An Ultra-Wideband Fully-Planar Inverted-L Element (FILE) Array with Dual-Polarization and Optimal Sampling

A novel dual-polarized ultra-wideband array, based on the fully-planar inverted-L element (FILE), is presented. The structure of our proposed dual-polarized FILE (DP-FILE) unit cell (UC) consists of two inverted L-shaped radiators. To include the required capacitive coupling in our UC, we strategically design the dual-polarized inverted-L radiators, to ensure capacitive coupling with a common ground via and with each other. Notably, an almost optimal sampling of $0.47\lambda_{h}$ is employed. Moreover, to improve matching performance under wide-angle scanning conditions, two superstrate layers, and perforations in the dielectric layers of our UC are introduced. Our proposed DP-FILE UC demonstrates a 2.75: 1 effective bandwidth (from 34 GHz to 94 GHz) with active VSWR < 3, port-to-port coupling between orthogonal ports less than -10 dB, and realized embedded gain (normalized to the maximum theoretical directivity) more than -1.5 dB, while scanning up to 45° in the E-, H-, and D-planes.