Compact Wideband Wide-Angle Polarization-Free Metasurface Lens Antenna Array for Multibeam Base Stations

A compact wideband wide-angle polarization-free metasurface lens (MSL) antenna array is proposed for a multibeam base station operating over the band of 1.71-2.2 GHz. The MSL element comprises of a planar wideband wide-angle polarization-free reflectionless MSL and three feeding sources of ±45° polarized cross-dipole antennas. With the shared lens aperture, the antenna achieves the three beams in the directions of 0° and ±30° in a horizontal plane. A five-layer patchbased metasurface loaded with metal poles are introduced to achieve consistent performance for wide-angle response. To reduce spillover loss, the feeding antennas are loaded with a metasurface and four directors for narrow beamwidth and low profile. With the optimized feeding antennas and MSL, a section of array with 1 × 4 MSL elements is prototyped for validation. The measured results show that an impedance bandwidth for return loss ≥10 dB is 1.63-2.24 GHz with the isolation larger than 22.3 dB. The measured gain ranges for 0° and 30° beams are 11.8-13.5 and 10-12.2 dBi with the sidelobe levels less than -22.6 and -13.6 dB, respectively.