Metasurface Dome for Above-the-Horizon Grating Lobes Reduction in 5G-NR Systems

The use of 5G New Radio (NR) spectrum around 26 GHz is currently raising the quest on its compatibility with the well-established Earth Exploration-Satellite Service (EESS), which may be blinded by the spurious radiation emitted Above-the-Horizon (AtH) by Base Station (BS) antennas. Indeed, AtH grating lobes are often present during cell scanning due to the large inter-element spacing in BS array antennas for achieving higher gains with a reduced number of RF chains. In this letter, we propose an approach based on an electrically thin metasurface-based dome for the reduction of AtH grating lobes in 5G-NR BS antennas. The proposed scanning range shifting approach exploits the natural lower amplitude of the grating lobes when the antenna array scans in an angular region closer to the broadside direction. The grating lobe reduction is here demonstrated considering a 1x4 phased linear antenna array operating under dual-liner 45deg-slant polarization. A simple design procedure for designing the metasurface dome is reported, together with the antenna performances, evaluated through a proper set of numerical experiments. It is shown that the grating lobe radiation towards the satellite region is significantly reduced, whereas the overall insertion loss is moderate.