A CPW feed guitar shaped ultra wide band antenna is designed on FR4 ((ε r=4.3) substrate of thickness 1.53 mm. This antenna exhibits the excellent measured impedeance matching over the frequency range of 2.99GHz to 18.0GHz and beyond. Critical design parameters have been optimized to achieve the UWB bandwidth as well as to observe the effect of design parameters on impedance bandwidth. The measured radiation patterns of this antenna are omnidirectional in H-plane and bidirectional in E-plane. The bandwidth and peak gain satisfy the FCC standard requirement. An extended impedance bandwidth is achieved by having the antenna of guitar shape. The proposed antenna can be used for medical imaging, vehicular radar and modern Ultra wideband systems, etc. © 2012 ISRAMT.