2009 Technical Papers

A Nonredundant NF-FF Transformation with Spherical Spiral Scanning Using a Flexible AUT Model

Authors: F. D’Agostino, F. Ferrara, J.A. Fordham, C. Gennarelli, R. Guerriero, C. Rizzo

Publication: AMTA 2009

Copyright Owner: University of Salerno

In this work, a probe compensated near-field – farfield transformation technique with spherical spiral scanning suitable to deal with elongated antennas is developed by properly applying the unified theory of spiral scans for nonspherical antennas. A very flexible source modelling, formed by a cylinder ended in two half-spheres, is considered as surface enclosing the antenna under test. It is so possible to obtain a remarkable reduction of the number of data to be acquired, thus significantly reducing the required measurement time. Some numerical tests, assessing the accuracy of the technique and its stability with respect to random errors affecting the data, are reported.

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An Effective NF-FF Transformation with Helicoidal Scan Tailored for Elongated Antennas: an Experimental Validation

Authors: F. D’Agostino, F. Ferrara, J.A. Fordham, C. Gennarelli, R. Guerriero, M. Migliozzi, G. Riccio, C. Rizzo

Publication: EuCAP 2009

Copyright Owner: IEEE

This work concerns the experimental validation of a new near-field – far-field transformation technique with helicoidal scanning tailored for elongated antennas. Such a transformation is based on the theoretical results relevant to the nonredundant sampling representations of the electromagnetic fields and uses a proper source modelling particularly suitable to deal with this kind of antennas. By employing such an effective modelling, instead of the spherical one, it is possible to remarkably reduce the error related to the truncation of the scanning zone, since measurement cylinders with a diameter smaller than the source height can be used. The validity of this innovative scanning technique is assessed by comparing the reconstructions obtained from the data directly measured on the classical cylindrical grid with those recovered from nonredundant measurements on the helix.

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An Evaluation of the Aperture Back-Projection Technique Using Measurements Made on a Flat Plate Array with a Spherical Near-Field Arch

Authors: Doren W. Hess, Scott McBride

Publication: AMTA 2009

Copyright Owner: NSI-MI Technologies

We describe two theoretical bases for an algorithm for back-projection. The first is (1) Fourier inversion of the mathematical expression for the far electric field components in terms of the aperture electric field. The second is (2) Fourier inversion of the complete vectorial transmitting characteristic of Kerns' scattering matrix. It is this characteristic that results from the standard process of planar near-field (PNF) scanning and the ensuing reduction of the PNF transmission equation. We demonstrate that the theoretical approaches (1) and (2) yield identical back-projection algorithms.

We report on back-projection measurements of an 18 inch X-band flat plate phased array using the far-field obtained from both planar and spherical near-field scanning. The spherical measurements were made on a large arch range.

Distributed RF Systems for Antenna Measurements

Authors: Bert Schluper, David S. Fooshe

Publication: AMTA 2009

Copyright Owner: NSI-MI Technologies

It is well known that modern, high-performance antenna range instrumentation requires fast sources and receivers. What is often overlooked is that the locations of the components making up the RF subsystem need to be considered as well. RF sources and receivers that are controlled over a LAN interface can easily be located remotely, where they are closer to the transmitting and receiving antennas. In addition to using remote mixers, other components such as amplifiers and multipliers can be mounted remotely, on a positioner or probe carriage. This allows using lower-frequency cables with lower loss, and dramatically increases the available power level at the transmitting antenna. Use of fiber optics is also becoming an option for transmission of RF signals in distributed RF systems. Automated configuration control can be achieved using remotely controlled switches.

This paper will present comparisons of distributed and more traditional geometries, including performance and cost benefits.

Focal-Plane Scanner for Measuring Radome Beam Deflection in a Compact Range

Author: Scott T. McBride

Publication: ATMS India 2009

Copyright Owner: NSI-MI Technologies

Measurement of radome beam deflection and/or Boresight shift in a compact range generally requires a complicated set of positioner axes. One set of axes usually moves the radome about its system antenna while the system antenna remains aligned close to the range axis. Another set of axes is normally required to scan the system antenna through its main beam (or track the monopulse null) in each plane so the beam pointing angle can be determined. The fidelity required for the beam pointing angle, combined with the limited space inside the radome, usually make this antenna positioner difficult and expensive to build...

GlobalStar II RX L-Band Antenna Spherical Near Field Measurement

Author: Trenta Damiano, Diego Vicentini

Publication: AMTA 2009

Copyright Owner: NSI-MI Technologies

Thales Alenia Space is in charge for the development, integration and production of the whole Global Star II satellite constellation. To support the production of the RX L-Band Active Antennas, a new Spherical Near test facility was developed and installed at Thales Alenia Space Italy premises. This paper gives an inter-comparison of the measurement results obtained among three facilities that are a Test Range installed at TAS-France, a Spherical Near-Field already available at TAS-Italy and the new SNF facility. The test comparison has been considered as a part the new SNF facility validation. In particular the comparisons of copolar and crosspolar patterns, peak directivity and general Antenna performances are shown...