Design and bandwidth enhancement of circularly polarized aperture antennas using L-shaped probe

An L-shaped monopole antenna on a ground plane is unable to generate circular polarization, however, combining with surrounding aperture, such as waveguides, the L-shaped probe can generate circular polarization. In addition to that, such structures has broadband characteristics in both axial ratio and input impedance. This paper reviews a present study of authors' group on a circularly polarized broadband antennas consisting of aperture structure and L-shaped probe (L-probe). Though the discussion, reducing technique for higher-order modes (HOM) is also discussed to expand the -10-dB S11 and the 3-dB axial ratio(AR) characteristics.