scholarly journals Near-Field/Far-Field Transformation with Helicoidal Scanning from Irregularly Spaced Data

2010 ◽  
Vol 2010 ◽  
pp. 1-8 ◽  
Author(s):  
Francesco D'Agostino ◽  
Flaminio Ferrara ◽  
Claudio Gennarelli ◽  
Rocco Guerriero ◽  
Massimo Migliozzi
Keyword(s):  
Field Data ◽  
Iterative Scheme ◽  
Near Field ◽  
Optimal Sampling ◽  
Far Field ◽  
Interpolation Algorithm ◽  
Random Errors ◽  
Numerical Tests ◽  
Positioning Errors ◽  
Field Transformation

A fast and accurate technique for the compensation of the probe positioning errors in the near-field/far-field transformation with helicoidal scanning is proposed in this paper. It relies on a nonredundant sampling representation using a spherical modelling of the antenna under test and employs an iterative scheme to evaluate the near-field data at the points fixed by the helicoidal nonredundant representation from the acquired irregularly distributed ones. Once these helicoidal data have been recovered, those required by a classical cylindrical near-field/far-field transformation are efficiently determined by using an optimal sampling interpolation algorithm. Some numerical tests assessing the effectiveness of the proposed approach and its stability with respect to random errors affecting the near-field data are shown.

scholarly journals An Innovative Direct NF-FF Transformation Technique with Helicoidal Scanning

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Francesco D’Agostino ◽  
Flaminio Ferrara ◽  
Claudio Gennarelli ◽  
Rocco Guerriero ◽  
Massimo Migliozzi
Keyword(s):  
Electromagnetic Fields ◽  
Field Data ◽  
Near Field ◽  
Transverse Dimension ◽  
Computational Effort ◽  
Far Field ◽  
Transformation Technique ◽  
Spherical Antenna ◽  
Field Transformation ◽  
Mechanical Scanning

A direct near-field-far-field transformation with helicoidal scanning is developed. It is based on the nonredundant sampling representation of electromagnetic fields and uses a spherical antenna modelling to determine the number of helix turns. Moreover, the number of voltage samples on each of them is fixed by the maximum transverse dimension of the antenna, both to simplify the mechanical scanning and to reduce the computational effort. This technique allows the evaluation of the antenna far field directly from a minimum set of near-field data without interpolating them. Although the number of near-field data employed by the developed technique is slightly increased with respect to that required by rigorously applying the nonredundant sampling representation on the helix, it is still remarkably smaller than that needed by the standard near-field-far-field transformation with cylindrical scanning. The effectiveness of the technique is assessed by numerical and experimental results.

Nonredundant near-field-far-field transformation from probe positioning errors affected bi-polar data

2017 ◽  
Author(s):  
Francesco D'Agostino ◽  
Flaminio Ferrara ◽  
Claudio Gennarelli ◽  
Rocco Guerriero ◽  
Massimo Migliozzi
Keyword(s):  
Near Field ◽  
Far Field ◽  
Positioning Errors ◽  
Field Transformation

scholarly journals Non-redundant Spherical Near-Field to Far-Field Transformation for a Volumetric Antenna in Offset Configuration

2019 ◽  
Vol 13 (1) ◽  
pp. 19-29 ◽  
Author(s):  
Francesco D’Agostino ◽  
Flaminio Ferrara ◽  
Claudio Gennarelli ◽  
Rocco Guerriero ◽  
Massimo Migliozzi
Keyword(s):  
Near Field ◽  
Measurement Techniques ◽  
Data Gathering ◽  
Experimental Tests ◽  
Precise Determination ◽  
Far Field ◽  
Interpolation Algorithm ◽  
Classical Technique ◽  
Field Transformation

