A beam waveguide is a mechanism for guiding electromagnetic radiation from one part of an antenna to another through a series of reflectors. Appropriate placement of reflectors on an antenna allows a beam to be guided around the elevation axis and/or below the alidade. The beam waveguide permits placement of all electronics in a room on the alidade below the elevation axis, or below the alidade; feed horn covers to be protected from the weather; and feed electronics to be in spacious rooms rather than in crowded cones, and always level rather than tipping with change in elevation angle. These factors can lead to lower costs in implementation such as Ka-band, better antenna performance at X-band, more efficient and stable performance of transmitters and receivers, and lower maintenance and operating costs. Studies are underway to determine methods for converting the major antennas of the Deep Space Network (DSN) to beam waveguide operations by 1995

Clauss, R. C.

Smith, J. G.

English

NASA Technical Reports Server

TDA ProgressReport42-88
N87-17966
October-December 1986
Beam Waveguides in the Deep Space Network
R. C. Clauss and J. G. Smith
Telecommunications andData Acquisition Technology DevelopmentOffice
A beam waveguide is a mechanism for guiding electromagnetic radiation from one part
of an antenna to another through a series of reflectors. Appropriate placement of reflec-
tors on an antenna allows a "beam" to be guided "around the elevation axis" and/or
"below the alidade. " The beam waveguide permits placement of all electronics in a room
on the alidade below the elevation axis, or below the alidade; feed horn covers to be
protected from the weather; and feed electronics to be in spacious rooms rather than in
crowded cones, and always level rather than tipping with change in elevation angle. These
factors can lead to lower costs in new implementation such as Ka-band, better antenna
performance at X-band, more efficient and stable performance of transmitters and receiv-
ers, and lower maintenance and operating costs. Studies are underway to determine
methods for converting the major antennas of the Deep Space Network (DSN) to beam
waveguide operation by 1995.
I. Introduction
A beam waveguide is an open waveguide where electromag-
netic propagation does not depend on the boundary condi-
tions of the walls. A beam waveguide system typically consists
of an arrangement of reflectors that direct the beam from one
location to another. The set of reflectors may be contained in
large tubes, where minimal interaction occurs with the walls of
the tubes.
Beam waveguide systems are used on antennas as a means
of moving the focal point to a more convenient location. For
example, on the Weilheim, Germany, 30-meter antenna shown
in Figs. 1 and 2, the secondary focal point is located behind
the main reflector, beyond the elevation bearing on the eleva-
tion axis. This has the primary advantage of allowing space for
a large room that contains a dual frequency feed horn, two
X-band masers, two S-band parametric amplifiers, receivers,
and a transmitter; it also allows the electronics to remain level
and keeps the feed horn cover dry despite rain.
Beam waveguide systems typically use curved reflectors or
combinations of curved and flat reflectors. Flat reflectors sim-
ply redirect the beam; curved reflectors may refocus the beam
in order to control beam divergence along the waveguide.
Curved reflectors may be ellipsoidal, or paraboloidal; the
shapes are sometimes modified to favor one frequency. Design
considerations are addressed elsewhere (Ref. 1).
Beam waveguide systems can use a pair of reflectors along
the elevation axis to bring the beam down to a feed electronics
room on the alidade. Again, the reflectors can be fiat or curved
as desired. A second pair of reflectors can be used to advantage
174
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along the vertical axis to bring the beam to a pedestal room
that is below the alidade (Ref. 2). Figure 3 shows these two
configurations conceptually; Fig. 4 shows one of the three
COMSAT antennas at Roaring Creek, Pennsylvania, where all
feeds and electronics are within the stationary buildings on
which the three 32-meter antennas are mounted. Figures 5
and 6 show the 64-meter deep space antenna at Usuda, Japan,
with its three-story alidade building. The spacious interior of
the Usuda alidade rooms provide a laboratory environment for
transmitters, cryogenically cooled low-noise amplifiers, receiv-
ers, and much other equipment (see Fig. 7).
Beam waveguide systems can include many reflectors,
including movable ones, in order to move the beam to any of
several desirable locations. The 45-meter radio astronomy
antenna at Nobeyama, Japan (Fig. 8), has the configuration
of reflectors shown in Figs. 9 and 10. Note that the reflectors
can be moved to redirect the beam. Vernier pointing of the
antenna beam can be accomplished by movement of reflectors.
Figures 11 and 12 show such a system for an aircraft-mounted
98-GHz radiometer, using a 43-cm × 63-cm scanning reflector
(Ref. 3).
The DSN has used reflectors in a fashion similar to those in
beam waveguides for over 10 years. As Fig. 13 shows, the dual-
