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

Compact Range

Comparison of three field scanning techniques in the compact range
H.C.M. Yuan (Hughes Aircraft Company), November 1989

A major concern for any user of a compact range for RCS or antenna measurements is the quality of the wavefront over the quiet zone and background chamber levels at the desired frequency band. Amplitude and phase ripple in the quiet zone is an indicator of how well the electromagnetic energy is collimated coherently by the reflector system. The amount of ripple depends on the reflector system, reflector edge treatment to reduce diffraction, frequency band and chamber interactions. Edge treatment techniques such as serrations on the reflector edge helps to reduce diffraction of unwanted energy into the quiet zone. Constructive and destructive interference of diffracted of energy in the quiet zone causes the amplitude and phase ripple. The goal is to reduce the ripple to a minimal amount. Previous studies by the author have compared two-way and angle transform field scanning techniques. The results strongly indicate that both techniques provide good agreement. The two-way method has the disadvantage of strong dependence on the scanning target directivity. A directive target will tend to disregard diffraction from the reflector edges because of its low sidelobes. Its advantage is that there is no need for external mixing equipment for the microwave receiver. The angle transform is simple in configuration consisting of a narrow flat plane or bar mounted on an azimuth positioner and rotated. The disadvantage is a summing of energy in the zero-doppler cell yielding an artifact ripple. Both of these methods also depend upon software gating algorithms including gate shape and width which directly influence the amplitude and phase ripple. The aim of this study is to compare the two-way, one-way field scanning techniques and the angle transform method. Can comparisons be made between the methods? Can a fairly good agreement be made? Are multi-path considerations addressed in one-way scan techniques? Hughes Aircraft will use one of the compact ranges at the Antenna Test Facility of Motorola GEG at Scottsdale, Arizona with the March Microwave (Vokurka) dual reflector system. Field scans will be measured using both the two-way and one-way techniques. The two-way method will use the 8 cm diameter disk as the scanning target, mounted on a horizontally traversed scanner. The one-way method will use a standard gain horn mounted on the same scanner. The angle transform method will use an 8 ft narrow flat plate rotated in the quiet zone. The field scans will be measured and studied at 10 GHz.

Planewave spectral range probe experiment
R.D. Coblin (Lockheed Missiles and Space Co.), November 1989

The weakest link in antenna metrology is the antenna range itself. Unknown reflections can cause large errors in antenna measurements and can change unpredictably. The planewave spectral (PWS) probe technique is one proposed method for identifying the location and magnitude of range scattering. This paper presents the results of a PWS probe of a compact range. The interpretation of the PWS plots is discussed in comparison with the range geometry. Nine separate scattering centers are identified. The meaningfulness of the PWS picture was tested by introducing a known dipole source.

Instrumentation and computer control of the U.S. Army EPG compact range
C.D. Milum (Georgia Tech Research Institute),B.S. Mitchell (Georgia Tech Research Institute), J.E. Ruda (Georgia Tech Research Institute), J.L. Patterson (Georgia Tech Research Institute), R.B. Cotton (Georgia Tech Research Institute), S.T. McBride (Georgia Tech Research Institute), November 1989

Georgia Tech Research Institute has designed, developed and installed a large outdoor compact range for the U.S. Army Electronic Proving Ground at Ft. Huachuca, Arizona. Some of the unique hardware and software developed as part of the instrumentation and computer control tasks for the compact range are described.

Analysis of blended rolled edge reflectors using numerical UTD
S.W. Ellingson (The Ohio State University ElectroScience Laboratory),I.J. Gupta (The Ohio State University ElectroScience Laboratory), W.D. Burnside (The Ohio State University ElectroScience Laboratory), November 1989

An accurate and efficient method to compute the scattered fields in the target zone of a compact range main reflector is presented in this paper. This method is valid for reflectors of arbitrary rim shape with convex rolled edge terminations. The method is based on the uniform geometrical theory of diffraction (UTD) where the diffraction coefficients are obtained numerically using a procedure involving a physical optics line integration. Results obtained using the numerical UTD (NUTD) are compared to those obtained using UTD and corrected physical optics surface integration solutions for reflectors with both unblended and blended rolled edges. It is shown that the results are in good agreement. In addition, the NUTD is much more efficient than the traditional physical optics surface integration and provides diagnostic information on the effects of individual scattering mechanisms.

