We study the wave propagation between two glidesymmetric metallic plates drilled with periodic rectangular holes. A mode-matching method is proposed in order to derive efficiently the dispersive properties of these periodic structures. The method takes advantage of the higher symmetry of the structure reducing the computational cost by enforcing boundary conditions on the field on only one of the two surfaces. Physical insight on specific symmetry properties of Floquet harmonics in glide-symmetric structures is also gained. The code is validated with commercial software assessing its accuracy when varying the most influential/critical parameters. We confirm the potential of glide-symmetric structures to tune the effective refractive index. Specifically, we demonstrate that glide-symmetric structures with rectangular shapes can be employed to synthesize anisotropic refractive indexes with a large band of operation, which makes such metasurface structures applicable for realization of UWB planar lenses.
New high-frequency 5G and satellite communication systems require fully-metallic antennas and electromagnetic components. These components can be implemented with truncated versions of periodic structures. In order to achieve the desired performance of these future devices, it is of crucial importance to have a precise control of the propagation properties, i.e. the frequency dispersion behavior and stop-bands. Here, we demonstrate the potential use of higher symmetries to diminish the frequency dispersion of periodic structures and control the width of stop-bands with a new type of fully-metallic transmission line, which is loaded with holes on a twist-symmetric configuration. Simulated and experimental results confirm the intrinsic link between the propagation characteristics and the symmetries of a periodic structure. Additionally, we provide a definitive explanation of the recently discovered polar glide symmetry and its potential combination with twist symmetries to produce low-dispersive materials and reconfigurable stop-bands. The promising properties of these structures are demonstrated with a fully-metallic reconfigurable filter, which could be used for future high-frequency 5G and satellite communication systems.
In this work, monitoring of the transmit power for several base stations operating in a live 5G network (Telstra, Australia) was conducted with the purpose of analyzing the radio frequency (RF) electromagnetic field (EMF) exposure levels. The base stations made use of state-of-the-art massive MIMO antennas utilizing beamforming in order to optimize the signal strength at the user’s device. In order to characterize the actual EMF exposure from 5G base stations, knowledge of the amount of power dynamically allocated to each beam is therefore of importance. Experimental data on the spatial distribution of the base stations’ transmit power were gathered directly from the network by extracting information on the radio and baseband operations. Out of more than 13 million samples collected over 24 h, the maximum time-averaged power per beam direction was found to be well-below the theoretical maximum and lower than what was predicted by the existing statistical models. The results show that assuming constant peak power transmission in a fixed beam direction leads to an unrealistic EMF exposure assessment. This work provides insights relevant for the standardization of EMF compliance assessment methodologies applicable for 5G base stations.
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