Background: The development of fast Near-Field (NF) measurement techniques allowing the precise determination of the Far-Field (FF) radiation features of an antenna is becoming more and more challenging nowadays. Objective: The goal of the article is the development of an NF To FF Transformation (NFTFFT) with spherical scan for offset mounted volumetric Antennas Under Tests (AUTs) requiring, unlike the classical technique, a reduced set of NF data, that is of the same amount as for the onset mounting case, thus making data gathering faster. In fact, the number of NF data needed by the standard approach may considerably increase in this case, since the size of the smallest sphere surrounding the AUT and centered at the center of the measurement sphere rises. Methods: This goal has been achieved by profitably exploiting the non-redundant sampling representation of electromagnetic field and assuming a volumetric AUT as contained in a sphere. An optimal sampling interpolation algorithm is then employed to precisely reconstruct the input NF data for the traditional spherical NFTFFT from the reduced set of the collected ones. Conclusion: The numerical simulations and experimental tests demonstrate the effectiveness of the developed approach accounting for an offset mounting of the AUT.

scholarly journals 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

Sensors ◽  
2021 ◽  
Vol 21 (5) ◽  
pp. 1644
Author(s):  
Francesco D’Agostino ◽  
Flaminio Ferrara ◽  
Claudio Gennarelli ◽  
Rocco Guerriero ◽  
Massimo Migliozzi ◽  
...  
Keyword(s):  
Near Field ◽  
Field Pattern ◽  
Far Field ◽  
Interpolation Algorithm ◽  
Radial Line ◽  
Sample Spacing ◽  
Field Samples ◽  
Field Transformation ◽  
Redundant Representation ◽  
Far Field Pattern

An efficient near-to-far-field transformation (NTFFT) technique, wherein the near-field (NF) measurements are acquired along a planar spiral with a uniform step to make the control of the involved positioners easier, is developed in this article. Such a technique is tailored for quasi-spherical, i.e., volumetric, antennas under test and makes use of a reduced number of NF data. An effective two-dimensional sampling interpolation algorithm, allowing the accurate reconstruction of the input NF data for the standard NTFFT with plane-rectangular scan, is obtained by setting the spiral step equal to the sample spacing required for interpolating along a radial line according to the spatial bandlimitation properties of electromagnetic fields, and by properly developing a non-redundant representation along such a spiral. Tests results are reported to demonstrate that the proposed NTFFT technique retains the same accuracy as the standard plane-rectangular one.

scholarly journals Phaseless spherical near-field antenna measurements for low and medium gain antennas

2010 ◽  
Vol 8 ◽  
pp. 43-48 ◽  
Author(s):  
C. H. Schmidt ◽  
S. F. Razavi ◽  
T. F. Eibert ◽  
Y. Rahmat-Samii
Keyword(s):  
Special Interest ◽  
Field Data ◽  
Measurement Accuracy ◽  
Near Field ◽  
Far Field ◽  
Radiation Patterns ◽  
Phase Measurements ◽  
Modal Expansion ◽  
Field Transformation ◽  
Phase Data

Abstract. The characterisation of antenna radiation patterns by measurements in the near-field and a following near-field far-field transformation require accurate amplitude and phase data. Especially at higher frequencies phase measurements are demanding in terms of instrumentation and measurement accuracy. Phaseless techniques which require amplitude only data on one or more measurement surfaces are therefore of special interest. In this paper a phaseless spherical algorithm based on spherical modal expansion is presented. The algorithm works with amplitude only near-field data measured on two spheres of different radii and is therefore not restricted to certain types of antennas as for planar measurements for example. Simulated as well as measured results of low and medium gain antennas are shown.

scholarly journals Effective Antenna Modellings for NF-FF Transformations with Spherical Scanning Using the Minimum Number of Data

2011 ◽  
Vol 2011 ◽  
pp. 1-11 ◽  
Author(s):  
Francesco D'Agostino ◽  
Flaminio Ferrara ◽  
Claudio Gennarelli ◽  
Rocco Guerriero ◽  
Massimo Migliozzi
Keyword(s):  
Electromagnetic Fields ◽  
Near Field ◽  
Two Dimensions ◽  
Geometric Parameters ◽  
Optimal Sampling ◽  
Far Field ◽  
Aperture Diameter ◽  
The Third ◽  
Numerical Tests ◽  
Minimum Number

