A simple and compact coplanar waveguide (CPW)-fed ultra wide band antenna is presented. The UWB antenna consists of a rectangular patch, which is etched onto an FR4 printed circuit board(PCB) with an overall size of 30mmX35mmX0.76mm. The simulation show that the UWB antenna achieves good impedance matching, consistent gain, and consistent group delay over an operating bandwidth. The correlation between the mode-based field distribution is discussed. Extended from the UWB antenna, four notch (5-6GHz) designs are also presented as a desirable feature for UWB application.