A planar circularly polarized (CP) frequency beam scanning Fabry-Perot resonator antenna (FPRA) with enhanced gain property is presented in this paper. The antenna consists of two layers. The CP substrate integrated waveguide (SIW) beam scanning leaky-wave antenna (LWA) is used as the feeding antenna. It provides good impedance matching and stable radiation pattern over the working band. Then, partially reflecting surface (PRS) layer is introduced to improve the gain property by using a single substrate with metal patches array printed on both top and bottom surfaces. After comparisons among four patch types, circular patch type is chosen. It is an ideal choice for CP antenna because of its completely symmetrical structure along φ-plane and gentler phase slope. Parameter analysis is made for better understanding of the working principle. Finally, the antenna is fabricated and measured for verification. It shows that the main beam scans from -38° to 28° within the operating frequency band from 9.1 to 14.6 GHz (or 47.8%). The 3-dB axial ratio (AR) bandwidth is from 10.2 to 13.5 GHz (or 28.7%). Maximum gain is 14.6 dBic, and 3-dB gain bandwidth is from 11 to 14 GHz (or 26.1%). Gain enhancement of about 3.3 ~ 6 dB is achieved, compared with the unloaded type. Due to the advantages of high gain, CP beam-scanning capability, and easy fabrication, this method is a good option to design antennas in wireless communication and radar systems.
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