Gain and AR Improvements of the Wideband Circularly Polarized Fabry-Perot Resonator Antenna

Abstract

A method to improve the performance of a wideband circularly polarized (CP) Fabry–Perot resonator antenna (FPRA) is presented in this communication. First, a wideband CP FPRA composed of a partially reflective surface (PRS) with a positive reflection phase gradient and a wideband CP patch antenna is proposed. Then, a transmission metasurface (MS) with a high transmission magnitude and tunable transmission phase in a broadband range is proposed to correct the electric field phase above the antenna. This MS has the ability to independently tune the transmission phases of two orthogonally polarized waves. On the one hand, the nonuniform phase distribution on the aperture field of the antenna can be transmitted to be nearly uniform, so the gain of the antenna will be enhanced. On the other hand, the transmission phases of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$x$ </tex-math></inline-formula> - and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$y$ </tex-math></inline-formula> -polarized waves are corrected to maintain a 90° phase difference at every position, which leads to a wider axial ratio (AR) bandwidth. Therefore, after the phase correction of the MS, the gain and AR performances of the antenna are both improved significantly. The measured results suggest that the overlap of the 10 dB return loss bandwidth, 3 dB gain bandwidth, and 3 dB AR bandwidth of the antenna is 9–11.1 GHz (21%). The peak gain of 18.3 dBic is achieved at 10.2 GHz. The results indicate that the proposed MS can achieve excellent performance improvement of the CP FPRA.