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.)
Characterization of radiated EMI by means of near zone measurements is examined by computer simulations. Electric field radiated by a test structure is expanded in spherical wave modes. The influence of the number of spherical wave modes on the accuracy to predict the maximum far-field magnitude and the total radiated power is examined. The examinations of this paper support the electric field measurements of small equipment at small measurement distances in the standard radiated EMI frequency range 30 - 1000 MHz. Results are presented as a function kr0, where k is the wave number and r 0 is the radius of the minimum sphere which fully encloses the EUT. Results of this paper give valuable guidelines for choosing an appropriate number of measurement locations for predicting the far field by means of a near-zone measurement.
The tapered chamber has been used for more than 35 years for mainly lower-frequency antenna measurements. The basic design of the tapered chamber has not changed significantly since its inception. Tapered chambers provide better quiet zone fields by placing the feed antenna's phase center at the vertex of the tapered walls, virtually eliminating reflections from the side walls. Recent innovations that better chamber versatility include an ultra-wideband SBH feed antenna [1,2], a less visible rotating support structure for the AUT and a new Chebyshev-based absorber treatment [3]. Utilizing these new features, a tapered chamber has been designed to have a large bandwidth, yet have an overall structure that is small enough to allow portability. This paper describes a chamber that operates from 400MHz to 40GHz and has an overall length less than 30' long. Structure, components, and field results are presented in this paper.
Errors arising in the measurement of reflection coefficient are identified and analyzed. The presence of multiple reflections due to poor connectors, transmission line discontinuities, and terminal loads is described, modeled and applied. Various measurement scenarios are analyzed, and measured results are presented as a guide for laboratory troubleshooting and as a validation of the measurement models. Improvements to Vector Network Analyzer calibration methods are proposed, including computer corrected calibration for one-port radiating elements and elementary improvements to two-port TRL calibration. An extensive error evaluation of the somewhat forgotten slotted line measurement is finally presented as a robust alternative, and computer automation, acquisition, and calibration of this measurement is outlined.
Over the last ten years, MRC has designed, fabricated, and installed a number of compact range reflector systems. This paper presents such reflector programs illustrating a variety of alternatives for reflector composition. Such programs include the MRC Scattering Measurements Lab (SML), the Air Force Research Lab's Advanced RCS Measurements Range (ARMR), Honeywell's Antenna Measurements Range, the new GE/NT Compact Range, and the new TRW Compact Antenna Test Range. Variations within these programs include single or dual-reflector configurations, single piece to panelized designs, and all composite to all aluminum construction. All approaches present excellent alternatives for various compact range needs.
In early 1999 a number of broadband absorbers were tested to evaluate their high power performance. In this paper the procedure for the tests is described and some results are presented. Later this year some additional tests were done to see effects of cooling by forced air. A conclusion is drawn that a standard procedure for verification of the high power capabilities of absorbers is needed in industry and that existing high power absorber does not necessarily meet specification as stated.
The increase of output power for telecommunication satellites give constraints on design and manufacturing of antenna reflectors. Any non-linearity, such as a junction between two conductive materials, is a potential generator of inter-modulation products (PIM's). ALCATEL SPACE INDUSTRIES implemented a PIM test bench for reflectors. The objective is to validate, as early as possible in the satellite program, the reflector design, with regards PIM specification. The test principle consists in two separate transmit channels, each one having a single carrier at a well selected frequency. This configuration avoids the generation of PIM's by the bench itself. A basic conditions relevant to the output power for the test is that the flight conditions must be covered, in terms of Power Flux Density (PFD), on the reflector surface. The post-processing of the test results is based on a model whose parameters allow the following correlation : - variation of a given PIM order versus transmit power - variation between two consecutive PIM odd orders for a given transmit power. The model allows to correlate the reflector performance in terms of PIM to the flight conditions and to the customer's specification.
A fully-polarimetric compact range operating at 524 GHz has been developed for obtaining Ka-band RCS measurements on 1:16th scale model targets. The transceiver consists of a fast switching, stepped, C W , X-band synthesizer driving dual X 4 8 transmitmultiplier chains and dual X 4 8 local oscillator multiplier chains. Software range-gating is used to reject unwanted spurious responses in the compact range. A motorized target positioning system allows for fully automated sequencing of calibration and target measurements over a desired set of target aspect and depression angles. A flat disk and a dihedral at two seam orientations are used for both polarization and R C S calibration. Cross-polarization rejection ratios of better than 45 d B are routinely achieved. The compact range reflector consists of a 1.5m diameter aluminum reflector fed from the side to produce a 0. 5 m diameter quiet zone. Targets are measured in free-space or on a variety of ground planes designed to model most typical grou nd surfaces. A description of this 524 GHz compact range along with 30 ISA R measurement examples are presented in this paper.
The development and measured performance of a hologram type compact antenna test range (CATR) for submillimetre wavelengths are presented. A 60 cm diameter hologram has been designed for the 310 GHz CATR. The instrumentation used for the compact range performance verification is described. This includes a millimetrewave vector network analyzer with alternative source oscillator configurations. Finally, future improvements to the hologram CATR such as a dual-reflector feed system are discussed.
