Analysis and Characterization of a Wide-Angle Impedance Matching Metasurface for Dipole Phased Arrays

The effects of mutual coupling impact the performance of phased arrays as the beam is scanned off broadside. Wide-angle impedance matching (WAIM) alleviates this problem from a transmission-line impedance matching viewpoint, increasing the useable scan range of the array. Traditionally, a dielectric slab is placed at some distance above the array, resulting in a match at some given angle off broadside. We propose a simpler and more effective solution, replacing the dielectric slab with an ultra-thin metasurface composed of a sheet of split-ring resonators (SRRs) to improve the scanning characteristics of a dipole phased array. It is shown that the presence of the metasurface results in significant improvements in multiple scan planes. A generalized equivalent transmission-line model is introduced for the classical WAIM configuration and adapted for the metasurface. A quasi-analytical model based on the equivalent transmission-line model and the extracted scattering parameters of the metasurface properly predicts the scan range of the full structure, and allows for an accelerated design process.