frequency (S-band and X-band) arrangement of dichroic plate
and ellipsoidal reflector is like a beam waveguide system. How-
ever, these do not move the beam below the elevation axis
and/or alidade. Hence, today DSN antennas contain their
front-end electronics in cones and rooms that are crowded and
that tip.
It is proposed to retrofit beam waveguide systems into
existing DSN antennas, and to employ them on all new DSN
antennas. These beam waveguides will be used to direct the
beam below the elevation axis and/or the alidade, to provide
vernier pointing where needed, to provide frequency sensitive
beam splitting, and to redirect the beam with a movable re-
flector to allow the use of different or redundant sets of
electronic equipment.
II. Performance Gains for the DSN
All advantages to the DSN will accrue because sophisticated
electronic equipment now mounted above the elevation axis in
DSN antennas without beam waveguides can be mounted in
rooms below the elevation axis once beam waveguides are
added. This means that the traditional single or multiple
cones and transmitter rooms above the elevation axis can be
eliminated.
Instead, all electronics will be housed in either a stationary
feed room that does not tip or rotate (typical of COMSAT), or
in a feed room that rotates, but does not tip (typical of Usuda
and Nobeyama).
This has many implications for improved performance and
operation. First, the crowded cones are replaced with spacious
rooms in which new implementations can be installed without
expensive rework. The electronics in the antenna are accessible
all of the time - no need for downtime for maintenance on
the electronics. Equipment can be moved in or out with no
loss of antenna time, and without need for use of the antenna
structure itself as a crane for moving heavy equipment.
Second, equipment can be simpler and easier to maintain
within operating conditions. Cryogenic system gas lines will no
longer traverse hundreds of feet from alidade platforms around
the elevation axis. The lines will be short and fixed with no
flexible sections. The long bundles of power and signal cables
now running from alidade to above the elevation axis will
largely disappear. Cables will be short and fixed. There will be
no gas lines, water lines, or cables above the elevation axis
except for electrical connections for the subreflector control
and aircraft warning lights.
Transmitters will be cheaper to build and easier to main-
tain. For example, a non-tipping transmitter can use steam
rather than water cooling - in fact, an increase in output
power is possible without changing water flow rate because of
increased efficiency of cooling through steam. Tolerances
required for the proposed 34-GHz gyroklystron will be easier
to obtain with a stationary design than with one designed to
be tilted.
Cryogenic systems will a!so be cheaper and more reliable.
Stationary units that store large volumes of liquid helium can
be used to operate at temperatures below 4.2 K and extend
mean time between failure for cryogenic systems from 2000
hours to 20,000 hours. Operating at temperatures near 1.5 K
will reduce maser noise temperature by a factor of three, triple
maser gain-bandwidth product, and allow operation of super-
conducting frequency standards in the front-end area equip-
ment room on the antenna.
Frequency stability will be improved by eliminating flexing
cables, controlling the environment for critical equipment and
cable, and measuring and stabilizing or compensating in real
time for beam waveguide length variations.
Finally, beam waveguides can provide increased antenna
performance at X-band in the rain. This is because systems can
be built so that feed horn covers and dichroic plates are not
exposed to moisture. Light rain that should cause only 2 K
additional noise at X-band can add 40 K due to water in the
feed horn cover and dichroic plate with our current system.
175
The resulting signal-to-noise-ratio loss of 4 dB can be circum-
vented with beam waveguides. Figure 14 shows relative per-
formance during rain at Weilheim, Germany, and as specified
in the DSN at the 95% weather probability.
III. Converting the DSN
Tests conducted with a DSN S-band traveling wave maser
on the 64-meter antenna in Usuda, Japan (Ref. 4) showed that
the zenith system temperature was 1 K lower than that of a
DSN 64-meter antenna, while at 30 degree and 10 degree
elevation angles, the Japanese system temperature was 2.3 K
and 3 K lower than the DSN's (Fig. 15). Usuda's lower noise
temperature is thought to be due to less microwave scattering
off the smaller quadripod support of the Usuda antenna.
There does not appear to be any major cost difference
between an antenna with or without beam waveguide when
building and equipping a new antenna. Probably the beam
waveguide system has a lower cost. That is, the cost of the
reflector system and large feed equipment room is more than
offset by the reduced costs from not providing a cone, trans-
mitter room, heavier quadripod, added counterweights, added
cryogenic lines, added cabling, and the added cost of "tight"
layout design in the crowded space above the elevation axis.
Thus, since neither lower performance nor higher cost