We have designed and are building a 30 foot diameter spherical near-field range with some unusual and useful features. The range is designed to test up to 10 GHz. The range design is a double gantry arm type, the RF probe is moved and the antenna is normally stationary. The antenna is mounted to an anti-spin bearing (on the azimuth arm) located coaxially over an azimuth positioner. The antenna can be held stationary or rotated to check for room reflections. The azimuth positioner rotates a post supporting an elevation positioner, which in tum rotates a counterweighted elevation probe arm. Holding the antenna stationary means the cables and waveguides are not moved or twisted during testing. Testing in a stationary position is more accurate when gravity or thermal loads are significant. High power RF testing is safer and cheaper with a stationary antenna.
Saab Ericsson Space and Ericsson Microwave Systems have recently completed the installation of a new efficient test facility. The facility is a fully automated test range designed for high th roughput of measurements. The facility is mainly used for tests of antennas for satellites and for mobile com munication. It is used as a far-field range for small antennas or as a spherical near field range for directive antennas. The frequency range covered is 0.8 - 40 GHz. A design driver for the facility was the logistics of measurements, short test time and easy access to the AUT during measurements. To achieve this, high speed positioners and easy access to the AUT via a drawbridge in the anechoic chamber were introduced. The computer controlled RF system allows the use of automatic mode switching to test the AUT in either receive or transmit mode and to change frequencies and mixers without operator intervention.
RATSCAT has pursued a wide gamut of technical enhancements and upgrades to its Mainsite and RATSCAT Advanced Measurement System (RAMS) locations. Acquisition of three radar systems has provided RATSCAT with the most capable radar systems available. RAMS is capable of acquiring full scattering matrix (FSM) data from 120 MHz to 36 GHz. Mainsite is capable of acquiring bistatic FSM data from 2 GHz to 18 GHz and monostatic FSM data from 1 GHz to 36 GHz. RATSCAT is pursuing unparalleled background levels through the acquisition of new pylon technology at RAMS and is expanding its target handling capability via construction of additional target storage as well as the addition of a mobile target handling shelter and new 50' and 14' pylons at Mainsite. RATSCAT has acquired a full feature data processing capability at both sites that uses a reflective memory interface between data acquisition and data processing resulting in faster validation of data cuts. Through acquisition programs and partnership with industry RATSCAT has improved their RCS test capability to become the technical leader in outdoor static RCS testing.
The Boeing Near Field Test Facility (NFTF) in St. Louis, MO was constructed in 1991 to conduct near field RCS measurements of production parts, models, and full-scale operational aircraft. Facility upgrades were identified in 1997 to support operational aircraft testing, such as the F/A-18 E/F. Target rotation mechanization, measurement antennas, and the test radar were identified as requiring upgrades. The target rotation hardware was upgraded to a 40-foot diameter turntable capable of handling production fighter aircraft. Antennas were mounted in an elevation box, which also contains the radar and an absorber aperture. The elevation box translates vertically, and pitches in elevation for different view angles. A new Lintek Elan radar, with a frequency range of 2ml8 GHz, 200 Watt Traveling Wave Tube (TWT) amplifiers, and Programmable Multi-Axis Controller cards (PMAC), controls all motion in the facility. In addition, modifications to the facility were completed to improve efficiency and ergonomics.
In this paper, a novel means of assessing the RF performance of modern helicopters at Aviation Applied Technology Directorate (AATD) is presented through a newly built facility called the Modular Helicopter Communications Measurement Facility (MHCMF). The MHCMF provides AATD personnel the ready ability to perform a wide range of communications measurements on a number of different helicopters. Based around a novel process of utilizing compressed air as a means to "float" the vehicle or helicopter under test (HUT) over a smooth concrete surface abutting the Felker Army Airfield at Fort Eustis, VA, the HUT is rotated under computer control and the radio frequency (RF) characterization of the HUT is acquired and displayed for the operator and antenna engineer as well.
This paper will describe the measurement series performed on Global Horn flight antennas to be used on the Intelsat IX satellite series. The work was performed by MEMCO under contract to Space Systems I Loral. The Global Horn antenna system provides highly isolated RHCP and LHCP beams that cover the earth disc, as viewed from synchronous orbit. The corrugated wall horn is designed to maximize the gain at the edge of earth coverage angle, which in this case is defined as plus or minus 9.8 degrees from the beam peak. The horn has near perfect E-and H-plane amplitude and phase equality to achieve low off-axis cross-polarization (-55dB) across the earth disc. A well-matched orthomode transducer (OMT) and low axial ratio polarizer complete the antenna assembly. The paper will describe the anechoic chamber measurement series and techniques used to measure the circularly polarized cross-polarization isolation values in the -50dB (A.R.=0.05 dB) to -60dB (A.R.=0.02dB) region. Bench measurements of the polarizer, which has a measured axial ratio less than 0.02dB, will also be presented. Directive gain measurements of the flight antennas will also be presented and discussed. The techniques presented in this paper are also used by MEMCO to design and measure circularly and linearly polarized probes and source antennas used in Nearfield Scanners and Compact Antenna ranges.
