A novel compact ultra wideband(UWB) antenna for UWB application is proposed in this paper. The proposed antenna with $22mm{ imes}26mm{ imes}1.6mm$ covers the entire UWB bandwidth and has band notch characteristic for the frequency band of $5.15{sim}5.825GHz$ limited by WLAN. The antenna has a concaved ground plane and staircase shape patch to achieve the wide bandwidth, and has an U shape slot with $lambda/4$ length to notch the band. The return loss and group delay of the proposed antenna are measured.