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
    
    




Sort By:  Date Added   Publication Date   Title   Author

Polarization

Enhancement of efficiency and accuracy of near-field measurement
G. Seguin,T. Pavlasek, November 1995

This paper examines the possibility of increasing the speed of Near-Field measurement of an Antenna, by reducing the number of measurement points and by determining the degree of truncation permissible while maintaining a prescribed degree of precision of the reconstructed far-field. The Near-Field of a planar radiating array is analysed in depth. A formulation and a procedure to correct the spectral domain of the field are established. It is shown that correction in the spectral domain can improve the accuracy of the Far-Field while using the same amount of Near-Field data. The technique has a good potential to be applied to Near­ Field data of large radiating Antennas leading to new information about the accuracy and speed of measurement achievable.

Frequency dependent scattering effects on Fourier domain imaging of ultra-wideband data
G. Fliss,S. Li-Fliss, November 1995

Forming radar images from large fractional band­width data can often lead to unusual artifacts or resolutions degraded from "expected" theoretical point-target values. The frequency dependencies of typical scatter­ ing mechanisms, such as diffractions, surface waves and speculars, can be significant over processing apertures when data are collected using large fractional bandwidth measurement systems. For example, it is well known that resonant scatterers exhibit blurring in the down­range direction of an image. Other scattering mechanisms have linear or quadratic amplitude dependencies which can also alter the impulse response from that of an ideal point scatterer. This paper will first provide a brief description of the frequency dependencies of various scattering mechanisms. The paper will then describe the corresponding effects seen in the impulse response, primarily in the range profile domain. Impulse response plots will be compared for data with large and small fractional band­widths. Lastly, the effects of frequency dependent scattering on the impulse response will be shown using images generated from data collected in indoor compact ranges.

Polarimetric calibration of reciprocal-antenna radars
L.A. Muth,R. Lewis, R.C. Wittmann, November 1995

We discuss how RCS target depolariza­ tion enhances cross-polarization contamination, and we present a graphical study of measurement error due to depolarization by an inclined dihedral reflector. Error correction requires complete polarimetric RCS measure­ ments. We present a simple polarimetric calibration scheme that is applicable to reciprocal antenna radars. This method uses a dihedral calibration target mounted on a rotator. Because the calibration standard can be ro­ tated, there is no need to mount and align multiple sepa­ rate standards, and clutter and noise may be rejected by averaging over rotation angle.

Triband radome measurement system: installation and testing results, A
V. Jory,G.W. Pearson, J.R. Jones, L.L. Oh, S.J. Manning, T.L. Norin, V. Farr, November 1995

In an earlier paper ("System Engineering for a Radome Test System," John R. Jones, et al, AMTA, October 1994) the system level design of a compact range enhancement for the testing of the Triband Radome was presented. This paper will discuss the installation and testing of the radome measurement system in the compact range. The purpose of the radome measurement system is to determine (within close tolerances) boresight shift, transmission loss, antenna pattern changes and polarization effects caused by the radome. Unique features include novel coordinate transformation and correction by means of a laser autocollimator and data reduction algorithms. Also featured is the tracking subsystem which consists of a specially designed two-axis track pedestal, an autotrack controller, and three five-horn compact range feed arrays operating at X, K, and Q-bands. The performance of the triband radome measurement system in the compact range setting will be presented.

Investigation of circular Archimedean spiral antenna for automobile applications
C.J. Reddy,C.R. Cockrell, D.T. Fralick, F.B. Beck, M.D. Deshpande, November 1995

Due to the revolution in communication technology very sophisticated communicative and navigational tools are becoming a part of automobile electronics. These different applications need antennas that operate at various frequencies and with different polarization requirements. One such antenna is a cavity-backed Circular Archimedean Spiral Microstrip Antenna (CASMA). This pa per will compare radiation pattern measurements of a CASMA with pattern predictions using a hybrid FEM /M oM/GT D technique. The measurements were done at NAS A-Langley Research Center's Low Frequency Antenna Chamber. The predicted and measured patterns are presented and are shown to exhibit a reasonable degree of agreement.

Development and measurement of a frequency selective surface highway stripe
J.D. Young,D. Farkas, L. Henderson, November 1995

A frequency selective surface has been developed for use as a part of an automatic highway system. The FSS is attached as a stripe along the edge or center of the lane, and is designed to a strong retro-reflective echo for the design frequency, polarization, and elevation angle of the forward-looking radar installed on an automobile. The stripe provides directional information for automated steering, as well as other coded information such as lane number, and exit advance warning. This paper reports on initial development and testing of a prototype FSS highway stripe. The stripe was designed for an operating frequency of 10.5 GHz, and was built and tested using a prototype autonomous vehicle. Both FSS stripe performance, and performance of the vehicle will be reported.

Cross-polarized pattern measurement on point-source compact ranges
D.W. Hess, November 1994

Earlier measurement results are reviewed to understand the result that cross -polarized patterns agree well when compared between a point-source compact range and spherical near-field scanning. By taking account of the symmetry of the aperture distribution, one can see how the cross-polarized pattern can be affected only moderately by the classic polarization feature of an offset reflector geometry.

Anechoic chamber evaluation
K. Haner, November 1994

This paper details the evaluation of a major aerospace company's tapered anechoic chamber. Using an NSI 3' x 3' near-field scanner and software, the chamber was evaluated at 11 frequencies and two polarizations. SAR imaging techniques were used to map the chamber reflections. A new addition to the software provided the ability to map the difference between the measured phase front and the theoretical spherical phase front; the software also derives the x,y,z phase centers of the source. Error estimates for all aspects of the evaluation will be discussed.

