Flat metamaterial antenna with dual-circular-polarization at the −1st-order-resonance mode, applicable to reconfigurable RF systems

In this paper, a novel compact and dual-circular-polarized antenna is proposed. To be physically small, the electromagnetic wave is radiated at the -1st-order resonance mode of a planar composite right- and left-handed(CRLH) antenna, instead of the +1st resonance mode. To enable two circular polarizations in one structure, the orthogonal coaxial feed points for the 90°-angular difference are decided at the -1st resonance mode, and connected to the output ports of a hybrid branch-line coupler for 90°-phase difference. The functional block diagram is given, and is followed by the steps of full-wave simulations for design and the performance is verified by the measurement of the fabricated antenna with the test frequency of the 2.37-2.40 GHz band. The LHCP and RHCP will be observed with good inter-polarization isolation and axial ratio, and the applicability to a compact reconfigurable RF device will be considered.