Broadband Circularly Polarized Metasurface Antenna Based on Characteristic Mode Analysis

A broadband circularly polarized (CP) metasurface antenna based on characteristic mode analysis (CMA) is proposed. The antenna consists of a truncated corner square driver patch loaded with L-shaped branches, sandwiched between a
$4\times 4$
metasurface and a ground plane. The CP wave is generated by exciting the driving patch, and the CP wave excites the surface wave propagating on the metasurface, resulting in a wide impedance bandwidth and Axial ratio (AR) bandwidth. The overall size of the antenna is
$36\text{mm}\times 36\text{mm}\times 4.5\text{mm}\ (0.72\ \lambda_{0}\times 0.72 \lambda_{0}\times 0.09\ \lambda_{0})$
. The simulation results show that the bandwidth of
$\vert \mathrm{S}_{11}\vert < -10\ \text{dB}$
is 4.04-8.83 GHz (74.44%), the 3dB AR bandwidth is 4.65-6.92 GHz (39.24%), and the peak gain is 6.83 dBic. In addition, the antenna has good left-handed CP radiation performance within the operating bandwidth, which is suitable for C-band satellite communication applications.