This paper presents the design of a Small Size ultra-wideband microstrip patch antenna. The antenna, which is microstrip-line fed, has a partial ground plane flushed with the feed line. The substrate is based on the inexpensive FR4 material, and the patch is circular in shape with a rectangular slot incorporated. The antenna was designed, simulated and optimized over HFSS (high frequency structures simulator) and the computer simulation technology (CST) Microwave Studio (MWS). The antenna's resulting return loss, input impedance, radiation patterns, gain and VSWR figures are presented. The proposed UWB antenna meets the FCC bandwidth authorization.