Enhancing 5G Propagation into Vehicles and Buildings using Optically Transparent and Polarisation Insensitive Metasurfaces over Wide-Incidence Angles

This article presents two transmissive metasurfaces coated on a glassy window to enhance the 5G outdoor to indoor (O2I) coverage inside vehicles and buildings. Two different wide-incident angle, and polarization insensitive unit cells are proposed for both single-glazing and double glazing glasses and have been arranged in a periodic structure to construct the transmission surfaces. Both metasurfaces are optically transparent as Indium Tin Oxide (ITO) is used as a conductive part of each unit cell. The proposed transmission surfaces empower the indoor coverage of 5G signals at 3.5 GHz band for wide range of incident angels. Although multi-layer structures are generally more sensitive to angle of incidence, however, both proposed two layered transmissive surfaces offer wide angular stability up to 65 and 75 degrees for double-and single-glazed glass accordingly. In order to achieve wide stable angular response, evolutionary optimization techniques have been used to optimise the proposed unit-cells. Both designs support high transmission coefficient over the operating frequency for wide incident angles which are higher than reported structures in the literature review. The fabricated prototypes have been evaluated experimentally and from measured results, it appears that both metasurfaces offer significant potential to improve propagation into buildings and vehicles.