Fast and Accurate Antenna Pattern Evaluation from Near-Field Data Acquired via Planar Spiral Scanning

Two fast and accurate probe compensated planar spiral near-field-far-field (NF-FF) transformation techniques, using nonredundant NF data, are experimentally assessed. These techniques allow a remarkable measurement time saving since they require a reduced number of NF data, which are collected on fly by properly and continuously moving the positioners. They have been achieved by applying the unified theory of spiral scannings for nonvolumetric antennas and adopting either an oblate ellipsoid or a double bowl to shape an antenna with a quasi-planar geometry. By using these modelings, instead of the spherical one, it is possible to significantly reduce the error due to the truncation of the scanning zone, since the NF data can be acquired on a spiral lying on a plane located at a distance smaller than one half of the antenna maximum size. The NF data required by the standard plane-rectangular NF-FF transformation are then accurately recovered from those collected along the spiral. Some experimental results, obtained at the Antenna Characterization Lab of the University of Salerno and assessing the effectiveness of the techniques, are shown.