fr1.t03.5 igarss_2011_albers_22jul2011.ppt
TRANSCRIPT
Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 1
Development, Fabrication, and Testing of 92 GHz Radiometer For Improved
Coastal Wet-tropospheric Correction on the SWOT Mission
Darrin Albers, Alexander Lee, and Steven C. ReisingMicrowave Systems Laboratory, Colorado State University,
Fort Collins, CO
Shannon T. Brown, Pekka Kangaslahti, Douglas E. Dawson, Todd C. Gaier, Oliver Montes, Daniel J. Hoppe, and Behrouz
Khayatian Jet Propulsion Laboratory, California Institute of Technology,
Pasadena, CA
Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 2
Scientific Motivation• Current satellite ocean altimeters include a nadir-viewing, co-located
18-37 GHz multi-channel microwave radiometer to measure wet-tropospheric path delay. Due to the large diameters of the surface instantaneous fields of view (IFOV) at these frequencies, the accuracy of wet path retrievals begins to degrade at approximately 50 km from the coasts.
• Conventional altimeter-correcting microwave radiometers do not provide wet path delay over land.
Along track direction
High frequency footprint
Low frequency footprint
Along track directionAlong track direction
High frequency footprintHigh frequency footprint
Low frequency footprintLow frequency footprint
LandOcean• Advanced technology development
of high-frequency microwave radiometer channels to improve retrievals of wet-tropospheric delay in coastal areas, small inland bodies of water, and possibly over land such as for the Surface Water Ocean Topography (SWOT), a Tier-2 Decadal Survey mission.
Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 3
SWOT Mission Concept Study
Low frequency-only algorithm
Low frequency-only algorithm
Low and High frequency algorithm
Low and High frequency algorithm
High-resolution WRF model results show reduced wet path-delay error using both low-frequency (18-37 GHz) and high-frequency (90-170 GHz) radiometer channels.
Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 4
Objectives
Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 5
System Block Diagram
Waveguide Components
92-GHz multi-chip module
130-GHz multi-chip module
166-GHz multi-chip module
Common radiometerback end, thermal
control anddata
subsystem
Tri-Frequency Feed Horn
Coupler
Coupler
Noise Diode
Coupler
Noise Diode
Noise Diode
MMIC Components
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Tri-Frequency Horn Antenna
A single, tri-band feed horn and triplexer are required to maintain acceptable antenna performance, since separate feeds for each of the high-frequency channels would need to be moved further off the reflector focus, degrading this critical performance factor. The tri-frequency horn was custom designed and produced at JPL, with an electroform combiner from Custom Microwave, Inc. Measurements show good agreement with simulated results.
WR-5(166 GHz)
Feed Horn Rings
WR-8(130 GHz)
Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 7
Tri-Frequency Antenna (Detail)
WR-8 Waveguide
Port
WR-10 Waveguide
Port
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Example of a Ring to Produce Horn Corrugation
Largest Horn Ring
Pencil TipFor Scale
Ring Cross Section
Fin for theRing-Loaded Slot
Detail of Feed Horn Rings17
.9 m
m
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Antenna Return Loss
Bandwidth measurement with 15-dB return loss or better
Center Frequency (GHz)
Waveguide Band
Bandwidth (GHz)
92 WR-10 11
130 WR-08 18
166 WR-05 26
Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 10
Antenna Pattern92 GHz 130 GHz
Center Frequency (GHz)
Waveguide Band
Half-power Beamwidth (°)
92 WR-10 22
130 WR-08 24
166 WR-05 32
166 GHz
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Noise Diodes for Internal Calibration
• Nadir-pointing radiometers are flown on altimetry missions with no moving parts, motivating two-point internal radiometric calibration, as on Jason-2. Highly stable noise diodes will be used to achieve one of these two points.
• Radiometric objectives
• Provide an electronically-switchable source for calibrating the radiometer over long time scales, i.e. hours to days.
• RF design objectives from radiometer requirements
• Noise diode output will be coupled into the radiometer using a commercially-available waveguide-based coupler.
• Stable excess noise ratio (ENR) of 10-dB or greater, yielding ~300 K of noise deflection after a 10-dB coupler.
