Two Effective Approaches to Correct the Positioning Errors in a Spherical Near-Field-Far-Field Transformation

Two techniques are developed to efficiently compensate known positioning errors affecting the near-field measurements in a non-redundant spherical near-field-far-field transformation for quasi-planar antennas, and they are fully assessed through numerical and experimental tests. They rely on a non-redundant sampling representation of the voltage measured by the probe, obtained by assuming that the antenna is enclosed in a surface formed by two circular bowls with the same aperture diameter. Both techniques use a two-step procedure. In the first step, the near-field data at the points fixed by the sampling representation are recovered from the irregularly spaced measured ones by properly applying an iterative technique or the singular value decomposition method. Then the near-field data needed by the standard spherical near-field-far-field transformation are effectively reconstructed by means of an optimal sampling interpolation algorithm.