AMTA Paper Archive

 

Welcome to the AMTA paper archive. Select a category, publication date or search by author.

(Note: Papers will always be listed by categories.  To see ALL of the papers meeting your search criteria select the "AMTA Paper Archive" category after performing your search.)

 

Search AMTA Paper Archive
Keyword/Author:
After Date: (mm/dd/yy)  
 
Sort By:   Date Added  ▲  |  Publication Date  ▲  |  Title  ▲  |  Author  ▲
= Members Only
Far Field
Alignment measurements using a special purpose phased array antenna
L.D. Poles (Rome Air Development Center), November 1989
A special purpose 80 element linear phased array antenna was aligned using an iterative phase cycling method. First, the array was aligned to yield maximum main-beam power in the reactive near-field zone and then in the far-field zone. A record of the phase-shifters settings achieved for each zone was kept for use as look-up table during operation. In situ electronic main-beam steering was performed to compare sidelobe performance for the two cases. This report describes the measured results obtained using the phased cycling alignment procedure and compares the measured one-way radiation pattern for the two distance conditions.
Design of a short range for testing large phased arrays
L. Goldstone (Norden Systems), November 1989
Large arrays require large separations between the transmit antenna and the antenna under test (AUT) to measure pattern parameters in the far field. For the subject AUT, a range of 6 miles with a spurious signal level of -58 dB was necessary to obtain the required accuracy. Measurements have been performed on a significantly shorter range without serious degradation. The antenna was focused for the angle of electronic scan and the resulting pattern measured. The theoretical far field patterns were compared with the calculated focused patterns for the short range. The maximum sidelobe error of 1/2 dB occurred at 60 degrees scan. There was no noticeable degradation in beamwidth, gain, or foresight at any scan angle. A 6-mile range would have produced a 2-dB sidelobe error. The measured range reflection level was -50 dB. The transmit dish with sidelobes of 22 dB was replaced with an array that had 40 dB sidelobes. This change reduced the reflections to below the required -58 dB. The antenna was focused using a range calibration technique and the measurements substantiated the theory.
Radar cross section measurements in a cluttered environment
E. Walton (The Ohio State University ElectroScience Laboratory),L. Beard (The Ohio State University ElectroScience Laboratory), November 1989
Under many circumstances it is necessary to experimentally estimate the radar cross section of targets in a cluttered environment. A significant reduction in the clutter can be obtained when cross range filtering can be done. In this experimental RC measurement concept, scattering measurements are performed using a moving radar antenna. Thus scattering as a function of target plus clutter versus aspect angle in the near field can be measured. Next, a back projection algorithm can be used to estimate the scattering as a function of position in the neighborhood of the target. The known range to which the signal is to be focussed is used to project back to the target area. An estimate of the RCS at points along a line in the plane of the target is computed. The clutter responses can then be removed from the data, and the remaining target-only values projected forward again (possibly to the far field) to estimate the RCS of the target alone.
A Quasi-far-field measurement systems: hardware, software and experimental results
R.E. Shields (CSIRO Division of Radiophysics, Australia),G.M. Simms (CSIRO Division of Radiophysics, Australia), November 1989
The hardware and software developments undertaken to upgrade two far-field measurement facilities - a 12-m anechoic chamber and a 35-m outside range - are described. A method (termed quasi-far-field, QFF) for deriving antenna far-field patterns from a single plane scan at a distance less than the traditional distance of 2D2/? is described. The QFF technique involves pattern sample and subsequent pattern transform and reconstruction, from the easement distance to the far-field distance. A discussion of the limitations inherent in the QFF transform, including range length, is given. Experimental results for measurements made on circular-aperture antennas with both symmetric and asymmetric illumination, and on antennas with elliptical apertures, are described.
Methods of transforming antenna Fresnel region fields to far region fields
K. Wu (Electrospace Systems, Inc.),S. Parekh (Electrospace Systems, Inc.), November 1989
For transforming a Fresnel region pattern to a far-field pattern, we present here two methods, the "discrete beam sampling" method (DBSM) and the "displaced beam" method (DBM), which allow an accurate characterization for both linear as well as circular antenna apertures. Both methods assume a simple Fourier transform relationship between the aperture field distribution and the far-field of the antenna. The Fresnel region field is then essentially perturbed by an aperture quadratic phase error assumed to exist because of the finite distance at which the field pattern is characterized. Numerical simulation and its results are presented to show the accuracy of the reconstructed far-field data. Finally, an error analysis is performed to show the sensitivity of the above two methods.
