The High-Resolution Microwave Survey (HRMS) Sky Survey project will be implemented on the DSS 24 beam waveguide (BWG) antenna over the frequency range of 2.86 to 10 GHz. Two wideband, ring-loaded, corrugated feed horns were designed to cover this range. The horns match the frequency-dependent gain requirements for the DSS 24 BWG system. The performance of the feed horns and the calculated system performance of DSS 24 are presented

Lee, P. R.

Reilly, H. F.

Stanton, P. H.

English

NASA Technical Reports Server

126- g,_9
TDA Progress Report 42-114 August15,1993
N94-14397
HRMS Sky Survey Wideband Feed System Design
for DSS 24 Beam Waveguide Antenna
P. H. Stanton, P. R. Lee, and H. F. Reilly
Ground Antennas and Facilities Engineering Section
The High-Resolution Microwave Survey (HRMS) Sky Survey project will be im-
plemented on the DSS 24 beam waveguide (BWG) antenna over the frequency range
of 2.86 to 10 GHz. Two wideband, ring-loaded, corrugated feed horns were designed
to cover this range. The horns match the frequency-dependent gain requirements
for the DSS 24 BWG system. The performance of the feed horns and the calculated
system performance of DSS 24 are presented.
I. Introduction
The High-Resolution Microwave Survey (HRMS) pro-
ject includes a sky survey over the frequency range of 1
to 10 GHz. The DSS 24 34-m beam waveguide (BWG)
antenna will be used from 2.86 to 10 GHz; for frequen-
cies below this, DSS 24 is unsuitable and another antenna
will be utilized. To minimize complexity and expense, two
wideband feed horns were designed to cover this broad fre-
quency range on DSS 24. The performance of the horns
was analyzed, and the upper-frequency horn was built and
tested. The system performance of the horns installed on
DSS 24 was also analyzed using computer software.
II. Feed-Horn Design
Two wideband conical feed horns were designed cov-
ering the frequency ranges of 2.86 to 5.35 GHz and 5.34
to 10 GHz. These ranges were chosen to match those of
the upper-band HRMS orthomode transitions. A wide-
band feed horn for the DSS 24 BWG antenna, needs to
track specific gains and phase-center locations versus fre-
quency to obtain high antenna efficiency and low spillover
noise. Curves were fitted to the existing DSN narrow-
band designs for DSS 24 at 2.1625 GHz, 7.8725 GItz, and
33.25 GHz, and used as initial design values for the HRMS
horns. Figure 1 shows these curves. The wideband (ap-
proximately 1:1.9) HRMS feeds for the DSS 24 antenna
were matched to the fitted gain curve using the Gaussian
beam model in [1] by adjusting the horn output flare angle
and the aperture diameter. Fortunately, these wideband
HRMS BWG feed designs adequately track the desired
phase-center location versus frequency curve.
Once the horn output flare angle and the aperture di-
ameter were determined, the detailed design followed the
one presented in [2]. The horn parameters used in the de-
sign of the HRMS BWG feed horns are listed in Table 1.
Figure 2 shows the four sections of the horn design: ring-
loaded mode converter, frequency transition, angle transi-
tion, and output flare. Figures 3(a) and 3(b) show profiles
316
https://ntrs.nasa.gov/search.jsp?R=19940009924 2020-06-16T21:35:17+00:00Z
of the 2.86- to 5.35-GHz horn and the 5.34- to 10-GHz
horn, respectively.
III. Horn Fabrication
The corrugated horn beyond the mode converter was
fabricated using computer numerical control (CNC) lathe
techniques. This procedure uses a computer-generated
program written and checked on plotters before fabrication
begins. It reduces the possibility of human error caused
by repetitious movement.
The ring-loaded slot mode converter section at the horn
input (see Fig. 2) presented a different problem. With the
ring-loaded grooves, the mode converter section is impos-
sible to fabricate as a single unit on conventional equip-
ment. Several fabrication techniques were investigated.
