A Broadband Circularly Polarized Patch Antenna Using Characteristic Mode Analysis

A broadband circularly polarized (CP) patch antenna is proposed based on characteristic mode analysis (CMA). It's known that the bandwidth of a CP patch antenna can be enhanced by adding two or four parasitic elements. However, it's found that only one of the two characteristic modes (CM) newly introduced by parasitic patches is excited. According to the idea of “degenerate mode separation”, these same parasitic patches are adjusted as unequal length. Then both parasitic CMs can be excited well, which resulted in wider bandwidth of axial-ratio (AR) and impedance. The CMA is used for analysis and optimization of the proposed antenna. A classical prototype at 10GHz is designed to verify this concept, and its 3dB AR bandwidth can be increased from 2.8% to 6.3%, while its −10dB impedance bandwidth is improved from 10.2% to 13.4%.