Synergizing Radiation Regulation and Cross‐Band Stealth with Passive Folded Metasurfaces.

Radiation‐stealth integration, merging radiation regulation and scattering suppression into a unified framework, is essential for advanced radar communications and stealth technology. However, current state‐of‐the‐art solutions that simultaneously modulate radiation and stealth characteristics encounter two main challenges: limited scalability due to high energy demands from active components, and constrained stealth bandwidth stemming from the inherent incompatibility between radiation and scattering. Here, passive folded metasurfaces (PFM) that integrate radiation regulation with stealth capabilities, eliminating the necessity for active components while achieving both in‐ and off‐band stealth, referred to as cross‐band stealth, are proposed. The PFM employs a hybrid architecture, cascading a quad‐focal asymmetric metasurface (QFAM) and a polarization‐conversion meta‐mirror (PCM) incorporated with patterned feed arrays. The QFAM leverages local quad‐focal phases and polarization selectivity to regulate radiation modes generated by encoded‐excited feeds, enabling efficient beamforming reconfiguration without active components. Furthermore, the synergy between the QFAM and PCM dissipates in‐band impinging waves through internal reflections and absorptions, while off‐band waves undergo destructive interference enabled by checkboard‐patterned modulators atop the QFAM, achieving cross‐band stealth. To validate the capabilities of the proposed PFM, a prototype is fabricated and its versatile radiation‐stealth functionalities, including 1D narrow‐ and wide‐beam scanning, 2D beamforming, and cross‐band stealth, are experimentally demonstrated. [ABSTRACT FROM AUTHOR]