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In general, the RF test setups of antenna test facilities are designed and optimized for antenna pattern and gain measurements. However, the operation of test facilities, especially the here considered 'Double Reflector Compact Ranges', can be extended, so that they can also be used for RCS testing. A simple and very practical expansion of the RF antenna test setup - while maintaining the real-time capability - can be achieved with the aid of a hardware gating system. With this type of setup, RCS measurements have successfully been performed in the Compensated Compact Ranges of EADS Astrium. The applied gating system was the high resolution Hard- gating System HG2000 of EADS Astrium, developed together with the Munich Univ. of App. Sciences. Within this paper, the applied facility and the gating system will be described firstly. Subsequently, the modified test setup and the test results obtained by calibration measurements will be shown. They will give an indication of the achievable resolution for the extended test system w.r.t. object size detection and resulting amplitude dynamic range.
This paper describes the methodologies and processes used for the development, installation, alignment and qualification of a Compact Range Rolled Edge Reflector purchased by the MIT Lincoln Laboratory and installed at their test facility located at Hanscom Air Force Base. The Ohio State University, under contract to MIT Lincoln Laboratory, performed the electromagnetic design and analysis to determine the desired surface shape and required mechanical accuracy of various zones of that surface. The requirement for operation over a very broad frequency range (400 MHz to 100 GHz) resulted in a surface specification that was both physically large (24 ft × 24 ft) and included extremely tight tolerance requirements in the center section. The mechanical design process will be described, including the generation of a solid “Master Surface” created from the “cloud” of data points supplied by The Ohio State University, verification of the “Master Surface” with The Ohio State University, segmentation of the reflector body into multiple panels, design, fabrication and factory qualification of the structural stands, panel adjustment mechanisms, and panels. Results of thermal cycling of the reflector panels during the fabrication process will be presented. The processes used for installation of the reflector and the alignment of each panel to the “Master Surface” will be presented and discussed. Final verification of the surface accuracy using a tracking laser interferometer will be described. Color contour plots of the reflector surface will be provided, illustrating the final surface shape and verifying compliance to the surface accuracy requirement
CAMELIA is one of the three anechoïc chambers of the French Atomic Energy Center (CEA). It is equipped with a compact range reflector and a pulsed radar allowing antenna and RCS measurements from 800 MHz to 18 GHz. Below 800 MHz, measurements are made with different kind of antennas (log- periodic, horns, arrays…). Nevertheless, measurements at such low frequencies suffer from serious artifacts due to coupling effects. This paper describes a particular array we designed, realized and characterized to cover the 100 MHz – 2000 MHz bandwidth. Although the antenna diagram shape was the most constraining factor, the ability to cover the whole bandwidth with as few handling as possible was the major issue.
Large satellites antennas are best measured in specially designed compact range systems designed for aerospace applications, located in a clean room environment. This testing requires very large, high accuracy positioners to accommodate full size satellites. Typical requirements include positioning accuracy of 0.003 degrees for a payload of 5 tons. ORBIT/FR has recently delivered to Astrium a unique payload positioner system specifically built for such high accuracy applications. This positioner provides the ability to accurately locate satellite payloads in the Astrium compact range system chamber to within the tolerances necessary to perform all radiated payload tests for specification compliance. In order to realize the required accuracy performance, an extremely stable positioner construction is required, such that near-perfect orthogonality between the rotary axes is maintained, and minimum structural bending is exhibited. This level of construction quality is realized by a unique elevation axis bearing configuration, in conjunction with an adjustable counter-weight system. In addition, very high accuracy absolute optical encoders are used; these exhibit higher accuracies than the traditional Inductosyn type of encoder. All axes are equipped with brakes on the primary axis to eliminate backlash. Alignment requirements further accentuate the need to be able to position to within a few thousandths of a degree. This in turn places difficult requirements on low speed operation and on the control system. This paper details the design and performance of such a positioning system as measured for two compact range installations utilized for satellite antenna testing applications.
