Compensation of the probe positioning errors in the spherical NF - FF transformation for elongated antennas

An effective approach to compensate the positioning errors in a spherical near field - far field transformation for long antennas is proposed in this work. It relies on a nonredundant sampling representation of the electromagnetic fields assuming the antenna under test as enclosed in a cylinder ended in two half spheres and employs the singular value decomposition method to evaluate the near-field data at the points fixed by the nonredundant representation from the irregularly spaced ones. Once these data have been recovered, those needed by a near field - far field transformation with spherical scanning are efficiently evaluated by using an optimal sampling interpolation algorithm. Numerical tests assessing the effectiveness of the proposed approach are shown.