Design of A Low-profile Broadband Circularly Polarized Metasurface Antenna Based on Characteristic Mode

A circularly polarized (CP) metasurface (MS) antenna with wide operating band and low-profile is proposed. To reveals the working mechanism of the broadband MS CP antenna, characteristic mode analysis (CMA) which can provide physical insight is introduced. The desired modes are selected to construct CP radiation and then excited by a L-shaped slot while the undesired modes are shifted towards higher frequencies. After modulating the higher order mode, the in-band boresight gain is improved. After full-wave simulation, the results show the impedance matching bandwidth and the axial ratio (AR) bandwidth are 24% and 32.1% respectively. Besides, the radiation patterns are greatly improved comparing with the reference antennas.