Cross-Polarization Uncertainty in Near-Field Probe Correction [AMTA Corner]

The probe correction of near-field measured data can be considered to be composed of two parts. The first part is a pattern correction that corrects for the effects of the aperture size and shape of the probe, and can be analyzed in terms of the far-field main component pattern of the probe. The second part is due to the non-ideal polarization properties of the probe. If the probe responded to only one vector component of the incident field in all directions, this correction would be unnecessary. However, since all probes have some response to each of two orthogonal components, the polarization correction must be included. The polarization correction will be the focus of the following discussion. Previous studies have derived and tested general equations to analyze polarization uncertainty. This paper simplifies these equations for easier application. The results of analysis and measurements for planar, cylindrical, and spherical near-field measurements will be summarized in a form that is general, easily applied, and useful. Equations and graphs will be presented that can be used to estimate the uncertainty in the polarization correction for different AUT/probe polarization combinations and measurement geometries. The planar case will be considered first, where the concepts are derived from the probe-correction theory and computer simulation, and are then extended to the other measurement geometries.