Long-term stability of an SiGe HBTbased active cold load

Transcription

1 Long-term stability of an SiGe HBTbased active cold load Emilie Leynia de la Jarrige 1, LEscotte 1, EGonneau 2, JMGoutoule 3 1 CNRS ; LAAS ; Université de Toulouse, 7 avenue du colonel Roche, F Toulouse, France 2 LERISM, Université Paul Sabatier, 118 route de Narbonne, Toulouse, France 3 EADS- Astrium, 31 rue des Cosmonautes, Toulouse France 1

2 Introduction Radiometer calibration onboard a satellite 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) 2

3 Introduction Active cold loads Year author Technology Frequency Noise temperature 1981 RH Frater GaAs MESFET 14 GHz 50 K 1997 LP Dunleavy 015 μm InP HEMT 18 GHz 126 K 2000 PM Buhles 015 μm GaAs MHEMT 2-10 GHz GHZ 90 K 125K 2009 N Skou GaAs PHEMT 1069 GHz 77 K 2010 C Bredin 70 nm GaAs MHEMT 238 GHz 72 K -> several technologies, topologies and frequency ranges : FET-based ACL SiGe HBT : low cost, low excess noise : feasibility? 3

4 I ACL implementation 1 Topology 2 Results Outline II Radiometer for long-term stability measurements 1 Test-bed 2 Characteristics III Stability results 1 Short-term 2 Long-term Conclusion 4

5 I ACL implementation 1 Topology 2 Results Outline II Radiometer for long-term stability measurements 1 Test-bed 2 Characteristics III Stability results 1 Short-term 2 Long-term Conclusion 5

6 Min noise temperature (K) ACL implementation 1/2 Technical specifications : Frequency band : MHz Return loss > 30 db Noise temperature < 80 K Stability : to be evaluated Typically for sea surface salinity and soil moisture measurements applications 80 Active device : SiGe HBT from Infineon Technologies (BFP640 SOT343 package) T min < 40 K GHz 14 GHz 09 GHz Ic (ma) 6

7 Electrical circuit : ACL implementation 1/2 Vcc Cdec mm alumina substrate Cdec Rb Rc Cdec - Surface Mount Components - 50 Ω microstrip lines Stub L1 L2 Cc output Lb Cb Le Lc 50Ω Bias stability : - Resistive collector-to-base circuit - Adjustable voltage regulator Photograph of the ACL 7

8 Reflection Coefficient (db) Noise temperature (K) ACL implementation 2/2 2 Results For Ic = 56 ma and Vcc = 112 V ,2 1,25 1,3 1,35 1,4 1,45 1,5 1,55 1,6 1,39 1,4 1,41 1,42 1,43 1,44 Frequency (GHz) Frequency (GHz) Sensitivity test of temperature variations : 03 K/ C (ex : GaAs FET-based ACL : 035 and 038 K/ C) Reflection coefficient < -35 db Noise temperature < 66 K 8

9 I ACL implementation 1 Topology 2 Results Outline II Radiometer for long-term stability measurements 1 Test-bed 2 Characteristics III Stability results 1 Short-term 2 Long-term Conclusion 9

10 1 Test-bed Radiometer for long-term stability measurements Dedicated radiometer : two-load radiometer with noise injection measurements errors due to power gain variations are reduced matched load ACL T n + T 0 A/D + Receiver T R, G cold load T 2 Typical measurement cycle Directional coupler + Noise diode 10

11 1 Test-bed Radiometer for long-term stability measurements Temperature-stabilized enclosure Matched load USB Output voltage ACL Noise diode LNA Receiver dc amplifier Thermistors DAQ device Command circuit - DAQ U2351A from Agilent Thermistors for temperature control t 0 t 1 t 2 t 11

12 Transmission coefficient (db) 1 Test-bed Radiometer for long-term stability measurements Temperature-stabilized enclosure Coaxial switch : ACL Matched load Noise diode LNA Receiver dc amplifier Output voltage Thermistors USB DAQ device Insertion loss : 004 db Isolation : > 120 db Command circuit 70 LNA +Filter : Gain > 60 db Noise Bandwidth : 60 MHz Noise temperature : 40 K Frequency (MHz) 12

13 1 Test-bed Radiometer for long-term stability measurements Temperature-stabilized enclosure ACL Matched load Noise diode LNA Receiver DC amplifier Thermistors Output voltage USB DAQ device Command circuit Square-law detector: - Tunnel diode - Responsivity : 1 mv/µw à 14GHz - Noise : 2 nv/ Hz à 100Hz 13

