A Study on the 3-D Probe Position Errors Correction in a Non-Redundant Spherical NF/FF Transformation for Quasi-Planar Antennas

In this work, a novel two-steps technique to correct 3D probe positioning errors affecting the non-redundant (NR) spherical near-field/far-field transformation (NF/FFT) technique for quasiplanar antennas, modeled with a double bowl, is presented. The developed approach benefits from the synergy of two complementary correction steps. In the first one, the so-called NR correction compensates for the phase errors due to the deviations of the sampling points from the nominal scanning sphere. This is achieved through an adhoc phase correction scheme, whereby an optimal phase factor is extracted from the acquired samples, accounting for their actual (i.e., erroneous) position. In the second step, an iterative approach is exploited to manage the residual 2-D errors affecting the data attained at the end of the previous step, allowing for an accurate and efficient restoration of the correctly located samples. Ultimately, the large number of input data for the classical spherical NF/FFT, uniformly spaced on the scanning spherical grid, are obtained via an optimal sampling interpolation formula. Numerical results showing the effectiveness of the proposed method in compensating even severe 3-D positioning errors are reported.