Focusing and Linear-to-Circular Polarization Conversion of a Hemispherical Metasurface

With the aim of enhancing the radiation of the antenna system conventionally containing a protective dome, a transmission-type linear-to-circular polarization conversion electromagnetic metasurface lens which approximates a hemispherical shell profile is presented in this study. The presented design bearing structural compatibility with the existing dome geometry can facilitate the link enhancement of compact system through its potential for a circularly-polarized high gain antenna. To fulfill both the focusing and polarization conversion requirements, transmission phase distribution on the hemispherical surface is analyzed first. Then, polarization-dependent unit cell geometry is designed to achieve the objective transmission phase distribution. The hemispherical metasurface is thus obtained through building all unit cells with determined dimensions and orientations onto the corresponding hemispherical surface positions. Finally, using an aperture-coupled linearly-polarized patch antenna as the primary radiating source of the metasurface, enhanced main lobe gain and circularly-polarized secondary radiation is observed within a wide band. The agreement between simulation and measurement validates the design.