Analysis of serrated edge compact range reflectors
I.J. Gupta (The Ohio State University ElectroScience Laboratory),R.J. Mariano (The Ohio State University ElectroScience Laboratory), November 1989

A Physical optics (PO) analysis of serrated edge reflectors is presented. It is shown that to obtain the true scattered fields in the target zone, one should use PTD (physical theory of diffraction) along with the PO solution. Using PTD, scattered fields of various serrated edge reflectors are presented. From these scattered fields, one can see that by proper design of the serrations, the edge diffracted fields can be reduced in the target zone. The edge diffracted fields, however, still may be too large for certain applications.

On the determination of the quiet zone field of compact range antennas with serrated edges
J.P. McKay (University of California at Los Angeles),Y. Rahmat-Samii (University of California at Los Angeles), November 1989

A novel technique is presented for the determination of the quiet zone field distribution of compact range antennas with serrated edges. The main reflector has a linearly serrated rim, so that the rim projection onto the reflector aperture plane is an arbitrary polygon. Additionally, the reflector aperture field is uniform in both amplitude and phase, and can therefore be expressed as a window function. The plane wave spectrum of the aperture field can then be obtained in closed form. Next, the spectrum is expressed at a plane in the quiet zone and the field is obtained by implementing an inverse fast Fourier transform (FFT) algorithm. Quiet zone field distributions are computed for various serrated rim configurations.

RCS measurement errors caused by reflector edge diffraction
T-H. Lee (The Ohio State University ElectroScience Laboratory),W.D. Burnside (The Ohio State University ElectroScience Laboratory), November 1989

This paper evaluates the RCS errors associated with measuring a large flat plate which is illuminated by a compact range reflector with significant edge diffraction stray signals. This is done by evaluating the true fields incident on the plate and then using a physical optics technique to predict the backscattered fields. Results are compared with and without the edge diffracted fields present. A simple analytic expression is developed which can approximate the size of this potential error.

Multiple reflections in ISAR images - imaging of an open box
A. Jain (Hughes Aircraft Company),I.R. Patel (Hughes Aircraft Company), November 1989

Images of an open box, closed box, and open and closed box on a ground plane were taken at the Hughes/Motorola Compact Range. Comparison of these images show the effect of multiple reflections in the image of an open box. A simple analytic/computer model was developed to interpret these multiple images. Data and analysis are presented on the various mechanisms that come into play in scattering from the open/closed box and the ISAR images generated as a function of the viewing angle for the box.

Verification method for the serration design of CATR reflectors
H.F. Schluper (March Microwave Systems B.V.), November 1989

Serrations are used on Compact Antenna Test Range reflectors to reduce the effects of edge diffraction. It has been found that the traditional triangular shape for these serrations is not optimal and that more continuous shapes should perform better. To verify this, RCS measurements were performed on test targets consisting of strip reflectors terminated by end sections of various shapes. The RCS vs. angle data were corrected for the field irregularities caused by the measurement range and then converted to the induced current distributions on the targets, from which the fields in front of the targets were calculated using Physical Optics. These fields are equivalent to the test-zone fields of an actual Compact Range. The results are compared with theoretical data. The agreement is good.

Design development and qualification of an advanced, large compact test range
E. Dudok (Messerschmitt-Bolkow-Blohm GmbH),H-J. Steiner (Messerschmitt-Bolkow-Blohm GmbH), J. Habersack (Messerschmitt-Bolkow-Blohm GmbH), T. Fritzel (Messerschmitt-Bolkow-Blohm GmbH), November 1989

To fulfill the future demand of highly accurate antenna-, RCS- and payload testing, MBB built a new antenna test centre at Ottobrunn (Ref. 1). This paper describes the development and qualification of the large, dual reflector Compact Range (CR) which has a plane wave zone of 5.5 x 5.0 x 6.0 m (w x h x d). It starts with the results of a detailed electrical trade-off study between different CR-concepts, followed by some mechanical/thermal construction aspects of the large, highly accurate reflectors. Finally, some qualification results are shown, covering the frequency range from 3.5 GHz up to 200 GHz (lowest frequency of operation approx. 2 GHz). The achieved plane wave performance (amplitude ripple ±5o, phase ripple ±5o, cross-polarization isolation > 40 dB) verifies the high quality overall system design.