The cost, tolerance, and ability to make minor changes
were the drivers in choosing the technique used. Each ring-
loaded slot was split down the center, and half of each slot
was machined into adjacent disks (Fig. 4). All of the disks
had the same precise outside diameter. A holder with a
precision bore and length was fabricated to align and com-
press these disks. Interfaces between the horn, the holder,
and the disks were treated like typical waveguide joints.
This design allows changes to individual ring-loaded slots
by changing disks.
IV. Horn Performance
The horns were analyzed with a JPL computer pro-
gram) The program uses field matching techniques to
determine the scattering matrices of the transverse electric
(TErns) and transverse magnetic (TMm_) modes of the
horns [3]. From the scattering matrices, the aperture mode
fields and the return loss of the horns are known. The
radiation patterns of the horns can be calculated from the
aperture mode fields by using the radiation integral.
The calculated gain and near-field phase-center location
of the horns versus the frequency are shown in Figs. 5
and 6, along with the initial design gain and phase-center
location. The calculated gain is somewhat higher than
the initial design gain because of the approximation of
the Gaussian beam model used in [1]. Computer analyses
on DSS 24 revealed that the higher gain provided better
noise temperature performance than the initial design gain
but still had a comparable gain-to-noise temperature ratio
(C/T).
1 D. J. I{oppe, Scattering Matrix Program for Ring-Loaded Circu-
lar Waveguide Junctions (unnumbered, internal docalment), Jet
Propulsion Laboratory, Pasadena, California, August 3, 1987.
The upper-frequency horn has been built and tested.
The lower-frequency horn has been fabricated, but has not
been fully tested. The return loss of the upper-frequency
horn was measured on a Hewlett Packard 8510C network
analyzer. The measured return loss, along with the calcu-
lated return loss of both horns, is shown in Fig. 7. Far-field
radiation patterns of the upper-frequency horn were mea-
sured on JPL's Mesa Antenna Range at several frequencies
from 5.34 to 11 GHz. The copolarization measurements
matched the calculated patterns very well. Figure 8 com-
pares one typical measurement with the calculated pat-
tern. The maximum measured cross-polarization signal is
32.6 dB below the peak copolarization signal within the
operating band of 5.34 to 10 GHz. The maximum error
between the measured and the calculated values is 4.4 dB.
Figure 9 shows the measured values for the 5.34- to 10-
GHz horn, and the calculated values for both horns.
V. DSS 24 Performance
The performance of tile DSS 24 BWG antenna with
the HRMS feeds was predicted by using JPL computer
programs 2 based on physical optics (PO) and physical
optics/Jacobi-Bessel (POJB) techniques [4,5]. These pro-
grams are numerically intensive and consume large
amounts of computer time. They were run on tlle JPL
Cray Y-MP2E supercomputer, Voyager.
With the PO program results, it is possible to calculate
the total spillover power of the BWG reflectors, the subre-
flector, and the main reflector. For the spillover power of
the BWG mirrors, an effective noise temperature value of
280K was used in the pedestal room, and a value of 230K
was used in the shroud above the pedestal room. 3 The
effective noise temperature values for the spillovers past
the main and subreflectors were taken to be 240K and 5K,
respectively, for the antenna at zenith.
To find the best physical positions of tile feeds, sev-
eral feed locations were analyzed until the peak G/T was
found. Five frequencies in each feed operating band were
examined. The optimal position for each feed varies less
than 23 cm over its frequency band. By locating the feeds
in the center of their respective optimal position ranges,
2 R. E. ttodges and W. A. hnbriale, Computer Program POMESH
]or Diffraclion A nalysis o] Reflector Antennas (unnumbered, inter-
nal document), Jet Propulsion Laboratory, Pasadena, California,
February 1992.
3 W. Veruttipong and M. Franco, "A Technique for Computation of
Noise Temperature Due to a BWG Shroud," JPL hlteroffice Memo-
randum 3328-92-0149, Rev. A (internal document), Jet Propulsion
Laboratory, Pasadena, California, November 3, 1992.
317
less than 0.05 dB/K is lost and the feed horns do not need
to be relocated during operation.
