Dual Circularly Polarized Metasurface Antenna

This paper proposes the design and numerical validation of a low-profile dual-polarized antenna where two opposite circular polarizations are obtained by exciting the same modulated metasurface either with a radially outward traveling surface wave (SW) or with an inward traveling SW. The outward traveling SW is launched from a vertical pin located at the center of the radiating aperture, as in conventional MTS antennas, while the inward traveling SW is excited from the aperture edge, through an underlying parallel plate waveguide. The MTS is characterized by a modulation designed to achieve broadside radiation and by an anisotropy providing a different circular polarization depending on the traveling direction of the SW. The modulation index is designed to equalize the efficiency of the beams radiated in the two polarizations. A practical two-port feeding structure has also been designed and numerically analyzed.