Near-field - far-field transformation from helicoidal near-field data affected by probe positioning errors

An effective algorithm for compensating the probe positioning errors when using a near-field to far-field transformation technique with helicoidal scanning for long antennas is here proposed. It is based on a prolate ellipsoidal modelling of the antenna under test and makes use of an iterative scheme to reconstruct the uniformly distributed helicoidal near-field data from the irregularly spaced ones. Once these data have been recovered, those needed by a standard near-field - far-field transformation technique with cylindrical scanning are efficiently evaluated via an optimal sampling interpolation algorithm. Some numerical tests, assessing the accuracy of the approach and its robustness with respect to random errors affecting the data, are reported.