AMTA Paper Archive


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Near Field

Determining antenna near-field magnitude data using infrared thermographic measurements
J.E. Will (University of Colorado),A. Pesta (US Air Force Rome Laboratory), J. Cleary (US Air Force Rome Laboratory), J. Norgard (University of Colorado), M. Seifert (US Air Force Rome Laboratory), R.M. Sega (University of Colorado), November 1996

This paper describes a technique for determining the magnitude of a radiating field from measurements taken using an Infrared (IR) camera. A thin resistive screen of low conductivity is positioned in the radiating field. The resistive screen absorbs energy from the radiating field and converts this energy into heat within the screen. An IR thermal picture is then taken of the heat distribution on the screen. The resulting 2D image is called an IR thermogram, i.e. and iso-temperature contour map of the data which is a representation of the electric field. The thermogram is then processed to determine the intensity (magnitude) of the radiating field at each pixel location in the thermal image. We describe the technique and show comparisons made between standard probe measurements and results from measured IR thermographs.

Antenna near field phase data from infrared thermograms by Fourier iterative plane-to-plane techniques
J.E. Will (University of Colorado),A. Pesta (US Air Force Rome Laboratory), C.F. Stubenrauch (National Institute of Standards and Technology), J. Cleary (US Air Force Rome Laboratory), J. Norgard (University of Colorado), K. MacReynolds (National Institute of Standards and Technology), M. Seifert (US Air Force Rome Laboratory), R.M. Sega (University of Colorado), November 1996

This paper describes the application of the plane-to-plane (PTP) iterative Fourier processing technique to infrared (IR) thermographic images of microwave fields for the purpose of determining the near-field and far-field patterns of radiating antennas. The PTP technique allows recovery of the phase by combining magnitude-only measurements made on two planes, both in the radiating near field of the antenna under test. We describe the PTP technique and show excellent comparisons between the predicted results and results from measured IR thermograms of the field of a 36 element patch array antenna operating at 4 GHz.

Antenna near field phase data from infrared thermograms by Fourier iterative plane-to-plane techniques
J.E. Will (University of Colorado),A. Pesta (US Air Force Rome Laboratory), C.F. Stubenrauch (National Institute of Standards and Technology), J. Cleary (US Air Force Rome Laboratory), J. Norgard (University of Colorado), K. MacReynolds (National Institute of Standards and Technology), M. Seifert (US Air Force Rome Laboratory), R.M. Sega (University of Colorado), November 1996

This paper describes the application of the plane-to-plane (PTP) iterative Fourier processing technique to infrared (IR) thermographic images of microwave fields for the purpose of determining the near-field and far-field patterns of radiating antennas. The PTP technique allows recovery of the phase by combining magnitude-only measurements made on two planes, both in the radiating near field of the antenna under test. We describe the PTP technique and show excellent comparisons between the predicted results and results from measured IR thermograms of the field of a 36 element patch array antenna operating at 4 GHz.

Automated EIRP measurements on a near-field range
G. Masters (Nearfield Systems Inc.),R. Young (Nearfield Systems Inc.), November 1996

Accurate EIRP measurements are possible to make on a near-field range but require great care and attention to detail. NSI has recently implemented a near-field test range for the Globalstar satellite program which makes automated EIRP and gain measurements. Automation for this program is extremely important since the production cycle requires testing many antenna systems per month, each of which has two antennas with 16 separate beams per antenna. Among the various range measurements, EIRP is the key parameter of the Transmit antenna’s performance. This paper reviews the measurement theory of EIRP measurements and presents some of the results of this automated activity.

Single-plane collimators for measurements on large antennas
V.J. Vokurka (Eindhoven University of Technology),S.C. van Someren Greve (March Microwave Systems B.V.) S. Cook (Division of Avnet Inc.) I. Henringer (Division of Avnet Inc.), November 1996

For indoor antenna measurements, compact ranges or near-field/far-field techniques are most frequently used. One of the major problems is the handling of physically large antennas. Compact ranges will in general provide test-zone sizes up to approximately 5 meters in diameter. Applying the planar NF/FF technique, even larger test-zone sizes can be realized for certain applications. On the other hand, requirement of real-time capability, for instance in production testing, will exclude NF/FF techniques. It has been shown previously that single-plane collimators have a pseudo real-time capability which makes these devices comparable to compact ranges. Furthermore, the physical test-zone sizes which can be realized when compared to compact ranges are approximately 2-3 times larger for the same size of the anechoic chamber. Finally, it will be shown that the accuracy in sidelobe level determination, gain and cross polarization is considerable higher than with other indoor techniques, even at frequencies below 1 GHz.

