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 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 Comparison of non-convex cost functionals for the consideration of phase differences in phaseless near-field far-field transformations of measured antenna fields

2017 ◽  
Vol 15 ◽  
pp. 11-19
Author(s):  
Josef Knapp ◽  
Alexander Paulus ◽  
Carlos Lopez ◽  
Thomas F. Eibert
Keyword(s):  
Minimization Problem ◽  
Near Field ◽  
Stationary Points ◽  
Data Sets ◽  
Far Field ◽  
Additional Information ◽  
Field Transformation ◽  
Cost Functionals ◽  
Antenna Field ◽  
Phase Differences

Abstract. This work introduces two methods which extend the non-convex minimization problem arising in phaseless (NF) far-field (FF) transformations. With the new extensions, knowledge about phase differences between measurement points can be incorporated into the minimization problem. The additional information helps to avoid stationary points of the minimization cost functional which would otherwise compromise the result of the near-field far-field transformation. The methods are incorporated into the Fast Irregular Antenna Field Transformation Algorithm (FIAFTA), analyzed and compared. Their effectiveness is shown by transforming synthetic near-field data sets with partial knowledge of phase differences to the far-field.

scholarly journals A fully probe corrected near-field far-field transformation technique employing plane-wave synthesis

2013 ◽  
Vol 11 ◽  
pp. 47-54
Author(s):  
R. A. M. Mauermayer ◽  
T. F. Eibert
Keyword(s):  
Plane Wave ◽  
Antenna Array ◽  
Field Measurement ◽  
Near Field ◽  
Measurement Data ◽  
Synthesis Process ◽  
Far Field ◽  
Field Transformation ◽  
Wave Synthesis ◽  
Near Field Measurement

Abstract. The far-field behavior of an antenna under test (AUT) can be obtained by exciting the AUT with a plane wave. In a measurement, it is sufficient if the plane wave is artificially generated in the vicinity of the AUT. This can be achieved by using a virtual antenna array formed by a probe antenna which is sequentially sampling the radiating near-field of the AUT at different positions. For this purpose, an optimal filter for the virtual antenna array is computed in a preprocessing step. Applying this filter to the near-field measurements, the far-field of the AUT is obtained according to the propagation direction and polarization of the synthesized plane wave. This means that the near-field far-field transformation (NFFFT) is achieved simply by filtering the near-field measurement data. Taking the radiation characteristic of the probe antenna into account during the synthesis process, its influence on the NFFFT is compensated. The principle of the plane-wave synthesis and its application to the NFFFT is presented in detail in this paper. Furthermore, the method is verified by performing transformations of simulated near-field measurement data and of near-field data measured in an anechoic chamber.

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 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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