AMTA Paper Archive

 

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Instrumentation
Portable RCS diagnostic system
R. Harris,B. Freburger, D. Maffei, R. Redman, November 1993
This paper describes the most recent version of the Model 200 portable RCS diagnostic radar. The Model 200 was designed to provide high-resolution RCS measurements in unprepared rooms indoors as well as on outdoor ranges. The system can provide real aperture measurements, ISAR measurements, or SAR measurements without changing system configuration.
Analytic spherical near field to near/far field transformation, An
T.K. Sarkar,A. Taaghol, P. Petre, R.F. Harrington, November 1993
An efficient and accurate spherical near field to far field transformation without probe correction is presented. The indices m of the Legendre polynomials is summed up analytically, thereby reducing the computation time. Computations with both synthetic and experimental data illustrate the accuracy of this technique.
Algorithm for editing RFI from antenna measurements
R.B. Dybdal,G.M. Shaw, November 1993
Techniques for editing RFI from antenna measurements are developed for vector network analyzer instrumentation, and include the processing within the analyzer. An algorithm was devised for identifying data that may contain RFI; this algorithm is based on the electrical size of the antenna. Once data containing RFI are identified, extrapolation techniques based on the electrical size of the antenna are used to produce continuous data.
Dual-frequency,dual-polarized millimeter wave antenna characterization
J.P. Kenney,D. Mooradd, E. Martin, L.D. Poles, November 1993
The radiation characteristics for a dual-frequency, dual-polarized millimeter wave antenna for a radar operating at 33 and 95-GHz were measured at the Ipswich Research Facility. On-pole and cross-pole radiation patterns were measured using the 2600 foot far field range. In this paper we'll discuss the general design of the antenna feed system and the instrumentation ensemble used to perform the far field characterization of this high performance large aperture dielectric lens antenna.
Ground-to-air RCS diagnostic system
R. Harris,A. Strasel, B. Freburger, C. Zappala, M. Lewis, R. Redman, November 1993
The initial phase of METRATEK's new Model 300 Radar System has been installed at the Navy's Chesapeake Tests Range (CTR) at Patuxent River, MD. This ground-to-air Multimode, Multifrequency Instrumentation Radar System (MMIRS) is a high-throughput frequency-and-polarization agile radar that is designed to drastically reduce the cost of measuring the radar cross section of airborne targets by allowing simultaneous measurements to be made at VHF through Ku Band.
High duty instrumentation radar transmitters
F.A. Miller, November 1993
Today's requirements for dynamic Radar Cross Section (RCS) test data set new demands upon instrumentation Radar systems. Transmitters must deliver high power and operate at high data rates. Additionally, noise floor reduction of coherent spurious signals improves raw data and minimizes the need for manipulation of data.
High-speed, pulsed antenna measurements using the Scientific-Atlanta Model 1795P
O.M. Caldwell, November 1993
Characterizing antennas under pulsed RF conditions has focused attention on a class of measurement challenges not normally encountered in CW measurements. The primary problems often include high transmit power, thermal management of the AUT, and a close interaction between the antenna and its transmitting circuitry. This paper presents instrumentation techniques for pulsed RF antenna measurements using the Scientific-Atlanta 1795P Pulsed Microwave Receiver as an example of a commercially available solution applicable to both active and passive apertures. Emphasis is given to measurement speed, dynamic range, linearity, single pulse versus multiple pulse measurements, pulse width, pulse repetition frequency (PRF), frequency coverage, system integration and automation, and suitability of equipment for antenna range applications.
V-band and W-band upgrade for a compact RCS range
S. Yadre, November 1993
This paper will describe the requirement, design, implementation, and performance evaluation of MMWRCS measurement subsystems to be integrated with an existing RCS measurement system in the Sikorsky Compact Range in Bridgeport, CT. The subsystems will operate at V-band (58-62 GHz) and W-band (92-98 GHz). The requirements to test at V-band and W-band is driven by limitations of quiet zone physical volume. The Harris model 1606 reflector system produces a 6 foot diameter zone of virtual uniform amplitude and phase. Therefore scale models are fabricated for test. This translates to approximately 1/6 scale of contemporary Sikorsky Helicopter designs. Testing at 60 and 95 GHz will provide accurate simulated full scale RCS data at X and Ku-bands.
