Near-Field Antenna Measurement Techniques

Abstract

A complete description of the near-field antenna measurement techniques is provided in this chapter. After a discussion of the state of the art, the key steps of the classical near-field–far-field (NF-FF) transformations with plane-rectangular, cylindrical, and spherical scannings, in their probe-uncompensated and probe-compensated versions, are summarized, by also providing some analytical details on the wave expansions commonly adopted to represent the antenna radiated field. The nonredundant sampling representations of electromagnetic field are then introduced and applied to drastically reduce the number of required NF data and related measurement time with respect to the classical NF-FF transformations. At last, the NF-FF transformations with innovative spiral scannings, allowing a further measurement time saving, are described. © Springer Science+Business Media Singapore 2016. All rights reserved

Pattern Reconstruction of 3-D Modular Antennas by Means of a Non-Redundant Near-Field Spherical Scan

“…Peculiarities, advantages, and disadvantages of NF versus FF measurements are wellknown to engineers and researchers working on this topic. Obviously, a proper NF-FF transformation technique is needed if NF data are used for FF pattern reconstruction [1][2][3][4][5][6][7]. Planar, cylindrical, and spherical NF-FF transformation techniques are associated to planar, cylindrical, and spherical NF scanning surfaces, respectively, and utilize the corresponding modal expansion of the AUT near field to achieve the FF pattern.…”

Reconstruction of the Far-Field Pattern of Volumetric AUTs from a Reduced Set of Near-Field Samples Collected along a Planar Spiral with a Uniform Step

“…This suggests that one should perform the characterization through an indoor test range, which benefits from the fact that measurements are performed in a controlled shielded environment, i.e., the anechoic chamber. However, only NF measurements are usually allowed there, and the required FF pattern has to be properly determined by means of a near-to-FF transformation (NTFFT) technique [1][2][3][4][5][6][7]. Although the complexity grows in such a case, the NF measurements allow us to not only obtain the complete FF pattern of the AUT, but also to exploit the available information for diagnostic purposes (microwave holography).…”

Laboratory testing of an SVD‐based approach to recover the non‐redundant bi‐polar NF data from the positioning error affected ones

“…Obviously, when the dimensions of the antenna under test (AUT) grow in terms of wavelength, only near-field (NF) measurements are allowed, since, due to the limited chamber sizes, it is not possible to perform the measurements at a distance greater or equal than that required to measure the EM field radiated by the AUT directly in the Fraunhofer region. In such a case, the desired farfield radiation pattern can be reconstructed by resorting to NF to far-field (NFTFF) transformations [1][2][3][4]. These techniques make usually use of a modal expansion of the AUT near field in terms of plane, cylindrical, or spherical waves, whose modal expansion coefficients can be evaluated from the complex voltages acquired by the measurement probe in two its orientations on a proper grid of the considered scanning surface (a plane, a cylinder, or a sphere), by exploiting the orthogonality properties of the modes on it.…”