Wide-Angle Impedance Matching of a Patch Antenna Phased Array Using Artificial Dielectric Sheets

One main challenge with wide-angle scanning phased arrays is the substantial variation of the active reflection coefficient with scan angle. In this article, the use of artificial dielectric sheets is proposed for reducing the spread of the active reflection coefficient with scan angle. The design method is illustrated based on the impedance matching performed in front of the array face using the admittance seen looking into the array from space. A novel metasurface is developed based on subwavelength-sized conductive particles patterned on both sides of a thin dielectric sheet. Loading a thin dielectric sheet with these particles enables the effective susceptance of the sheet to be tuned. The variation of the array reflection coefficient with scan angle is reduced by providing the required susceptance at a certain distance in front of the array face using the sheet. Two different particle shapes are used to load the dielectric sheet, namely strips and split rings. It is shown that the proposed artificial dielectric sheet is capable of improving the active reflection coefficient when the mutual coupling is the primary factor in limiting the scan range. Moreover, it is shown that the proposed design is suitable for phased arrays with a wide frequency bandwidth. Finally, simulation and measurement results for a uniform
$9\,\, {}\times {}9$
element patch antenna array, compensated using this method, are presented. The finite compensated array has an active VSWR less than 2 for approximately a ±45° scan range in the E-plane, a ±65° scan range in the H-plane, and a ±80° scan range in the D-plane.