To place the feeds in the pedestal room of DSS 24,
a flat plate must be used with each feed. The 5.34- to
10-GHz horn will fit in the available space with its axis
vertical and a flat plate above it (Fig. 10). However, the
2.86- to 5.35-GHz horn will not fit so easily. The horn will
be placed with its axis horizontal, which, unfortunately,
causes extra wear on the low-noise-amplifier refrigeration
vacuum pump. Figure 11 shows the configuration of the
horn and the mirror.
Beam squint was examined at the highest and lowest
frequencies in both horn bands by running both right-
circular and left-circular polarizations (RCP and LCP) of
the horn patterns through the PO programs. The tilt an-
gle varied from 6 millidegrees at 2.80 Gttz to 2 millidegrees
at 10 GHz. The tilt angle to half-power beamwidth ratio
remained fairly constant, varying from 0.031 to 0.034. The
loss due to squint ranged from 0.011 dB at 2.86 GHz to
0.013 dB at 10 GHz.
Major RF system requirements 4 are listed in Table 2.
Table 3 shows the calculated system performance for the
antenna at zenith, including noise temperature, 5 aperture
efficiency, beam efficiency, gain, 6 G/T, and target G/T. 7
VI. Conclusions
Two HRMS Sky Survey wideband (approximately
1:1.9) feed horns were designed to be compatible with
4 G. A. Zimmerman, Search for Extra-Terrestrial Intelligence -- Mi-
crowave Observing Project Sky Survey Element, JPL 1720-4100
(internal document), Jet Propulsion Laboratory, Pasadena, Cali-
fornla, November 12, 1991.
s The noise temperature includes contributions from the sky and
atmosphere, reflector spillover, reflector ohmic losses, main reflec-
tor leakage, horn ohmic losses, scattering from the subreflector
support structure, and the low-noise amplifier (LNA) assembly.
Sky and atmosphere and LNA assembly values fi'om: JPL-ARC
Front-End Design Team, NASA SETI Common Radio Frequency
System Design Team Report (internal report), Appendix D, p. 6,
NASA, Washington, DC, August 1, 1991. Reflector ohmic losses,
main reflector leakage, and scattering from the subreflector sup-
port structure based on estimated values at 2.295 GHz and 8.45
GHz from W. Veruttipong and D. Bathker, JPL Interoffice Mem-
orandum (unnumbered, internal document), Jet Propulsion Labo-
ratory, Pasadena, California, February 7, 1992.
the DSS 24 BWG antenna, covering a combined frequency
range of 2.86 to 10 GHz. The upper-frequency horn has
been fabricated and tested. The RF measurements were
in close agreement with the calculated values in both the
radiation patterns and return loss. Based on the results of
the upper-frequency horn, the performance of the lower-
frequency horn is expected to closely match the calculated
performance.
The predicted DSS 24 aperture efficiency is greater than
0.747 over this'frequency range. At the lower end of each of
the two feed-horn frequency ranges, the noise temperature
is higher than the 25 K maximum required. The predicted
G/T, however, is at least 0.3 dB greater than is required
over the entire frequency range. The beam efficiency is in
the range of 0.772 to 0.881, short of the >0.9 requirement, r
The beam efficiency could be improved at the expense of
the aperture efficiency.
A DSN frequency in the HRMS 2.86- to 10-GHz range
available for comparison is 8.45 GHz (X-band). The design
expectations of DSS 24 for DSN operation at 8.45 GHz,
excluding the S-/X-band dichroic plate, are 0.766 aperture
efficiency and 24.20 K noise temperature, s For tile HRMS
design at 8.45 GHz, substituting the DSN estimated values
for the DSN preamplifier assembly for the HRMS pream-
plifier assembly, an aperture efficiency of 0.732 and a noise
temperature of 23.16 K are predicted. The HRMS design
has a resulting G/T of 54.56 dB/K compared to 54.57
dB/K for the DSN design.
