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.)
Earlier (AMTA'97, AMTA'98), we have proposed a new low-cost laboratory method named the quasi-optical waveguide modeling (QWM) method to study power and amplitude-phase scattering characteristics of objects, in particular the RCS of targets or their scale models, in the near millimeter (NMM) and submillimeter (SMM) wave regions. A specific feature of this technique in that an investigated object (or its scale model) is mounted inside a quasi-optical waveguide structure in the form of a hollow dielectric waveguide (HDW), in which the scattering characteristics of the waveguide dominant HE11 mode are determined. These characteristics are related to the wanted scattering characteristics of the test object in free space by definite relationships. At the same time the HDW serves several functions: it forms a quasiplane incident wave within the scattering area where test object is placed, performs the low-loss and low-distortion transmission of the scattered wave carrying information of the object being tested to the receiver, effectively filters the unwanted modes arising at the scattering on the test object, and insulates the measurement area from the ambient conditions containing parasitic sources. In this paper we consider the possibility of using the QWM method to study polarization backward scattering characteristics of physical objects, in particular the complex elements of the scattering matrix with relative phase (SMR). A quasi-optical polarimetric micro-compact range (PMCR) based on the circular HDW and quasi-optical devices has been developed and built. The measurement results of the SMR and backward scattering patterns of a reference object as a square metallic cylinder obtained in the PMCR for the different linear polarization basic sets at the 4-mm wave band are presented. The comparison between the experimental results for the reference object and the theoretical data calculated by the geometrical theory of diffraction have shown a good agreement, and demonstrated the possibilities of the QWM method, and its good perspectives for backward scattering polarization characteristics modeling in the NMM and SMM wave regions.
An accurate and reliable target positioning system is mandatory for a good antenna and/or radar cross section (RCS) measurement facility. Most measurements involve characterizing the radiation or scattering of the unit under test as a function of angle and frequency. Accuracy and repeatability become increasingly important in RCS measurements where background subtraction is utilized. Any error in target position will reduce the subtraction effectiveness. Wear and tear of existing equipment coupled with improvements in motion control technology may compel some measurement facilities to upgrade their positioning system. Doing so, while keeping the rest of the measurement system intact, poses integration challenges that cannot be over emphasized. Problems will inevitably be encountered. Their source could be the new positioning system, the old measurement system, or the communication between the two. Subtleties of how the motion control system works can be overlooked during the requirements definition phase of the project. Further idiosyncrasies can be missed during acceptance testing of the system. The Air Force Research Lab compact range has recently upgraded their target positioning system and will share the lessons learned as a result.
The design of a compact range facility in the National University of Singapore is presented. The range is designed for antenna and RCS measurements from L band to Ka-band and for test objects up to about 2 metres in size. The reflector in the range is parabolic in shape with a focal length of 3.5 metres. The instrumentation is standard measurement equipment with some purpose-built controllers for the positioners and the scanner.
Quiet zone field probe data of a recently built compact range system is presented. The com pact range uses an optimally designed blended rolled edge reflector to operate from 800 MHz to 18 GHz. The absorber on the walls, floor and ceiling of the chamber is also designed and placed for optimal performance. It is shown that the range is free of any significant stray signals over the whole frequency band.
CAMELIA is a large RCS measurement facility (45m.12m. 13m in dimensions) whose compact range is optimized in the SHF band (1-18 GHz). Exploiting it at lower frequencies requires the modification of the absorbers and the use of huge broad band horns as RF sources (since the compact range is now not well adapted). To help understanding the radioelectric behavior of the large scale facility, we have developed a 1:10 small scale model as well as 1:10 scale horns, that are operated in the SHF band. It enables the experimental simulation of RCS measurements in the V/UHF band. Thus, all dimensions and frequencies are homothetic, only electromagnetic properties of materials are not. RCS measurements of several canonical targets have been performed in both facilities and compared. Due to non directive transmitting/receiving antenna, coupling between the targets and the wans has been exhibited. A simple ray tracing model, taking into account the measured reflection coefficient of the walls and the bistactic RCS of the target, shows good agreement with the measurements.
