Laboratory Proofs on the NF-FF Transformation with Spherical Spiral Scanning Optimized for Quasi-planar Antennas

The experimental validation of a probe compensated near-field - far-field (NF-FF) transformation with spherical spiral scanning for quasi-planar antennas is provided in this work. It is based on a nonredundant sampling representation of the probe output voltage, obtained by using the unified theory of spiral scans for nonspherical antennas and adopting an oblate ellipsoid to model a quasi-planar antenna. Its main feature is to reduce the measurement time due to the employment of continuous and synchronized movements of the positioning systems and antenna, and to the reduced number of needed NF measurements. An optimal sampling interpolation algorithm is employed to efficiently reconstruct the NF data required by the NF-FF transformation with spherical scanning. Some experimental results, carried out at the UNISA Antenna Characterization Lab and assessing the effectiveness of such a NF-FF transformation technique, are shown.