Radar absorbing material thermal characteristics
R.M. Taylor,H.D. Reynolds, M. Matteson, November 1994

The Benefield Anechoic Facility, Edwards AFB, California contains a large anechoic chamber for avionic integration test and evaluation. Because of the large chamber size, operational tests can require high-power aircraft radar emissions. To define the range of energy safely accommodated by currently installed radar absorbing material (RAM), a detailed analysis was performed and the results presented. The incident radar energy generates a heat transfer to the RAM. The RAM boundaries dissipate heat through convection, conduction, and radiation. A finite-difference solution demonstrates the temperature distribution in the material varies with the angle and polarization of the incident electric field. Discussions include the use of the RAM thermal characteristic's pretest evaluation to improve operating capability determinations and to facilitate assessment of customer requirements.

Efficient antenna testing using current antenna test systems
A.R. Koster,R. Munoz, November 1994

Accurate, fast, and cost effective antenna test equipment is necessary to meet many programs measurement requirements and schedule and budget constraints. Testing time may be significantly reduced y measuring multiple channels of data simultaneously. Further time savings are realized via the electronic storage of data, which allows easy pattern overlays and changes in the page setup parameters. Electronic storage of data also allows the user to accurately ascertain test parameters. Test data for a dual band, multi-channel antenna measured wit the Scientific Atlanta 1590 Pattern Recorder and multi-channel 1795 Microwave Receiver is presented. This antenna has transmit and receive ports, multiple polarization capability, data and tracking channel outputs and multiple frequency bands. The substantial savings in testing costs are estimated.

High performance medium gain antenna applications in the compensated compact range
T. Jakob,H-J. Steiner, J. Neve, J.F. Coroller, M. Boumans, November 1994

The Compensated Compact Range (CCR) has been proven to be a high performance test facility for payload and large satellite antenna measurements. To efficiently measure complete antenna farms with various types of antennas on the spacecraft in the same test campaign led to the growing demand for testing e.g. Global Horn antennas on the spacecraft in the CCR. As a matter of fact, medium gain antennas feature a small aperture simultaneously requiring larger test angles. Therefor, main interferer like "direct leakage" between the CCR feed and the antenna under test have to be quantified and their impact on the measurement accuracy have to be reconsidered. The presented paper will investigate theoretically the feasibility of testing high performance widebeam antennas in the Top-Fed-Cassegrain double reflector system. Qualified measurement results of INTELSAT Global Horn Antennas featuring medium gain and extreme crosspolarization purity will be presented.

Polarization extraction of circularly polarized antennas
F. Colomb,J. Gentle, J. Swanstrom, P. Klock, P. Mayes, November 1994

A technique is presented for obtaining the radiation patterns and the antenna gain of elliptically polarized antennas from two vector measurements of the far-field. The two measurements correspond to different polarizations which can be obtained by rotating one of the antennas around its boresight axis. The discussion emphasizes a particularly interesting case, for which accurate radiation patterns and gain of the antenna under test (AUT) can be obtained without prior knowledge of the polarization of the second antenna. The radiation pattern of a nearly circularly polarized (CP) antenna is conveniently represented by the CP co-polarized and cross-polarized components. The axial ratio and any other quantities commonly used to specify the antenna polarization can also be obtained since the pair of initial vector measurements completely characterize the polarization of the AUT. The technique is illustrated by measurements of a CP patch antenna.

Instrumentation upgrade for ultra-high speed data acquisition in the DASA compensated compact range
H.F. Schluper,H-J. Steiner, J.F. Aubin, T. Jakob, November 1994

Deutsche Aerospace is developing and testing high­ performance communications antennas for the INTELSAT program. A large number of antenna measurements must be performed, for two polarizations, multiple frequencies and multiple beams. To measure all parameters in a single rotation of the antenna, a high­speed instrumentation system is required. The instrumentation was upgraded using the latest technology in receivers, sources and control systems. Commercially available components were used for all components. The resulting system can perform a complex antenna measurement consisting of over four million data points within only two hours.

Automated production test facility for a MMW radar system
W.S. Arceneaux, November 1994

Martin Marietta has developed a new, automated facility for high-volume production testing of the Longbow millimeter wave missile. Two dedicated far field anechoic chambers were designed, both automated to support component test and analysis in the production environment. One standard far field chamber is used to perform the complete characterization of the antenna and rac1orne; it allows very accurate measurements of power sidelobes, monopulse errors, and cross­ polarization isolation. The completed radar missile sensor group is evaluated in the second far field chamber, which can reach higher-level parameters of the antenna, transceiver, and gimbal. This paper describes chamber and test station capabilities; time reduction benefits; and the novel, new assembly technique which allows for future portability of these chambers with limited downtime.

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.

Measurement speed and accuracy in switched signal measurements
J. Swanstrom,R. Shoulders, November 1993

The interdependence of accuracy and speed should be considered when analyzing measurement requirements. Tradeoffs can be made to optimize the measurement when accuracy is of primary importance, or where speed is critical. Several different measurement modes of the HP 8530A Microwave Receiver are presented, each with different measurement speed and accuracy tradeoffs. Examples are given that illustrate which acquisition modes would be appropriate to optimize the acquisition speed and accuracy in a variety of applications

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.

Simplified polarization measurements
E. Gordon, November 1993

The mathematical language of wave polarization has been somewhat cryptic; usually involving vectors, tensors, or complex numbers or symbolic equations. By using the Poincare' sphere and dot product multiplication, it is possible to reduce the comutation of wave polarization mathematics to simple trigonometric formulas. Furthermore, visual representation of wave polarization on the Poincare; sphere is straight-forward and simple.

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.

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.







help@amta.org
2024 Antenna Measurement Techniques Association. All Rights Reserved.
AMTA_logo_115x115.png
 
 

CONNECT WITH US


Calendar

S M T W T F S
1 2
3 4 5 6 7 8 9
10 11 12 13 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30
31