Broadband wide beam-width circularly polarized microstrip Yagi antenna

A dual-fed circularly polarized (CP) microstrip Yagi antenna with two-stage double-patch directors is proposed. By removing part of the ground plane, the gain and beamwidth at the end-fire direction is enhanced effectively. Due to the use of the dual-feed with equal amplitude but different phase, broadband CP radiation is realized as well. Numerical and measured results show that the overlapped bandwidth of voltage standing wave ratio less than 1.5 and axial ratio lower than 3 dB at the end-fire direction is about 11%. The proposed antenna has CP radiation from elevation angle 0° to 80° at the elevation plane, while at the azimuthal plane the half power beamwidth is 88° with large front-to-back ratio, which indicates that the proposed antenna is a good candidate for aircraft-or missile-borne communications.