Abstract
In this paper, an effective technique to compensate the positioning errors in a near-field—far-field (NF-FF) transformation with helicoidal scanning for elongated antennas is presented and validated both numerically and experimentally. It relies on a nonredundant sampling representation of the voltage measured by the probe, obtained by considering the antenna as enclosed in a cylinder ended in two half-spheres. An iterative scheme is used to reconstruct the helicoidal NF data at the points fixed by the representation from the acquired irregularly spaced ones. Once the helicoidal data have been retrieved, those needed by a classical NF-FF transformation with cylindrical scanning are efficiently evaluated by using an optimal sampling interpolation algorithm. Some numerical tests, assessing the accuracy of the approach and its stability with respect to random errors affecting the data, are reported. Experimental tests performed at the Antenna Characterization Lab of the University of Salerno further confirm the validity of the proposed technique.
Highlights
Nowadays, the reduction of the time required to acquire the near-field data is assuming an ever growing relevance for the antenna measurement community
As suggested in [1], an effective way for reducing the measurement time is the use of innovative spiral scanning techniques [2,3,4,5,6,7,8,9,10,11], which can be implemented by means of continuous and synchronized movements of the positioning systems of the probe and antenna under test (AUT)
These scans rely on the nonredundant sampling representations of electromagnetic (EM) fields [12] and use optimal sampling interpolation (OSI) formulas [13] to retrieve the NF data required by the near-field - far-field (NF-FF) transformation with the corresponding classical scanning from the acquired nonredundant ones
Summary
The reduction of the time required to acquire the near-field data is assuming an ever growing relevance for the antenna measurement community. As suggested in [1], an effective way for reducing the measurement time is the use of innovative spiral scanning techniques [2,3,4,5,6,7,8,9,10,11], which can be implemented by means of continuous and synchronized movements of the positioning systems of the probe and antenna under test (AUT) These scans rely on the nonredundant sampling representations of electromagnetic (EM) fields [12] and use optimal sampling interpolation (OSI) formulas [13] to retrieve the NF data required by the NF-FF transformation with the corresponding classical scanning from the acquired nonredundant ones. This last transformation assumes the AUT as enclosed in a cylinder ended in two half-spheres and, due to the flexibility of such a modelling, results to be more effective from the data reduction viewpoint than the one [6,8] employing the prolate ellipsoid
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