Wide-Angle Tunable Metasurface Retroreflector by Loading Cylindrical Luneburg Lens

Simultaneously achieving self-retroreflection and dynamic control of electromagnetic (EM) waves is a pressing challenge in electronic countermeasures. In this work, a novel tunable retroreflector is proposed by integrating a cylindrical Luneburg lens (LL) and a conformal tunable absorbing metasurface (TAM) for large operational bandwidth and wide angular stability. The cylindrical LL, fabricated via 3-D printing based on equivalent medium theory, achieves broadband and wide-angle self-retroreflection. The TAM is conformally integrated onto the lens side facet to enable dynamic manipulation of retroreflected waves. By introducing gap capacitance and parallel meander inductors, its operational bandwidth is extended to 4–10GHz while maintaining dual-polarization stability. The experimental results demonstrate that the proposed retroreflector achieves self-retroreflection and monostatic radar cross section (RCS) control over an incident azimuth range of nearly −60° to +60°. Its operational bandwidth ranges from 5 to 9GHz, with a tunable RCS magnitude approaching 10dB. Simultaneous independent RCS control for EM waves incident from distinct directions is validated, further indicating its potential application in future complex EM environments.