Low-Profile Planar Ultra-Wideband Phased Array Antenna with FSS Superstrate Loading

A low-profile planar ultra-wideband phased array antenna is proposed in this paper. The proposed antenna element adopts a dual-polarized topology and utilizes two orthogonal polarized printed dipoles as radiation structures. To achieve better scanning ability, the wide-angle impedance matching (WAIM) layers consisting of the frequency selective surface (FSS) superstrate are loaded above the dipole patches, and the parasitic metal strips are introduced and placed below for a lower profile. The sizes of the proposed antenna element are $0.5\times 0.5\lambda_{high^{2}}$($\lambda_{high}$ is the free-space wavelength at the highest operating frequency), and the profile is only 0.228$\lambda_{high}$. Calculated results show that the active VSWRs of the proposed infinite array are below 2.9 at broadside radiation and scanning to ± 60° in the E/H planes within 2-6 GHz. Meanwhile, the isolations between orthogonal ports are mostly greater than 20dB. To verify the proposed designs, an array prototype is fabricated and measured. The measured results are in an acceptable agreement with the calculated ones.