Nonredundant Spiral NFTFF Transformation for a Long Antenna Mounted with an Offset with respect to the Scan Sphere

A fast and accurate near-field to far-field (NFTFF) transformation technique with spherical spiral scanning for an offset mounted long antenna, which requires practically the same number of NF data both in its onset and offset mounting, is proposed in this work. It relies on the nonredundant sampling representations of electromagnetic fields and is developed by properly applying the unified theory of spiral scans for nonvolumetric antennas, when the antenna under test is modelled by a prolate ellipsoid. Some numerical results assessing the accuracy of the proposed technique and its robustness with respect to random errors affecting the NF data are shown.