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Noise Diode MeasurementsNoise Diode Measurements
*Noise diode manufactured for NASA/GSFC
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92-GHz Radiometer Design
• This direct-detection Dicke radiometer uses two LNAs and a single bandpass filter for band definition.
• Direct-detection architecture is the lowest power and mass solution for these high-frequency receivers. Keeping the radiometer power at a minimum is critical to fit within the overall SWOT mission constraints, including the power requirements of the radar interferometer.
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92-GHz Bandpass Filter: Modeled and Measured
4.6 mm
• 5-mil (125-µm) thick polished alumina substrate
• Measured using a probe station with WR-10 waveguides
• Modeled and measured in open air
Frequency (GHz)
Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 15
Matched Load for Calibration: Modeled and Measured Results
1.45 mm
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92-GHz Multi-Chip Module
92-GHz direct-detection radiometer with Dicke switching and integrated matched load
17.9 mm
Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 17
92-GHz Multi-chip Module (Close-up)
Matched Load
PIN-Diode Switch
Low-Noise Amplifier #1 Band Pass
Filter
Waveguide to Microstrip
Transition
Low-Noise Amplifier #2
DetectorAttenuator1 mm
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92-GHz Radiometer Prototype
Multi-Chip ModuleIsolator
WR-10 Horn Antenna
Coupler
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92-GHz Radiometer Noise Analysis
Component Gain (dB)Noise Figure
(dB)Cumulative Noise Temperature (K)
Noise Source - -
Directional Coupler -0.75 0.75 55
Waveguide Through Line -0.20 0.20 71
Waveguide to Microstrip transition -0.50 0.50 115
Switch -2.75 2.75 473LNA 28.00 3.00 1232BPF -5.50 5.50 1235
Attenuator -4.25 4.25 1235LNA 28.00 3.00 1254
Attenuator -4.25 4.25 1254
Total Receiver Gain (dB) 37.80Receiver noise factor 5.32
Receiver noise figure (dB) 7.26Receiver noise temperature (K) 1253.53
Preliminary Noise Temperature Measurement of 1375K
Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 20
92-GHz Radiometer Performance Analysis
Albers et al., FR1.T03 IGARSS 2011 Vancouver, BC July 29, 2011 21
• Conventional altimeters include a nadir-viewing 18-37 GHz microwave radiometer to measure wet-tropospheric path delay. However, they have reduced accuracy within 40 km of land.
• Addition of high-sensitivity mm-wave channels to Jason-class radiometer will improve wet-path delay retrievals in coastal regions and provide good potential over land.
• We have developed noise sources at 92 and 130 GHz and a tri-frequency feed horn for wide-band performance at center frequencies of 92, 130, and 166 GHz.
• To demonstrate these components, we have produced a millimeter-wave MMIC-based low-mass, low-power, small-volume radiometer with internal calibration sources integrated with the tri-frequency feed horn at 92 GHz.
Summary
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Backup Slides
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ENR Equation
Equation 10.6. Pozar. Microwave Engineering 3rd edition.
0 dB ENR with Tg = 580 K and To = 290K-2 dB ENR with Tg = 473 K and To = 290K
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Move to Higher Frequency• Supplement low-
frequency, low-spatial resolution channels with high-frequency, high-spatial resolution channels to retrieve PD near coast
• High-frequency window channels sensitive to water vapor continuum
• 183 GHz channels sensitive to water vapor at different layers in atmosphere
22.235 GHz (H2O)
55-60 GHz (O2)118 GHz (O2)
183.31 GHz (H2O)
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92-GHz Radiometer with Two LNAs
• Current MMIC detector from HRL has sensitivity of 15,000 V/W• One LNA– System Gain of 26.05 dB and cumulative noise temperature of 727.4 K
– Antenna Temperature of 600 K results in 550 µV, i.e. 417 nV/K
– Antenna Temperature of 77 K results in -46 dBm
• Two LNAs– System Gain of 54.55. dB and cumulative noise temperature of 727.6 K
– Antenna Temperature of 600 K results in 392 mV, i.e. 295 µV/K
– Antenna Temperature of 77 K results in -18 dBm
• TSS (Tangential Sensitivity) of these detectors is typically -44 dBm so might be measuring the noise at 77 K if more loss is in system than expected so two LNAs results in a more robust system