The time domain modeling of a coplanar wave guide (CPW) fed band-notched antenna for Ultra Wide band (UWB) applications is presented. The annular ring antenna has a dimension of 36x36 mm2 when printed on a substrate of dielectric constant 4.4 and thickness 1.6 mm. The uniplanar nature and compact structure of the antenna make it apt for modular design. The crescent shaped slot provides a notch in the 5.2-5.8 GHz frequency band to avoid interference with Wireless Local Area Network (WLAN). The pulse distortion is insignificant in the operating band and is verified by the measured antenna performance with high signal fidelity and virtually steady group delay.