Complex body scattering is a major problem facing the electromagnetic researcher today. Computer codes are one important method for predicting such scattering. With funding from Langley, Ohio State University has developed such a code. A 30:1 scale model of the Space Station was constructed to be used as a scattering target in the verification of this code. The purpose here is to document the methods used to make these measurements and present the results which will be used by others for code verification

Langford, Berkley A., Jr.

Vaughan, Roger K.

Young, W. Robert

English

NASA Technical Reports Server

NASA Technical Memorandum 102632
Experimental Measurements of Space
Station Antenna Patterns at 60 GHz for EM
Analysis Verification
W. Robert Young, Berkley A. Langford, Jr.,
and Roger K. Vaughan
October 1991
National Aeronautics and
Space Administration
Langley Reeearch Center
Hampton, Virginia 23665-5225
_/ >
https://ntrs.nasa.gov/search.jsp?R=19920006087 2020-03-17T14:09:44+00:00Z

NASA Technical Memorandum 102632
ANTENNA SCATTERING AT 60 GHz
MEASURED IN A COMPACT RANGE
W. Robert Young, Berkley A. Langford, Jr.,
and Roger K. Vaughan
October 1991
Attached is a corrected copy of NASA Technical Memorandum 102632. An incorrect
title was shown on the report which was previously sent to you. The title of the
report should be "Experimental Measurements of Space Station Antenna Patterns at 60
GHz for EM Analysis Verification." Please destroy all copies of the report that you
previously received.
Issued January 1992

