A Novel All-Metal Tunable Broadband Frequency-Selective Surface

In this study, we design an all-metal tunable broadband frequency selective surface (FSS) that eliminates the need for lossy dielectric substrates and active devices requiring complex bias DC voltage-based control circuits. The FSS is constructed from three cascaded all-metallic plates, each comprising cells formed by uniting two concentric four-arm substructures. Those cascaded configuration exploits multi-order filtering to obtain broadband and independently controllable odd-mode resonance to generate tunable bandpass response. The operating mechanism of the proposed FSS is analyzed and verified by the results from full-wave simulation, equivalent circuit calculation, and mode-related analysis. The measured and simulated results show that the structure can provide a tunable bandwidth range from 6.40 to 10.0 GHz, with a maximum bandwidth of 43%. Additionally, the FSS maintains low insertion losses and stable performance for both TE and TM polarization across a wide range of incidence angles.