Zi-Jian Han, Wei Song, and Xin-Qing Sheng. “Broadband Circularly Polarized Antenna by Using Polarization Conversion Metasurface”. Applied Computational Electromagnetics Society Journal (ACES), vol. 35, no. 6, June 2020, pp. 656-61, https://journals.riverpublishers.com/index.php/ACES/article/view/7833.