Design of low-profile broadband circularly polarized flat-top metasurface antenna

Abstract In this paper, a low-profile broadband circularly polarized flat-top metasurface antenna is proposed. The array patch forms a diamond-shaped metasurface structure. It is fed by the stepped rotated microstrip line at the bottom through the slot of the ground plane. The design of the stepped rotated microstrip line does not require additional layers to achieve circular polarization as reported in other literature, and it cooperates with the metasurface to obtain good impedance bandwidth and axial ratio bandwidth, making the design simpler and easier to manufacture. The final design has an overall size of 1.76 × 1.76 × 0.07 λ 0 at 5 GHz. The simulation results compare well with the measured results. The maximum gain of the left-hand circular polarization gain is 8.5 dBic, the impedance bandwidth is 4.3–6 GHz (33%), the 3 dB axial ratio bandwidth is 4.6–5.6 GHz (20%), the flat-top bandwidth is 4.6–5.6 GHz (20%). The 3 dB flat-top beam bandwidth in the xoz plane and yoz plane of 4.6–5.0 GHz is stable greater than 90° and 91°, and the 3 dB flat-top beam bandwidth in 5.1–5.6 GHz is stable greater than 72° and 68°. Compared with other works, this antenna has the advantages of broadband circular polarization, low profile, and wide beam. The stable flat-top radiation pattern makes it more popular in the field of microwave power transmission.