Aperiodic sunflower like metasurface for diffusive scattering and RCS reduction

This article 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 non-uniform and has a sunflower seeds like distribution, i.e., outwardly logarithmic spiral lattice of no transitional periodicity. The proposed metasurface has 600 PB meta-atoms of sub-wavelength size of 5 mm ≈ ${0.33\lambda_{20GHz}}$ and exhibits a randomly chosen diffusive reflection phase between 0o and 360o. 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 dB from 16 GHz to 23.8 GHz. Furthermore, the low-level diffuse scattering can be preserved under oblique incidence up to 60o. As a result of using 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 typically unknown.