CHALMERS INDUSTRITEKNIK Commercial R&D STIFTELSEN CHALMERS INDUSTRITEKNIK Social media and HEPTech.
Chalmers University of Technology Development of a Coolable Decade Bandwidth Eleven Feed System for...
-
Upload
hana-hunley -
Category
Documents
-
view
219 -
download
0
Transcript of Chalmers University of Technology Development of a Coolable Decade Bandwidth Eleven Feed System for...
Chalmers University of Technology
Development of a Coolable Decade Bandwidth Eleven Feed System for SKA &
VLBI 2010 Radio Telescopes
Per-Simon Kildal
Chalmers University of Technology
Gothenburg, SWEDEN15 cm diameter for 2-13 GHz
Chalmers University of Technology
Start in 2003: ATA array, forrunner of US SKA (500 MHz – 10 GHz)
Chalmers University of Technology
Size and complexity for fmin = 500 MHz
ATA feed:Too large
& Problem
with phase center
variations
Eleven feed:Eleven times
smaller&
No problem with phase
center variations
Chalmers University of Technology
Size and complexity for fmin = 500 MHz
ATA feed:Too large
& Problem
with phase center
variations
Eleven feed:Eleven times
smaller&
No problem with phase
center variations
Chalmers University of Technology
Idea behind Chalmers feed• Two parallel dipoles over ground
– from book about Radio Telescopes by Christiansen and Högbom– equal E- and H-plane patterns– phase center is locked to the ground plane – low far-out sidelobes and backlobes.
• Bandwidth by– Logperiodic– Folded dipoles
• ”Eleven” name inspired by– Basic dual-dipole geometry– Directivity 10-11 dBi and S11 <-10 dB– Over more than decade bandwidth (>11)– And size eleven times smaller than
classical log-periodic feeds
Chalmers University of Technology
Interdisciplinary team developing coolable VLBI2010 hardware from Sept 2008
• Interdisciplinary research at Chalmers– Department of Signals and Systems, Chalmers
– Department of Radio and Space Sciences, Chalmers
– Department of Microtechnology and Nanoscience
– Chalmers Industriteknik (CIT) for helping to commercialize:
• No dedicated SKA funding since 2003-2005 (US SKA project)
• Hardware orders from VLBI 2010 partners: – Vertex (BKG) in Germany
– Statkart in Norway
– Haystack radio telescope in USA
Chalmers University of Technology
Main contributions• Dr Jian Yang: “Electrical design”
• Dr Miroslav Pantaleev and Leif Helldner: “Mechanical and cryogenic design”
• Benjamin Klein, South Africa “Noise modeling”
• Drawing, assembled feed, cooled feed
Chalmers University of Technology
Assembled 2-13 GHz hardware and drawing
Chalmers University of Technology
The following choices were made during the project
• All materials MUST stand cryogenic temp
• 4 separate panels (petals) with log-per. dipoles
• PCB technology for antenna petals
• Minimize thickness of dielectric in center
• 2x4 ports with no crossing lines in center puck
• Differential feed line impedance 200 Ohms
• Experimental model has 2x4 coaxial ports, transf to 50 Ohms
• We work also with 4 differential 200 Ohms LNAs, 2 per polarization
Chalmers University of Technology
Front and back sides of Eleven feed with 8 single-ended ports
