Abstract: A compact ultra wideband antenna with the size of 10mm-17mm is designed by half cutting and trimming the planar elliptical monopole ultra wideband antenna. A notch structure is placed in the radiator, to improve the omni-directional radiation pattern of the proposed antenna. The simulated results show that the improved antenna has good impedance match and omni-directional radiation pattern, over the whole ultra wideband frequency band. The measured results are closed with the simulated results very well.