Planar Ultra-Wideband Wide-Angle Scanning Array Antenna with Improved WAIM Layer

An ultra-wideband wide-angle scanning dual-polarized tightly coupled dipole antenna array is proposed with an improved wide-angle impedance matching (WAIM) layer. One unit with period boundaries is investigated to illustrate radiation and impedance matching performances for an infinite array. The bandwidth can cover S-band, X-band, and C-band. A shorted circular plate is placed beneath the junction area between dipoles to shift the common-mode resonance frequency down out of the operating band. A couple of metal ribs are added into the feed lines to improve impedance matching between dipole and 50$\Omega$ coaxial probe. An improved wide-angle impedance matching (WAIM) layer is proposed which consists of two couple metallic sheets loaded on the dipole element. It can be modeled by an LC series circuit paralleled with the dipole, which achieves a smoother impedance transform from the dipole to the free space so that the scanning angle is much wider. The proposed dual-polarized infinite array can achieve 4:1 bandwidth (3.51-14.28GHz) when scanning ± 60° in E plane and ± 50° in H plane mostly.