AbstractIn the letter, a circularly polarized (CP) patch antenna is proposed, which consists of a slotted radiation patch, a slotted parasitic loop with a short pin, and a ground plane. The slot with one open and one circular end is etched in the radiation patch, and the current distribution of the radiation patch is disturbed to excite the first CP mode. The currents distributed on the slotted radiation patch and parasitic loop can superimpose or cancel each other to produce the second CP mode. Impedance matching and the performance of the first CP can be improved by the two slots and short pin introduced into the parasitic loop, but without effect on the second CP mode. A prototype is designed, and a −10 dB impedance bandwidth of 21.3% (3.10–3.84 GHz), a 3‐dB axial‐ratio bandwidth of 10.1% (3.29–3.64 GHz), an in‐band radiation efficiency of 75%, and unidirectional left‐hand circular‐polarized radiation pattern with in‐band gain of 8.0 dBi are realized.