Design of polarization-insensitive and angularly stable metasurfaces with symmetric cubic phase distribution for broadband RCS reduction

This article presents an efficient and formulated approach to the design of polarization-insensitive metasurfaces adopting a symmetric cubic phase distribution for both wideband and wide-angle reduction of radar cross section (RCS). The proposed approach offers several key advantages, including the efficient calculation of the phase distribution across the metasurface and at each unit cell using an efficient and straightforward design formula, eliminating the need for time-consuming optimization algorithms. Moreover, the design phase formula is independent of the wavelength, allowing for its extension to various frequency bands. Geometric phase theory is used to design a unit cell where any reflection phase value from 0° to 360° can be achieved by rotating the resonator in each unit cell. Then the proposed symmetric cubic phase distribution can be applied to the metasurface aperture. When circularly polarized (CP), linearly polarized (LP), and elliptically polarized (EP) plane waves illuminate the metasurface, both simulated and experimental results demonstrate that the polarization-insensitive metasurface with symmetric cubic phase distribution can substantially reduce the RCS and achieve diffusive scattering patterns. The scattering is significantly suppressed and exceeds 10 dB of RCS reduction from 11 to 28 GHz resulting in a fractional bandwidth (FBW) = 87.1%. Furthermore, the proposed metasurface maintains excellent angular stability and the RCS reduction exceeded 10 dB even under off-normal incidence when the elevation and azimuthal angles of incidences reached 60°.