Chalmers University of Technology
Integration with differential 200 ohm LNAs from Caltech
• Four cryogenic differential 200 ohm LNAs from Caltech mounted on the back side of the ground plane
• Requires in addition two power combiners to get two polarizations out from the cryostat
• Expected delivery of LNAs: June 2010
Chalmers University of Technology
Early computed still valid efficiency vs. subtended half angle
Optimum subtended angle >50 deg
Chalmers University of Technology
Early computed figure of Merit versus F/Doptimum F/D = 0.4 (i.e. 64 deg)
Useful range 0.33 < F/D < 0.50, i.e. 75 deg < 55 deg
Chalmers University of Technology
Simulations and Measurements at Chalmersof input reflection coefficient (4 ports excited)
(power dividers and cables were calibrated away)
1 3 5 7 9 11 13 15 1718-20
-18
-16
-14
-12
-10
-8
-6
-4
-2
0
Frequency (GHz)
Re
fle
cti
on
co
eff
icie
nt
(dB
)
measuredsimulated
Chalmers University of Technology
Co- and crosspolar patterns in 45 deg planetotal and with removed higher order variations
-150 -100 -50 0 50 100 150-30
-25
-20
-15
-10
-5
0
theta (deg)
ampl
itude
(dB
)
2GHz2.1GHz
2.2GHz
2.3GHz
2.4GHz2.5GHz
2.6GHz
2.7GHz
2.8GHz2.9GHz
-150 -100 -50 0 50 100 150-30
-25
-20
-15
-10
-5
0
[o]
Re
lati
ve
le
ve
l [d
Bi]
2.00 GHz2.10 GHz
2.20 GHz
2.30 GHz
2.40 GHz2.50 GHz
2.60 GHz
2.70 GHz
2.80 GHz2.90 GHz
Chalmers University of Technology
-150 -100 -50 0 50 100 150-30
-25
-20
-15
-10
-5
0
[o]
Re
lati
ve
le
ve
l [d
Bi]
3.00 GHz3.10 GHz
3.20 GHz
3.30 GHz
3.40 GHz3.50 GHz
3.60 GHz
3.70 GHz
3.80 GHz3.90 GHz
-150 -100 -50 0 50 100 150-30
-25
-20
-15
-10
-5
0
theta (deg)
ampl
itude
(dB
)
3GHz
3.1GHz3.2GHz
3.3GHz
3.4GHz
3.5GHz
3.6GHz
3.7GHz3.8GHz
3.9GHz
Co- and crosspolar patterns in 45 deg planetotal and with removed higher order variations
Chalmers University of Technology
-150 -100 -50 0 50 100 150-30
-25
-20
-15
-10
-5
0
[o]
Re
lati
ve
le
ve
l [d
Bi]
4.00 GHz4.10 GHz
4.20 GHz
4.30 GHz
4.40 GHz4.50 GHz
4.60 GHz
4.70 GHz
4.80 GHz4.90 GHz
-150 -100 -50 0 50 100 150-30
-25
-20
-15
-10
-5
0
theta (deg)
ampl
itude
(dB
)
4GHz
4.1GHz4.2GHz
4.3GHz
4.4GHz
4.5GHz
4.6GHz
4.7GHz4.8GHz
4.9GHz
Co- and crosspolar patterns in 45 deg planetotal and with removed higher order variations
Chalmers University of Technology
-150 -100 -50 0 50 100 150-30
-25
-20
-15
-10
-5
0
[o]
Re
lati
ve
le
ve
l [d
Bi]
5.00 GHz5.10 GHz
5.20 GHz
5.30 GHz
5.40 GHz5.50 GHz
5.60 GHz
5.70 GHz
5.80 GHz5.90 GHz
-150 -100 -50 0 50 100 150-30
-25
-20
-15
-10
-5
0
theta (deg)
ampl
itude
(dB
)
5GHz
5.1GHz5.2GHz
5.3GHz
5.4GHz
5.5GHz
5.6GHz
5.7GHz5.8GHz
5.9GHz
Co- and crosspolar patterns in 45 deg planetotal and with removed higher order variations
Chalmers University of Technology
-150 -100 -50 0 50 100 150-30
-25
-20
-15
-10
-5
0
[o]
Re
lati
ve
le
ve
l [d
Bi]
6.00 GHz6.10 GHz
6.20 GHz
6.30 GHz
6.40 GHz6.50 GHz
6.60 GHz
6.70 GHz
6.80 GHz6.90 GHz
-150 -100 -50 0 50 100 150-30
-25
-20
-15
-10
-5
0
theta (deg)
ampl
itude
(dB
)
6GHz
6.1GHz6.2GHz
6.3GHz
6.4GHz
6.5GHz
6.6GHz
6.7GHz6.8GHz
6.9GHz