Planar near-field alignment
D. Kremer,A. Newell, A. Repjar, A. Trabelsi, C. Rose, M. Pinkasy, November 1993
This paper will discuss one method of characterizing the scan plane for planar near-field measurements. The method uses a theodolite auto-collimator, a laser interferometer, an electronic level and an optical square. The data obtained using these techniques are first used to make alignment corrections to the scan plane; then new data are used to determine the best fit for the realigned scan plane. The normal to this place is referenced using a permanently placed mirror. In addition, the final data obtained can be used in probe position-correction techniques, developed for planar near-field measurements.
Scattering by a simplified ship deckhouse model
B. Badipour,M.,J. Coulombe, T. Ferdinand, W. Wasylkiwskyj, November 1993
To gain greater insight into the design of surface ships with reduced radar cross-section characteristics, a structure resembling a ship deckhouse was physically modeled and measured. The structure was represented as a truncated pyramid. Four scaled pyramids were fabricated, all identical except for the radii of the four vertical (slanted) edges. The pyramids were measured at the University of Massachusetts, Lowell Research Foundation, submillimeter laser compact range. Measurements were made a scaled X-band using a laser-based system that operates at 585 GHz with the pyramids scaled at a ratio of 1:58.5. These shaper were measured at 0.75 degrees depression angles on a smooth metal ground plane at both HH and VV polarizations. The goal of this study was to determine if small changes in the radius of the curvature of the slanted edges could significantly affect the radar cross-section of the pyramid. In this paper the results of measurements of the pyramids will be presented. The data are compared with computer code predictions and the differences are discussed.
RCS measurements of circular patch antennas
A.S. Ali,B.W. Deats, November 1993
There has been a great deal of interest in microstrip antennas and arrays in the past decade or so due to their low cost, light weight, and conformability. Most research to date on microstrip antennas has been focused on developing techniques for characterizing their radiation properties. However, interest in evaluating the scattering properties of such antennas is increasing. The RCS of three configurations of circular patch antennas have been measured versus frequency and are compared to Moment Method predictions; a single open-circuited element, a single element terminated in a 50 ohm load, and a 3 x 3 array of open-circuited elements. In most cases, the measurements and predictions are in good agreement.
Characterization of aeronautical antennas for INMARSAT communication
S. Mishra,J. Moraces, J. Smithson, J.G. Dumoulin, P. Charron, November 1993
Aeronautical SATCOM systems for INMARSAT typically employ circular polarized electronically or mechanically steered multi beam antennas. Characterization of thee antennas requires extensive measurements that differ from conventional antenna pattern measurements. Some of these are: A. Multiple frequently CP gain, axial ratio, and discrimination measurements over a hemisphere for a large number of beams. B. Noise temperature and G/T measurements C. Carrier to multipath rejection D. Intermodulation characteristics E. Receiver and Transmitter system characteristics Details of instrumentation and procedure for these tests are presented with special emphasis on issues such as measurement speed, accuracy and processing of large amounts of data.
High-speed, pulsed antenna measurements using the Scientific-Atlanta Model 1795P
O.M. Caldwell, November 1993
Characterizing antennas under pulsed RF conditions has focused attention on a class of measurement challenges not normally encountered in CW measurements. The primary problems often include high transmit power, thermal management of the AUT, and a close interaction between the antenna and its transmitting circuitry. This paper presents instrumentation techniques for pulsed RF antenna measurements using the Scientific-Atlanta 1795P Pulsed Microwave Receiver as an example of a commercially available solution applicable to both active and passive apertures. Emphasis is given to measurement speed, dynamic range, linearity, single pulse versus multiple pulse measurements, pulse width, pulse repetition frequency (PRF), frequency coverage, system integration and automation, and suitability of equipment for antenna range applications.
Lockheed's large compact range
A.J. Kamis, November 1993
Lockheed has recently completed the construction of a Large Compact Range (LCR) for antenna and RCS measurements. The dimensions of the facility are 60' (h) x 100' (w) x 120' (l) with a 20' x 20' cylindrical quiet zone and operational capabilities from 0.1 to 18.0 GHz. The requirement to measure low RCS levels in a room which is smaller that the desired has resulted in a unique system design. Elements of this design include a feed pit, a feed hood, and a rolled edge reflector; special absorber layouts to minimize background scattering, a high performance instrumentation radar, fast ring down feed antennas, and a unique string suspension and positioning system. This paper presents the various sub-systems that make up the LCR along with chamber validation methods and preliminary performance data. The subsystems listed in this paper are LCR's: Reflector, radar system, feed antennas, feed positioner, absorber, target handling equipment, and string positioning system. Initial design requirements are listed for some sub-systems along with range characterization data such as un-subtracted clutter levels, background subtraction performance, and theory vs. measured data for some simple conical shapes.
