On the Practical Effectiveness of the Nonredundant Spherical NF-FF Transformation for Offset Mounted Long AUTs

A laboratory assessment of a recently proposed spherical near-field to far-field (NF-FF) transformation technique for a long antenna under test (AUT) mounted in offset configuration, which requires an amount of NF measurements minimum and equal to that needed for the onset mounting, is provided in this work. The interest for this technique is due to the fact that sometimes, for practical limitations, it can be impossible an onset mounting, where the AUT center and the scanning sphere one coincide. In this case, the amount of NF measurements and the corresponding acquisition time required by the traditional spherical NF-FF transformation can remarkably raise, owing to the minimum sphere rule. Instead, in the proposed NF-FF transformation, the massive data necessary for the traditional one are efficiently recovered from the measured nonredundant samples using an optimal sampling interpolation formula, got by suitably exploiting the nonredundant sampling representations and modeling the AUT by a prolate spheroid. Some laboratory results, fully confirming the efficacy of such a nonredundant NF-FF transformation from the practical viewpoint, are reported.