Design of a Flat Gain Broadband Metasurface Antennas Using Characteristic Mode Analysis

This paper presents a flat gain broadband metasurface antenna with a central frequency of 6.53 GHz. It consists of two substrate layers and three metal layers. The upper layer of the antenna including an array of 3x3 squared patches, which constitutes a metasurface radiator. It is fed by a microstrip line at the bottom through an ellipse slot etched on the middle ground plane. By loading four parasitic patches on the upper layer, the impedance matching of the antenna is improved. The bandwidth can then be broadened. Then two slots along x-axis are loading in part of the unit cells of the metasurface for improving the radiation performance of the proposed antenna using characteristic mode analysis (CMA). The proposed antenna realizes 56% (4.7 GHz-8.36 GHz) impedance bandwidth for $\vert S_{11}\vert \leq-10\mathbf{dB}$ and peak gain of 10 dBi.