Low-Profile Planar Ultrawideband Modular Antenna Array Loaded With Parasitic Metal Strips

A low-profile dual-polarized planar ultrawideband modular antenna (PUMA) array is proposed in this article. The overall profile is as small as 11.4 mm (
$0.228\lambda _{high}$
, where
$\lambda _{high}$
is the free-space wavelength at the highest operating frequency) based on element sizes
$25\times25$
mm
²
(
$0.5\times 0.5\lambda _{high}^{2}$
) and a large operating frequency bandwidth achieved by loading lossless parasitic metal strips between the dipole patches and the ground plane. The loop-mode resonance that causes deterioration of the port isolation around the lowest operating frequency is comprehensively analyzed and suppression methods are proposed. To further reduce the overall profile, a metasurface-based wide-angle impedance matching (MS-WAIM) layer is introduced. The surface waves guided by the MS-WAIM layer during wide-angle scanning in H-plane are suppressed by cutting properly-sized square holes at critical positions. The calculated results show that the proposed infinite array can scan up to ±60° in E-/H-planes with active voltage standing wave ratios (VSWRs) below 2.9 within 2-6 GHz and orthogonal port isolations beyond 20 dB. A
$12\times11$
array prototype is fabricated and reasonable agreement is achieved between the calculated and measured results.