Wide-Angle Stable Dual-Layer Orthogonal FSS with Controllable Stopband Bandwidth via Independent Transmission Zero Manipulation

This paper presents a double-layer bandstop frequency selective surface featuring wide-angle stability and controllable bandwidth. The design adopts a double-layer metallic orthogonal configuration that enables bandwidth control by manipulating the transmission zeros. An equivalent circuit model (ECM) is developed to elucidate its operating mechanism. Simulation results confirm that the proposed FSS achieves a stopband spanning 6 - 12 GHz while maintaining angular stability for incidence angles up to 60°. Through the adjustment of central metallic stub length, continuous bandwidth variation is demonstrated across 6.00 - 8.48 GHz with a relative bandwidth of 66.67% - 82.81%. Experimental measurements show excellent agreement with simulated results, validating both the filtering characteristics and angular robustness. Furthermore, owing to the structural optimization based on the ECM, the FSS achieves controllable bandwidth operation in the C-, X-, or Ku-band without compromising wide-angle stability, showcasing remarkable design versatility for modern frequency-agile systems.