Two approaches to design a tri-band reflector antenna for the Advanced TDRSS are examined. Two reflector antenna configurations utilizing frequency selective surfaces for operation in three frequency bands, S, Ku, and Ka, are proposed. Far-field patterns and the antenna feed losses were computed for each configuration. An offset-fed single reflector antenna configuration was adapted for conceptual spacecraft design. CADAM drawings were completed and a 1/13th scale model of the spacecraft was constructed

Fujikawa, Gene

Lee, Shung-Wu

Sharp, G. Richard

Zimmerman, Martin L.

English

NASA Technical Reports Server

NASA Technical Memorandum 103754
Designs for the ATDRSS Tri-Band
Reflector Antenna
Shung-Wu Lee and Martin L. Zimmerman
University of Illinois, Urbana-Champaign
Urbana, Illinois
and
Gene Fujikawa and G. Richard Sharp
Lewis Research Center
Cleveland, Ohio
Prepared for the
1991 IEEE AP-S International Symposium and URSI Radio Science Meeting
London, Ontario, Canada, June 24 -28, 1991
NASA
https://ntrs.nasa.gov/search.jsp?R=19910010871 2020-03-19T18:34:40+00:00Z
DESIGNS FOR THE ATDRSS TRI-BAND REFLECTOR ANTENNA
Shung-Wu Lee and Martin L. Zimmerman
University of Illinois, Urbana-Champaign
Urbana, Illinois 61801
Gene Fujikawa and G. Richard Sharp
National Aeronautics and Space Administration
Lewis Research Center
Cleveland, Ohio 44135
NASA's Tracking and Data Relay Satellite System (TDRSS) presently provides a
vital link in space communications. The TDRSS satellites substantially increase
Earth-to-space link availability and provide a near continuous exchange of informa-
tion. A single TDRSS satellite can transmit and receive high-data-rate information
to and from low earth orbiting spacecraft via two single access (SA) reflector
antennas. These steerable SA antennas can provide simultaneous S-band and Ku-band
communications with one spacecraft at a time. Communications to and from orbiting
spacecraft can also be accomplished via an S-band multiple access phased array
antenna, though at much lower data rates. A separate space-to-ground link antenna
operating at Ku-band provides communications between a TDRSS satellite and the TDRSS
White Sands Ground Terminal in New Mexico.
In order to provide additional bandwidth for increased communications demand, the
advanced TDRSS, or ATDRSS project has been proposed and is scheduled for launch in
1997. As conceived, the ATDRSS satellites will incorporate Ka-band capability in the
SA reflector antennas, in addition to the S-band and Ku-band services. Therefore, in
order to meet these future requirements, the development of a tri-band reflector
antenna for ATDRSS is critical.
There are two approaches to designing a tri-band reflector antenna. The first
approach utilizes multi-band feeds (e.g. one feed for S-band and another for Ku-band
and Ka-band). However, it is difficult to optimize the antenna performance for a
single feed at more than one frequency. The task is made more difficult by the broad
bandwidth required for the Ka-band (21%).
In this paper, we use a second approach, in which three separate feeds are used.
This allows each feed to be optimized for a single band. The feeds are isolated by
means of frequency selective surfaces (FSS). The FSS will transmit certain fre-
quencies while reflecting others. Conventionally, most FSSs are designed to be used
in two frequency bands. The challenge is to design an FSS that works for three bands
(e.g. transmitting two bands and reflecting a third). Two reflector antenna configu-
rations are presented below, an offset single reflector (fig. 1) and a symmetric
shaped dual reflector (fig. 2). The advantages of each design are presented in
table I.
FSS designs have been developed that will provide the necessary transmission and
reflection characteristics. Using these designs, far-field patterns have been
computed for the above antenna systems, including losses due to the FSS effects. In
general, the FSS losses are only a few tenths of a dB. One of the worst cases for
the offset configuration, at the upper edge of the wide Ka band, is shown in fig-
ure 3. Losses here are only 0.4 dB, based on theoretical calculations.
The offset fed single reflector antenna configuration has been selected for
integration into proposed ATDRS designs. The offset design uses a solid reflector
and planar FSSs, which can be accurately modeled by existing computer programs using
modal analysis. The offset fed single access antenna geometry shown in figure 1 has
been adapted for a conceptual spacecraft design. Some of the assumptions for this
design are (1) an Atlas Centaur launch vehicle, (2) an Advanced Communications
Technology Satellite (ACTS) size spacecraft body and ACTS type solar arrays and (3)
the S-band amplifier can be located in the spacecraft body and the Ku- and Ka-band
