long-term stability of an sigehbt-based active cold load.pdf
TRANSCRIPT
Long-term stability of an SiGe HBT-based active cold load
1
Emilie Leynia de la Jarrige1,[email protected]
L.Escotte1, E.Gonneau2, J.M.Goutoule3
1CNRS ; LAAS ; Université de Toulouse, 7 avenue du colonel Roche, F-31077 Toulouse, France2 LERISM, Université Paul Sabatier, 118 route de Narbonne, 31062 Toulouse, France
3 EADS- Astrium, 31 rue des Cosmonautes, 31042 Toulouse France
Introduction
2
Reference sources
External target:
- cold sky, pole…
Internal reference:
- passive termination, noise diodes …
Cold source : Low value of noise temperature (< target brightness temperature) +
Long-term stability
Alternative solution : Active Cold Load (ACL)
=> Significant improvement (> 40%) in radiometric resolution has been reported at L-band (with traditional noise injection radiometer)
Radiometer calibration onboard a satellite
3
Year author Technology Frequency Noisetemperature
1981 R.H. Frater GaAs MESFET 1.4 GHz 50 K
1997 L.P. Dunleavy 0.15 μm InP HEMT 18 GHz 126 K
2000 P.M. Buhles 0.15 μm GaAs
MHEMT
2-10 GHz
10-26 GHZ
90 K
125K
2009 N. Skou GaAs PHEMT 10.69 GHz 77 K
2010 C. Bredin 70 nm GaAs MHEMT 23.8 GHz 72 K
Introduction
Active cold loads
-> several technologies, topologies and frequency ranges : FET-based ACL
SiGe HBT : low cost, low excess noise : feasibility ?
Outline
4
I – ACL implementation
1. Topology2. Results
II – Radiometer for long-term stability measurements
1. Test-bed2. Characteristics
III – Stability results
1. Short-term2. Long-term
Conclusion
Outline
5
I – ACL implementation
1. Topology2. Results
II – Radiometer for long-term stability measurements
1. Test-bed2. Characteristics
III – Stability results
1. Short-term2. Long-term
Conclusion
ACL implementation 1/2
Technical specifications :
• Frequency band : 1400 – 1427 MHz
• Return loss > 30 dB
• Noise temperature < 80 K
• Stability : to be evaluated
Active device :
SiGe HBT from Infineon Technologies(BFP640 – SOT343 package)
Tmin < 40 K
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Typically for sea surfacesalinity and soil moisturemeasurements applications
0
20
40
60
80
0 2 4 6 8 10 12 14
Min
. n
ois
e te
mp
era
ture
(K)
Ic (mA)
1.8 GHz
1.4 GHz
0.9 GHz
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Cdec
Cc
Lc 50ΩCb
Lb Le
output
Stub
Cdec
Vcc
Rc
Rb
L1 L2
Cdec
Photograph of the ACL
Electrical circuit :
- 0.635 mm alumina substrate
- Surface Mount Components
- 50 Ω microstrip lines
ACL implementation 1/2
Bias stability :
- Resistive collector-to-base circuit
- Adjustable voltage regulator
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-45
-40
-35
-30
-25
-20
-15
-10
-5
0
1,2 1,25 1,3 1,35 1,4 1,45 1,5 1,55 1,6Ref
lect
ion
Co
effi
cien
t (d
B)
Frequency (GHz)
50
55
60
65
70
1,39 1,4 1,41 1,42 1,43 1,44
No
ise
tem
per
atu
re(K
)
Frequency (GHz)
Sensitivity test of temperature variations : ≈ 0.3 K/°C(ex : GaAs FET-based ACL : 0.35 and 0.38 K/°C)
Reflection coefficient < -35 dBNoise temperature < 66 K
2. Results
For Ic = 5.6 mA and Vcc = 1.12 V
ACL implementation 2/2
Outline
9
I – ACL implementation
1. Topology2. Results
II – Radiometer for long-term stability measurements
1. Test-bed2. Characteristics
III – Stability results
1. Short-term2. Long-term
Conclusion
10
Radiometer for long-term stability measurements
Dedicated radiometer : two-load radiometer with noise injection measurements errors due to power gain variations are reduced
1. Test-bed
+
+Receiver
Tn
T2
T0
TR , G
ACL
matched
load
cold
load
A/D
Directional coupler +
Noise diode
Typical measurement cycle
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1. Test-bed
Output voltage
Receiver
ACL
Noisediode
LNAdc amplifier
Matched load
DAQdevice
USB
Temperature-stabilized enclosure
Commandcircuit
Thermistors...
- DAQ U2351A from Agilent
Thermistors for temperature control
Radiometer for long-term stability measurements
tt2t1t0
…
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LNA +Filter :
Gain > 60 dB
Noise Bandwidth : 60 MHz
Noise temperature : 40 K
-10
0
10
20
30
40
50
60
70
1200 1250 1300 1350 1400 1450 1500 1550 1600
-10
0
10
20
30
40
50
60
70
1200 1250 1300 1350 1400 1450 1500 1550 1600
-10
0
10
20
30
40
50
60
70
1200 1250 1300 1350 1400 1450 1500 1550 1600
Frequency (MHz)
Tran
smis
sio
n c
oef
fici
ent
(dB
)
1. Test-bed
Coaxial switch :
Insertion loss : 0.04 dB
Isolation : > 120 dBOutput voltage
ReceiverACL
Noisediode
LNA dc amplifier
Matched load
DAQdevice
USB
Temperature-stabilized enclosure
Thermistors...
