In this paper, we present a detailed study of a printed square monopole antenna for Ultra Wide Band (UWB) communication applications. The 2:1 VSWR bandwidth of the proposed antenna is from 2.87–14 GHz. The antenna can be made to reject particular frequency bands by introducing narrow slits on the patch. In addition, the rejection band can be easily tuned for centre frequency, VSWR and rejection bandwidth by adjusting the slit parameters. In the proposed antenna, slits are introduced to reject the IEEE802.11a and HIPERLAN/2 bands used for WLAN applications. The antenna is analyzed in both frequency and time domains. Radiation patterns of the antenna are omnidirectional with appreciable gain throughout the band. Transient analysis indicates linear phase response and minimum pulse distortion.