Circularly polarized antenna with gain enhancement via a single-layer Near-Zero-Index metasurface superstrateChaymae Chahboun, Safia Jaouad, Fatima Z. Khoutar, Otman Mrabet and Mariem AznabetEPJ Web Conf., 380 (2026) 01018DOI: https://doi.org/10.1051/epjconf/202638001018