Experimental Testing of an Effective Near to Far-Field Transformation for Flat Antennas using Non-redundant Spiral Data

The experimental validation of a near to far-field transformation (NTFFT) with planar spiral scan for flat antennas under test (AUTs) is provided in this work. Such a technique is based on the non-redundant sampling representations of electro-magnetic fields and has been developed by properly exploiting the unified theory of spiral scans for non-volumetric antennas when these AUTs are assumed as enclosed in a disk with diameter equal to their maximum dimension, thus allowing to better shape their actual geometry. Moreover, it uses an efficient two-dimensional optimal sampling interpolation algorithm to reconstruct the near-field data needed by the classical plane-rectangular NTFFT from those gathered along the spiral. Since the smaller the area of the modeling surface, the lower the number of near-field data and spiral turns, a further time saving is accomplished as compared to the non-redundant planar spiral NTFFTs using the modelings for quasi-planar AUTs, which instead involve a residual volumetric redundancy in such a case. The reported experimental results as-sess the practical feasibility of the developed technique.