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International Journal of Antennas and Propagation
Volume 2014 (2014), Article ID 143084, 13 pages
http://dx.doi.org/10.1155/2014/143084
Review Article

Near-Field to Far-Field Transformation Techniques with Spiral Scannings: A Comprehensive Review

1Dipartimento di Ingegneria dell’Informazione, Elettronica e Telecomunicazioni, Università di Roma “La Sapienza”, Via Eudossiana 18, 00184 Roma, Italy
2Dipartimento di Ingegneria Industriale, Università di Salerno, Via Giovanni Paolo II, 132-84084 Fisciano, Italy

Received 12 June 2014; Accepted 16 July 2014; Published 10 August 2014

Academic Editor: Diego Caratelli

Copyright © 2014 Renato Cicchetti et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

An overview of the near-field-far-field (NF-FF) transformation techniques with innovative spiral scannings, useful to derive the radiation patterns of the antennas commonly employed in the modern wireless communication systems, is provided in this paper. The theoretical background and the development of a unified theory of the spiral scannings for quasi-spherical and nonspherical antennas are described, and an optimal sampling interpolation expansion to evaluate the probe response on a quite arbitrary rotational surface from a nonredundant number of its samples, collected along a proper spiral wrapping it, is presented. This unified theory can be applied to spirals wrapping the conventional scanning surfaces and makes it possible to accurately reconstruct the NF data required by the NF-FF transformation employing the corresponding classical scanning. A remarkable reduction of the measurement time is so achieved, due to the use of continuous and synchronized movements of the positioning systems and to the reduced number of needed NF measurements. Some numerical and experimental results relevant to the spherical spiral scanning case when dealing with quasi-planar and electrically long antennas are shown.