Dual-Band Spin-Decoupled Metasurface for Generating Multiple Coaxial OAM Beams

In this article, we propose a shared-aperture metasurface (MS) combining spin-decoupled strategy to generate four coaxially circularly polarized (CP) beams carrying orbital angular momentum (OAM) at Ku-band and Ka-band. First, the frequency selective surface (FSS) is adopted to suppress the mutual coupling between the Ku-band and the Ka-band. Next, at each band, the spin-decoupled meta-atom is designed to realize the independent control for dual circular polarizations. Subsequently, the designed MS illuminated by CP feed source would generate left-hand CP (LHCP) beam with OAM mode +1 and right-hand CP (RHCP) beam with OAM mode −1 at Ku-band; meanwhile, the LHCP beam with OAM mode +2 and the RHCP beam with OAM mode −2 are generated at Ka-band. Finally, the MS is designed, manufactured, and measured. Both simulated and measured near-field and far-field performance verify that the proposed MS can generate four independent CP OAM beams along the same spatial axis at dual bands. On the other hand, the experimental results and the corresponding theoretical analysis verify that the proposed MS illuminated by a linear-polarized (LP) feed source could also generate eight correlative LP OAM beams at dual bands.