The paper presents the design and performance measures of a printed stepped patch monopole antenna with semi-elliptical ground plane and band notch for ultra wideband applications. The proposed antenna operates in the frequency range 3.15 ~ 12.2 GHz with average gain of 4.27 dBi. Inverted U - shaped slot is introduced in the feed line for WLAN band rejection and the rejection band ranges from 5.08 GHz to 5.93 GHz. The radiation pattern is directional in the elevation plane and omnidirectional in the azimuth plane. The consistency of the radiation pattern exists within the operating band. The performance of the proposed antenna is confirmed by simulation and experiment results.