14 1 Test-bed Radiometer for long-term stability measurements Temperature-stabilized enclosure ACL Matched load Noise diode LNA Receiver DC amplifier Thermistors Output voltage USB DAQ device Command circuit Square-law detector: - Tunnel diode - Responsivity : 1 mv/µw à 14GHz - Noise : 2 nv/ Hz à 100Hz Low-noise voltage amplifier: - Gain : 80 db - Noise floor : 1 nv/ Hz 14

15 1 Test-bed Radiometer for long-term stability measurements Temperature-stabilized enclosure ACL Matched load Noise diode LNA Receiver DC amplifier Thermistors Output voltage USB DAQ device Command circuit Square-law detector: - Tunnel diode - Responsivity : 1 mv/µw à 14GHz - Noise : 2 nv/ Hz à 100Hz Low-noise voltage amplifier: - Gain : 80 db - Noise floor : 1 nv/ Hz Low-pass filter (RC circuit) - Time constant : 5 ms 15

16 1 Test-bed Radiometer for long-term stability measurements Temperature-stabilized enclosure ACL Matched load Noise diode LNA Receiver DC amplifier Thermistors Output voltage USB DAQ device Command circuit Noise injection : - Excess noise ratio of 156 db at 14 GHz - Coupler : 16 db - Noise temperature : T 2 280K 16

17 1 Test-bed Radiometer for long-term stability measurements -> in order to limit the impact of temperature variations, we realize temperature stabilized enclosure : ACL temperature 384 C ACL temperature variations : < 001 C during 1 day < 003 C during 45 months 10 mm- thick aluminum enclosure + 50 mm-thick extruded polystyrene + Temperature control circuit 17

18 2 Characteristics Radiometer for long-term stability measurements matched load ACL noise temperature : T n T 0 L V V V 0 1 T 2 V 1 2 ACL T n + T 2 T 0 + Receiver cold load T R, G A/D matched load Injected noise temperature loss of the coupler T n LT 2 V 0 ² V 2 1 V 1 ² V 1 ² V ( V 0 2 V2 V )² 1 ² V 2 ² V ( V 1 2 V V 0 1 )² ² Important characteristics : - low value for L - V 0 and V 2 close - smallest variance values ; depend on integration time 18

19 Allan deviation (mv) 2 Characteristics Conditions : Radiometer for long-term stability measurements Allan variance: - T amb 384 C - Maximum deviation < 001 C - Period = 150 min 2 1 y ( t ) ( yn1 yn) 2 1 Diode Matched load 2 Optimum integration time: τ 0 = 50 s τ 1 = 15 s τ 2 = 30 s 0,1 0,01 White noise 0, Integration time (s) ACL Flicker noise Random walk noise - Sensitivity < 31mK - Stability < 25mK for a total integration time of 95s 19

20 I ACL implementation 1 Topology 2 Results Outline II Radiometer for long-term stability measurements 1 Test-bed 2 Characteristics III Stability results 1 Short-term 2 Long-term Conclusion 20

21 ACL Noise Temperature (K) 1 Short-term Stability results Time (day) Characteristics : - Mean : 8748 K - Standard deviation : 32 mk - Maximum deviation : 0205 K 21

22 ACL Noise Temperature (K) 2 Long-term Stability results ACL noise temperature : Maximum deviation < 035 K - Slope : -21 mk/day extrapolated stability < 1 K/year Time (day) 22

23 I ACL implementation 1 Topology 2 Results Outline II Radiometer for long-term stability measurements 1 Test-bed 2 Characteristics III Stability results 1 Short-term 2 Long-term Conclusion 23

24 ACL - Reflection coefficient < -35 db - Noise temperature < 66 K Conclusion Radiometer - Sensitivity < 31 mk - Stability < 25 mk for a total integration time of 95 s - Long-term stability (45 months) : Gain : maximum deviation < 003 db Receiver noise temperature : maximum deviation < 1 K Physical temperature variations < 003 C Long term stability (45months) - Maximum deviation < 035 K - Slope : -21 mk/day extrapolated stability < 1 K/year Author Frequency Technology Noise Stability Duration temp N Skou 1069 GHz GaAs PHEMT 77 K 2 K 1 K 1 year 8 months LP Dunleavy 18 GHz 015 μm InP HEMT 126 K 2 K 1 year C Bredin 238 GHz 70 nm GaAs MHEMT 72 K 04 K 1 month 24

25 Thank you for your attention 25