Polarization-Multiplexed Metasurface Integrating Transmissive Vortex Beam Generation and Monostatic RCS Reduction

Integrating transmissive orbital angular momentum (OAM) beam generation and reflective monostatic radar cross section (RCS) reduction within a single aperture remains challenging because the two functions require distinct transmission and reflection phase responses. This paper proposes a polarization-multiplexed metasurface based on a multilayer anisotropic unit cell and a unified phase-superposition strategy. In the transmission channel, the vortex phase is combined with a beam-steering phase to generate OAM beams propagating along the normal or a prescribed deflected direction. In the reflection channel, the diffusion phase is superimposed with the vortex phase to redistribute the reflected energy and suppress the broadside backscattering. Depending on the polarization and propagation direction of the incident wave, the same aperture generates transmissive OAM beams with topological charges of +3 and −3 or performs monostatic RCS reduction. Full-wave modal analyses verify the designed OAM states, while measurements confirm the corresponding beam and scattering characteristics. Under normally incident y-polarized waves, the measured RCS reduction exceeds 10 dB from 12.4 GHz to 15.6 GHz, corresponding to a relative bandwidth of 22.8%, with a peak reduction of 30.15 dB at 13.3 GHz. Under normally incident x-polarized waves, the measured RCS reduction is approximately 15–24 dB from 11 GHz to 16 GHz. These results demonstrate the feasibility of integrating direction-dependent OAM transmission and polarization-dependent RCS reduction within a single metasurface aperture.