A Narrowband Energy-Selective Surface With High-Selectivity for 5G Wireless Communications

Energy-selective surfaces (ESSs) have attracted significant attention in electromagnetic (EM) compatibility and protection applications due to their nonlinear transmission capabilities in response to varying EM field intensities. This article proposes the design of a narrowband high-selectivity ESS for 5G wireless communications based on a dual-stopband equivalent circuit model (ECM). This ECM allows for the adjustment of bandwidth without affecting the resonant frequency of the operating band, achieved by directly controlling the resonant frequencies of the stopbands flanking the passband. Consequently, the stopbands can be brought closer together or moved further apart, indirectly adjusting the operating bandwidth. A physical model of a narrowband ESS operating at 3.5 GHz is presented based on the dual-stopband ECM. Both steady- and transient-state simulations demonstrate the efficacy of the design. The simulation results indicate that under low-power signals, the insertion loss (IL) at 3.5 GHz is 0.3 dB, and within the frequency range of 3.31–3.53 GHz, the IL remains below 1 dB. Under high-power conditions, the shielding effectiveness (SE) reaches up to 48 dB, with an SE greater than 20 dB in the range from 3.11 to 3.93 GHz. The fabricated ESS was measured in both rectangular waveguide and free-space environments, whose experimental results were in good agreement with simulation data at various power levels. These findings suggest that the proposed ESS offers significant potential for applications in EM shielding and compatibility, particularly in 5G communication systems.