A compact circularly polarized antenna with wide axial ratio bandwidth (ARBW) using quasi-self-complementary (QSC) structure is presented. A 3-dB ARBW is achieved by shortening the ground plane of the QSC structure. Furthermore, the wide ARBW is obtained by the introduction of a stepped stub in the extended ground plane of the QSC structure. The antenna is fabricated on a FR4 substrate with the overall dimensions of 25 mm × 22 mm × 0.8 mm. The proposed antenna has an impedance bandwidth of 5.9 GHz (2.4–8.3 GHz, 110%) and 3 dB ARBW of 1.6 GHz (2.4–4 GHz, 50%). A peak gain of 1–3 dBi is observed within the 3 dB ARBW.
