In this paper, the authors propose a novel printed monopole antenna for Ultra Wide Band (UWB) applications with notch band characteristics. UWB system requires band notch filters in order to prevent sensitive components. Recently these filters can be integrated into the UWB antenna. This paper presents a new method to generate a band notched characteristics, they use an open loop resonator which is located on the back side of the substrate. A simulation was done and good results have been obtained with notched band at 5.1 GHz WLAN.