Analytical cross-polarization nulling technique

Abstract

Previously, boresite cross-polarization nulling was achieved by using hardware techniques. In this method, a nulling network was constructed to transmit or receive a degree of elliptical polarization to perfectly offset the AUT radiation co-polarization on boresite. This was achieved by manual adjustment of variable attenuators and phase shifters in a hardware network. The principle drawback to this method is that it is restricted to single frequency measurements and the stability of the hardware. Modern far-field ranges are capable of collecting large amounts of amplitude and phase data over broad frequency sweeps. It is convenient in post-processing to perform the task of the nulling network by synthesizing an elliptical polarization to achieve true co- and cross-polarization at boresite. Two orthogonal linear orientations for a probe antenna provide the required components to synthesize an ideally nulled boresite cross-polarization. This definition is then applied to the rest of the scan.