As satellite communication systems grow increasingly complex, so has the need for spacebased phased array antennas. After these antennas have been designed and assembled, they need to be tested. This paper describes the new antenna measurement facility that NGST (Northrop Grumman Space Technology) has installed to that end. This includes descriptions of near-field and compact ranges that are integral parts of the Phased Array Assembly, Integration and Test Area.
A calibration uncertainty analysis was conducted for the Air Force Research Laboratory’s (AFRL) Advanced Compact Range (ACR) in 2000. This analysis was a key component of the Radar Cross Section (RCS) ISO-25 (ANSI-Z-540) Range Certification Demonstration Project. In this analysis many of the uncertainty components were argued to be small or negligible. These arguments were accepted as being reasonable based on engineering experience. Since 2000 the ACR radar has been replaced with an Aeroflex Lintek Elan radar system. A new measurement uncertainty analysis was conducted for the ACR using the Elan radar and for a general (non-calibration) target. We present results comparing the previous results to the current analysis results.
A continuous discussion exists in comparing the theoretical and measured performance differences of serrated versus rolled edge treatment for compact ranges. Since rolled edge reflectors are significantly more expensive, the price / performance trade off needs to be well justified. Such an evaluation is very application dependent. A large amount of measurement data has been published for serrated edges, and comparisons between serrated edge theoretical data and measurement data shows good agreement. However, only a very small amount of measuerement data has been published for rolled edge compact ranges. For evaluation purposes, ORBIT/FR built a rolled edge and a serrated edge compact range. Both were designed for 2 ft quiet zones and have equal focal length and offset angle. Measurement data was acquired for both configurations, and is presented here.
Instead of moving the antenna under test (AUT), it is possible to change the direction of arrival of the plane wave. This is done moving the feed horn in the reflector focal area. Scanning the feed antenna allows measurement of the AUT without moving it. This is useful in cases, when moving the AUT is difficult or even impossible. In the Compact Payload Test Range (CPTR) at ESA-ESTEC, the linearity of the scanning has been measured before [1] and scanning has been proven to be nearly linear (1%). What was not known, is that how do the quiet zone properties (amplitude and phase ripple) change during the scanning. It will be shown the basic properties of the quiet zone remained almost the same, but some other properties of the range were found.
Highly accurate antenna and payload measurements in antenna test facilities require highly accurate alignment and boresight determination. The Angle of Arrival (AoA) of the plane wave field in the quiet zone of the CCR Compensated Compact Range CCR 75/60 of EADS Astrium GmbH, installed at Alcatel Space in Cannes . France, has been measured using three different methods (optical geometrical determination using theodolites, Radar Cross Section (RCS) maximization, planar scanner phase plane alignment). The proposed paper describes the three methods and the performed measurement campaign and provides the correlation between the resulting angles via a comparison of the results. The achieved absolute worst case values of lower than 0.005° demonstrates the high level of accuracy reached during the campaigns.
This paper describes and discusses relevant performance issues concerning the quiet zone illumination of a baseline interferometer antenna using a compact range system. Typical baseline interferometer antennas are utilized for precision direction finding applications, and are designed on the principle of detecting the incoming phase wave front as a means to determine the direction of arrival of the detected signal. Quiet zone illumination of the antenna using a compact range deviates from the ideal illumination by introducing some levels of amplitude and phase taper and ripple. Unwanted relative differences in the illumination of the individual elements of the interferometer antenna will introduce errors in the subsequent analysis of the direction finding accuracy and precision of the array. Sources of these errors are examined in this paper, and relevant compact range performance trade-offs are discussed to optimize the range. Considerations are given to both utility of the range, as many interferometer antennas are broadband EW type arrays, and thus require single feed, single test broadband measurements, as well as to the accuracy in characterizing the performance of the interferometer over its full operating bandwidth. In addition, this paper discusses the analysis of high precision compact range field probe data, and the subsequent application of relevant statistical parameters to characterize the data. The analysis techniques utilized highlight the important performance features required of the compact range to effectively test baseline interferometers. The implementation of an automated utility is described that applies the relevant corrections, and applies the statistical algorithms, to the data to effectively reduce the data and summarize it in a fashion that provides immediate utility to the field probe test operator.
