Broadband Circularly Polarized Metasurface Antenna Based on Characteristic Mode Analysis

A broadband circularly polarized metasurface antenna is proposed. The initial metasurface structure is first diagonally chamfered and a rectangular slot is etched at the chamfer. The chamfering operation can cause an imbalance in the surface impedance of the hypersurface patch, and this imbalance creates a phase difference between the incident wave and the reflected wave, which is considered to be circularly polarized when the phase difference is close to 90° and the amplitudes of the two are equal. Analyze the metasurface structure after chamfering using the characteristic mode theory (CMT), further optimize it based on the obtained characteristic mode analysis results, and analyze it again using the characteristic mode. Finally, two target modes with a phase difference close to 90° were formed. The two characteristic modes are successfully excited by microstrip slot-coupled feeding structure to achieve circularly polarized radiation of the antenna. Finally, the antenna is fabricated and measured. Based on the measured results, it can be observed that the antenna has 35.4% −10 dB impedance bandwidth, and 17% 3 dB axial ratio bandwidth, and the antenna simulated and measured results match.