Commandcircuit
Radiometer for long-term stability measurements
13
Square-law detector:
- Tunnel diode- Responsivity : 1 mV/µW à 1.4GHz- Noise : 2 nV/√Hz à 100Hz
Output voltage
ReceiverACL
Noisediode
LNA DC amplifier
Matched load
DAQdevice
USB
Temperature-stabilized enclosure
Thermistors...
Commandcircuit
1. Test-bed
Radiometer for long-term stability measurements
14
Square-law detector:
- Tunnel diode- Responsivity : 1 mV/µW à 1.4GHz- Noise : 2 nV/√Hz à 100Hz
Low-noise voltage amplifier:
- Gain : 80 dB- Noise floor : 1 nV/√Hz
Output voltage
ReceiverACL
Noisediode
LNA DC amplifier
Matched load
DAQdevice
USB
Temperature-stabilized enclosure
Thermistors...
Commandcircuit
1. Test-bed
Radiometer for long-term stability measurements
Low-noise voltage amplifier:
- Gain : 80 dB- Noise floor : 1 nV/√Hz
Square-law detector:
- Tunnel diode- Responsivity : 1 mV/µW à 1.4GHz- Noise : 2 nV/√Hz à 100Hz
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Low-pass filter (RC circuit)
- Time constant : 5 ms
1. Test-bed
Output voltage
ReceiverACL
Noisediode
LNA DC amplifier
Matched load
DAQdevice
USB
Temperature-stabilized enclosure
Thermistors...
Commandcircuit
Radiometer for long-term stability measurements
16
1. Test-bed
Output voltage
ReceiverACL
Noisediode
LNA DC amplifier
Matched load
DAQdevice
USB
Temperature-stabilized enclosure
Thermistors...
Commandcircuit
Noise injection :- Excess noise ratio of 15.6 dB at 1.4 GHz- Coupler : 16 dB- Noise temperature : T2 ≈ 280K
Radiometer for long-term stability measurements
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-> in order to limit the impact of temperature variations, we realize temperature stabilizedenclosure :
10 mm- thick aluminum enclosure +
50 mm-thick extruded polystyrene+
Temperature control circuit
1. Test-bed
ACL temperature ≈ 38.4°C
ACL temperature variations :
< 0.01 °C during 1 day< 0.03 °C during 4.5 months
Radiometer for long-term stability measurements
1818
ACL noise temperature :
matched load Injected noise temperature
loss of the coupler
²)²(
²²)²(
²²1
²12
012
12
201
1202
VV
VVV
VV
VVV
VVVLTTn
Important characteristics :
- low value for L- V0 and V2 close- smallest variance values ; depend on integration time
20
12
10 TVV
VVLTTn
2. Characteristics
+
+ Receiver
Tn
T2
T0
TR , G
ACL
matched
load
cold
load
A/D
Radiometer for long-term stability measurements
- Sensitivity < 31mK- Stability < 25mK for a total integration time of 95s
Optimum integration time:
τ 0 = 50 sτ 1 = 15 sτ 2 = 30 s
Allan variance:
Conditions :
- T°amb ≈ 38.4°C - Maximum deviation < 0.01°C- Period = 150 min
2
12 )(
2
1)( nny yyt
0,01
0,1
1
0,1 1 10 100
All
an
dev
iati
on
(m
V)
Integration time (s)
Matched load
Diode
ACLWhite noise
Flicker noiseRandom walk noise
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2. Characteristics
Radiometer for long-term stability measurements
Outline
20
I – ACL implementation
1. Topology2. Results
II – Radiometer for long-term stability measurements
1. Test-bed2. Characteristics
III – Stability results
1. Short-term2. Long-term
Conclusion
Stability results
21
Characteristics :
- Mean : 87.48 K- Standard deviation : 32 mK- Maximum deviation : 0.205 K
87.3
87.4
87.5
87.6
0 1 2 3
Time (day)
AC
L N
ois
e T
emp
erat
ure
(K
)
87.35
87.45
87.55
87.65
1. Short-term
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ACL noise temperature :
- Maximum deviation < 0.35 K- Slope : -2.1 mK/day
extrapolated stability < 1 K/year
2. Long-term
Stability results
87.2
87.3
87.4
87.5
87.6
87.7
0 20 40 60 80 100 120 140
Time (day)
AC
L N
ois
e T
emper
ature
(K
)
Outline
23
I – ACL implementation
1. Topology2. Results
II – Radiometer for long-term stability measurements
1. Test-bed2. Characteristics
III – Stability results
1. Short-term2. Long-term
Conclusion
Conclusion
24
ACL
- Reflection coefficient < -35 dB- Noise temperature < 66 K
Radiometer
- Sensitivity < 31 mK- Stability < 25 mK for a total integration time of 95 s- Long-term stability (4.5 months) :
• Gain : maximum deviation < 0.03 dB• Receiver noise temperature : maximum deviation < 1 K• Physical temperature variations < 0.03°C
Long term stability (4.5months)
- Maximum deviation < 0.35 K - Slope : -2.1 mK/day extrapolated stability < 1 K/year
Author Frequency Technology Noisetemp.
Stability Duration
N. Skou 10.69 GHz GaAs PHEMT 77 K 2 K1 K
1 year8 months
L.P. Dunleavy 18 GHz 0.15 μm InP HEMT 126 K 2 K 1 yearC. Bredin 23.8 GHz 70 nm GaAs MHEMT 72 K 0.4 K 1 month
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Thank you for your attention