UWB antenna transfer functions using minimum phase functions

When computing the antenna transfer function for an ultra-wideband (UWB) antenna from a series of port-to-port S₂₁ measurements between identical antennas, it is necessary to know the distance R between the antennas. UWB antennas often do not have a well- defined phase center; therefore, some other defined reference point on the antenna structure is needed. We propose using the minimum phase function, computed via a Hilbert transform, to define the transfer function phase. The remaining phase from the S₂₁ measurements is in principle linear, and can be used to define the distance R and a unique reference point for the antenna. Experimental results show a high degree of linearity for the remaining phase and consistency in the resulting extracted distance.