Dual-Cap Mushroom-Like Metasurface Used in CP Reconfigurable Monopole Antenna for Performance Enhancement

A dual-cap mushroom-like metasurface (MS) is proposed. The proposed MS is called dual-cap mushroom-like MS because each unit cell has a simple patch with a centered via on one side of the substrate and a meandered slot on the other side, while conventional mushroom-like MS has one side of the substrate being a plain conducting plate. The meandered slot on the other side of the substrate introduces inductive effects to lower down the operating frequency and increases the operating bandwidth of the unit cells. Comparison is made with other unit cells. The proposed MS is then used as a reflector in the design of a planar circular-polarization reconfigurable (CPR) monopole antenna for the global navigation satellite system (GNSS). Simulation results show that, by placing at only
$0.09{\lambda }_{0}$
from the antenna, the MS can increase the boresight gain and the operating bandwidth from 0.4 to 6.6 dBi, and 1.46–1.79 GHz to 1.42–1.88 GHz, respectively.