Paul Lilie EVLA Front-End CDR – OMT Development April 24, 2006 1 EVLA Front-End CDR Octave Bandwidth OMT Development in the 1-8 GHz Range
EVLA Front-End CDR
Dec 30, 2015
EVLA Front-End CDR. Octave Bandwidth OMT Development in the 1-8 GHz Range. Frequency Ranges. L: 1- 2 GHz2:1(“Octave”) S: 2 – 4 GHz2:1(“Octave”) C: 4 – 8 GHz2:1(“Octave”) X: 8 – 12 GHz1.5:1 Ku:12 – 18 GHz1.5:1 K:18 – 26 GHz1.44:1 Ka:26 – 40 GHz1.54:1 - PowerPoint PPT Presentation
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Paul Lilie EVLA Front-End CDR – OMT DevelopmentApril 24, 2006
1
EVLA Front-End CDR
Octave Bandwidth OMT Development in the 1-8 GHz Range
Paul Lilie EVLA Front-End CDR – OMT DevelopmentApril 24, 2006
2
Frequency Ranges
• L: 1- 2 GHz 2:1 (“Octave”)• S: 2 – 4 GHz 2:1 (“Octave”)• C: 4 – 8 GHz 2:1 (“Octave”)• X: 8 – 12 GHz 1.5:1• Ku: 12 – 18 GHz 1.5:1• K: 18 – 26 GHz 1.44:1• Ka: 26 – 40 GHz 1.54:1• Q: 40 – 50 GHz 1.25:1
Paul Lilie EVLA Front-End CDR – OMT DevelopmentApril 24, 2006
3
Why Quad-Ridge?
• Septum, Boifot types ~ 1.5:1 maximum
• cf. Q-R horns 2-18 GHz
• Low impedance structure
Paul Lilie EVLA Front-End CDR – OMT DevelopmentApril 24, 2006
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“Good” Mode
fco = 0.68
“Z” ~ 50 W fco = .74 fco = .91
“Z” ~ 500W
Paul Lilie EVLA Front-End CDR – OMT DevelopmentApril 24, 2006
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“Bad Mode”
fco = .69
fco = .88 fco = 1.28
Paul Lilie EVLA Front-End CDR – OMT DevelopmentApril 24, 2006
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fco vs. distance
Modes in Square Quad-Ridge GuideModes "sorted"
0.0000
0.5000
1.0000
1.5000
2.0000
2.5000
3.0000
0.000 0.500 1.000 1.500 2.000 2.500 3.000 3.500 4.000 4.500 5.000
Gap
Fc
o, G
Hz
TE01
TE10
TE11
TM11
TE02
TE20
TE12
TE21
TM12
TM21
TE22
TM22
TE30
TE33
TExx
PAL 021019 sqqrfco.xls
Paul Lilie EVLA Front-End CDR – OMT DevelopmentApril 24, 2006
7
Quad-Ridge
Paul Lilie EVLA Front-End CDR – OMT DevelopmentApril 24, 2006
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OMT Components
Window
Circular-to-Square
thermal gap
Square-to-QR QR-to-coax
mode suppression
Paul Lilie EVLA Front-End CDR – OMT DevelopmentApril 24, 2006
9
Sliding Load
Paul Lilie EVLA Front-End CDR – OMT DevelopmentApril 24, 2006
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Paul Lilie EVLA Front-End CDR – OMT DevelopmentApril 24, 2006
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Return Loss
OMT Return Loss
-40.00
-30.00
-20.00
-10.00
0.00
1 1.2 1.4 1.6 1.8 2
GHz
dB EVLA Front
EVLA Rear
Paul Lilie EVLA Front-End CDR – OMT DevelopmentApril 24, 2006
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vs. ERA OMT
OMT Return Loss
-40.00
-30.00
-20.00
-10.00
0.00
1 1.2 1.4 1.6 1.8 2
GHz
dB
EVLA Front
EVLA Rear
ERA Front
ERA Rear
Paul Lilie EVLA Front-End CDR – OMT DevelopmentApril 24, 2006
13
Isolation
EVLA OMT Isolation
-60.00
-50.00
-40.00
-30.00
-20.00
-10.00
0.00
1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2
GHz
dB
Paul Lilie EVLA Front-End CDR – OMT DevelopmentApril 24, 2006
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90-degree hybrid
2/1
Hybrid
In
Iso.
Coup.
Thru2/j
RCP
Nothing
Paul Lilie EVLA Front-End CDR – OMT DevelopmentApril 24, 2006
15
Mis-matched90-degree hybrid
2/1
Hybrid
In
Iso.
Coup.
Thru2/j
Less RCP
Some RCP
Gx
Gy
Gr
Gl
Paul Lilie EVLA Front-End CDR – OMT DevelopmentApril 24, 2006
16
Math
)(
)(
and ))((2
input, RCP pureWith
1 2
YXL
YRL
XYR
BGAGGBA
AGBGGBAj
R
L
BGBGGBAd
jR
kBkSinA
Paul Lilie EVLA Front-End CDR – OMT DevelopmentApril 24, 2006
17
Axial Ratio (Amplitudes;Voltages)
0575.122.1 ,dB" 1 " for
||
|| where
1
1
R
L
Paul Lilie EVLA Front-End CDR – OMT DevelopmentApril 24, 2006
18
For a< 1 dB
• (With some assumptions) we can specify that the return losses of a pair of ports must sum to better than ~34 dB
• This sort of tradeoff applies to any polarizer.
• With perfect amplitude & phase, the sum would be ~25 dB.
Paul Lilie EVLA Front-End CDR – OMT DevelopmentApril 24, 2006
19
Next to do
• Reduce mass of OMT.
• Improve Cooling.
• Better window material.
• Investigate manufacturability.
Paul Lilie EVLA Front-End CDR – OMT DevelopmentApril 24, 2006
20
Conclusions
• Prototypes have been built
• Return loss is acceptable across band
• Isolation is good across band
• “Suck-out” suppression is effective
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