The gain calculations include the following: illumination efficiency,
reflector spillover loss, reflector ohmic loss, reflector surface RMS
loss, main reflector leakage, BWG return loss, subreflector support
structure blockage, reflector alignment loss, horn ohmic loss, horn
return loss, and pointing squint. The values for all losses other than
illumination efficiency, spillover losses, and horn losses are based on
estimated values at 2.295 GHz and 8.45 GHz from W. Veruttlpong
and D. Bathker, JPL Interoffice Memorandum (unnumbered, inter-
nal document), Jet Prop/dslon Laboratory, Pasadena, California,
February 7, 1992.
r The target G/T is for 65-percent aperture efficiency and 25 K noise
temperature.
s W. Veruttlpong and D. Bathker, JPL Interoffice Memorandum
(unnumbered, internal document), Jet Propulsion Laboratory,
Pasadena, California, February 7, 1992.
318
References
[1] P.-S. Kildal, "Gaussian Beam Model for Aperture-Controlled and Flareangle-
Controlled Corrugated Horn Antennas," IEE Proceedings, vol. 135, no. 4, part H,
pp. 237-240, August 1988.
[2] B. M. Thomas, G. L. James, and K. L. Greene, "Design of Wide-Band Corru-
gated Conical Horns for Cassegrain Antennas," IEEE Transactions on Antennas
and Propagation, vol. AP-34, no. 6, pp. 750-757, .June 1986.
[3] G. L. James and B. M. Thomas, "TEll to HEll Cylindrical Waveguide Mode
Converters Using Ring-Loaded Slots," IEEE Transactions on Microwave Theory
and Techniques, vol. MTT-30, no. 3, pp. 278-285, March 1982.
[4] V. Galindo-Israel and R. Mittra, "A New Series Representation for the Radi-
ation Integral with Application to Reflector Antennas," IEEE Transactions on
Antennas and Propagation, vol. AP-25, no. 5, pp. 631-641, September 1977.
[5] Y. Rahmat-Samii and V. Galindo-Israel, "Shaped Reflector Antenna Analysis
Using the Jacobi-Bessel Series," IEEE Transactions on Antennas and Propaga-
tion, vol. AP-28, no. 4, pp. 425-435, July 1980.
319
Table 1. Feed-horn design parameters.
Parm_eter 2.86- to 5.35-GHz horn 5.34- to 10-GHz horn
Mode converter section
Low-frequency limit, fL, GHz
Output design frequency /i (= 1.15fL), GHz
Normalized input radius, kial
Normalized converter length, zl/)_i
Conical semiangle, Oi, deg
Slot width-to-pitch ratio, 6i
Normalized slot pitch, pi/Ai
2.86 5.159
3.289 5.933
2.9 2.9
1 1
6 6
0.75 0.75
0.1 0.1
Normalized length, zt_/,\i
Frequency transition section
3
Normalized length, zt'/Ai
Angle transition section
1
Output flare section
Conical semiangle, 0i, deg 11
Normalized aperture radius, ao/,_L 3.44
Slot width-to-pitch ratio, 6o 0.75
Pitch, Po 0.1
9.85
5.33
0.75
0.1
320
Table2.MajorRFsystemrequirements.
Parameter Required value
Noise temperature, K <25
Polarization RCP a and LCP b (simultaneous)
Instantaneous bandwidth, MHz >360
Aperture efficiency, % >65
Beam efficiency, _ >_90
a Right-circular polarization.
b Left-circular polarization.
Table 3. DSS 24 system performance at zenith.
Frequency, Noise Beam Aperture Gain, G/T, Target G/T,
GHz temperature, K efficiency efficiency dB dB/K dB/K
2.86- to 5.35-GHz feed horn
2.86 27.64 0.857 0.774 59.04 44.62 44.31
3.289 25.88 0.877 0.783 60.31 46.18 45.53
3.87 24.21 0.879 0.783 61.72 47.88 46.94
4.54 23.64 0.861 0.788 63.14 49.40 48.33
5.34 23.61 0.881 0.750 64.33 50.60 49.74
5.34- to 10-GHz feed horn
5.34 25.56 0.810 0.787 64.54 50.46 49.74
5.933 25.03 0.803 0.786 65.45 51.47 50.65
7.1 24.60 0.792 0.767 66.90 52.99 52.21
8.45 22.27 0.803 0.757 68.36 54.88 53.72
10.0 23.30 0.772 0.747 69.76 56.09 55.19
321
30.01 1 I I I I 1 I I |550 O
I -t UJIu
2s.oI- t "" _ H 450 a.-,__i o_
w ,,-00
Z _ Wcr
_ u__
(.9 20.0 350 < cc
-I- Uj LU
a.l-a
zuJq_o.
