A Low-Profile Planar 8:1 Bandwidth Long Slot Array With Planar Cross-Stack Impedance-Matching Layers

This letter introduces an ultrawideband, wide-scanning long slot array with planar cross-stack impedance-matching layers (PCMLs). The gradually decreasing size patches are designed as the preliminary impedance-matching layers. Additionally, the cross-stacked impedance-matching layers are added to enhance impedance matching at high frequency. The specialized coaxial-to-coplanar waveguide and then slot coupling are used to feed the long slot. The common-mode resonance is moved out of the operational band effectively by incorporating a metal vias wall. To address the increase of active-voltage standing-wave ratios (VSWRs) in high-frequency wide scanning in the H-plane, slots are built for the long slot and PCMLs along the y-axis. The proposed array achieves an 8:1 bandwidth (2 GHz to 16 GHz) with an active-VSWR below 2 in the broadside. A 17 × 17 prototype has been fabricated. Measurements show that when scanning to 60°, the frequency ranges with active VSWR less than 3 for the E-plane (2.1 GHz to 15 GHz), H-plane (2 GHz 9.9 GHz and 10.1 GHz to 15.8 GHz), and D-plane (2 GHz to 16 GHz).