should arise, it appears to be appropriate to build only beam
waveguide designs for future DSN antennas. The new research
and development antenna planned for the Venus site will not
only utilize beam waveguides, but also be used to conduct
extensive tests to answer questions about how the DSN can
best utilize beam waveguide. Replacements for the old HA-
DEC 34-meter antennas are expected to use beam waveguides.
The remaining issue deals with conversion of the existing 64-/
70-meter and 34-meter high efficiency (HEF) antennas.
Figure 16 shows one "conventional" beam waveguide
configuration that is suitable for a 34-meter antenna (Ref. 5).
For the ttEF antennas, this would require rework of the eleva-
tion axis truss - that is, replacement of the horizontal beam
with a "donut" support to allow the beam to be directed
through to the center of the dish. This configuration is a
possibility for the replacements for the old HA-DEC antennas.
Figure 17 shows a "bypass" mode that transfers the beam
"through" the reflector, but requires no structural changes in
the elevation axis truss. This is a candidate for the HEF antenna
since the horizontal support can be retained; both configura-
tions are being considered for tests in the new research and
development antenna at the Venus site.
Beam waveguide conversion for the 70-meter antennas
remains uncertain. Initial surveys show that at least one
approach can place the beam within the central column now
used for the master equatorial pointing system. This could
permit the pedestal area to be used for all transmitter and
receiver equipment now housed above the elevation axis.
This assumes, however, that the 70-meter antennas will not
use a master equatorial pointing system. Studies are now
underway to find ways of converting to beam waveguide with-
out loss of the master equatorial pointing system, and to find
ways of pointing the 70-meter antenna without the master
equatorial system.
IV. Concluding Remarks
The advantages of beam waveguides to DSN future imple-
mentation and operation are significant. Long range plans call
for conversion of the DSN antennas during the 1990s. Replace-
ment of the old HA-DEC 34-meter antennas is slated for the
early 90s, conversion of the 70-meter antenna for the mid-90s,
consistent with plans to add Ka-band reception; conversion of
the 34-meter HEF antennas are less definite, but expected to
occur .in the late 90s.
176
References
1. Veruttipong, T., Withington, J., Galindo-lsrael, V., Imbriale, W., and Bathker, D.,
"Design Considerations for the Beam-Waveguide Retrofit of a Ground Antenna Sta-
tion," TDA Progress Report 42-87, pp. 10-23, Jet Propulsion Laboratory, Pasadena,
California, November 15, 1986.
2. Satellite Communications Engineering, Miya, K., editor, Lattice Company, Ltd.,
Tokyo, Japan, 1975.
3. Wilson, W. J., Howard, R. J., Ibbott, A. C., Parks, G. S., and Ricketts, W. B., "Millimeter-
Wave Imaging Sensor," 1EEE Transactions on Microwave Theory and Techniques, Vol.
MTT-34, No. 10, pp. 1026-1035, October 1986.
4. Fanelli, N. A., Goodwin, J. P., Petty, S. M., Hayashi, T., Nishimura, T., and Takano, T.,
"Utilization of the Usuda Deep Space Center for the United States International
Cometary Explorer (ICE)," Proceedings of the Fifteenth International Symposium on
Space Technology and Science, Tokyo, Japan, 1986.
5. Katow, S., Cucchissi, J. J., Chuang, K. L., Lansing, F. L., Levy, R., Menninger, F. J.,
and StoUer, F. W., "Structural Design Options for the New 34-meter Waveguide
Antenna," TDA Progress Report 42-88, this issue, Jet Propulsion Laboratory, Pasa-
dena, California, February 15, 1987.
177
SUB REF LECTOR 
PLANE REFLECTOR 4 
ELEVATION AXIS 
AZIMUTH AXIS 
-REFLECTOR 2 
(CURVED O R  FLAT) 
REFLECTOR 1 
(CURVED OR FLAT) 
\ 
-MAIN REFLECTOR 
-CURVED 
REFLECTOR 3 
Fig. 1. Weilheim 30-m antenna viewed from front 
Fig. 3. Conceptual configuration of a beam waveguide 
Fig. 2. Weilheim 30-m antenna viewed from rear 
Fig. 4. 32-m COYSAT antenna at Roaring Creek, Pennsylvania 
178 
Fig. 5. Usuda 64-m antenna 
Fig. 7. Interior of Usuda alidade room 
/ .  . 
Fig. 8. 45-m radio astronomy antenna at Nobeyama, Japan 
Fig. 6. Usuda 64-m antenna rear view 
179 
EL BEARING 
90-120GHz 
22 GHz es 
I AXIS 
AZ AXIS 
Fig. 9. Nobeyama 45-m antenna feed configuration 
Fig. 10. Nobeyama 45-m antenna feed configuration and 
beam waveguide 
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Fig. 11. Millimeter wave imaging sensing system 
Fig. 12. Photograph of millimeter wave imaging sensing system 
antenna and scanning system 
180 
Fig. 13. DSS 14 64-m antenna feed system 
30 
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6 7 8 10 12 15 20 30 60 90 
ELEVATION ANGLE, deg 
Fig. 14. X-band system temperature increase versus 
elevation angle 
15 - - 
ANTENNAS 
10 - 
5 -  
0 
8 10 12 15 20 30 90 
ELEVATION ANGLE, deg 
Fig. 15. S-band system temperature versus antenna 
elevation angle 
181 
ELEVATION
WHEEL
FEED H
Fig. 16. Beam waveguide configuration for DSN 34-m
HEF antenna
,i
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Fig. 17. Bypass-mode beam waveguide configuration for OSN
34-m HEF antenna
182


Beam waveguides in the Deep Space Network

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