Cylindrical wave helicopter antenna pattern measurements, corrections, and comparisons
C.A. Balanis (Arizona State University),C.R. Birtcher (Arizona State University), D.G. Shively (NASA ), G.C. Barber (NASA ), M. Gilreath (NASA Langley Research Center), V.J. Vokurka (Eindhoven University), November 1989

To perform antenna measurements, it is necessary that the entire antenna structure is illuminated by a uniform plane wave. Since almost all sources radiate spherical waves, plane wave field configurations can be achieved locally only at very large distances from the source. The proliferation of compact range designs have reduced the distance required to achieve nearly plane wave field configurations to distances which can be satisfied by indoor facilities. While most compact ranges have been designed to create a nearly plane wave field configuration, at Arizona State University an operational compact range exists which creates a nearly cylindrical wave field structure. The pattern measured under cylindrical wave illumination is transformed, using analytical and numerical methods, to obtain the plane wave response of the antenna system. Measurements have been performed, using the cylindrical wave compact range, of a 15 GHz axial waveguide antenna on a 1/10 scale Advanced Attack Helicopter model. The measurements were then transformed and compared with those made of the same antenna system in a plane wave compact range facility.

String support in compact ranges
J.B. Elbert (Boeing Advanced Systems), November 1989

In the past, models suspended indoors for radar cross-section measurements have weighed up to several hundred pounds, suspended on the order of 20' or less from the ground, and measured statically or rotated for great circle cuts. Under these circumstances it has been acceptable to choose the best string configuration from a signature point of view and simply wait for the model to reach a visually calm state before testing. However, indoor ranges are now requiring suspension of models weighing several thousand pounds 40' or more above the floor. In addition, the demand for imaging data during model conics requires both precise dynamic control and model stability. This work discusses techniques developed at Boeing's 9-77 Range in Seattle, to achieve model stability during suspension and manipulation. In addition, techniques to determine spring and damping constants of suspension systems for individual models are addressed.

Target alignment techniques for the compact range
H. Shamansky (The Ohio State University),A. Dominek (The Ohio State University), M. Poirier (The Ohio State University), November 1989

Many targets today exhibit radar cross sections sensitive to the angular orientation of the target. While some of these targets have prominent scattering centers which can be exploited to obtain a relative positional reference, many targets unfortunately do not. In addition, many complex targets have a highly directional scattering behavior requiring careful alignment to the incident planar field. This need for accurate positioning has prompted the development of laser alignment techniques for the compact range. One such system has been under development at the ElectroScience Laboratory, and the designs and results of the first prototype are presented here. Performance goals and design criteria are discussed, and future improvements are considered. In addition, similar systems for feed and pedestal location reference systems are presented.

The Positioner for the U.S. Army EPG compact range
T.L. Wilkey (Georgia Institute of Technology),E.H. Atkinson (Georgia Institute of Technology), H.P. Cotten (Georgia Institute of Technology), J.F. Kirksey (Georgia Institute of Technology), J.M. Hudgens (Georgia Institute of Technology), O.D. Asbell (Georgia Institute of Technology), November 1989

The Georgia Tech Research Institute has designed and installed a large outdoor compact range for the U.S. Army Electronic Proving Ground at Ft. Huachuca, Arizona. This range will primarily be used to obtain performance data for antennas installed on full-size tanks, aircraft and other vehicles to characterize antenna/vehicle interactions. This paper describes the vehicle positioner that is being used with the compact range. Design considerations have resulted in a challenging positioner design. Some of the features of the positioner include: * positioning of large vehicles weighing up to 70 tons approximately 42.5 feet above ground * using a hydraulic servo system to drive the positioner * minimizing RF reflections by using ogive shaped shells on the positioner legs and tilting the legs forward

Characterizing the bistatic performance of anechoic absorbers
S. Brumley (Denmar, Inc.),R.G. Immell (Motorola Govt. Elect. Group), November 1989

