Upgrade of the VLBA C-Band Feed & Receiver Design Review Presented by S durand Designed by Bob...
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Transcript of Upgrade of the VLBA C-Band Feed & Receiver Design Review Presented by S durand Designed by Bob...
![Page 1: Upgrade of the VLBA C-Band Feed & Receiver Design Review Presented by S durand Designed by Bob Hayward and: Sivasankaran Srikanth (Feed Design) Hollis.](https://reader035.fdocuments.net/reader035/viewer/2022062517/56649ed15503460f94bdf658/html5/thumbnails/1.jpg)
Upgrade of the VLBA C-Band Feed & Receiver
Design ReviewPresented by S durand
Designed by Bob Hayward and:Sivasankaran Srikanth (Feed Design)
Hollis Dinwiddie (Mechanical Design)
Everett Callan (Master Receiver Builder)
Gordon Coutts & Craig Hennies (OMT Testing)
Marian Pospieszalski & the CDL Amplifier Group
Pat Madigan & the VLA Machine Shop
Michael Hedrick & the Green Bank Machine Shop
21 April 2011
![Page 2: Upgrade of the VLBA C-Band Feed & Receiver Design Review Presented by S durand Designed by Bob Hayward and: Sivasankaran Srikanth (Feed Design) Hollis.](https://reader035.fdocuments.net/reader035/viewer/2022062517/56649ed15503460f94bdf658/html5/thumbnails/2.jpg)
• Astronomers were eager to:• Access the Methanol Maser at 6,668 MHz GHz• Access to OH at 6016-6049 MHz• Carry out continuum observations with two IF’s separated
by several GHz to allow the effects of the atmosphere to be subtracted out
Example : IF-AC=4.0-4.5 and ID-BD=7.5-8.0 GHz
• Limitations of the existing C-Band system:• Mediocre sensitivity due to old GAsFET LNA’s• Narrow bandwidth due to:
– Septum Polarizer (4.5-5.2 GHz)– LNA’s (4.5-5.2 GHz)– Warm IF (4.5-5.2 GHz)– T105 Conversion (4.5-5.2 GHz)
Why Upgrade the VLBA C-band ?
![Page 3: Upgrade of the VLBA C-Band Feed & Receiver Design Review Presented by S durand Designed by Bob Hayward and: Sivasankaran Srikanth (Feed Design) Hollis.](https://reader035.fdocuments.net/reader035/viewer/2022062517/56649ed15503460f94bdf658/html5/thumbnails/3.jpg)
T(Rx) for Old VLBA vs. New EVLA Rx’sAverage of 8 Dual-Channel Receivers
4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.00
5
10
15
20
25
30
35
40
45
50
Receiver Noise Temperature - VLBA vs. EVLA Receivers
VLBA RxEVLA Rx
Frequency (GHz)
Noi
se T
emp
erat
ure
(K
)
![Page 4: Upgrade of the VLBA C-Band Feed & Receiver Design Review Presented by S durand Designed by Bob Hayward and: Sivasankaran Srikanth (Feed Design) Hollis.](https://reader035.fdocuments.net/reader035/viewer/2022062517/56649ed15503460f94bdf658/html5/thumbnails/4.jpg)
Required Specifications
• To modify the VLBA Receiver to give us the RF performance that is as close to that achieved by an EVLA Receiver as possible.
![Page 5: Upgrade of the VLBA C-Band Feed & Receiver Design Review Presented by S durand Designed by Bob Hayward and: Sivasankaran Srikanth (Feed Design) Hollis.](https://reader035.fdocuments.net/reader035/viewer/2022062517/56649ed15503460f94bdf658/html5/thumbnails/5.jpg)
Sri’s VLBA 4-8 GHz Feed Design
• Profiled Corrugated Horn• Four machined sections • Ring-Loaded Mode Converter• Plugs into old feed location• Total Length = 37.5”• Outer Diameter = 18.5”• Weight = 55 lbs
![Page 6: Upgrade of the VLBA C-Band Feed & Receiver Design Review Presented by S durand Designed by Bob Hayward and: Sivasankaran Srikanth (Feed Design) Hollis.](https://reader035.fdocuments.net/reader035/viewer/2022062517/56649ed15503460f94bdf658/html5/thumbnails/6.jpg)
Installation of the New Feed at VLBA Pie Town• Done with Feed S/N 01• And Unmodified C-Band Rx• Uses a Transition Plate so an
old Receiver can be attached to a new Feed and thus allow installation of lateral support brackets and turnbuckles.
• Luckily feed is small enough to fit through the hatch (i.e., a crane is not required for hoisting it over the dish).