EXPERIMENTAL MEASUREMENTS OF SPACE STATION
ANTENNA PATTERNS AT 60 GHZ FOR EM ANALYSIS VERIFICATION
SUMMARY
In 1985, the Antenna and Microwave Research Branch (AMRB) at the Langley
Research Center initiated a research effort to develop the analytical methods for
predicting the radiation performance of antennas on various structural concepts being
considered for Space Station operations. Since the design, development, and
subsequent performance of spacecraft antennas is largely dependent upon the antenna
concept, size of the vehicle in wavelengths, mounting location, and potential
obscuration effects, due to line-of-site blockage, it was expected that the availability of
a special analysis code which could include these design parameters would be very
valuable for Space Station configuration studies. So, in that regard, AMRB initiated a
research program which included the development of analytical methods for radiation
pattern predictions as well as an experimental program to verify the EM analytical
methods through actual antenna measurements. The analytical effort has been
reported previously (ref. I) and was developed by the Ohio State University
ElectroScience Laboratory as part of the Langley research program.
Therefore, the purpose of this report is to document the experimental pattern test
approach, present some typical experimental data, and to show a comparison between
selected experimental and analytical data. Several other antenna types and locations
were investigated, but only representative results are discussed in this report.
INTRODUCTION
To satisfy all the communication, navigation, and tracking requirements of the
proposed Space Station, several onboard antennas will be needed. Due to the large
physical size of the Space Station, making full-scale antenna pattern measurements is
not practical, therefore, methods must be developed that can be used to predict the
performance of these antennas. One such method, a computer program for analyzing
antenna performance on complex structures such as the Space Station, was recently
developed through a Joint effort between the Ohio State University ElectroScience
Laboratory and Langley Research Center, Antenna and Microwave Research Branch.
Thecomputer program, the Numerical Electromagnetic Code - Basic Scattering Code
(NEC-BSC), was used to calculate the far-field radiation patterns for a 60 GI-Iz
broadbeam slot antenna mounted on a 1/30 scale model of the middle section of the
Space Station. A 2 GHz frequency on the full-scale Space Station was simulated in this
manner. Measurements were made at 60 GI-Iz in the Compact Range Pilot Facility using
a precision 1/30 scale model of the Space Station to provide experimental data used for
verification of the NEC-BSC analytical results.
The purpose of this report is to document the methods used to make these
measurements, present some typical experimental, and show a comparison between
selected experimental and analytical data. The pertinent details of the test
configuration and measurement procedures are presented as well. Several other
antenna types and locations were investigated, however, the results are not discussed
herein.
TEST CONFIGURATION
The Space Station model (fig. I) was mounted on a Scientific Atlanta model 53
positioner in the AMRB Compact Range Pilot Facility (fig. 2). The posiUoner is
configured in a manner to allow the making of both azimuth and roll patterns. The test
signal is transmitted from a low gain feed antenna, Scientific Atlanta part no. 253342,
located at the focal point of the compact range reflector.
A model 1783 Scientific Atlanta receiver with the addition of Scientific Atlanta
model 1784/1785 down converters extended the frequency range of the receiver to 60
GHz. One of the down converters was used to provide a sample of the transmitted signal
so the receiver could be phase locked to the source. The other down converter was used
in the received signal path and was located as close as possible to the receive horn to
minimize waveguide loss (see the block diagram in fig. 3).
A Varian model 2101A16 Klystron was chosen as the signal source for noise
considerations. It was found that at least 100 mW of source power was required for an
acceptable noise level near the -40 dB signal level. Unfortunately, the residual FM
modulation on this Klystron made it impossible to use the automatic data acquisition
feature of the Scientific Atlanta 2080 antenna/radar cross section analyzer. The
incidental FM caused the receiver to occasionally loose phase lock which in turn causes
the automatic data acquisition to abort the data file being generated. Loss of phase lock
would occur on an average of three or four times during the time required to generate a
single pattern cut.
2
TEST ANTENNAS
Theantenna used for these measurements was fabricated from a section of open
ended WR-15 waveguide which was terminated in a 2-in. square ground plane (fig. 4).
This antenna was selected because it has a broad radiation pattern which simulates the
class of antennas that is being considered for use as the Space Station communications
antenna.
Figure 1 shows the location on the Space Station model chosen for mounting the
antenna. Antenna patterns were measured with the antenna in the position shown and
in the 90 ° rotated position relative to the Space Station model. Each time the Space
Station antenna was rotated 90 °. the source antenna was also rotated 90 ° for copolar
operation (fig. 5). The extra vertical and horizontal lines shown on the drawing are
used to indicate the axis of rotation. The arrows around these lines indicate the
direction the model rotates to increase the indicated angle. This illustration shows the
Space Station with the aximuth angle at +90 ° and the roll angle at 23 °. In this position,
the front surfaces of the model are perpendicular to the received signal path.
RESULTS
Measurements were made in the Compact Range Pilot Facility at the Langley
Research Center. These measurements were made at 60 GI-Iz using a broadbeam slot
antenna. Experimental data from the measurements are presented in figures 5 thru 1 I.
In addition, the analytical results from the computer program (NEC-BSC) are also
shown (figs. 12-16 and ref. I).
By making a comparison of the analytical and experimental data. one can see that
there is a close agreement between these data that were generated by different methods.
CONCLUSION
In conclusion, our test showed that there was a very good comparison between the
measured and calculated patterns, and figure 12 compares the measured and calculated
results from the antenna measurements. It is also noted that the large reflector of this
facility was used at 60 GHz for the first time with these tests.
REFERENCES
I° Bracalente, E. M.; Gilreath, M. C.; and Marhelka, R. J.: Development of Numerical
Electromagnetlc-Baslc Scattering Code for Space Station ApplicaUons: A
Description and Antenna Chamber Evaluation. Published at the IEEE AP-S
International Symposium and URSI Radio Science Meeting, Paper No. 75-1, Dallas,
Texas. May 7-11, 1990.
4
Component/Parts List
M1, M3 - Mixers, Hughes Model 47444H1002A
M2, M4 - Mixers, Scientific Atlanta Model 14-5
ATI, AT2 - Attenuators, TRG Model V510
K1 - KLYSTRON, Varian Model VRE-2101A16
PS1 - KLYSTRON, Power Supply, Polytechnic Institute of New York Model 819-A
C 1 - Converter, Scientific Atlanta Model 1785
C2 - Converter, Scientific Atlanta Model 1784
LO Unit - Scientific Atlanta Model 1780
Receiver - Scientific Atlanta Model 1783
DC1 - Directional Coupler, Hitachi Model M2101 lOdB
Transmit Antenna - Scientific Atlanta Part 253342 40.0 - 60.0 GHz
Receive Antenna - See Fig. # 1
* Ref. is a 949.22 MHz signal used to phase lock the 1784/85.
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1. AGENCY USE ONLY (Leave blank) 2. REPORT DATE 3. REPORT TYPE AND DATES COVERED
October 1991 Technical Memorandum
4. TITLE AND SUBTITLE
Experimental Measurements of Space Station Antenna
Patterns at 60 GHz for EM Analysis Verification
6. AUTHORS)
W. Robert Young, Berkley A. Langford, Jr., and
Roger K. Vaughan
7. PERFORMINGORGANIZATIONNAME(S)ANDADDRESS(ES)
NASA Langley Research Center
Hampton, VA 23665-5225
9. SPONSORING/MONITORINGAGENCYNAME(S)ANDADDRESS(ES)
National and Aeronautics and Space Administration
Washington, DC 20546-0001
5. FUNDING NUMBERS
WU 505-64-70-01
B. PERFORMING ORGANIZATION
REPORT NUMBER
10. SPONSORING / MONITORING
AGENCY REP_a_IT NUMBER
NASA TM-I02632
It. SUPPLEMENTARYNOTES
Young and Langford: Langley Research Center, Hampton, VA.
Vaughan: Lockheed Engineering & Sciences Company, Hampton, VA.
IZa. DISTRIBUTION/AVAILABILITYSTATEMENT
unclassified - unlimited
subject category 32
12b. DISTRIBUTION CODE
13. ABSTRACT (Maximum 200words)
Complex body scattering is a major problem facing the electromagnetic researcher
today. Computer codes are one important method for predicting such scattering.
With funding from Langley, the Ohio State University has developed such a code.
A 30:1 scale model of the Space Station was constructed to be used as a scattering
target in the verification of this code. The purpose of this report is to document
the methods used to make these measurements and present the results which will be
used by others for code verification.
|4. SUBJECTTERMS
Space Station; EM Analysis Code; Compact Range Pilot Facility
17. SECURITY CLASSIFICATION
OF REPORT
unclassified
NSN 7540-01-280-5500
18. SECURITY CLASSIFICATION
OF THIS PAGE
unclassified
15. NUMBER OF PAGES
22
16. PRICE CODE
A03
19. SECURITY CLASSIFICATION 20. LIMITATION OF ABSTRACT
OF ABSTRACT
Standard Form 298 (Rev 2-89)
Prescribed by ANSI Std Z]9-18
298-I02


Experimental measurements of Space Station antenna patterns at 60 GHz for EM analysis verification

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