MTI Technology and Engineering Ltd. in Israel has installed an antenna test facility for the development and production testing of communication link antennas. Link antennas are typically high gain, medium size (< 2 ft) and medium to high frequency (10 to 50 GHz), with strict requirements on sidelobes, back-radiation and cross-polarization. Production testing is typically done on the main cuts. The facility is also used for PTMP and WLL antennas down to 2 GHz. This is an ideal requirement for a small size compact range. The ORBIT/FR single reflector compact range with a cylindrical quiet zone of a size 4 x 4 ft (diameter x length) was selected. The performance is compliant to international regulations (e.g. FCC, ETSI, DTI-MPT), and has a cross polarization as low as –40 dB for 0.4-m antennas. The total chamber size is 31 x 18 x 15 ft (L x W x H). The positioner system is roll over model tower over azimuth over lower slide. The instrumentation is Agilent 8530 based. The system was installed and qualified in late 2002. Qualification was performed from 2 to 50 GHz for quiet zone field probing and antenna sidelobe level accuracy testing. A system description, as well as an excerpt of the qualification data are presented in the paper.
The Intelsat-IX spacecraft carries a C- and Ku-Band payload. It provides coverages from five different orbital locations over Atlantic (AOR) and Indian (IOR) ocean regions. The feed arrays for the C-band multifeed offset parabolic reflector antennas were designed, manufactured and tested by EADS Astrium GmbH in Munich, Germany. Design drivers for the antenna subsystem were the high power requirement for the transmit antenna and stringent isolation specification for both transmit and receive antennas. The final designs feature as many as 145 feed horns and up to ten switches. Due to the complexity of the beam forming network and the large number of SCRIMP (Short Circular Ring loaded Horn with Minimized Cross-Polarization) horns at every feed array a special test philosophy was introduced in order to detect any malfunction of the array at an early stage of the antenna assembly and integration. This paper will present details of the applied test sequence starting at the initial beam forming network measurements and the intermediate near-field feed testing under extreme environmental conditions up to the final antenna testing in a compact range at unit and at spacecraft level. The used inhouse data evaluation software platform allows the evaluation of any measurement at any stage of the testing sequence independent of the actual applied losses and /or design error allocations.
This paper describes the new ORBIT/FR StingRay Gated-CW radar implementation that provides both performance and speed improvements over those previously utilized and fielded in RCS measurement systems. The radar is implemented using one or multiple pulse modulators used to provide gating of the transmit and receive signals, in conjunction with the new class of Performance Network Analyzer recently introduced by Agilent Technologies. The radar features an order of magnitude improvement in speed over that previously offered using implementations with the Agilent 8510 or 8530 network analyzer/receiver. In addition, base sensitivity improvements are realized, and the radar is more flexible with user selection among many IF bandwidth settings now available. The physical profile of the radar is also improved, meaning that additional performance gains may be realized by creating a more efficient packaging scheme where the radar may be located closer to the radar antennas, either in a direct illumination configuration or in a compact range implementation. These factors, when considered in aggregate, result in the new ORBIT/FR StingRay Gated-CW radar offering that provides a higher performance-to-cost value trade-off than was previously available to the RCS measurement community.
The ability to perform radar cross section (RCS) measurements, where background subtraction is applied, requires a measurement system that is very stable throughout the measurement time span. Background subtraction allows the measurement of low RCS components mounted in high RCS test bodies by permitting the scattering from the test body to be removed by coherently subtracting the test body (background) RCS from the target RCS measurement. Amplitude and phase variation of the illumination signal between the time that the target and background measurements are performed will limit the quality of subtraction achievable. Modern instrumentation radars can maintain extraordinary stability when exposed to controlled temperature environments, but controlling the temperature of a large compact range can be difficult. Other components of the measurement system, such as the reflector, can also be influenced by temperature fluctuations. Methods of controlling the thermal environment can have significant consequences. Lessons learned in the Advanced Compact Range at the Air Force Research Laboratory will be described.