Application of nonuniform sampling techniques for antenna pattern measurements
Y. Rahmat-Samii (University of California Los Angeles), November 1989
The nonuniform sampling technique utilizes measured (or simulated) amplitude and phase far-field data at nonuniformly sampled data points and constructs the pattern from these limited number of measured data. The technique relies on the fact that the antenna far-field pattern is proportional to the Fourier transform of a function which is related to the induced current on the antenna. The application of nonuniform sampling technique becomes important in the situation for which it will be difficult (or impossible) to measure the far field at regular intervals. In this paper, the application of the nonuniform sampling technique is demonstrated for antenna pattern measurements. The foundation of the technique is first reviewed and the required mathematical steps for the implementation of the technique is summarized. Both one dimensional and two dimensional cases are reviewed with attention given to the applicability of closed form expressions for the determination of the sampling coefficients. Numerical results are presented and comparison to measurements are shown. In particular, the application of this technique to a recently proposed space-station based antenna experiment is presented.
Application of nonuniform sampling techniques for antenna pattern measurements
Y. Rahmat-Samii (University of California Los Angeles), November 1989
The nonuniform sampling technique utilizes measured (or simulated) amplitude and phase far-field data at nonuniformly sampled data points and constructs the pattern from these limited number of measured data. The technique relies on the fact that the antenna far-field pattern is proportional to the Fourier transform of a function which is related to the induced current on the antenna. The application of nonuniform sampling technique becomes important in the situation for which it will be difficult (or impossible) to measure the far field at regular intervals. In this paper, the application of the nonuniform sampling technique is demonstrated for antenna pattern measurements. The foundation of the technique is first reviewed and the required mathematical steps for the implementation of the technique is summarized. Both one dimensional and two dimensional cases are reviewed with attention given to the applicability of closed form expressions for the determination of the sampling coefficients. Numerical results are presented and comparison to measurements are shown. In particular, the application of this technique to a recently proposed space-station based antenna experiment is presented.
Antenna far-field pattern accuracies at millimeter wave frequencies using the planar near-field technique
M.H. Francis (National Institute of Standards and Technology), November 1989
In recent years there has been an increasing demand for antenna calibrations at millimeter wave frequencies. Because of this the National Institute of Standards and Technology (NIST) has been developing measurement capabilities at millimeter wave frequencies. The development of gain and polarization measurement capabilities have been previously reported. This paper reports on the development of the capability to measure an antenna pattern which has been achieved during the last year. Measurement accuracies of better than 4 dB have been achieved for sidelobes which are 40 dB below the mainbeam peak. NIST is now providing a new measurement service for antenna patterns in the 30-50 GHz frequency range.
Aramis - a flexible near-field antenna test facility
O. Silvy (Electronique Serge Dassault), November 1989
A flexible near-field antenna test-facility is presented. This system gathers all that is necessary to design, to debug and to validate the high performance antennas which are made by ESD. ARAMIS has been operational since January 1988. Its applications are: - Near-field measurements (for diagrams): * planar, * cylindrical. - High speed field mapping (for default analysis): * planar radiating surface, * cylindrical radiating surface. - Generation of element excitation (active phased array testing): * planar antennas, * cylindrical antennas. - Direct far-field measurements (probes, small antennas), - Circuit measurement (S parameter). The facility features a specially designed scanner. Thanks to its six degrees of freedom, this positionner allows the differents types of measurements to be made. The instrumentation is based upon the HP 8510 B network analyzer. A single computer performs the measurements, transforms the data and presents the graphics (linear diagrams, color maps, three-dimensional colored projections). In order to grant a high scan speed, the system uses the FAST CW mode of the HP 8510 B. An external trigger is provided during the motion process of the probe. A rate of 500 measurements/sec. has been proved. This on-the-fly process is clearly depicted. Experimental results are presented which include: - Low sidelobe (-38 dB) antenna diagrams. - Default analysis through: * Amplitude mapping (leakage short-circuit in a microstrip antenna). * Phase mapping (out-of band comparison between two radiating element technologies). * Measurement of excitation laws. * 3-D transformation. - Simultaneous on-the-fly acquisition of up to three antenna outputs.
A Low cost portable near-field antenna measurement system
