Evaluation of the Far Field Radiated by a Flat AUT from Non-Redundant Near-Field Bi-Polar Samples

A probe-compensated near-field to far-field (NF/FF) transformation with bi-polar scanning particularly suitable for dealing with a flat antenna under test (AUT) is proposed in this work. It properly exploits the non-redundant sampling representations of the electromagnetic fields to develop an efficient sampling representation of the voltage acquired by the measuring probe over the scanning plane, which uses a minimum number of NF bi-polar samples. A two-dimensional optimal sampling interpolation formula is then applied to precisely reconstruct the NF data needed by the classical NF/FF transformation with plane-rectangular scan from the knowledge of these samples. To properly account for the flatness of the AUT, a disk with diameter equal to the AUT maximum dimension is assumed as modeling surface. Such a modeling is much more effective from the NF data reduction viewpoint than the other modelings for quasi-planar AUTs (an oblate spheroid or a double bowl), since, shaping very well the AUT geometry, it allows one to reduce as much as possible the related volumetric redundancy. Numerical results are shown to assess the accuracy of the proposed NF/FF transformation.