In this paper, a novel UWB (Ultra-wide Band) antenna is proposed. This design mainly consists of a wide slot square ground plane and a frequency independent feed line-a 0.5 turn equiangular spiral, which are etched on each side of a substrate separately. Additionally, a circular patch connected with the slotted ground is introduced to tune the working bandwidth of this antenna. Prototypes are instructed and tested to know the performance of the proposal. From the results, it can be seen that the proposed antenna has enough impedance bandwidth for UWB applications with VSWR (Voltage Standing Wave Ratio) less than 2, acceptable radiation patterns, as well as relatively high gains.