The requirement to measure lower radar cross-section (RCS) levels within anechoic chambers has demonstrated the need to further analyze the performance of microwave absorbers. The interactions of the feed system, compact range reflector, target mount, and target/test body with the microwave absorber greatly effect both the measurement accuracy and ambient noise level within the anechoic chamber. Better absorber characterization and understanding leads to improved chamber performance analysis and chamber design modeling. Past absorber studies have evaluated the backscatter performance of most absorber types, however, bistatic performance characterizations have been limited. This paper will discuss a method of obtaining bistatic absorber data which offers the advantages of time gating and synthetic aperture imaging to improve measurement isolation and accuracy. The approach involves illuminating a large absorber test wall about several incidence angles with the plane wave generated by a compact range. A receive antenna is then moved about the test wall and bistatic scattering is observed. The technique provides improved measurement results over methods utilizing NRL arch type systems. Bistatic absorber data has been collected and analyzed over angles from normal to near grazing incidence. Test results will be demonstrated with different absorber shapes, sizes, orientations, and material transitions from wedge to pyramidal. Various bistatic conditions will be analyzed for both polarizations over a number of frequencies.

Circularly polarized RCS measurements
T.S. Watson (Texas Instruments Incorporated), November 1989

Circularly polarized radar cross-section (RCS) measurements place stringent requirements on an RCS range. Indoor compact ranges without the problems of ground reflections have the potential of making accurate circular polarization (CP) measurements. A simple method for CP RCS measurements is described using broadband meander-line polarizers over the compact range feed horns. Axial ratio and differential phase measurements were performed to evaluate the polarizer fabrication accuracy. Basic scattering shapes were measured to test the performance of the CP measurement system. Comparison of CP measurements with analytical predictions demonstrated the success and limitations of the technique.

A Wideband RF feed for RCS compact range facilities
K. Miller (Scientific-Atlanta, Inc.),W.G. Swarner (Scientific-Atlanta, Inc.), November 1989

Compact range facilities designed for RCS measurements have exhibited a performance-limiting effect commonly referred to as "feed ringing". "Feed ringing" is a phenomenon in which energy is stored in or about the RF feed structure and is sustained for a sufficient period off time after the source is turned off such that its presence contaminates the true target return. This effect has placed severe constraints on the design of the RF feed for the compact range, particularly in regard to its operating bandwidth. This paper presents the design of a lossless, waveguide type RF feed suitable for compact range application with a demonstrated useful bandwidth approaching a full octave.

Broad band antenna for compact range use
A. Lai (The Ohio State University ElectroScience Laboratory),E.H. Newman (The Ohio State University ElectroScience Laboratory), W.D. Burnside (The Ohio State University ElectroScience Laboratory), November 1989

Due to the limited size of a compact range, an antenna with low sidelobes, broad bandwidth, broad beam, small physical signature, low scattering level and reasonably high power handling are required. Historically, slot line antennas are circuit board type antennas noted for their thin cross-section, low cost of fabrication, scalability and high package density in array applications. A broadband version, fed by a microstrip line (and therefore easily connected to microstrip transceiver circuits etched on the same circuit board) is described in this paper. Test models with different shapes and using different dielectric materials were built and tested. The measured VSWR, radiation and scattering patterns of the various antenna designs are presented.

Scattered fields of metallic tapes used to cover gaps in compact range reflectors
I.J. Gupta (The Ohio State University ElectroScience Laboratory),W.D. Burnside (The Ohio State University ElectroScience Laboratory), November 1989

The effects of metallic tapes which are used to cover gaps in a compact range reflector are studied in this paper. To study these effects, the normalized tape scattered fields are computed in the target zone. A method of moments technique is used to compute the tape scattered fields. It is shown that the tape scattered fields are directly proportional to the thickness and width of the tape and are inversely proportional to the square root of the distance from the tape. Using the computed results, an empirical formula for the tape scattered field is developed. One can use the empirical formula to compute the highest frequency for which a given size tape can be used.

Next generation Harris compact range, The
J. Cantrell (Harris Corporation),C.J. Koepsell (Harris Corporation), November 1989

After having delivered a model 1630 and a model 1640 compact range plus a number of smaller 1606 and 1603 ranges, Harris has improved their product to meet the demanding needs for operating frequencies of 35 GHz and higher. In characterizing the two large ranges, it was discovered that the surface accuracy as originally optimized would not support the highest operating frequency. Achieving the required surface accuracy required additional surface measurement data in combination with RF contour plots and was very time consuming. From those lessons learned, several features have been incorporated into the next generation of compact ranges that make more accurate reflector surfaces easily achievable. The features include optimally located adjustment mechanisms, additional targets on each panel, software for best fitting the panel surface to minimize steps, techniques for eliminating panel steps in place, and gravity bias setting of panels.







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