In this paper, a wideband loop antenna for UWB applications is studied. The structure of the proposed wideband loop antenna is a circular loop antenna with appended circular sectors to obtain an ultra-wideband characteristic. The circular sectors are used instead of conventional triangular sectors to match with the 50 ohm feed line. Optimal design parameters are obtained by analyzing the effects of the gap between the circular sectors and the radius of the circular loop on the input reflection coefficient and gain characteristics. The optimized wideband loop antenna is fabricated on an FR4 substrate with a dimension of 41 mm by 41 mm. Experiment results show that the proposed antenna has a frequency band of 3.1-11.0 GHz for a VSWR < 2.25, which assures the operation in the UWB band. Measured gain ranges 1.3-5.3 dBi in the UWB band.