Low-profile wideband circularly polarised single-layer metasurface antenna
A novel low-profile single-fed circularly polarised single-layer metasurface antenna for wideband operation is proposed in this Letter. The metasurface antenna consists of nine unit cells arranged in a 3 × 3 layout. Four slits are incorporated into four of them, respectively, to form two orthogonal currents with 90° phase difference; hence, circularly polarised fields are excited. Moreover, a modified L-type slot is etched on the middle lattice to improve impedance bandwidth and axial ratio performance. The proposed dielectric-filled (ɛ r = 3.5, tan δ = 0.001) antenna with a low profile of 0.038λ 0 (λ 0 is the working wavelength at 5.7 GHz in free space) achieves about 18.0% measured −10 dB impedance bandwidth. The measured 3-dB axial ratio bandwidth of the proposed antenna is about 12.8% (5.35–6.08 GHz) with a broadside gain of more than 6.9 dBi.
