S.Halte, OPS-GSS, 16/10/09
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Cryogenic Receivers:
Closer to the noise floor
Present and future of Cryogenic Receivers in ESTRACK
S.Halte, OPS-GSS, 16/10/09
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About Myself
Ground Station engineering division / RF and signal processing section.
– Cryogenic receivers/ amplifiers– Frequency converters (Ka band deep space up/down converters)– Radiometer.– Studies with European universities– DSA3– SSA radar development
S.Halte, OPS-GSS, 16/10/09
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Introduction
– What is a Receiver?• an electronic device that changes a radio signal from a transmitter into
useful information
– What does Cryogenics deal with?• The word cryogenics comesfrom Greek and means "the production of
freezing cold“. It is commonly admitted that the field of Cryogenics covers range of temperature below -180 °C (Nitrogen boiling temperature).
– Why cryogenic receiver?• Because during propagation a radio signal is affected by external
perturbation. In particular noise created by cosmic radiation and thermal noise due to the particles random movement. Cooling down the devices reduces this noise drastically.
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Introduction
How a deep space telemetry signal is propagated.
Very Low noise Technology.
Cryogenic technology
Deep space cryogenic receivers and improvements
Compact, miniaturized cryogenics Low Noise Amplifiers
Future developments
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Deep space telemetry
P transmit= 28 W
Ant diameter = 2.2 m
Distance= 500 million km
Ant diameter = 35 mP receive= 1x10- 16 Watt (0.0000000000000001 W)
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Noise in space communication
Ground Noise
Cosmic noiseSun noise
Clouds + rain noise
Atmosphere noise Antenna noise
Total sky noise and antenna noise power= 1 x 10 -17 W (16 zero after the point)
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Noise in electronic equipment
Sun
Earth
Atmosphere
ReceiverOutput
LNA
Resistive loss
Standard amplifier: Receiver Noise = 2x10-15 W
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Signal over Noise Ratio
Signal 1x10-16 W Antenna + Atmosphere Noise 1x10-17 W Receiver Noise 1x10-17 W
----------------------------------------
Signal/Noise 5 (7dB)
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Very low noise amplifiers
The noise power generated by a standard amplifier and receiver thermal noise is higher than the signal power to recover…
Need to develop very low noise amplifier using:– Very low noise transistor technology– Cool down the receiver in order to decrease the thermal noise
Deep Space antenna uses High Electron Mobility Transistors cooled down at 15K in order to be able to retrieve deep space signal from the noise
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High Electron Mobility Transistors
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InP Technology
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InP Technology
GaAs (gallium arsenide ) transistors are widely use in the Telecom industry and can be provided easily by standard manufacturers (Mitsubishi)
InP technology is not available from standard manufacturer and was only available in USA but protected by ITAR regulation.
It has been necessary to develop InP devices in X and Ka band with European universities in order to minimize the receiver noise.
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InP Transistors
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X band Low Noise Amplifier
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Ka band low noise amplifier
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Cryogenic cycle
Heat removed from outside
Heat transferred outside
PV=cstxT
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Vacuum Dewar: Heat transport mechanism
Convection
Conduction
IR Radiation
Gas molecule
Vacuum Enclosure
Cooled Sample, cryogenic temperature
Sample support structure
Dewar wall
Convection, conduction, radiation
How to reduce these thermal loads ?
Convection: remove physical support = air molecules = process vacuum (pressure <10-3 mbar) inside the Dewar.
Conduction: Remove physical support when possible (i.e. process vacuum); select material with low thermal conductivity at operational temperature.
Radiation: Use Infra-Red reflective materials such as MLI (Multi-Layer Insulations) to stop radiations. Select material with low emissivity factors to reduce absorption of IR at operational temperature.
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Cryogenic Receiver in Deep Space Antennas
- 2 S- Band in New Norcia
-4 X- Band in New Norcia and Cebreros
-2 Ka Band in Cebreros
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Cryogenic Receiver
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Cryogenic receiver
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Gain and noise performance (room/ cryo)
Equivalent Noise Temperature: 11K
Pnoise=1.2 x10 -17 W
Gain=57 dB
Signal is amplified 1 000 000 times
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S Band Cryogenic Receiver
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Ka Band multichannel Receivers
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In the Antenna Equipment Room
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Reliability
0
2
4
6
8
10
12
14
1000 3000 5000 7000 9000 11000Running time before failure (hours)
Nd
of
fail
ure
s
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Maintainability
Time to cool down = 7 hours Time to warmup = 12 hours Time for repair= 3 hours Test = 2 Warmup / cool down cycle to
declare the system operational
The system is unavailable for 41 hours minimum during servicing/repair
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Reliability and maintainability improvement
High vacuum is difficult to maintain and needs regular pumping– Replace vacuum insulation with new generation solid insulator
(aerogel) The cryocooler is not reliable as a lot of failures occurs before the
recommended maintenance period– Change cryocooler with a more reliable solution: Summitomo
cryocooler is used in 90% of medical magnetic imaging machines In case of failure the exchange or repair of the cooler has to be
done by specially qualified staff and is very time consuming.– Implement a cold head sleeve for rapid exchange of the cooler– Implement heaters in order to reduce the warmup time to 2 hours
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Cold head sleeve
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Aerogel
nanotechnology product = dried silica gel
nullify three methods of heat transfer:
Convection: aerogel is a closed lattice and thus limits air convection
Radiation: aerogel selected is IR opacified to stop radiations
Conduction: . @ atmospheric pressure, aerogel is one of the most insulative material ever
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Second generation
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Thermal simulation
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Kourou cryogenic LNA
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Kourou cryogenic LNA Integration
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Miniaturized cryogenic LNA
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Miniaturized cryo LNA
RF housing For the MMIC
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Microwave Monolithic Integrated Circuit
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Miniaturized cryogenic LNA
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Data rate limitation
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DSN array (JPL)
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DSN Array (JPL)
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X Ka band cryogenic receiver
Dual frequency feed
31-38 GHz Ka LNAs
8-8.8 GHz X LNAs
15 K refrigerator
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Conclusion
Next generation of cryogenic receiver will include all the passive elements in front of the Low Noise Amplifier to lower thermal noise.
New technology of low noise amplifier to be developed for high frequency (SiC, GaP)
Cryogenic receiver will be included in arrays antenna to increase the gain and reduce the noise simultaneously