HSC's new near-field measurement facility
J. Way (Hughes Space & Communications Co.), November 1996

The Hughes Space and Communications Company (HSC) is in the process of completing the construction, installation and validation of two large horizontal near-field antenna measurement ranges. These new measurement systems are located in the existing HSC satellite factory building. These ranges will be used to measure various types of directive satellite antennas both at a unit level and at spacecraft level. The facility will accommodate mechanical integration of the test articles as well. This facility is the result of Hughes committing the time and money to create a state of the art antenna measurement facility that will be highly efficient and accurate. A detailed description of this facility’s configuration, design and current status will be discussed herein.

Accurate determination of main beam position and beamwidth from near field measurements
M.H. Paquay (TNO Physics and Electronics Laboratory), November 1996

For narrow beam antennas or track antennas some parameters like main beam or null position and 3 dB beamwidth need to be determined with an accuracy of less than a mill or mrad. With Near Field measurements, the Far Field is normally calculated by FFT-processing. This does, however, not provide the required accuracy. Nevertheless, the measured Near Field data contains information about any Far Field point. An iterative approach is presented to determine the Far Field antenna characteristics with high accuracy.

System design and measurement procedures in spherical near field antenna testing
M. Dich (Technical University of Demark),H.E. Gram (Technical University of Demark), November 1996

A new measurement control and data preprocessing system has been implemented at the TUD-ESA Spherical Near Field Antenna Test Facility. This facility is located at the Technical University of Denmark (TD) and operated in cooperation with European Space Agency (ESA). The measurement control system as well as a flexible information system is described. The data collected during measurements are passed through a preprocessor before the data are stored on disc. By taking advantage of the band-limited nature of the measured near field the preprocessor is able to detect RF leakages and to correct for the non-ideal sampling that is caused by non-zero integration time of the receiver.

An Environmental reflection filtering strategy for plane-polar near-field antenna measurement
O.M. Bucci (Universita di Napoli “Federico II”),G. D'Elia (Universitá di Napoli “Federico II”), M.D. Migliore (Universitá di Napoli “Federico II”), November 1996

A new strategy reducing the effect of the environmental noise in the evaluation of the radiated far field by means of a near-field far-field transformation technique is presented. A plane-polar scanning system is considered although the approach holds for general scanning geometries. Numerical and experimental results confirm the effectiveness of proposed the technique.

Spherical antenna measurement range enhancement tools
D.A. Leatherwood (Georgia Institute of Technology),E.B. Joy (Georgia Institute of Technology), K.E. Murphy (Georgia Institute of Technology), November 1996

This paper presents several enhancement tools that were developed to improve the Georgia Tech Spherical Far-Field/ Near-Field Antenna Measurement Range. Measurement amplitude and phase drift was quantified by sampling an antenna measurement signal over long time intervals while leaving the AUT rotation positioners fixed. A return-to-point drift correction tool was implemented to correct for the long-term drift component for spherical surface measurements. Temperature sensitive components of the receiver were moved from an area with severe temperature variations to a temperature stable area to reduce the phase variation. A software tool was developed to display a histogram of the variation in repeated spherical scan measurements. Histogram vales show that drift correction improves the repeatability of an antenna pattern measurement. The shapes of the histograms have been helpful in identifying random and deterministic variations.

Range upgrades
R. Kaczur (ORBIT Advanced Technologies, Inc./Flam & Russell, Inc.),A. Trabelsi (ORBIT Advanced Technologies, Inc./Flam & Russell, Inc.), November 1996

In the antenna measurement field, large investments are typically required for installations; however, these installations soon become obsolete due to advances in technology. In order to recover as much of the original investment as possible, upgrading the original installation becomes an attractive alternative. Here, we detail an ongoing upgrade of a planar near-field system. The original single-beam, single frequency system was installed approximately twenty years ago. By replacing the network analyzer, and installing a faster computer controller and accompanying software, the system was upgraded to a state-of-the-art measurement system. The upgraded system is capable of high-speed beam and frequency switching on the fly. Using the existing scanner, motor control hardware, and laser positioning sensors, the system was delivered at a significantly reduced cost.

Globalstar satellite near-field measurement systems
G. Hindman (Nearfield Systems Inc.), November 1996

NSI recently completed installation of two large 7m x 7m horizontal planar scanners to support the Globalstar satellite program test activity. These systems were installed at Alcatel in France, and Alenia in Italy. These two systems are similar to the NSI system installed at Space Systems/ Loral in Palo Alto, CA. described in previous AMTA papers. The companies are part of the Globalstar satellite consortium, committed to launching a constellation of satellites for mobile telephone communications. The paper will summarize the hardware configuration and the unique features of the two new test systems including high power phased array testing and the interface to the Globalstar payload for active antenna control and payload testing. In addition, range data comparing all 3 test ranges will be shown.

