High-Order Modes Modulation for Analysis and Design of Angle-Stable FSS

This letter proposes a novel analysis and design methodology for angle-stable frequency selective surface (ASFSS) based on high-order modes modulation. The theory of characteristic mode (TCM) is introduced to expand these resonance properties into the modal space. The provided orthogonal eigen-solutions can effectively distinguish the high-order modes that destroy angular stability. With the supplementary field information, these modes can be physically handled, including modal tuning and suppression, to address the performance degradation with respect to angle. As a proof of concept, a miniaturized ASFSS is designed, fabricated and experimental validation. Both simulation and experimental results show that the ASFSS exhibits excellent angular stability up to 70° with polarization insensitivity. These results of the designed ASFSS demonstrate that the high-order modes modulation-based method has the potential to enhance ASFSS performance.