institute of atmospheric physics fast calibration of weather radar systems for multi polarization...

Institute of Atmospheric Physics

Fast Calibration of Weather Radar Systems for Multi Polarization Radar Measurements

Jens Reimann, Martin HagenDLR-Institute of Atmospheric Physics

> Jens ReimannInstitute of Atmospheric Physics

POLDIRAD

• Research Radar

• C-Band Doppler Weather Radar

• Polarization agile:

– Tx/Rx any Polarization

– Switch Polarization

every Radar Pulse


Polarization Network

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

Schematics

VariablePower Divider Phase Shifter


Requirements

• Fast → adjust polarization switch settings

Measure any Polarization

Independent Rx/Tx measurements

Repeatable


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


Polarimetric Calibration (PARC)

Very flexible:

1) Polarization measurement

2) Power calibration

3) PRF

4) Frequency

5) Pulse shape

6) Independent Rx/Tx Measurement

7) Automatic Calibration

8) Polarimetric Antenna Pattern

Calibrated: H, V, 45°, 135°, R, L


Scan Strategies

Hybrid/STAR-Mode

Tx: 45° linear Rx: both H and V

Only two parameters

H/V-Switching Mode

• Tx: alternating H and V• Rx: both H and V

Full Scattering Matrix

VVVH

HVHH

SS

SS

VVS

SHH

S

S

VH

HV

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

R/L-Mode

t t+1


Multi Polarization Radar Measurement

Combination of H/V-Switching and STAR-Mode

t

H V 45° HTx

RxH/V H/V H/V H/V H/V H/V

V 45°

H/V-Mode STAR-Mode

H/V-Mode STAR-Mode


Combination of Polarimetric Modes

H/V- and STAR-Mode• Simultaneous measurement

in H/V- and STAR-Mode• Direct comparison

• For high Depolarization

→ large discrepancy


Combination of Polarimetric Modes

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

t

45° R 45°Tx

RxH/V H/V H/V

STAR-Mode II

STAR-Mode I

STAR-Mode I

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

Institute of Atmospheric Physics

Huynen-Parameters

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

Mechanism

Target Size Orientation

Ellipticity

Example: 24. Aug 2011, 17:58, near Alps, Germany


Conclusion

Calibration

• Very flexible, automatic calibration device

• Adaptable for other radars

Measurement

• First Results for Multi Polarization Measurements

• Influence of Polarization Errors

• Huynen-Parameter


Dipl.-Ing. Jens Reimann <[email protected]>

German Aerospace CenterInstitute for Atmospheric Physics

Muenchner Strasse 2082234 Oberpfaffenhofen-Wessling, Germany

Contact

institute of atmospheric physics fast calibration of weather radar systems for multi polarization...

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