Investigation and Comparison Between Radiation Center and Phase Center for Canoncial Antennas

The phase center is defined as the point on an antenna from which the far field radiation seems to originate. Phase center calculations are often uncertain and vague, and very little concrete information is available on the subject. Recently, a replacement parameter called the radiation center was introduced in [5]. The radiation center is more rigorously defined than the phase center and possesses additional qualities, such as uniqueness, no need for user input, etc. This thesis evaluates the validity of the radiation center as a replacement for the phase center and also compares it with Muehldorf’s analytically calculated phase center [17]. The far-field is simulated in CST and evaluated in Matlab, using Ericsson Antenna ModelLibrary(eamlib)tocalculatetheradiationcenter. Phasecentercalculations are carried out in CST and the Muehldorf phase center is evaluated numerically in Matlab. The radiation center minimizes the phase well, achieving the same smoothness as the phase center. The radiation center varies according to the predicted behaviour of the phase center for most antennas. For the spiral antenna the radiation center does not adhere to the predicted behaviour of the phase center. For some antennas, specifically those that have wide or narrow beam widths in a certain direction, the radiation center seems to mainly be influenced by the phase function in the plane with wider radiation pattern. This strengthens the theoretical argument in [5] that the radiation center minimizes the phase according to far-field amplitude. Theradiationcenterproducesresultswithintheboundsoftheantenna structure for all antennas presented in this thesis. In contrast the phase center does not, specifically for the Yagi-Uda antenna and the Leaky Lens antenna [18]. The phase function in the main radiation lobe is regarded explicitly for some of the simulated antennas. The radiation center does not seem to minimize the phase for these antennas any better or worse than the phase center. These results suggest that the radiation center is a good candidate for origin of radiation for antennas. (Less)