In this paper, we present a new planar waveguide-fed ultra wideband (UWB) antenna. This antenna is designed for 50 Ω feed on a loss less glass as a substrate. The impedance bandwidth with VSWR < 2 is from about 4.4 GHz to more than 12 GHz in simulation results but from 3.8 GHz to about 11.5 GHz in measurement. This Antenna also has a directional gain pattern. Other important features of this antenna are its high gain and directivity as well as its easy shape to design. The reliable full wave simulation analysis by HFSS and CST Microwave Studio show that this novel structure can easily realize a good linear variation for the sweep gain as well as high directivity within a controllable bandwidth.