Investigation on the phase centre of ultra wideband circular monopole antennas

The phase centre of an UWB circular monopole antennas working over the frequency band from 3.1 to 13.5 GHz was determined. The displacement of the coordinate origin on the Z-axis that leads to a minimum change in the phase of the far field was calculated for different thetas ranges at phi =0, 45 and 90 degrees. It was found that although the antenna has a good impedance and radiation pattern bandwidths, its phase centre is moving on the Z-axis with changing the frequency. This movement is within different lambda ranges over the frequency band for different thetas ranges. This information is useful to better understand how well this antenna ill act and where the radiation will be coming from for different angles at different frequencies. More results for other UWB monopole antennas will be shown and discussed during the presentation of this paper in the conference.