This paper proposes a differentially fed antenna of circular polarization. The antenna is composed of a circular slot and two oppositely deployed semi-circular feeding metal strips. The circularly polarized (CP) antenna is designed in a rotationally symmetric fashion to give good differential-mode (DM) performance and high common-mode (CM) suppression. The circular slot antenna is loaded with stubs for tuning impedance matching and CP characteristic. A fabricated prototype circuit of the proposed differentially fed CP antenna was measured, and results show that the CP antenna has a 10-dB DM passband of 2.33-2.72 GHz and a 3-dB DM axial-ratio band of 2.38-2.51 GHz. In addition, within the passband, the CM signals can be effectively rejected since the CM return loss is less than 0.77 dB; the DM-to-CM conversion is negligible because it is smaller than-43.25 dB.