This paper presents a procedure to model an ultra wide-bandwidth (UWB) microstrip monopole antenna. The proposed antenna is composed of three different lengths of semi-circular shapes connected with circular disk and half circular modified ground plane. The proposed antenna has a size of 50 × 50 mm2 on a low-cost FR4 substrate. The antenna demonstrates impedance bandwidth of −10 dB extended from 1.5 to 11 GHz with discontinuous bandwidth at different interior operating bands. Two pairs of split ring resonator as metamaterial structure cells are inserted closely located from feeding transmission line of the antenna to achieve good impedance matching over the entire band of operation and improve the antenna performance. The fundamental parameters of the antenna including reflection coefficient, gain, radiation pattern and group delay are obtained and they meet the acceptable UWB antenna standard. High-frequency structure simulator ver. 14 is used as full-wave electromagnetic solver then the prototypes are fabricated and measured. Results show that the antenna is very suitable for the applications in UWB as well as wireless communication systems.