An Effective Near-Field-Far-Field Transformation Technique for Elongated Antennas Using a Fast Helicoidal Scan

An experimental validation of a new near-field-far-field transformation technique with helicoidal scanning, tailored for elongated antennas, is provided in this paper. Such a transformation is based on non-redundant sampling representations of the electromagnetic fields. It makes use of a flexible source modeling, which allows one to very well fit many of these kinds of antennas by properly setting the geometric parameters. By employing such modeling instead of spherical modeling, it is possible to remarkably reduce the error related to the truncation of the scanning zone, since measurement cylinders with a diameter smaller than the antenna's height can be used. A comparison of the reconstructions recovered from the non-redundant measurements on the helix with those obtained from data directly measured on the classical cylindrical grid assesses the validity of this innovative scanning technique.