Co- and crosspolar patterns in 45 deg planetotal and with removed higher order variations
Chalmers University of Technology
-150 -100 -50 0 50 100 150-30
-25
-20
-15
-10
-5
0
theta (deg)
ampl
itude
(dB
)
7GHz
7.1GHz7.2GHz
7.3GHz
7.4GHz
7.5GHz
7.6GHz
7.7GHz7.8GHz
7.9GHz
-150 -100 -50 0 50 100 150-30
-25
-20
-15
-10
-5
0
[o]
Re
lati
ve
le
ve
l [d
Bi]
7.00 GHz7.10 GHz
7.20 GHz
7.30 GHz
7.40 GHz7.50 GHz
7.60 GHz
7.70 GHz
7.80 GHz7.90 GHz
Co- and crosspolar patterns in 45 deg planetotal and with removed higher order variations
Chalmers University of Technology
-150 -100 -50 0 50 100 150-30
-25
-20
-15
-10
-5
0
[o]
Re
lati
ve
le
ve
l [d
Bi]
8.00 GHz8.10 GHz
8.20 GHz
8.30 GHz
8.40 GHz8.50 GHz
8.60 GHz
8.70 GHz
8.80 GHz8.90 GHz
-150 -100 -50 0 50 100 150-30
-25
-20
-15
-10
-5
0
theta (deg)
ampl
itude
(dB
)
8GHz
8.1GHz8.2GHz
8.3GHz
8.4GHz
8.5GHz
8.6GHz
8.7GHz8.8GHz
8.9GHz
Co- and crosspolar patterns in 45 deg planetotal and with removed higher order variations
Chalmers University of Technology
-150 -100 -50 0 50 100 150-30
-25
-20
-15
-10
-5
0
[o]
Re
lati
ve
le
ve
l [d
Bi]
9.00 GHz9.10 GHz
9.20 GHz
9.30 GHz
9.40 GHz9.50 GHz
9.60 GHz
9.70 GHz
9.80 GHz9.90 GHz
-150 -100 -50 0 50 100 150-30
-25
-20
-15
-10
-5
0
theta (deg)
ampl
itude
(dB
)
9GHz
9.1GHz9.2GHz
9.3GHz
9.4GHz
9.5GHz
9.6GHz
9.7GHz9.8GHz
9.9GHz
Co- and crosspolar patterns in 45 deg planetotal and with removed higher order variations
Chalmers University of Technology
-150 -100 -50 0 50 100 150-30
-25
-20
-15
-10
-5
0
[o]
Re
lati
ve
le
ve
l [d
Bi]
10.00 GHz10.10 GHz
10.20 GHz
10.30 GHz
10.40 GHz10.50 GHz
10.60 GHz
10.70 GHz
10.80 GHz10.90 GHz
-150 -100 -50 0 50 100 150-30
-25
-20
-15
-10
-5
0
theta (deg)
ampl
itude
(dB
)
10GHz
10.1GHz10.2GHz
10.3GHz
10.4GHz
10.5GHz
10.6GHz
10.7GHz10.8GHz
10.9GHz
Co- and crosspolar patterns in 45 deg planetotal and with removed higher order variations
Chalmers University of Technology
-150 -100 -50 0 50 100 150-30
-25
-20
-15
-10
-5
0
[o]
Re
lati
ve
le
ve
l [d
Bi]
11.00 GHz11.10 GHz
11.20 GHz
11.30 GHz
11.40 GHz11.50 GHz
11.60 GHz
11.70 GHz
11.80 GHz11.90 GHz
-150 -100 -50 0 50 100 150-30
-25
-20
-15
-10
-5
0
theta (deg)
ampl
itude
(dB
)
11GHz
11.1GHz11.2GHz
11.3GHz
11.4GHz
11.5GHz
11.6GHz
11.7GHz11.8GHz
11.9GHz
Co- and crosspolar patterns in 45 deg planetotal and with removed higher order variations
Chalmers University of Technology
-150 -100 -50 0 50 100 150-30
-25
-20
-15
-10
-5
0
[o]
Re
lati
ve
le
ve
l [d
Bi]
12.00 GHz12.10 GHz
12.20 GHz
12.30 GHz
12.40 GHz12.50 GHz
12.60 GHz
12.70 GHz
12.80 GHz12.90 GHz
-150 -100 -50 0 50 100 150-30
-25
-20
-15
-10
-5
0
theta (deg)
am
plit
ud
e (
dB
)
12GHz
12.1GHz12.2GHz
12.3GHz
12.4GHz
12.5GHz
12.6GHz
12.7GHz12.8GHz
12.9GHz
Co- and crosspolar patterns in 45 deg planetotal and with removed higher order variations
Chalmers University of Technology
-150 -100 -50 0 50 100 150-30
-25
-20
-15
-10
-5
0
[o]
Re
lati
ve
le
ve
l [d
Bi]
13.00 GHz13.10 GHz
13.20 GHz
13.30 GHz
13.40 GHz13.50 GHz
13.60 GHz
13.70 GHz
13.80 GHz13.90 GHz
-150 -100 -50 0 50 100 150-30
-25
-20
-15
-10
-5
0
theta (deg)
am
plit
ud
e (
dB
)
13GHz
13.1GHz13.2GHz