equipment can be located in the antenna arms near the feed horns.
CADAM drawings have been completed for the design concept and a 1/13th scale
model has been constructed, employing this offset-fed antenna configuration. Fig-
ure 4 is a photograph of the spacecraft model in the launch ready state. Figure 5
shows the spacecraft model with both offset fed antennas fully deployed. This design
exceeds the original ATDRSS single access antenna pointing requirements in that it
allows a full 360 0 offset antenna scanning capability for Lunar access when using
both antennas.
TABLE I. - DESIGN SUMMARY
Main reflector FSS Advantages
Parabolic,	 offset 2 Planar Planar FSS only
figure 1 Smaller diameter main reflector
(12.5	 ft)
Solid reflector,	 not mesh
Shaped,	 symmetrical 1 Planar and 1 curved Smaller volume (shorter focal
figure 2 length)
Similar to existing TDRSS design
2
Gain/loss S-band Ku-band Ka-band
2.2 GHz 14.9 GHz 25.25 GHz
Ideal gain 38.87 dB 55.48 dB 60.06 dB(D = 150 in.)
Spillover/illumination -1.38 -1.36 -1.33
Blockage -0.05 -0.0 -0.0
FSS -0.30 -0.10 -0.80
Reflector surface -0.05 -0.17 -0.73
Radome -0.05 -0.0 -0.0
Feed loss -0.4 -0.5 -0.7
Total loss -2.23 -2.13 -3.56
Efficiency 60% 61 % 44%
Net gain 36.6 dB 53.3 dB 56.5 dB
180
160
140
120
100
c
r 80
60
40
20
-20
-20	 20 40 60 80 100 120 140 160 180
Z, in.
Figure 1.-Offset single reflector tri-band configu-
ration for ATDRSS with two planar FSS.
liam = 168 in.
-band
60
50
40
30
_T
> 20
U2 10
0
0
-10
-20
0-f --I
1	 -.6
	 -.2	 .2	 .6	 1
0, deg
Figure 3.-Far-field pattern for offset reflector configu-
ration (Fig. 1) with and without FSS. The frequency
is 27.5 GHz, the top edge of the Ka-band. These
are the worst results found for this configuration(0.4 dB loss due to FSS).
Gain/loss S-band Ku-band Ka-band
2.2 GHz 14.9 GHz 25.25 GHz
Ideal gain 39.85 dB 56.47 dB 61.05 dB(D = 168 in.)
Spillover/block/
illumination -2.0 -0.53 -0.6
Planar FSS -0.50 -0.50 -0.70
Additional loss for
curved FSS -0.20 -0.20 -0.20
Reflector surface(mesh) -0.05 -0.68 -2.3
Radome -0.05 -0.0 -0.0
Feed loss -0.4 -0.5 -0.7
Feed line run -0.4 -0.12 -0.37
Total loss -3.60 -2.53 -4.87
Efficiency 44% 56% 33%
Net gain 36.3 dB 53.9 dB 56.1 dB
100
80
60
40
20
c
'-	 0
> Ku - Kat
-20
-40
-60
-80
-100
-50 -40 -20 0 20 40 60 80 100 120 140
Z, in.
Figure 2.-Symmetric dual-shaped reflector con-
figuration for ATDRSS. The subreflector is an
FSS and a planar FSS (not shown) separates
the Ka-band and Ku-band.
4
C-91-02113
Figure 4.-1/13th scale model of ATDRS design concept incorpo-
rating offset-fed single reflector antennas in launch configuration.
C-91-02118
Figure 5.—Fully deployed 1/13th scale ATDRS model with offset-
fed antennas demonstrating a full 360° spherical scan capability.
NASA
National Aeronautics and 	 Report Documentation Page
Space Administration
1.	 Report No. 2. Government Accession No. 3.	 Recipient's Catalog No.
NASA TM -103754
4. Title and Subtitle 5. Report Date
Designs for the ATDRSS Tri-Band Reflector Antenna
6. Performing Organization Code
7. Author(s) 8. Performing Organization Report No.
Shung -Wu Lee, Martin L. Zimmerman, Gene Fujikawa and G. Richard Sharp E - 6008
10. Work Unit No.
316-60-13
9. Performing Organization Name and Address
11 . Contract or Grant No.National Aeronautics and Space Administration
Lewis Research Center
Cleveland, Ohio 44135 - 3 191
13. Type of Report and Period Covered
Technical Memorandum
12. Sponsoring Agency Name and Address
National Aeronautics and Space Administration
14. Sponsoring Agency CodeWashington, D.C. 20546 - 0001
15. Supplementary Notes
Prepared for the 1991 IEEE AP-S International Symposium and URSI Radio Science Meeting, London, Ontario,
Canada, June 24-28, 1991. Shung-Wu Lee and Martin L. Zimmerman, University of Illinois, Urban-Champaign,
Urbana, Illinois 61801; Gene Fujikawa and G. Richard Sharp, NASA Lewis Research Center. Responsible person,
Gene Fujikawa, (216) 433 - 3495.
16. Abstract
This paper examines two approaches to design a tri-band reflector antenna for the Advanced TDRSS. Two reflector
antenna configurations utilizing frequency selective surfaces for operation in three frequency bands, S, Ku and Ka, are
proposed. Far-field patterns and the antenna feed losses have been computed for each configuration. An offset-fed
single reflector antenna configuration has been adapted for conceptual spacecraft design. CADAM drawings have been
completed and a 1/13th scale model of the space craft has been constructed.
17. Key Words (Suggested by Author(s)) 18.	 Distribution Statement
ATDRSS Unclassified - Unlimited
Tri-band reflector antenna Subject Category 18
Frequency selective surfaces
19.	 Security Classif. 	 (of the report) 20.	 Security Classif. (of this page) 21.
	
No. of pages 22. Price'
Unclassified Unclassified 6 A02
NASA FORM 1626 OCT 86	
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