Radar Cross Section measurements require the target to be in the far field of the illuminating and receiving antennas. Such requirements are met in a compact range in the SHF band, but problems arise when trying to measure at lower frequencies. Typically, below 500 MHz, compact ranges are no more efficient, and one should only rely upon direct illumination. In this case, the wavefront is spherical and the field in the quiet zone is not homogeneous. Furthermore, unwanted reflections from the walls are strong due to the poor efficiency of absorbing materials at these frequencies, so the measurement that can be made have no longer something to see with RCS, especially with large targets. We first propose a specific array antenna to minimize errors caused by wall reflections in the V-UHF band for small and medium size targets. Then an original method based upon the same array technology is proposed that allows to precisely measure the RCS of large targets. The basic idea is to generate an electromagnetic field such that the response of the target illuminated with this field is the actual RCS of the target. This is achieved by combining data collected when selecting successively each element of the array as a transmitter, and successively each other element of the array as a receiver. Simulations with a MoM code and measurements proving the validity of the method are presented.
Composite Optics Inc (COI) has designed and constructed a Portable Far-Field Antenna Test Chamber to complement their Large Compact Range. The need for this chamber arose after COI won a contract to design, build, and test hundreds of small broadband antenna elements. Because of the portability requirement, COI chose to procure and modify an industrial container, suitable for transportation on a standard flatbed trailer. This paper discusses the design, fabrication, and installation of a chamber, suitable for pattern measurements of small (<2 feet) antennas in the 6-18 GHz frequency range.
When mounted on spacecraft , pattern of some antennas are perturbed by the presence of satellite body. The prediction of antenna performances including satellite structure effect is generally done at early stage of antenna design but is limited in terms of model complexity. The test on full spacecraft & in far field condition is then necessary. This solution is very expensive as it means for test at satellite level to use Compact antenna Test Range in order to satisfy cleanliness aspects. For the Meteosat Second Generation (MSG) program test on the toroidal antennas need to be performed on different model including a flight model. A good compromise was to use the external omnidirectional antenna range and a part of satellite structure representing the major contributor for the antenna pattern as identified via numerical analysis. The external range offer possibilities that cannot be reached in Compact range, e.g. low cost, full sphere pattern, low frequency range.
Boeing is currently pursuing certification of their 9-77 indoor compact range facility as a voluntary industrial participant in the ongoing DoD/NIST RCS certification demonstration program. In support of that process, V EI has applied a novel statistical method for analysis to VHF measurements of a canonical target from the Boeing 9-77 range. The dominant error sources in the range were identified and categorized according to their dependence on frequency, aspect angle, and the target under test. Range characterization data were collected on canonical targets and then used to estimate the statistical parameters of each of the errors. Finally, these were incorporated into expressions for the combined RCS measurement uncertainty for a test body whose RCS exhibits many of the characteristics of modern, high-value targets. The results clearly demonstrate the importance of accounting for the target-dependence of the errors and the bias they introduce into the overall uncertainty.
This paper describes how ANSI standard Z-540 [l,2,3] was applied in a DoD demonstration project to organize radar cross section (RCS) range documentation for the Air Force Research Laboratory Advanced Compact Range (ACR) and Patu:xent River Atlantic Test Range (ATR) Dynamic RCS measurement facility. Both parts of this paper represent a follow-up report on the DoD demonstration program introduced at AMTA 97 [4]. In June 2000, the DoD Range Commanders Council Signature Measurement and Standards Group (RCC/SMSG) certified that these two facilities met the ANSI-Z-540 documentation standards established by the DoD demonstration project. Since AFRL plans to require mandatory ANSI-Z-540 compliance for DoD contractors performing RCS measurements with AFRL after January 1, 2004, the review process described in this paper will be the likely model for industrial compliance. After a brief review of the ANSI-Z-540 standard, Part 1 of this paper will outline the certification review process and discuss the outcomes, results, and lessons learned from the DoD demonstration program from the perspective of the AFRL range and volunteer range reviewers.
