A Low-Profile Circularly Polarized Metasurface Antenna With Wide Axial-Ratio Beamwidth

This letter proposes a low-profile circularly polarized metasurface antenna with a wide axial-ratio beamwidth (ARBW). The proposed antenna consists of an array of square metallic metasurface cells that are excited by a microstrip line through four cross slots. The feeding structure can be seen as a symmetrical multiplefeed structure. Thus, E
_φ
and E
_θ
can be nearly equal in amplitude with a phase difference of 90° over a wide angle range. A wide ARBW is obtained. With a size of 0.93λ
_L
× 0.93 λ
_L
× 0.024 λ
_L
(λ
_L
is the wavelength in free space at the lowest operating frequency), the proposed antenna achieves an impedance bandwidth of 17% and an AR bandwidth of 14.5%. Moreover, the ARBW is more than 205°.