Two efficient probe-compensated near-field-far-field transformations with spherical scanning for antennas having two dimensions very different from the third one are here developed. They rely on the nonredundant sampling representations of the electromagnetic fields and on the optimal sampling interpolation expansions, and use effective antenna modellings. In particular, an antenna with a predominant dimension is no longer considered as enclosed in a sphere but in a cylinder ended in two half spheres, whereas a surface formed by two circular “bowls” with the same aperture diameter but different lateral bends is adopted to shape an antenna with two predominant dimensions. These modellings are able to fit very well a lot of antennas by properly setting their geometric parameters. It is so possible to remarkably lower the number of data to be acquired, thus significantly reducing the measurement time. Numerical tests assessing the accuracy and the robustness of the techniques are reported.

scholarly journals Correction of Known Position Errors in a Spherical Near to Far-Field Transformation for Long Antennas

2017 ◽  
Vol 11 (1) ◽  
pp. 141-153
Author(s):  
Renato Cicchetti ◽  
Francesco D’Agostino ◽  
Flaminio Ferrara ◽  
Claudio Gennarelli ◽  
Rocco Guerriero ◽  
...  
Keyword(s):  
Experimental Validation ◽  
Iterative Scheme ◽  
Sampling Point ◽  
Optimal Sampling ◽  
Far Field ◽  
Uniform Sampling ◽  
Position Errors ◽  
Sampling Formula ◽  
Field Transformation ◽  
Minimum Number

Background: This paper provides the experimental validation of an efficient iterative procedure to correct known position errors in a spherical near to far-field (NTFF) transformation for elongated antennas which uses a minimum number of NF measurements. Method: This transformation exploits a non-redundant sampling representation of the voltage detected by the probe obtained by shaping a long antenna with a prolate ellipsoid. The uniform samples, those at the points set by the representation, are accurately reconstructed from the acquired not regularly distributed (non-uniform) ones by using an iterative scheme, which requires a one to one relationship between each uniform sampling point and the corresponding non-uniform one. Then a 2-D optimal sampling formula is adopted to evaluate the input data needed to perform the traditional spherical NTFF transformation from the retrieved non-redundant uniform samples. Conclusion: Finally, laboratory proofs have been reported to demonstrate the validity of the presented technique from a practical viewpoint.

scholarly journals An Efficient Transformation Technique for the Direct Recovering of the Antenna Far-Field Pattern from Near-Field Measurements Collected along a Helix

2013 ◽  
Vol 7 (1) ◽  
pp. 21-30 ◽  
Author(s):  
F. D'Agostino ◽  
F. Ferrara ◽  
C. Gennarelli ◽  
R. Guerriero ◽  
M. Migliozzi
Keyword(s):  
Electromagnetic Fields ◽  
Field Data ◽  
Near Field ◽  
Field Measurements ◽  
Field Pattern ◽  
Far Field ◽  
Transformation Technique ◽  
Computational Burden ◽  
Field Transformation ◽  
Far Field Pattern

A near-field to far-field transformation technique with helicoidal scanning for elongated antennas, which allows the evaluation of the antenna far-field pattern in any cut plane directly from a nonredundant number of near-field data without interpolating them, is developed in this paper. It is based on the nonredundant sampling representations of electromagnetic fields and employs a flexible source modelling suitable for long antennas to determine the number of helix turns. The number of near-field measurements on each turn is on the contrary dictated by the minimum cylinder rule, as in the classical cylindrical scanning, in order to reduce the computational burden and to simplify the scanning from the mechanical viewpoint. Some numerical and experimental results assessing the effectiveness of the proposed technique are reported.

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