This paper describes how ANSI/NCSL standard Z- 540 [1, 2] was applied in a DoD demonstration project to organize radar cross section (RCS) range documentation for the Air Force Research Laboratory (AFRL) Advanced Compact Range (ACR) and the Naval Ai:r Warfare Center - Aircraft Division (NAWC-AD) Atlantic Test Range (ATR) Dynamic RCS measurement facility. Both parts of this paper represent a follow-up report on the DoD demonstration program introduced at AMTA 97 [3]. In June 2000, the DoD Range Commanders Council Signature Measurement and Standards Group (RCC/SMSG) certified that these two facilities met the ANSI/NCSL Z-540 documentation standards established by the DoD demonstration project. Since AFRL plans to require mandatory ANSI/NCSL Z- 540 compliance for DoD contractors performing RCS measurements with AFRL after January 1, 2004, the review process described in this paper will be the likely model for industrial compliance. Part I of this paper contained a brief summary of the ANSI/NCSL Z-540 standard, outlined the certification review process and discussed the outcomes, results, and lessons learned from the DoD demonstration program from the perspective of the AFRL range and volunteer range reviewers. Part II will discuss the review process as it applied to ATR, as well as the outcomes, results, and lessons learned.
Allgon Systems AB has put a new compact antenna test range into operation in July 2000. The investment was triggered by Allgon's planned move to a new building. An indoor facility was preferred for fast and efficient operation. The present primary application is the measurements of base station antennas. The compact range is constructed using a single reflector with serrated edges. A sophisticated feed carrousel enables automatic changing of 3 feed systems. The size of the quiet zone is 3 meters. The initial frequency range is from 800 to 6000 MHz. However, the reflector accuracy allows future extensions to 40 GHz and higher. The cha mber size is 21 x 12 x 10.5 m (L x W x H). Absorber layout comprises 24, 36 and 48 inch absorbers. An overhead crane spans the entire facility. The positioner system is configured as roll over azimuth with a lower elevation over azimuth for pick-u p and small elevation angle measurements. Different sizes of masts and roll positioners are available, depending on the AUT. Instrumentation is based on a HP 8753. Software is based on the FR-959 Plus. Antenna measurement results show the performance of the facility.
GE Aircraft Engines (GEAE) in Cincinnati, Ohio recently built a compact range facility to operate from 800 MHz to 18 GHz. The design process included visits to other :recently completed facilities so that industry best practices could be incorporated into the design of the state-of-the-art facility. The facility includes a 30 x 30-x 65-ft. chamber, corner fed blended rolled edge reflector, Chebyshev Multilevel absorbers, a 12-ft. diameter tu rntable, and rail mounted gantry crane for target mounting, Facility design, chamber, reflector, absorber, target handling and fire protection systems are discussed.
This paper presents the electromagnetic effects of low level non-random error on a compact range reflector surface. Physical optics computational analyses are presented illustrating the effect. Furthermore, actual case study results from the new GE/NT Compact Range Facility are also shown in which a non-random error of 3 mil RMS was discovered. Finally, a process is presented in which the non-random nature of the error was analyzed and removed from the surface. Before and after field probe measu rements illustrate the dramatic effect of such error.
An important source of error in a compact range antenna pattern measurement is the deviation of the quiet-zone field from the perfectly fiat amplitude and phase of a plane wave field. Although some guidelines and rules of thumb exist that relate the quiet-zone field to the error in the measured antenna patterns, the error or perturbation is dependent on the particular type of antenna that is being measured. For example, the non-ideal quiet zone field will produce very different errors for a small horn than for a large phased array. A realistic error budget or uncertainty analysis of the compact-range measurement requires knowledge of the antenna pattern uncertainty as a function of the quiet-zone field and the particular antenna of interest. A simulation method is derived using reciprocity that allows one to quantify the perturbations induced in a given antenna pattern when the quite-zone field distribution is known. This is particularly useful, since one typically has a fair estimate of the antenna pattern and has measured data of the quiet-zone field. The simulation is tested by modelling the antenna as a collection of elemental current sources and simulating the quiet-zone field as generated by elemental current sources. Using this simple simulation model, a closed-form near-field antenna pattern may be calculated for comparison with the more general computer simulation derived from reciprocity.
