Aperiodic Sunflower-Like Metasurface for Diffusive Scattering and RCS Reduction

This letter presents the design of aperiodic sunflower-like metasurface for circularly polarized (CP) wave diffusion and radar cross-section (RCS) reduction using Pancharatnam-Berry (PB) meta-atoms. The distribution of the PB meta-atoms across the metasurface aperture is nonuniform and has a distribution inspired by sunflower seeds, i.e., an outwardly logarithmic spiral lattice with no transitional periodicity. The proposed metasurface has 600 PB meta-atoms of subwavelength size of 5 mm ≈ 0.33λ20GHz and exhibits a randomly chosen diffusive reflection phase between 0° and 360°. Both simulated and experimental results demonstrate that the proposed sunflower-like metasurface can efficiently diffuse the backscattered energy into numerous directions when normally illuminated by a CP wave with RCS reduction >7 between 16 and 23.8 GHz. Furthermore, the low-level diffuse scattering can be preserved under oblique incidence up to 60°. As a result of using this PB concept, the polarization sensitivity of the proposed metasurface is released, and this is highly desired in applications when the polarization of the incoming wave is unknown.