scholarly journals Near-field to far-field transformation applied to UHF antennas over lossy ground

2019 ◽  
Vol 12 (3) ◽  
pp. 227-232
Author(s):  
Nicolas Bourey ◽  
Muriel Darces ◽  
Yves Chatelon ◽  
Marc Hélier
Keyword(s):  
Surface Wave ◽  
Near Field ◽  
Field Measurements ◽  
Directional Antennas ◽  
Far Field ◽  
Biconical Antenna ◽  
Field Transformation ◽  
Set Up ◽  
Dipole Sources

AbstractThis paper deals with a near-field to far-field transformation able to predict the radiation of UHF antennas located over a lossy ground. From in-situ near-field measurements, an equivalent set of dipole sources is obtained as a model of the characterized antenna. The paper details the main steps of the transformation and describes the specific experimental set-up designed for the application. Simple directional antennas (monopoles array) as well as more complex omnidirectional antennas (like a biconical antenna as a scaled-down model of a HF antenna) have been tested in realistic environments. This approach is very efficient for separating the contributions of the radiated waves: the sky wave and the surface wave.

scholarly journals Scattering centers modeling of non-anechoic measurement environments

2012 ◽  
Vol 10 ◽  
pp. 69-73 ◽  
Author(s):  
K. A. Yinusa ◽  
C. H. Schmidt ◽  
T. F. Eibert
Keyword(s):  
Near Field ◽  
Field Measurements ◽  
Field Pattern ◽  
Far Field ◽  
Scattering Centers ◽  
Field Transformation ◽  
Field Radiation ◽  
Echo Suppression ◽  
Multipath Signals ◽  
Far Field Pattern

Abstract. Near-field measurements are established techniques to obtain the far-field radiation pattern of an Antenna Under Test via near-field measurements and subsequent near-field far-field transformation. For measurements acquired in echoic environments, additional post-processing is required to eliminate the effects of multipath signals in the resulting far-field pattern. One of such methods models the measurement environment as a multiple source scenario whereby the collected near-field data is attributed to the AUT and some scattering centers in the vicinity of the AUT. In this way, the contributions of the AUT at the probe can be separated from those of the disturbers during the near-field far-field transformation if the disturber locations are known. In this paper, we present ways of modeling the scattering centers on equivalent surfaces such that echo suppression is possible with only partial or no information about the geometry of the scatterers.

A Novel Far-Field Transformation via Complex Source Beams for Antenna Near-Field Measurements on Arbitrary Surfaces

2017 ◽  
Vol 65 (12) ◽  
pp. 7266-7279 ◽  
Author(s):  
Hsi-Tseng Chou ◽  
Prabhakar H. Pathak ◽  
Shih-Chung Tuan ◽  
Robert J. Burkholder
Keyword(s):  
Near Field ◽  
Field Measurements ◽  
Far Field ◽  
Complex Source ◽  
Field Transformation

scholarly journals Fast near-field far-field transformation for phaseless and irregular antenna measurement data

2014 ◽  
Vol 12 ◽  
pp. 171-177 ◽  
Author(s):  
G. Schnattinger ◽  
C. Lopez ◽  
E. Kılıç ◽  
T. F. Eibert
Keyword(s):  
Near Field ◽  
Measurement Data ◽  
Field Measurements ◽  
Solution Procedure ◽  
Far Field ◽  
Unique Determination ◽  
Antenna Measurement ◽  
Submillimeter Wavelengths ◽  
Field Transformation ◽  
Antenna Field

Abstract. The characterization of antenna radiation patterns by transformed near-field measurements requires accurate amplitude and phase data. This represents a problem since expensive measurement equipment is required, especially at millimeter and submillimeter wavelengths (Isernia et al., 1996). Amplitude-only antenna field measurements are theoretically sufficient for the unique determination of antenna far-fields. Therefore, phaseless techniques are of special interest. However, the required field transformations are extremely challenging, since they are nonlinear and strongly ill-posed. In this work, the amplitude-only or phaseless near-field far-field transformation problem is formulated as a nonlinear optimization problem. The linear radiation operator within the nonlinear formulation is evaluated using the fast irregular antenna field transformation algorithm (FIAFTA). A hybrid solution procedure is described which combines a genetic algorithm with an iterative conjugate gradient (CG) search method. Numerical results prove the efficiency and flexibility of the formulation and it is shown that the algorithm remains stable when the noise level in the measurements is moderate. Nevertheless, regularization techniques might be beneficial to further improve the robustness of the algorithm.

scholarly journals Near-field measurement of continuously modulated fields employing the time-harmonic near- to far-field transformation

2019 ◽  
Vol 17 ◽  
pp. 83-89
Author(s):  
Fabian T. Faul ◽  
Jonas Kornprobst ◽  
Torsten Fritzel ◽  
Hans-Jürgen Steiner ◽  
Rüdiger Strauß ◽  
...  
Keyword(s):  
Near Field ◽  
Far Field ◽  
Single Measurement ◽  
Measurement Interval ◽  
Time Harmonic ◽  
Field Transformation ◽  
Long Time ◽  
Modulation Signal ◽  
Complete Frequency

Abstract. Near-field far-field transformations (NFFFTs) are commonly performed for time-harmonic fields. Considering arbitrary in-situ measurement scenarios with given transmission signals, time-varying aspects of modulated signals have to be taken into consideration. We investigate and characterize two methods for the measurement of modulated fields, which work with a time-domain representation of the radiated fields and, at the same time, allow to employ the standard time-harmonic NFFFT. One method is based on the fact that the modulation signal can be assumed to be constant in a short enough measurement interval under the condition that the modulation and carrier frequencies are several decades apart. The second method performs long-time measurements in order to obtain the complete frequency spectrum in every single measurement. Both methods are verified by the NFFFT of synthetic field data.

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.

Antenna Far Field Reconstruction by a Minimum Near Field Measurements

1984 ◽  
Author(s):  
G. D'Elia ◽  
G. Leone ◽  
R. Pierri ◽  
G. Schirinzi
Keyword(s):  
Near Field ◽  
Field Measurements ◽  
Far Field ◽  
Field Reconstruction
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