Diffusion-vortex composite phase metasurface for broadband RCS reduction

This paper proposes a composite phase approach that combines the diffusion phase and vortex phase to design a broadband metasurface for reducing the radar cross section (RCS) of circularly polarized waves. The gradient phase distributions of metasurface unit cells for converting circularly polarized incident waves into co-polarized reflected waves are realized by the Pancharatnam-Berry (PB) phase method. The diffusion phase distribution is employed to achieve uniform scattering within a specified solid-angle region, while the superimposed vortex phase is introduced to generate a reflection null in the normal direction of the metasurface. These dual-phase mechanisms synergistically deflect the scattered energy away from monostatic radar reception angles, thereby significantly reducing backward RCS and enhancing stealth capability against circularly polarized wave detection. Simulation results demonstrate that under normal incidence of left-handed circularly polarized (LCP) waves, the metasurface achieves an RCS reduction exceeding 10 dB for right-handed circularly polarized (RCP) waves over the frequency range from 12.63 GHz to 18.1 GHz, while the RCS of the LCP component remains at an extremely low level. Furthermore, conformal application of the metasurface on cylindrical surfaces preserves the central null characteristic in co-polarized diffuse scattering. The proposed composite phase methodology provides a novel way for wide-angle and multidimensional stealth technologies in complex electromagnetic environments.