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

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