D. Slater (Nearfield Systems Incorporated),G. Hindman (Nearfield Systems Incorporated), November 1989
Implementing an antenna test range has traditionally been viewed as a major and costly undertaking, requiring significant long term facility planning, computer hardware interfacing, and software development. This paper describes a complete low cost, yet high accuracy portable near-field measurement system that was privately built for less than $2,000 and interfaced to a PC compatible computer. The design and operation of this system, including the scanner, microwave hardware, and computer system will be described. This system has since been extended into a commercial product capable of providing rapid and accurate measurements of small to medium size feeds and antennas within a small office or lab space at significantly lower cost than standard antenna test techniques. The system has demonstrated an equivalent sidelobe noise level of less than -50 dB, includes a probe corrected far-field transform and holographic back projections, and can output pattern cuts, contour plots, 3D plots, and grey scale images of antenna performance.
Measurements and modeling of a focused scalar horn-lens antenna
D. Blejer (MIT Lincoln Laboratory), November 1990
The properties of a focused scalar horn-lens antenna are presented. The behavior of the field from the lens to the far field is determined from electromagnetic principles and measured antenna patterns at the focal distance are shown.
An HP-8510-based 45-GHz instrumentation radar for ISAR image and glint studies
R. Dinger (Naval Weapons Center),D.J. Banks (Naval Weapons Center), D.R. Gagnon (Naval Weapons Center), E. Van Bronkhorst (Naval Weapons Center), November 1990
A 45 GHz instrumentation radar system unique in several respects has been developed for inverse synthetic aperture radar (ISAR) and tracking angle scintillation (glint) studies. The system, based on a Hewlett-Packard HP-8510B network analyzer, is fully polarimetric and operates on a 1000-m outdoor far-field range. An amplitude monopulse receiver provides a measure of the instantaneous apparent-center-of-scattering of the target. Successful glint and ISAR measurements have been made on targets as large as 8 m.
Using a modified Hewlett Packard 8510 network analyzer as an automated far-field antenna range receiver
J.D. Terry (NASA Lewis Research Center),R.R. Kunath (NASA Lewis Research Center), November 1990
A Hewlett Packard 8410 Network Analyzer was modified to be used as an automated far-field antenna range receiver. By using external mixers, analog to digital signal conversion, and an external computer/controller, the HP8410 is capable of measuring signals as low as -110 dBm. The modified receiver is an intergral part of an automated far-field range which features computer controlled test antenna positioning, system measurement parameters, and data acquisition, as well as customized measurement file management. The system described was assembled and made operational taking advantage of off-the-shelf hardware available at minimal cost.
Adaptive alignment of a phased array antenna
H.M. Aumann (Massachusetts Institute of Technology),F.G. Willwerth (Massachusetts Institute of Technology), November 1990
A technique for aligning a phased array is described. Array element attenuation and phase commands are derived from far-field patterns measured without calibrations. The technique is based on iteratively forming mulls in the antenna pattern in the directions specified by a uniform array illumination. It may be applied in situations where array elements are not individually accessible, or where an array contains no build-in calibration capacity. The alignment technique was evaluated on a far-field range with a linear, 32-element array operating at L-band. The array containing transmit/receive modules with 12-bit amplitude and phase control. Insertion attenuation and phase measurements were comparable to those obtained by conventional techniques. However, the alignment procedure tends to compensate for the effects of nonuniform element patterns and range multipath. Thus, when used to implement other excitation functions, the array sidelobe performance with adaptive calibrations was substantially better.
On-line bite to accurately monitor beam position, beam shape, and system performance of electronically scanned phased array antennas
J.H. Acoraci (Allied-Signal Aerospace Company), November 1990
Electronically scanned phased array antennas typically have a large number of beam positions. Accurate on-line monitoring of phased array beam positions can be used to ensure proper antenna and total system performance. Bendix has developed and successfully implemented a beam-position monitoring technique designated the “RF Integral Monitor System”. Use of this on-line technique does not interfere with normal system operation and yields results that are comparable to results obtained on an actual far field antenna range. The RF Integral Monitor technique and specific hardware implementations, for both linear and circular electronically scanned phased arrays, will be described in this paper.
New algorithms for enhancing the performance of near field techniques
O.M. Bucci (Universita’ di Napoli),G. D'Elia (Universita’ di Salerno), G. Leone (Universita’ di Salerno), R. Pierri (Universita’ di Napoli), T. Isernia (Universita’ di Napoli), November 1990