The RFDM (Radio Frequency Development Model) of the PLANCK satellite has been tested in the Alcatel Space CATR (Compact Antenna Test Range) in 2002. The antenna was constituted by a telescope designed by the University of Minnesota for the Archeops balloon borne payload, and corrugated horns manufactured by electroforming process. At the beginning, characterization of the quiet zone of the Compact Range with a planar scanner is presented. A full amplitude/phase/co-pol and amplitude/cross-pol discrimination probing of a 5m x 5m quiet zone at 100 GHz is displayed. Then, we focus on measurements of the antenna response at 100 GHz performed in 4ð steradian with a dynamic range better than 100 dB. We cross-validate the measurement results with the RF predictions of the numerical model using the GRASP8 software developed by TICRA.
Undesirable antenna to antenna coupling has caused EMI problems between the WSC-6 SATCOM system and various systems in many shipboard installations. Long term solutions are currently being explored to resolve this EMI problem, which include adaptive interference cancellers and redesign of the WSC-6 feed and subreflector. However, these solutions are expensive and require several years to develop. An intermediate solution using RAM shrouds around the main reflector and subreflector edges of the WSC- 6 antenna has been proposed. The RAM shrouds were designed to reduce the spillover and diffraction of the antenna while having minimal impact on the antenna performances. A lightweight RAM was chosen to minimize the weight increase of the antenna. A prototype unit with the proposed modifications has been fabricated, assembled and tested in a tapered anechoic chamber, a near-field range, and a compact range. Significant reductions in the WSC-6 antenna sidelobes and backlobe have been verified via these measurements. Highlights of these modifications are described. Measured data (near field, compact range, tapered chamber, and shipboard) are presented.
In 2001, the Boeing 9-77 Indoor Compact Range successfully passed the range certification process. In preparation and during the On-Site Review in October 2001, RCS data on a pair of ultraspheres for the dualcalibration were collected. In this paper, we analyzed the data with regard to uncertainty analysis. An empirical approach for compensating the systematic error is presented.
Originally installed in 1992, the Advanced Compact Range (ACR) at Wright-Patterson Air Force Base was completely aligned using a Leica multi-theodolite measurement system. The Coherent Laser Radar (CLR) System provides an automated precision measurement capability which can gather significantly more data permitting a more complete characterization of the range in a relatively unobtrusive manner. This paper presents the process and results of applying Laser Radar Metrology as an optical range re-qualification tool within the Air Force Research Laboratory’s ACR.
A compact range was recently constructed at the Applied Physics Laboratory to measure broad-beam, fan-beam, and pencil-beam antennas (max aperture: 1 meters). Chebyshev absorber treatments, lightweight composite reflector, foam column mount for light-weight antennas, automated measurement software, and a novel feed spillover rejection algorithm are the technology elements implemented in this compact range measurement facility. This paper will describe a trade study that APL performed before the compact range antenna facility was built. Solutions to some of problems that were encountered during the construction will be discussed as well as the overall performance of the facility. The measurement of a broad-beam antenna will be compared to calculated pattern. This measurement will highlight the advantages of using a software range gate that was recently developed.
This paper presents a method for correcting RCS data obtained from objects extending beyond the boundaries of the test zone into the transition region of a large compact range collimator. The technique, exploiting the non-zero irradiation in the transition regions, uses results of calculated or measured field probes in conjunction with an image-based decomposition of the target angular response to correct for the field taper. The taper correction is developed as a weighting function applied to the spatial distribution with frequency-dependent coefficients derived from the field probes; the corrected RCS response is then obtained by an inverse operation. The paper addresses the conceptual notions of the approach and the limitations inherent to the underlying assumptions. Results of tests on canonical and actual targets are shown to demonstrate the applicability of the technique.