics simulations confirm insulation performances of the proposed FSS. Experimental verification involves the application of this attachable surface using commercial base stations and mobile devices in outdoor-to-indoor wireless communication scenarios. This invention is expected to provide a practical and concise solution for establishing reliable outdoor-to-indoor propagation channels.