To enhance the performance of existing near field techniques the new idea of far field pattern determination from only amplitude distributions of the near field is proposed. In this way the difficulties related to phase measurements are overcome. Some different algorithms are introduced and discussed. In particular, after recalling results for the planar geometry, cylindrical scanning surfaces are considered. The feasibility and the performances of the introduced algorithms are shown through numerical examples.
Array antenna diagnosis and calibration
M. Johansson (Ericsson Radar Electronics AB, Antenna Systems),B. Svensson (Ericsson Radar Electronics AB, Antenna Systems), November 1990
A method for obtaining the individual element excitations of an array antenna from measured radiation patterns is presented. Applications include element failure diagnosis, phased array antenna calibration, and pattern extrapolation. The measured far-field information is restricted to visible space which does not always contain the entire Fourier domain. A typical example is phased array antennas designed for large scan angles. A similar problem arises during near-field testing of planar antennas in which case the significant far-field domain is restricted by the scanning limitations of the near-field test facility. An iterative procedure is then used which is found to converge to the required solution. The validity of the approach has been checked both using the theoretical radiation patterns and real test cases. Good results have been obtained.
Lockheed's Advanced Development Company's electromagnetic measurement facility
R. Taron,L. Pellett, November 1990
Lockheed’s Advanced Development Company (LADC), located in Burbank, California, has recently completed construction of a state-of-the-art indoor Antenna/RCS test facility. This facility is housed in a dedicated 40,000 square foot building which is a maximum of 80 feet high. This building contains three anechoic chambers providing Antenna/RCS measurement capability from 100 Mhz to 100 Ghz. The largest chamber, with dimensions of 64 feet by 64 feet by 97 feet is configured as a compact range. This chamber utilizes the largest collimating reflector that Scientific-Atlanta has ever constructed. Primary test usage of this chamber is for RCS measurements in the frequency band of 700 Mhz to 100 Ghz. The second chamber is configured as a tapered horn test range. Its dimensions are 155 feet long with a 50 foot by 50 foot by 55 foot volume measurement zone. This chamber is utilized for RCS tests in the VHF, UHF, and L frequency bands and antenna tests from 100 MHz and up. The third chamber, with dimensions 14 foot by 14 foot by 56 foot, is a far field chamber designed to check out and evaluate small items up to 100 GHz. The entire facility has been designed to maximize efficiency, minimize the cost of operation, and produce outstanding quality data from Antenna/RCS measurements. A number of innovative techniques in model handling, model access, and model security were incorporated into the facility design. These features, as well as utilization of unique Lockheed designed and built pylons, allowed achievement of all these goals.
Testing an active airborne phased-array military SATCOM antenna with ARAMIS
C. Renard (Dassault Electronique),G. Coutet (Dassault Electronique), G. Debain (Dassault Electronique), O. Silvy (Dassault Electronique), November 1990
The Dassault Electronique flexible near-field antenna test facility, ARAMIS, has been used for test and calibration of state-of-the-art active phased-array antennas which were designed for military SATCOM operation. The 14-month successful program dramatically emphasized the benefits of a flexible antenna test facility such as ARAMIS. These benefits are the following: • Flexibility o Far-field mode (test of radiating elements and modules) o Planar near-field mode (test of sub-arrays and complete antenna) o High-resolution field mapping mode o Array Element testing • Speed: quick mode switching, “on the fly” multiplexed acquisition • Versatility: calibration of a module, a sub-array and the antenna; radiation patterns; gain; faulty element detection • Productivity: a single indoor facility performing different types of measurements, integrated software Test results gathered during this program and showing the ARAMIS contribution are presented.
Near-field testing of adaptive radar systems
A.J. Fenn (Massachusetts Institute of Technology), November 1990
Airborne or spaceborne radar systems often require adaptive suppression of interference and clutter. Before the deployment of this adaptive radar, tests must verify how well the system detects targets and suppresses clutter and jammer signals. This paper discusses a recently developed focused near-field testing technique that is suitable for implementation in an anechoic chamber. With this technique, phased-array near-field focusing provides far-field equivalent performance at a range distance of one aperture diameter from the adaptive antenna under test. The performance of a sidelobe-canceller adaptive phased array antenna operating in the presence of near-field clutter and jamming is theoretically investigated. Numerical simulations indicate that near-field and far-field testing can be equivalent.


This item is only available to members

Click here to log in

If you are not currently a member,
you can click here to fill out a member application.

We're sorry, but your current web site security status does not grant you access to the resource you are attempting to view.