A Planar near-field system with high precision 22M x 8M vertical scanner
M. Pinkasy (Orbit Advanced Technologies),E. Katz (Orbit Advanced Technologies Ltd.) J. Torenberg (Orbit Advanced Technologies Ltd.) S. Dreisin (Orbit Advanced Technologies Ltd.) A. Geva (Orbit Advanced Technologies Ltd.) M. Bates (Orbit Advanced Technologies Inc.), November 1996

A new 1-50 GHz Near-Field measurement system is now in operation at Matra Marconi Space, Portsmouth, UK. The system has the largest vertical planar scanner installed so far. The planar scanner is constructed of steel and has four moving axes: 22 meter horizontal X axis, 8 meter vertical Y axis, 25 cm Z axis for probe alignment and a 540o Roll axis for polarization. Precision bearings are used to ensure straightness over the full length of the X-Y travel. The vertical Y axis is exceptionally fast, 500 mm/sec, to minimize acquisition time. The scanner has extremely high positioning accuracy and planarity - ±0.2 mm over the entire 22m x 8m range – allowing uncorrected operation (without laser) up to 26.5 GHz. To achieve higher accuracy and a higher frequency range an advanced 3-axis (X, Y, Z) laser correction system automatically creates correction tables for use by the transformation routines. The scanner’s exceptional repeatability allows the use of correction tables created off-line, without need for an on-line laser correction system, considerably reducing measurement time. To create these correction tables, the scanner is fitted with laser interferometers for X and Y axes and with a spinning-diode laser to calibrate for planarity. Additional features include a shielded constant-radius cable carrier, giving minimal phase errors due to cable flexing.

3-D low frequency radar target imaging
M.J. Gerry,E. Walton, November 1995

The imaging of radar targets is typically accom­ plished by measuring the radar cross section (RCS) of the target as a function of frequency and az­ imuth angle. We measure a third dimension of the RCS by tilting the target and collecting data for conical cuts of the RCS pattern. This third dimension of data provides the ability to estimate the three-dimensional location of scattering centers on the target. Three algorithms are developed in order to process the three-dimensional RCS data.

Near-field/far-field transformation
E. Lebreton,J.R. Levrel, November 1995

RCS data measured under near-field conditions is corrected to the far-field. The algorithm uses the HUYGEN's principle approach. The processing technique is describes and validates using anechoic chamber data and simulations taken on flat plate target at a distance from the radar R << 2D2/A, where D is the target cross range extend and A the wavelength. Good agreement with the theoretically predicted far-field RCS patterns is obtained.

Near-field/far-field transformation
E. Lebreton,J.R. Levrel, November 1995

RCS data measured under near-field conditions is corrected to the far-field. The algorithm uses the HUYGEN's principle approach. The processing technique is describes and validates using anechoic chamber data and simulations taken on flat plate target at a distance from the radar R << 2D2/A, where D is the target cross range extend and A the wavelength. Good agreement with the theoretically predicted far-field RCS patterns is obtained.

Near-field measurement of a beam waveguide antenna
J. Way,J. Gentle, L., Jr. Anderson, November 1995

Both Near-field Antenna Measurement Technology and Beam Waveguide Antenna techology have been in existence for some time. This paper describes a measurement combining both of these technologies. During an internal study of beam waveguide implementation, a near-field antenna measurement was made of a development model. The model and techniques of measurement are described herein.

Comparison of polar, thinned-polar, and linear spiral sampling using the UCLA bi-polar planar near-field measurement system, A
L.I. Williams,R.G. Yaccarino, Y. Rahmat-Samii, November 1995

The UCLA hi-polar planar near-field scanner has a novel implemen tation which results in a polar sampling grid. The scanner was used to perform measuremen t comparisons using three sampl in g arrangements: polar, thinned-polar, and linear-spiral sampling. The data acquired using each was processed to the far-field for both simulated and measured near-field data. Excellent agreement was observed.

Applicability of rapid near-field techniques and SAF numerical approach to bistatic RCS measurements
P. Garreau,B. Cown, F. Gallet, J. Garat, J.C. Bolomey, P. Baudon, November 1995

The application of rapid near-field measurement systems based on the Modulated Scattering Technique (MST) and Spherical Angular Function (SAF) data processing of the measured data to extract far-zone RCS of complex targets is discussed in this paper. A first-generation Spherical near-field measurement system for efficiently determining bistatic RCS is presented.

Pattern measurement of ultralow sidelobe level antennas
A.E. Zeger,B.S. Abrams, November 1995

The development* of a real time electronic system to accurately measure the pattern of high gain, ultralow sidelobe level antennas in the presence of multipath scatterers is described. Antenna test ranges contain objects that scatter the signal from the transmitting antenna into the main beam of a receiving antenna under test (AUT), thereby creating a multipath channel. Large measurement errors of low sidelobes can result. The design and computer simulation of an Antimultipath System (AMPS) is complete. Fabrication of a feasibility demonstration model AMPS to operate with rotated AUTs to suppress indirect (scattered) components and permit accurate pattern measurements is almost done. Results to date show the likelihood of measuring sidelobe levels 60 dB below the main beam. * This project is sponsored in part by the Air Force Material Command under Rome Laboratory Contract Nos. F30602-92-C-0009, Fl9628-92-C-0130 and F 19628-93-C-02 l4.







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