![Page 7: Upgrade of the VLBA C-Band Feed & Receiver Design Review Presented by S durand Designed by Bob Hayward and: Sivasankaran Srikanth (Feed Design) Hollis.](https://reader035.fdocuments.net/reader035/viewer/2022062517/56649ed15503460f94bdf658/html5/thumbnails/7.jpg)
Existing VLBA C-Band Receiver
SeptumPol
RCP
LCP
LNA
LNA
PamtechCTB1107
PamtechCTB1107
Omni-Spectra2089-6203-00
T
-30 dB
Narda4014C-30
AtlanticMicrowaveAMC 0935
GAsFET4.5-5.2 GHz
GAsFET4.5-5.2 GHz
TNoiseDiode+20
-10 dB
High-Cal( Not implemented on VLBA)
TNoiseDiode
-6 dB
Omni-Spectra2020-6617-10
Om
ni-S
pectra
2020-6616-06
PulseCal
TCal
PA
Reactel6B1-4850-700S12
4.5-5.2 GHz
MiteqAMF-2B-4552
4.5-5.2 GHz
DitomD3I4080-14-8 GHz
DitomD3I4080-14-8 GHz
PA
Reactel6B1-4850-700S12
4.5-5.2 GHz
MiteqAMF-2B-4552
4.5-5.2 GHz
DitomD3I4080-14-8 GHz
DitomD3I4080-14-8 GHz
T
Narda4014C-30
-30 dB
TCal
& PCal
TCal
& PCal
PCal
The Cryogenic Pamtech Isolators were a surprise. There was no mention of them in the VLBA Technical Report #3. There must have been added after the 1st prototype Receiver was built.
Keep
New
N/A
Toss
Key:
Cryo
![Page 8: Upgrade of the VLBA C-Band Feed & Receiver Design Review Presented by S durand Designed by Bob Hayward and: Sivasankaran Srikanth (Feed Design) Hollis.](https://reader035.fdocuments.net/reader035/viewer/2022062517/56649ed15503460f94bdf658/html5/thumbnails/8.jpg)
Upgraded VLBA C-Band ReceiverO
MT
T
-30 dB
RCP
LCP
TCal
TCal
& PCal
PCal
LNA
LNA
Hyb
rid
Dorado3ICC60-1
Dorado3ICC60-1
Mac
tech
CA
7205
U
In HEMT4-8 GHz
InP HEMT4-8 GHz
-30 dB
T
Narda4014C-30
Narda4014C-30
Omni-Spectra2089-6203-00
T
NoiseDiode
-10 dB
Noise/ComNC3205-G
10 dB
Omni-Spectra2020-6617-10
PulseCal
TCal
& PCal
RCP4-8 GHz
Out
PA
TTEK5221-4/8G
4-8 GHz
CiaoCA48-281G=26dB
DitomD3I4080-14-8 GHz
DitomD3I4080-14-8 GHz
PA
TTEK5221-4/8G
4-8 GHz
CiaoCA48-281G=26dB
LCP4-8 GHz
Out
DitomD3I4080-14-8 GHz
DitomD3I4080-14-8 GHz
Note that we leave out the High-Cal feature, which has never been used on the VLBA
Keep
New
N/A
Toss
Key:
Cryo
![Page 9: Upgrade of the VLBA C-Band Feed & Receiver Design Review Presented by S durand Designed by Bob Hayward and: Sivasankaran Srikanth (Feed Design) Hollis.](https://reader035.fdocuments.net/reader035/viewer/2022062517/56649ed15503460f94bdf658/html5/thumbnails/9.jpg)
Modifications & Problems• Making the modifications to the RF path of the receiver were
relatively straight forward.• However, cooling the beast was a problem.
– The old VLBA receiver had its Septum Polarizer tied to the 50°K Stage.
– We wanted the new OMT to be tied to the 15°K Stage since it has more resistive losses.
• Hollis spent quite a while fighting to minimize the final temperature that the 15°K Stage reached.– It was hard to get it much below 30°K and the temperature was very
dependent on how many other receivers were on the same Helium line.
– Required reducing the weight of the OMT as well as adding Space Blankets around the 50°K Radiation Shield.
• It was also decided that the Thermal Gap assembly used in the EVLA design would need to be improved.
![Page 10: Upgrade of the VLBA C-Band Feed & Receiver Design Review Presented by S durand Designed by Bob Hayward and: Sivasankaran Srikanth (Feed Design) Hollis.](https://reader035.fdocuments.net/reader035/viewer/2022062517/56649ed15503460f94bdf658/html5/thumbnails/10.jpg)
EVLA-StyleOMT &
Thermal Gap
Includes:
“Old” Thermal Gap+
Heavy Blocks+
Absorber Strip
AN72 Absorber wrapped around
Thermal Gapto prevent
Cavity Resonances.
