A Novel Triband Circularly Polarized Metasurface Antenna Based on Characteristic Mode Analysis

Using characteristic modal analysis (CMA), this letter introduces a novel tri-band microstrip metasurface (MTS) circularly polarized (CP) antenna with dual sense. The radiation part of the antenna consists of double "king" shaped curved rings and cut corner units, and the feed network consists of orthogonal feeding slots and a T-shaped power divider. In order to clarify the design process of the proposed antenna, CMA is first performed on the 3 × 2 MTS units by replacing the rectangular units with lower radiating curved rings and adjusting the units edges to mitigate the resonance mode reverse current and achieve the CP. Subsequently, CMA is carried out on MTS loaded with feeding slots to stimulate resonance modes. The results show that three pairs of orthogonal modes constituting the CP are formed by the MTS unit modes and the slot modes excited by the feeding slots at frequencies of 7.75 GHz, 8.8 GHz, and 9.8 GHz, respectively. Finally, to verify the performance of the antenna, the incorporation of a T-shaped power divider is simulated. The prototype experiments validate the principle and design methodology, and the measured results are in good agreement with the simulation results.