On the Synthesis of Aperiodic Multi-Atom 1-Bit Reconfigurable Passive EMSs at 140 GHz

An innovative reconfigurable passive electromagnetic skin (RP-EMS) architecture is proposed to support a single reflection beam while suppressing undesired beams, using 1-bit switching with minimal hardware complexity. The architecture is the first to simultaneously optimize the meta-atom arrangement and their 1-bit switching descriptors using the integer-coded evolutionary algorithm, supporting multiple reflection scenarios. The process yields one aperiodic meta-atom arrangement that effectively mitigates periodic phase quantization errors typical of 1-bit RP-EMS layouts, while changing reflection angles solely through 1-bit switching. An aperture-coupled patch-based meta-atom topology with well-separated and linearized phase responses is employed to enable 1-bit switching using a short/open connection. As a proof of concept, 30×30 RP-EMS prototypes with a 3.14×3.14 cm2 aperture and λ/2 periodicity at 140 GHz are designed and fabricated, demonstrating reflection at 15∘, 30∘, and 45∘ under normal incidence. The prototypes exhibited robust beam steering with QLL consistently below -10 dB and SLL up to -10 dB, confirming the effectiveness of the proposed MASB layout. In addition, the structures achieve 3-dB gain bandwidth exceeding 11% and high reflection efficiencies over 15%, referenced to a conductor surface of the same size. These results validate the potential of the proposed architecture for implementing multi-functional 1-bit RP-EMS with controlled sidelobes and no grating lobe near 140 GHz.