Dual-Band Energy-Selective Surface With Enhanced Independence Based on Two-Layer Diode-Loaded FSS

This article presents an energy-selective surface (ESS) based on a two-layer resonant circuit model with high-power microwave (HPM) protection ability for two independent bands. An equivalent circuit model (ECM) engineering multiple stopbands and passbands with combinations of parallel and serial resonators is proposed for dual-band design. By loading diodes in the resonator accordingly, the operating band can be switched from a low insertion loss (IL) state to a high shielding effectiveness (SE) state power-dependently. Additionally, the independence of two bands is greatly improved by using two separate layers to mount the diodes, attributing to the enhanced difference of induced voltage between diodes in different layers resulting from shielding effect of top layer. Various functions in two-frequency coincidence scenarios are analyzed, demonstrating the advantage of independent modulation. Based on the ECM, a two-layer ESS is designed. Two wide bands with IL < 1 dB under low-power incidence and SE > 20 dB under HPM are achieved, due to second-order resonance produced by double-layer configuration. The multiple nonlinear functions of the design are verified by field-circuit cosimulations. The prototypes are measured, exhibiting 0.6 and 25.2 and 0.7 and 27.3 dB of IL and SE at two central operating frequencies for low-power and high-power incidences, respectively, with good agreement with the simulations.