 | Reimann J. On fast, polarimetric non-reciprocal calibration and multipolarization measurements von weather radars: Diss. … Dr.-Ing. / Deutsches Zentrum für Luft- und Raumfahrt, Institut für Physik der Atmosphäre, Oberpfaffenhofen. - Köln: DLR, 2013. - 161 p.: ill. - (Forschungsbericht; 2013-36). - Res. also Germ. - Bibliogr.: p. 143-149. - ISSN 1434-8454
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List of Symbols ................................................ 17
List of Abbreviation ........................................... 21
1 Introduction ................................................ 23
2 Basics ...................................................... 25
2.1 Electromagnetic Basics ................................. 25
2.2 Polarization Basics .................................... 26
2.2.1 Polarization Transformation ..................... 29
2.3 Scattering Matrix ...................................... 30
2.4 Radar Basics ........................................... 30
2.5 Radar Equation ......................................... 32
3 System Description of the Radar POLDIRAD .................... 35
3.1 Transmitter ............................................ 35
3.2 Polarization Network ................................... 37
3.3 Antenna ................................................ 40
3.4 Receiver ............................................... 41
3.5 Built-in Test Equipment ................................ 41
4 Radar Calibration ........................................... 43
4.1 Requirements ........................................... 43
4.2 Uncertainty Requirements ............................... 44
4.3 Calibration Model ...................................... 45
4.4 Standard Techniques .................................... 45
4.4.1 Internal calibration ............................ 46
4.4.2 Sphere .......................................... 46
4.4.3 Rain ............................................ 47
4.4.4 Astronomic Targets .............................. 48
4.5 Sun-Calibration for the POLDIRAD Radar ................. 49
5 Preliminary Investigation of an External Calibration
Device ...................................................... 59
5.1 Antenna Measurement Techniques ......................... 60
5.1.1 Near Field ...................................... 60
5.1.2 Compact Range ................................... 60
5.1.3 Far Field ....................................... 60
5.2 Polarization Measurement Techniques .................... 61
5.2.1 Single Rotating Linear Polarized Antenna ........ 62
5.2.2 Orthogonal Antenna Pair ......................... 62
5.2.3 Four-Antennas Power Measurement ................. 62
5.3 Prior Systems .......................................... 63
5.3.1 Single Antenna PARC ............................. 64
5.3.2 Automated Polarization Measurement Chamber ...... 64
5.3.3 DLR PARC ........................................ 64
5.3.4 Summary ......................................... 65
6 PARC ........................................................ 69
6.1 System Description ..................................... 69
6.2 First RF Power Estimation .............................. 71
6.2.1 Trigger Generation .............................. 71
6.3 System Development ..................................... 72
6.3.1 Hardware ........................................ 72
6.3.2 PARC Server Software ............................ 74
6.4 Calibration Technology for PARC ........................ 79
6.4.1 Calibration Model ............................... 79
6.4.2 Determination of the Polarization Independent
Loss ............................................ 80
6.4.3 Radar PARC Synchronisation ...................... 81
6.5 Calibration modules .................................... 83
6.5.1 Time Plot ....................................... 83
6.5.2 Radar Transmit Pulse Measurement ................ 83
6.5.3 Defined PARC Transmit Signal .................... 84
6.5.4 Radar Receive Signal Measurement ................ 84
6.5.5 Automatic Radar Receive Polarization
Optimization .................................... 85
6.5.6 Automatic Radar Transmit Polarization
Optimization .................................... 86
6.5.7 Radar Transmit/Receive Data Plot ................ 87
6.5.8 Polarization Phase Difference Measurement ....... 87
6.6 PARC Measurements ...................................... 88
6.6.1 Polarization Phase Calibration .................. 90
6.6.2 PARC Power Measurements ......................... 92
6.7 Limitations ............................................ 93
7 Radar Data Processing ....................................... 95
7.1 Introduction ........................................... 95
7.2 Signal Processing for the POLDIRAD Radar ............... 96
7.3 The New Realization of the Alternating H/V Mode ........ 97
7.4 Alternating Right/Left-hand Circular Mode ............. 104
7.5 Signal Processing for Multi-Polarization Scans ........ 105
7.5.1 Practical Implementation ....................... 106
7.6 Polarimetric Data Analysis ............................ 108
7.6.1 Huynen Fork-Parameters ......................... 108
7.6.2 Additional Parameters .......................... 111
8 Multi-Polarization Measurements ............................ 113
8.1 Influence of the Transmit Phase in Simultaneous H/V
Mode and Comparison to the Alternating H/V Mode ....... 113
8.1.1 Theoretical Predictions ........................ 113
8.1.2 Measurements of Copolar-Correlations-
Coefficient .................................... 115
8.1.3 Measurement of Differential Reflectivity ....... 117
8.2 Measurements of the Co-Cross-Correlation-Coefficient .. 119
9 Conclusions ................................................ 123
10 Outlook .................................................... 125
A PARC Specifications ........................................ 127
A.l Antenna ............................................... 127
A.2 PARC Circuits ......................................... 129
B Mfatctice in Weather Radar Calibration ..................... 131
B.1 Introduction .......................................... 131
B.2 Range ................................................. 131
B.3 Antenna Pointing ...................................... 132
B.4 Receiver Offset ....................................... 132
B.5 Absolute Power Calibration ............................ 132
B.6 Polarimetric Calibration .............................. 133
С Sun Scan Plots ............................................. 135
Bibliography .................................................. 142
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