Antenna Characterization from Spherical Spiral Near-Field Measurements Acquired over an Infinite Perfectly Conducting Ground Plane

This communication proposes an efficient NF-FF transformation with spherical spiral scan for volumetric antennas under test (AUTs), using a minimum number of spiral data, which, due to the presence of an infinite perfectly conducting ground plane, are collected over a proper spiral wrapping the upper hemisphere. Such a technique relies on the non-redundant sampling representation of electromagnetic fields and properly exploits the theoretical foundations of spiral scan for volumetric AUTs. Moreover, the principle of image is exploited to synthetize the voltage NF data which would be acquired over the spiral wrapping the lower hemisphere. Then, an efficient two-dimensional optimal sampling interpolation scheme is utilized to recover the NF data required by the classical NF-FF transformation with spherical scan. The reported numerical results prove the accuracy of the developed non-redundant NF-FF transformation with spherical spiral scan.