Practical feasibility of a NF-FF transformation with uniform planar spiral scan for quasi-spherical AUTs

This communication deals with the experimental validation of an effective near-field-far-field (NF-FF) transformation with planar spiral scanning. Such a technique, suitable for volumetric antennas, uses a reduced number of NF samples, which are collected along a planar spiral whose step is uniform to make easier the control of the velocity of the involved linear positioner. The NF data needed by the standard plane-rectangular NF-FF transformation are accurately reconstructed from the acquired spiral samples by employing an efficient two-dimensional optimal sampling interpolation (OSI) algorithm, which has been developed, by choosing the spiral step coincident with the sampling spacing needed to interpolate along a radial line, according to the spatial band-limitation properties of electromagnetic fields, and by arranging a proper non-redundant representation along such a spiral. Some experimental tests results are reported to assess the effectiveness of the FF reconstruction process.