1. W-BAND RADIOMETER SYSTEM
WITH SWITCHING FRONT-END FOR
MULTI-LOAD CALIBRATION
IGARSS 2011, Vancouver, Canada, session TH4.T03.2 July, 28th 2011
E. Weissbrodt, I. Kallfass, A. Hülsmann, A. Tessmann,
A. Leuther, H. Massler, O. Ambacher
Fraunhofer Institute
for Applied Solid-State Physics (IAF)
D-79108 Freiburg, Germany
© Fraunhofer IAF IGARSS 2011

2. Outline
motivation
radiometer architecture
packaging and modules
MMIC technology
millimeter-wave circuits
multi-load calibration IAF
outlook
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© Fraunhofer IAF IGARSS 2011

3. Motivation
Compact Internal Calibration
external hot-cold calibration
microwave black body (absorber)
reflectors to cold sky (cosmic background
radiation) or liquid nitrogen
internal calibration methods
noise diodes (ENR)
matched (ambient) loads
active loads
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© Fraunhofer IAF IGARSS 2011

4. W-Band Direct Detection Radiometer
Architecture
millimeter wave direct detection radiometer chain
SP5T switch
LNA LNA BP LNA detector OpAmp OpAmp OpAmp
SP5T
Video analog
switch sub.
50 Ω
20dB 20dB 20dB
noise + record
noise + 50Ω record DC
+0,4V
TTL
-1V
CLK
1kHz
switch voltage control
discrete modules with
Fraunhofer IAF 100nm
mHEMT technology
60 dB small-signal gain
analog read-out and
control electronics for
IAF Dicke-operation
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© Fraunhofer IAF IGARSS 2011

5. Packaging
Split Block Waveguide Modules
IAF
in-house CAD-design and milling
gold-plated brass split block
WR-10 waveguide
wedge-bonded 25 μm
gold wires
50 μm quartz substrates
EM-simulated microstrip-
to-waveguide transitions
IAF
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© Fraunhofer IAF IGARSS 2011

6. mHEMT Technology
High Frequency – Ultra Low Noise
parameters 100 nm
In content (%) 65
RC (Ωmm) 0.07
RS (Ωmm) 0.23
Rg (Ω/mm) 400
ID,max (mA/mm) 900
VBD (V) 4
Gm,max
InGaAs channels with high indium 1300
(mS/mm)
content on 4 inch GaAs wafers
fT (GHz) 220
metamorphic HEMT technology
(mHEMT), 100 nm, 50 nm, 35 nm fmax (GHz) 300
metamorphic buffer layer to adapt
lattice constant
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© Fraunhofer IAF IGARSS 2011

7. MMIC Technology
Passive Structures
microstrip technology 2.7 μm Au air bridge technology
grounded coplanar technology 225 pF/mm2 MIM capacitors
two metalization layers 50 Ω/□ NiCr resistors
250 nm CVD SiN passivation full-wafer backside process
METG
GATE
SiN SiN
MET1 MESA OH MET1 NiCr
M
SUBSTRATE
Au
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© Fraunhofer IAF IGARSS 2011

8. Millimeter-Wave Circuits
Low-Noise Amplifier
reactively matched
cascode mHEMTs
gate width 4 × 15 μm
chip-size 0.75 × 1.5 mm2
25 5
20 4 gain > 20 dB (75 - 105 GHz)
gain NF [dB]
gain [dB]
15 3 noise figure 2 dB @ T = 293 K
10 2 (noise temperature 170 K)
5 NF 1 power consumption 48 mW
(Vd = 1.6 V, Id = 30 mA)
0 0
80 85 90 95 100
Frequency [GHz]
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© Fraunhofer IAF IGARSS 2011

9. Millimeter-Wave Circuits
Single-Pole-Five-Throw Switch
1-dB bandwidth > 31 GHz
Open: S1X = SX1 > -4.3 dB
Close: S1X = SX1 < -24 dB
SXX < -10 dB
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© Fraunhofer IAF IGARSS 2011

