Experimental proofs on an effective near-field to far-field transformation technique with spherical spiral scan suitable for long antennas

This communication provides the experimental assessment of an efficient near-field - far-field (NF-FF) transformation with spherical spiral scanning for elongated antennas, which allows a remarkable measurement time saving with respect to the classical spherical NF-FF transformation. Such a saving is due both to the use of continuous and synchronized movements of the positioning systems and to the reduced number of NF data to be acquired. This technique relies on a nonredundant sampling representation of the probe output voltage, obtained by using the unified theory of spiral scans for nonspherical antennas and adopting a prolate ellipsoidal modelling of the radiating source. An optimal sampling interpolation scheme is then used to efficiently recover the NF data needed by a probe compensated NF-FF transformation with spherical scanning. The experimental tests have been carried out at the UNISA Antenna Characterization Lab and both the reported NF and FF reconstructions assess the effectiveness and reliability of the technique.