13.3GHz
13.4GHz
13.5GHz
13.6GHz
13.7GHz13.8GHz
13.9GHz
Co- and crosspolar patterns in 45 deg planetotal and with removed higher order variations
Chalmers University of Technology
Sub-efficiencies from measured radiation patterns at TUD
2 3 4 5 6 7 8 9 10 11 12 13-4
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0
Frequency (GHz)
Eff
icie
ncy
(dB
)
esp
eBOR1
epol
eill
e
eap
Looks good, except for BOR1 efficiency below 2.5 GHz and above 9 GHz.
BOR1 efficiency is power lost in sidelobes due to higher order variations.
Chalmers University of Technology
After survival test
to 14 K
Three stages of cryostat
(Dewar) can be seen
Chalmers University of Technology
Deformation simulations and testing at cryogenic temperatures
Chalmers University of Technology
Integration of Eleven feed in cryostat
The MIL infrared filter reduces the temperature to 25K
The 70K shield has infrared window of one layer Teflon
The temperature on the Feed surface is measured with temperature sensor Lakeshore DT-470 mounted on thin copper support soldered at the edge of the third dipole.
Chalmers University of Technology
Front and back sides of Eleven feed with 8 single-ended ports
Chalmers University of Technology
Noise Temperature Measurements
Chalmers University of Technology
Noise temperatures
Ohmic loss
LNA
Sky and ground
Total predicted and measured
Chalmers University of Technology
Summary of measurement results
• Hardware: Good. Appears solid and appealing• Matching: abs(S11) < -10 dB up to 13 GHz
– measured by removing effects of power dividers and cables by calibration
• Independent gain measurements at Technical University of Denmark – Losses smaller than 0.5 dB (Uncertainty due to multiple reflections between
180 deg hybrid, 3dB power divider and antenna, which were not calibrated out in this case)
– Radiation patterns: Good between 2.5 and 9 GHz. Otherwise low BOR1 efficiency
– Overall efficiency in reflector better than -2 dB between 2.5 and 9 GHz
• Promising system noise measurements with TLNA = 5 – 10 K
Chalmers University of Technology
Integration with differential 200 ohm LNAs from Caltech
• Four cryogenic differential 200 ohm LNAs from Caltech mounted on the back side of the ground plane
• Requires in addition two power combiners to get two polarizations out from the cryostat
• Expected delivery of LNAs: June 2010
Chalmers University of Technology
Planned work• Design and test compact 1-10 GHz SKA model
• Improve low BOR1 efficiency above 9 GHz
• More studies of radiation fields and S11 in cryostat
• Improve noise models
• Test with 4 differential LNAs
• Integrate and test with passive balun and 2 single-ended LNAs
• More optimizatioins and compare with horn solutions (narrow band)
Chalmers University of Technology
Comparison of figure of merit A/T (predicted)
A/T of the Eleven feed system• For a reflector of 1 m2 area with subtended half angle of 60o, i.e. F/D = 0.433. • Cooled system is with Caltech cryogenic LNA and cryostat is at 30 K. • The uncooled system is with Chalmers room temperature LNA at room temperature.