In flight VHF/UHF antenna pattern measurement technique for multiple antennas and multiple frequencies
J.S. DeRosa,D. Warren, November 1993
The Precision Airborne Measurement System (PAMS) is a flight test facility at Rome Laboratory which is designed to measure in-flight aircraft antenna patterns. A capability which provides antenna pattern measurements for multiple VHF and UHF antennas, at multiple frequencies, in a single flight, has recently been demonstrated. A unique half space VHF/UHF long periodic antenna is used as a ground receive antenna. Computerized airborne and ground instrumentation are used to provide the multiplexing capability. The new capability greatly reduces time and cost of flight testing. The design, construction, and calibration of the half-space log-periodic ground receiving antenna is discussed and the ground and airborne segments of the instrumentation are described.
Experimental range facility for RCS measurement and imaging research
J. Burns,D., Jr. Kletzli, G. Fliss, November 1993
A small compact range measurement facility has been installed at the Environmental Research Institute of Michigan (ERIM) for research aimed at improving RCS measurement and radar imaging techniques. This paper describes the facility, which is referred to as the Experimental Range Facility (ERF). The ERF has two instrumentation radars; a Flam & Russell FR959 gated CW radar and a Hughes MMS-300 pulsed radar. The radars are connected to a suite of workstations, which support a variety of internally and externally developed radar imaging and data exploitation software. The ERF is also equipped with sophisticated target positioning control and sensing equipment.
New antenna metrology and radar cross section facility at the U.S. Army Redstone Technical Test Center
J.B., Jr. A. Johnson,W.S. Albritton, November 1993
The U.S.Army Redstone Technical Test Center (RTTC), Test and Evaluation Command, has developed a comprehensive antenna metrology and Radar Cross Section (RCS) evaluation facility. This facility features the compact antenna test range technique for millimeter wave measurements and the near-field scanning technique for microwave measurements. This paper described RTTC's use of these measurement techniques, instrumentation with PC Windows based automation software, anechoic chambers, and types of tests performed. Planned future thrust areas are also discussed.
Minimum time for RCS measurements
D. Mensa,D. Wirtz, November 1993
The design of many modern RCS instrumentation systems is driven by the time required to complete a measurement which establishes the throughput rate of the RCS facility and therefore impacts the operating cost and efficiency. Time considerations are of particular importance when wideband systems are used to measure large targets with low RCS because multiple observations are required to span the frequency band or to increase sensitivity by coherent integration. Although significant improvements have been made to minimize inefficiencies in instrumentation systems, the fundamental limit of measurement time is governed by physical considerations of power, energy, noise, target dimension, and RCS. Evaluating the performance of a particular radar design can be facilitated by comparing the predicted measurement time with a theoretical optimum. The purpose of this paper is to develop estimates of the minimum measurement time under optimum conditions. Although likely precluded by practical considerations, the theoretical limits provide estimates of the maximum degree of radar performance and measures of optimality in practical systems.
Dynamic Radar Cross Section Measurements
James Tuttle, November 1993
Unique instrumentation is required for dynamic (in-flight) measurements of aircraft radar cross section (RCS), jammer-to-signal (J/S), or chaff signature. The resulting scintillation of the radar echo of a dynamic target requires special data collection and processing techniques to ensure the integrity of RCS measurements. Sufficient data in each resolution aspect cell is required for an accurate representation of the target's signature. Dynamic RCS instrumentation location, flight profiles, data sampling rates, and number of simultaneous measurements at different frequencies are important factors in determining flight time. The Chesapeake Test Range (CTR), NAVAIRWARCENACDIV, Patuxent River, Maryland, is a leader in quality dynamic in-flight RCS, J/S ratio, and chaff measurements of air vehicles. The facility is comprised of several integrated range facilities including range control, radar tracking, telemetry, data acquisition, and real-time data processing and display.
20 GHz active phased array characterization
J.P. Kenney,E. Martin, L.D. Poles, November 1994
The radiation characteristics for an active phased array receive antenna operating at K Band were measured at the Ipswich Research Facility. On-pole and cross-pole radiation patterns were measured for several scan angles. In this paper we'll discuss the general design of the antenna and the instrumentation ensemble used to perform the far field and near field characterization of this antenna. Measurements taken on a 2600 foot far field range vs. a near field planer scanner are compared.


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