Low Profile and High Gain Unidirectional Circularly Polarized S-Shaped Slot Antenna

In this paper, a low profile and high gain unidirectional circularly polarized (CP) S-shaped slot antenna is designed and fabricated. The antenna has 72.2% impedance bandwidth (
$\vert S_{11}\vert \leq-10\ \text{dB}$
) in the frequency range from 2.92 to 6.22 GHz and 13% (4.31-4.91 GHz) 3-dB axial ratio bandwidth. The designed antenna is unidirectional having the size of
$0.67\lambda_{0}\times 0.6\lambda_{0}\times 0.12\lambda_{0} (\lambda_{0}$
is the wavelength at the lowest operating frequency in free space) with the peak gain of 8.48 dBi at 5 GHz. The designed antenna is fabricated and simulated results are validated with measured results.