Low-Profile Design of Broadband High Gain Circularly Polarized Fabry-Perot Resonator Antenna and its Array with Linearly Polarized Feed

A novel low profile broadband circularly polarized Fabry-Perot resonator antenna (CP-FPRA) with a linearly polarized feed is proposed. The goal of this antenna is to generate circular polarization with high gain level in broad bandwidth, while maintaining low profile and simple feed configuration. The proposed antenna consists of a primary radiator aligned along 45° with linear polarization, a partially reflective surface, and a nonstandard artificial magnetic conductor acting as a reflective ground plane. Its profile can be reduced to a quarter of a wavelength. Furthermore, an array antenna of <inline-formula> <tex-math notation="LaTeX">$2\times 2$ </tex-math></inline-formula> arrangement using CP-FPRA as element with a compact sequential rotation feeding scheme is also proposed and fabricated to enhance the gain and to improve the axial ratio (AR) bandwidth. The array was optimized to minimize grating lobes and reduce the sidelobe level, even though the element spacing was about two wavelengths. Reasonable agreement between the simulated and measured results is observed. The measured common bandwidth of <inline-formula> <tex-math notation="LaTeX">$\vert \text{S}_{11}\vert \le -10$ </tex-math></inline-formula> dB, gain-drop ≤3 dB, and AR ≤3 dB is about 7.4%.