Phaseless Probe-Corrected Spherical Near-Field Antenna Measurements Using Two Scan Spheres

For near-field (NF) antenna measurements where the phase cannot be measured at all or with sufficient accuracy, it is necessary or it may be preferable to use phaseless measurements. Of the four main categories of phaseless measurement techniques, the well-known two-scan technique with two concentric measurement spheres is investigated systematically. Probe correction is included as an integral step of the phase retrieval. The method is validated numerically and experimentally using measured data of a large 12-GHz reflector antenna. Performance is examined with respect to the separation between measurement spheres, radius of the measurement sphere, and initial guess. It is demonstrated that the two-scan technique can perform very well for both co-and cross-polar radiation patterns of very high complexity using probe-corrected spherical NF antenna measurements with a dual-ported probe and on-the-fly sampling.