Fast Calibration of Weather Radar Systems for Multi Polarization Radar Measurements Jens Reimann, Martin Hagen DLR-Institute of Atmospheric Physics

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Fast Calibration of Weather Radar Systems for
Multi Polarization Radar MeasurementsJens
Reimann, Martin HagenDLR-Institute of
Atmospheric Physics
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Outline

• Introduction
• Polarimetric Calibration
• Multi Polarization Measurements
• Conclusion

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POLDIRAD

• Research Radar
• C-Band Doppler Weather Radar
• Polarization agile
• Tx/Rx any Polarization
• Switch Polarization
• every Radar Pulse

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Polarization Network

• High Power Ferrite Phase Shifter
• Not Linear, not Reciprocal
• Changing Losses
• No a priori known polarization

Schematics
Variable Power Divider
Phase Shifter
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Requirements

• Fast ? adjust polarization switch settings
• Measure any Polarization
• Independent Rx/Tx measurements
• Repeatable

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Polarimetric Calibration (PARC)

• Far Field
• Polarization determination by Power and Phase
  measurement
• Simple two channel Rx/Tx frontend
• Commercial SDR card, Measure every Pulse
• Data analysis in Software

Radar
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Polarimetric Calibration (PARC)

• Very flexible
• Polarization measurement
• Power calibration
• PRF
• Frequency
• Pulse shape
• Independent Rx/Tx Measurement
• Automatic Calibration
• Polarimetric Antenna Pattern
• Calibrated H, V, 45, 135, R, L

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Scan Strategies

• H/V-Switching Mode
• Tx alternating H and V
• Rx both H and V
• Full Scattering Matrix

• Hybrid/STAR-Mode
• Tx 45 linear
• Rx both H and V
• Only two parameters

R/L-Mode
t
t1

• Full description for further calculation
• Optimal Polarization
• Huynen Parameters

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Multi Polarization Radar Measurement

• Combination of H/V-Switching and STAR-Mode

Tx
V
45
V
45
H
H
Rx
t
H/V
H/V
H/V
H/V
H/V
H/V
STAR- Mode
STAR- Mode
H/V-Mode
H/V-Mode
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Combination of Polarimetric Modes

• H/V- and STAR-Mode
• Simultaneous measurement
• in H/V- and STAR-Mode
• Direct comparison
• For high Depolarization
• ? large discrepancy

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Combination of Polarimetric Modes

• Two STAR-Modes
• Polarimetric Sensitivity Analysis
• Transmit Circular and Linear

Tx
R
45
45
Rx
t
H/V
H/V
H/V
STAR- Mode II
STAR- Mode I
STAR- Mode I

• Any Combination of R/L,H/V, STAR-Mode possible

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Huynen-Parameters
Example 24. Aug 2011, 1758, near Alps, Germany
Orientation
Target Size
Ellipticity

• Decomposition
• Phenomenological Description
• Polarization Independent
• Insight into Scattering Mechanism

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Conclusion

• Calibration
• Very flexible, automatic calibration device
• Adaptable for other radars
• Measurement
• First Results for Multi Polarization Measurements
• Influence of Polarization Errors
• Huynen-Parameter

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Contact
Dipl.-Ing. Jens Reimann ltJens.Reimann_at_dlr.degt Germ
an Aerospace Center Institute for Atmospheric
Physics Muenchner Strasse 20 82234
Oberpfaffenhofen-Wessling, Germany