17.5_ 1300 ,T_
&o
¢(n..
uju-
15.0 I I I 1 I I I I 250 z
1 2 3 4 5 6 7 8 9 10
FREQUENCY, GHz
Rg. 1. Inltiai design gain and near-field phase-center location of feeds for DSS 24.
MODE _ _
CONVERTER
FREQUENCY
TRANSITION
ANGLE
< TRANSITION --'w"
Rg. 2, Basic wideband horn configuration.
OUTPUT
FLARE
322
(a) _ _
1
_ 2.7
8.4
159.7 _!
L
- 53.94.7 - -
.,_ 151.1 D,-
Rg. 3. Profiles of: (a) 2.86- to 5.35-GHz horn and (b) 5.34- to 10-GHz horn.
323
Fig. 4. Cross secUon of three adjacent
mode converter disks.
3O
28
_5 26
"o
<(.9 24
22
2C
2.5
' I ' I ' L ' I ' I ' I ' I
-- INITIAL DESIGN GAIN
i I i I I I i I , I i I i I
3.5 4.5 5.5 6,5 7.5 8.5 9.5
FREQUENCY, GHz
Fig. 5. Calculated horn gain.
55O
rt-
5oo
E
z450
,<
9 8 40oW
7m 350
300 /
2
I I I I I I I
J
- J
• • CALCULATED LOCATION FOR
2,86- TO 5,35-GHz FEED
• CALCULATED LOCATION FOR
5.34- TO 10-GHz FEED
-- INITIAL DESIGN LOCATION
I I I I I I I
3 4 5 6 7 8 9 10
FREQUENCY, GHz
Fig. 6. Calculated near-field phase-center Iocatlofl.
324
-20 _ 1 I I t t
-30 (a)
-40 f x
-50 N x x
-60
(fi-70 1 I I I I
(/)
O, 2.85 3.35 3.85 4.35 4.85 5.35
Z-20 L b ' I ' I ' 1 ' I ' I ' /
-30 ( ) x CALCULATED q/
/
-40
-50
-60
--70 I I I I I I ' I I I J I
4.96 5.8 6.64 7.48 8.32 9.16 10
FREQUENCY, GHz
Fig. 7. Return loss of: (a) 2.86- to 5.35-GHz horn and
(b) 5.34- to IO-GHz horn.
10
0
_ -10
_ -20
_-30
-40
-50
-35 -25 -15 -5 5 15 25
0, deg
Fig. 8. Far-field copolarization radiation pattern at 7.1 GHz.
I 1 I I I I
I _ ..... CALCULATED -
35
-10
_ -20 -
uJ
2 -30 -
z
_ --4O-
i
-50 _-
-60
2
I I I I t I I I I
• CALCULATED, 2.86- TO 5.35-GHz HORN
• CALCULATED, 5.34- TO 10-GHz HORN
• MEASURED, 5.34-TO 10-GHz HORN
I
• I •e •
• II •
I I I I I I I I t
3 4 5 6 7 8 9 10 11
FREQUENCY, GHz
12
Fig. 9. Maximum cross-polarization of feeds relative to peak
¢opolarization.
325
/_, //////////_Y//////,
N J//_ _ I PLATE, 149.9cm// r -/ ,NO,AM_ER
___ / yF_'°
_////. ._,'(//////////////
Fig. 10, Fiat-plate design lor 5.34- to tO-GHz horn.
(a)
y///////c#._',"/////A
/ .3,53_RCI RCULAR FLAT
LATE
REAR VIEW
Z3
LNA PACKAGE
_////////////#... Y///////////
(b)
o,.ouLA__ P_E,_"' _...
_- POINT A II
I_ /-- 2.86- TO 5.35-GHz
Fig. 11. Fiat-plate design for 2.86- to 5.35-GHz horn: (a) rear view and (b) view In x, y plane.
326


HRMS sky survey wideband feed system design for DSS 24 beam waveguide antenna

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server