10. Multi-Load Calibration
Switching Front-End
compact dimensions and lightweight, no mechanics
fast switching, moderate insertion loss
multiple external reference loads and/or multiple input channels
Integrated 50 Ω load, active loads will be integrated in subsequent
designs and reduce interface losses
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© Fraunhofer IAF IGARSS 2011

11. Multi-Load Calibration
vs. External Calibration
external calibration: internal multiload calibration:
mature process upcoming technology
well known references multiple references possible without
antenna is inside the calibration loop additional effort
active loads can be monolithically
moving parts and mechanical wear integrated in front-end
orbital manoeuvers lightweight and fast switching
limited speed of calibration reduced calibration time
heavy and bulky systems
increased front-end losses
antenna needs to be calibrated
separately
temperature monitoring necessary
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© Fraunhofer IAF IGARSS 2011

12. Mechanical Scanning System
Cassegrain Antenna
commercial antenna tracking system
60cm Cassegrain antenna
integrated webcam for optical reference
mechanical scan in azimuth and elevation
2.6 rpm max. (azimuth)
15.5°/sec max. (elevation)
positioning accuracy ±0.04°
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© Fraunhofer IAF IGARSS 2011

13. Passive Millimeter-Wave Image
Compared to Optical Image
IAF
IAF
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© Fraunhofer IAF IGARSS 2011

14. Outlook
packaging of active loads to connect to
the switching front-end module
example
switching front-end with integrated
active loads
digitalization of read-out electronics
for micro-controlled implementation
of calibration algorithms
IAF
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© Fraunhofer IAF IGARSS 2011

15. Thank You for Your Attention
we express our gratitude to
Michael Schlechtweg for his continuous support
Helmut Essen and our colleagues at Fraunhofer FHR for valuable
discussions and provision of antenna hardware
our colleagues at IAF for their excellent contribution during epitaxial
growth and wafer processing
this work was supported by
the German Federal Ministry of Defence (BMVg)
the Bundeswehr Technical Center for Information Technology
and Electronics (WTD81)
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© Fraunhofer IAF IGARSS 2011

16. Backup Slides
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© Fraunhofer IAF IGARSS 2011

17. Backup Slides
Highly Integrated Compact Radiometer Module
single-chip radiometer MMIC
50 dB small-signal gain SMA, detector video signal
integrated diode detector
integrated SPDT
internal matched load SMB, DC supply 5 V
SMB, switch control
WR-10 input
SMB, switch control
IAF
internal matched load
WR-10 input flange
SMA, detector reference signal
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© Fraunhofer IAF IGARSS 2011

18. Backup Slides
Participation in ESA Projects
54 GHz Radiometer With Digital Backend
22336/09/NL/EL
Cloud Radar Critical Microwave Technology
13521/99/NL/PB
LNAs for mmWaves
ITT AO/1-5619/08/NL/GLC
Calibration Loads for Radiometers
4000101234/10/NL/CLC
Direct Detection Radiometers
ITT AO/1-6606/10/NL/GLC
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© Fraunhofer IAF IGARSS 2011

19. Backup Slides
Hot-Cold Calibration
examples of earth observation missions and their calibration methods:
Oceansat-1 (MSMR): external blackbody / cold sky
Aqua (HSB): external blackbody / cold sky
SMOS (MIRAS): internal noise diode / cold sky
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© Fraunhofer IAF IGARSS 2011

20. Backup Slides
Status of IAF mHEMT Technology
transit frequencies Status:
fT = 220 GHz 35 nm mHEMT
fT = 375 GHz fT > 500 GHz
100 nm
fT = 515 GHz fmax > 900 GHz
50 nm
Target:
35 nm ⇒ 20 nm mHEMT fmax > 1.3 THz
20 nm
fT = 660 GHz
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© Fraunhofer IAF IGARSS 2011