A networked antenna measurement system based on Intranet technologies allows users to undertake different aspects of the measurement process (data acquisition, instrument control and analysis) remotely. It also allows for the efficient transfer of data between different nodes on the network. At the David Florida Laboratory, a project is currently underway to upgrade the antenna measurement system to a graphical user interface (GUI), developed in the LabVIEW Version 5.0 environment. Integral to this upgrade is the development and implementation of data analysis applications and a network based on Intranet technologies. The antenna measurement software application functions over the Intranet as a clienUserver model, which is designed to support a number of clients functioning concurrently on different machines. The design of the network permits use of a single server providing the control and interface between a client operation i.e. the test conductor and the data acquisition system. This paper describes the steps taken thus far to upgrade the antenna analysis software and provide an overview of the client server architecture developed and implemented using LabVIEW.
A sophisticated, low-cost Configuration Management Database (CMD) has been developed for the Active Array Measurement Test Bed (AAMTB) at the Crane Division, Naval Surlace Warlare Center, Crane, IN (NAVSURFWARCENDIV). By choosing three flexible COTS programs that feature object oriented models, a common programming language, and ODBC compliance, the software development and project cost was minimized. This paper describes how the database provides recording and retrieval of comprehensive hardware and software configurations of measurement test scans. Details of the database structure, including its advantages and limitations, are also presented.
The maintenance, test, and repair workload for the Air Force's AN/MSQ-118 satellite ground-based receiving communication system has been transferred from the closing McClellan Air Force Repair Facility in Sacramento, California to Tobyhanna Army Depot located in Tobyhanna, Pennsylvania. The workload requires the support of four maintenance shops and two planar near-field ranges. The shops are the antenna repair, power supply repair, low-noise amplifier (LNA) repair, and radome repair shops. The near-field ranges are a 4' x 4' planar scanner used for antenna diagnostics and an 8' x 8' planar scanner used for certification of the repaired antenna-under-test (AUT). This paper will bring the AMTA community up to date on the status of the new Tobyhanna Antenna Repair Facility, focusing on the techniques and methods used to quantify the alignment and performance characteristics of the planar near-field antenna measurement system used for certification. With the relocation complete, test data obtained at both locations will be analyzed and compared to show differences between the baseline measurements taken at McClellan Air Force Base versus those taken at Tobyhanna Army Depot.
Dual gridded, shaped reflector antennas have been designed, manufactured and measured respectivily by ALENIA, AEROSPATIALE Les Mureaux and ALCATEL for the EUTELSAT "W" satellites program. The tight requirements, for coverage gain and cross-polar discrimination together with in-coverage cross-polar level less than 44 dB below the peak, required sophisticated techniques for design and measurements. ALENIA used optimisation and prediction techniques, which took into account thermal deformation effects and the multi-layer structure of the assembled dual gridded antennas. The optimisation process led to high performance antennas associated with the complex surface shapes. Moreover, including the actual manufactured reflector surfaces in the analysis, an excellent correlation between measurements and predictions have been obtained. Measurements were performed in the Alcatel Space Industries Compact Antenna Test Range in Cannes. ALCATEL invested into high polarisation purity illuminators and special hexapod tools in order to efficiently optimise the assembled antenna performance. The measurement optimisation process led to antennas which all met their requirements.
ARCS acquisition software for antenna and RCS measurements has been modified such that it is now based on LabWindows/CVI of National Instruments. With open system architecture, industry-standard tools and platform flexibility, new ARCS software delivers all components which are required for an advanced antenna and RCS measurement system. This means tht the portability and modularity of the software is increased considerably. Such a concept has the major advantage of simple adaptation/modification by the user, for instance by adding new menu pages. The virtual instrument concept of CVI guarantees easy adaptation of the newest interface technology, such as USB and firewire. Furthermore, there is a large base of instrument drivers which can be readily used to extend the measurement capabilities of ARCS in a minimum of time Special care is taken in the design of the user interface. This is to avoid complex procedu res for entering measurement parameters. Even less experienced operators must be comfortable with the software and be able to perform complex calibration and data acquisition procedures. Finally, a large number of application programs is written for advanced antenna and RCS calibration, microwave holography, ISAR imaging and frequency extrapolation techniques.
Design optimization and measurement of the Luneburg lens antennas are the focus of this paper. One of the important design aspects of an optimal Luneburg lens antenna is to construct a high performance lens with as low number of spherical shells as possible. In a uniform Luneburg lens, the gain is decreased and unwanted grating lobes are generated by reducing the number of shells. This deficiency in the radiation performance of the uniform lens may be overcomed by designing a non uniform lens antenna. The optimized non-uniform spherical lens antenna is designed utilizing the dyadic Green's function of the multi-layered dielectric sphere integrated with a Genetic Algorithm (GA)/Adaptive Cost Function optimizer. Additionally, a novel 2-shell lens antenna is studied and its performance is compared to the Luneburg lens. Finally, measured results for far field patterns and holographic images are shown for the Luneburg lens antenna using the UCLA's bi-polar near field facility.