![Page 11: Upgrade of the VLBA C-Band Feed & Receiver Design Review Presented by S durand Designed by Bob Hayward and: Sivasankaran Srikanth (Feed Design) Hollis.](https://reader035.fdocuments.net/reader035/viewer/2022062517/56649ed15503460f94bdf658/html5/thumbnails/11.jpg)
VLBA-StyleOMT &
Thermal Gap
Includes:
New Circular Thermal Gapwith Choke Ring and long standoffs
+“Swiss Cheese” Blocks
to reduce thermal mass
+Mount for Hybridmakes for an integrated
Circular Polarizer
![Page 12: Upgrade of the VLBA C-Band Feed & Receiver Design Review Presented by S durand Designed by Bob Hayward and: Sivasankaran Srikanth (Feed Design) Hollis.](https://reader035.fdocuments.net/reader035/viewer/2022062517/56649ed15503460f94bdf658/html5/thumbnails/12.jpg)
Recent Cool-down Results• Thanks to Hollis’ new Thermal Gap Assembly, the
Model 22 is now cooling the RF Tree in the Prototype Receiver down to acceptable temperature levels.
• The 15°K Cold Stage temperature is also less susceptible to variations from other fridges being connected to the Helium lines:– ~12-14°K when alone– ~14-16°K with one Model 350 on the loop– ~16-18°K with two Model 350 on the loop
• The 2 x Model 350 scenario is what occurs on a VLBA Antenna.
• VLBA C-Bands typically 15-25°K
![Page 13: Upgrade of the VLBA C-Band Feed & Receiver Design Review Presented by S durand Designed by Bob Hayward and: Sivasankaran Srikanth (Feed Design) Hollis.](https://reader035.fdocuments.net/reader035/viewer/2022062517/56649ed15503460f94bdf658/html5/thumbnails/13.jpg)
VLBA C-Band Prototype (VC#11)
![Page 14: Upgrade of the VLBA C-Band Feed & Receiver Design Review Presented by S durand Designed by Bob Hayward and: Sivasankaran Srikanth (Feed Design) Hollis.](https://reader035.fdocuments.net/reader035/viewer/2022062517/56649ed15503460f94bdf658/html5/thumbnails/14.jpg)
4.0 4.5 5.0 5.5 6.0 6.5 7.0 7.5 8.00
5
10
15
20
25
30
35
40
45
50
Receiver Noise Temperature on VLBA C-Band #11-RCPUnmod (Circ) & Modified (Linear) Rx vs. EVLA Rx C#16 (Circ)
(RHH : 13 April 2011)
VLBA C#11, Unmodified, CircularEVLA C#16, Old T-Gap, CircularVLBA C#11, New T-Gap, Linear
Frequency (GHz)
Rec
eive
r T
emp
erat
ure
(K
)Early RF Sensitivity Tests on VC#11Old EVLA vs. New VLBA Thermal Gap
Using the new T-Gap assembly with its proper Choke Ring yields a vast improvement over that
achieved on the EVLA with the old T-Gap design.
![Page 15: Upgrade of the VLBA C-Band Feed & Receiver Design Review Presented by S durand Designed by Bob Hayward and: Sivasankaran Srikanth (Feed Design) Hollis.](https://reader035.fdocuments.net/reader035/viewer/2022062517/56649ed15503460f94bdf658/html5/thumbnails/15.jpg)
VLBA C-Band ReceiverOld vs. Interim vs. New Configuration
C
RCP
LCP
RCP
LCP
Old T1054.5-5.2 GHzConverter
Module
4.5-5.2GHz
L104 #2
IF OutputA & C
500-1000 MHz4.5-5.2 GHz
C
RCP
LCP
RCP
LCP
New T4054 - 8 GHzConverter
Module
4.0-8.0GHz
IF OutputA, B, C & D
500-1000 MHz
4.0-8.0 GHz
L104 #2
L104 #3
Old C-Band Rx with Old T105
Modified C-Band Rx with New T405
C
RCP
LCP
RCP
LCP
Old T1054.5-5.2 GHzConverter
Module
4.5-5.2 GHz
4.0-8.0GHz
IF OutputA & C
500-1000 MHz4.0-8.0 GHz
(From old Rx) L104 #2
4.5-5.2GHz
Modified C-Band Rx with Old T105 SMA
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Downconverter Design3900-5900 and 5600-7900MHz
Front Panel
Front Panel
Front Panel
Front Panel
3400 to 8600 MHz
512 to 1024 MHz3900 to 5900
5600 to 7900
![Page 17: Upgrade of the VLBA C-Band Feed & Receiver Design Review Presented by S durand Designed by Bob Hayward and: Sivasankaran Srikanth (Feed Design) Hollis.](https://reader035.fdocuments.net/reader035/viewer/2022062517/56649ed15503460f94bdf658/html5/thumbnails/17.jpg)
Conclusions• Thanks to the new Thermal Gap design, the
upgraded VLBA C-Band is now superior to the EVLA receiver.
• Expect T(Rx) < 10°K from 4.2-8.0 GHz• It is now probably the most sensitive
wideband system in the world at this frequency.
![Page 18: Upgrade of the VLBA C-Band Feed & Receiver Design Review Presented by S durand Designed by Bob Hayward and: Sivasankaran Srikanth (Feed Design) Hollis.](https://reader035.fdocuments.net/reader035/viewer/2022062517/56649ed15503460f94bdf658/html5/thumbnails/18.jpg)
Questions ?