Many aircraft radome structures are designed to operate simultaneously over multiple RF bands and incident polarizations. Critical parameters must be measured over the electrical apertures of the radome and across each operating band. Automated measurement techniques are required to efficiently collect the large volume of test data required. A modular broadband feed assembly has been developed to allow the simultaneous collection of multi-band, multi-polarization data on a compact range without the need to mechanically change feeds. The feed assembly utilizes a sinuous antenna as the radiating element and is capable of operation from 2-18 GHz with electronically selectable polarization states. Feed design criteria as they relate to compact range antenna and radome measurements are discussed. Of primary importance are reflector illumination pattern, linear polarization cross-polarization level, and circular polarization axial ratio. Polarization switching requirements for a specific test application are defined and the physical implementation of the integrated feed assembly is described. Measured feed and quiet zone performance data is presented for this application. The polarization switching configuration can be readily modified to support other applications.
Nowadays, highly accurate antenna pattern and RCS measurements are performed in compensated compact range test facilities, which fulfil the stringent space requirements for measurements up to 500 GHz and more. As the suppression of diffracted fields from the reflectors mainly determine the quiet zone field performance, the reflector edge treatment is an important design parameter for this type of test facilities. Within the present paper a novel serration design wm be shown. The analyses as well as measurement results exhibit a clear improvement of the quiet zone field performance when compared to previous solutions. The new serration design was implemented and proved with the CCR 20/17 of Astrium GmbH at the Munich University of Applied Sciences.
Compact ranges have found wide use in the pa rametric characterization of high performance radomes such as those found on modern military aircraft. A properly designed compact range facility provides a stable, repeatable test environment suitable for the measurement of small variations in antenna boresight position (beam deflection), antenna pattern distortion, and transmission loss. Radomes have increased in complexity from small structures housing a single antenna to multi-band, multi-system structures large enough to stand inside. Similarly, compact range reflectors have increased in commercial units available today provide quiet zone extents of 12 feet or larger. This paper describes the system design and performance of a compact range test facility designed to test a C-130 Combat Talon II nose radome measuring 7 feet in length and diameter. The facility was constructed at Robins AFB, GA, and is in operation. A description of the facility and its major subsystems is given. Sizing of the chamber and layout of equipment is described. Chamber electromagnetic design considerations are discussed. Electromagnetic design was complicated by the physical size of the structure required to mount the radome, by the fact that multiple antennas and gimbals are present inside the radome during testing, and by the need to use a broad band feed to eliminate mechanical feed changes. Absorber layout and control of spurious reflections is discussed. Electromagnetic performance data is presented.
This paper describes the alignment procedure for using a spherical near-field measurement facility to determine incident fields throughout a spherical volume. This information can be used, for example, to characterize an anechoic chamber or the quiet zone of a compact range. A probe is mounted on a standard roll-over-azimuth positioner and aligned looking out of the sphere so its aperture maps out the surface of a sphere. The probe measures the amplitude and phase of the fields incident on the sphere. This method differs from the standard spherical near-field measurement where the source antenna serves as the probe and is looking into a sphere containing the test antenna.
Microwave Instrumentation Technologies (MI Technologies) in cooperation with Hollandse Signaalapparaten B.V. (Signaal) and the Royal Netherlands Navy has designed and produced a compact antenna test range to specifically address the unique testing requirements imposed in the testing of active phased array antennas. The compact range was built specifically to test Signaal's new Active Phased Array Radar (APAR) prior to introduction into various naval fleets throughout the world. This reversible Compact Antenna Test Range (CATR) allows antenna testing in both transmit and receive modes. The measurement hardware is capable of testing both CW and pulsed waveforms with high dynamic range. In addition to conventional antenna pattern measurements the system is capable of measuring EIRP, Gff and G/NF, as well as providing analysis software to provide aperture reconstruction. A special Antenna Interface Unit (AIU) was designed and built to communicate with the Beam Steering Computer which controls the thousands of T/R modules which make up the APAR antenna system. A special high power absorber fence and other safeguards were installed to handle the transmit energy capable of being delivered from the APAR antenna system.