folie 1 performance investigation on the high-resolution wide-swath sar system operating in stripmap...
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Folie 1
Performance Investigation on the High-Resolution Wide-Swath SAR System Operating in Stripmap Quad-Pol and Ultra-Wide ScanSAR Mode
DLR - Institut für Hochfrequenztechnik und Radarsysteme
F. Bordoni, M. Younis, G. Krieger
IGARSS 2011, 24-29 July, Vancouver, Canada
2Microwaves and Radar Institute
Outline Introduction
HRWS (High-Resolution Wide-Swath) SAR (Synthetic Aperture Radar) System
Reference Parameters
Stripmap, Quad-Pol (Quadrature Polarimetric) Mode
Timing & Constraints
Proposed Solution
Performance:
NESZ (Noise Equivalent Sigma Zero)
RASR (Range Ambiguity to Signal Ratio)
AASR (Azimuth Ambiguity to Signal Ratio)
ScanSAR Mode: Ultra-Width Swath
Timing & Constraints
Proposed Solution
Performance (NESZ, RASR, AASR, Scalloping)
3Microwaves and Radar Institute
Displaced Phase Center Antenna>> high spatial resolution
Multichannel Antenna
Wide transmit pattern >> wide swath
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HRWS (High-Resolution Wide-Swath) SAR SystemThe HRWS SAR system is conceived to overcome the
conventional trade-off between resolution and swath width
Current SAR: 1 m v.s. 10 km; 16 m v.s. 100 km
HRWS: 1 m v.s. 70 km (stripmap single-pol)
4Microwaves and Radar Institute
Monostatic System
Planar phased array antenna
HRWS Reference System Parameters
2 Tile
1 Tile
12 Tile
...
Panel 1 Panel 7Panel 2 ...
1,06
m
8,75 m
Total Nr. TRMs (Transmit-Receive Modules)
Elevation: 12 dig. chan.
Azimuth: 7 dig. chan.
1,25 m
0,088 m
Orbit Height: 520 kmAntenna Tilt Angle: 34,3 deg
RF Center Frequency: 9,6 GHzPulse Bandwidth: 408 ÷ 194 MHzProcessed Doppler bandwidth: 5950 Hz (stripmap)
Averaged Tx Power: 2171 W
Fully Polarimetric
SCORE operationTx patterns in az. and elev. by Phase Spoiling
5Microwaves and Radar Institute
HRWS Basic Performance
The basic performance of the HRWS has been already investigated
In Stripmap single-pol Mode:
o 6 subswaths cover the complete access range
o Swath width: 70 - 80 km
o Spatial resolution: 1 m x 1 m
o NESZ < - 20.7 dB
o RASR: < - 28 dB
o AASR < - 26 dB
How performs the HRWS in Quad-Pol, ScanSAR Modes?
6Microwaves and Radar Institute
Stripmap Quad-Pol: Timing Diagram
Transmit alternately vertical & horizontal linear polarized pulses Double PRF (Pulse Repetition Frequency)
Single-pol Quad-pol
Timing Diagram
Spatial resolution: 1 m x 1 mNr. Subswaths: 12
Swath width smaller: 20 - 50 km
Spatial resolution: 1 m x 1 mNr. Subswaths: 6Subswath width: 70 - 80 km
PRF: 1650 – 1780 Hz PRF double: 3400 – 3800 Hz
7Microwaves and Radar Institute
Requirements & Constraints
2) Multichannel: Less degrees of freedom in the PRF choice (PRF uniformity*)
AASR (particularly low)
NESZ (multichannel processing)
Flexibility Design Elevation Patterns
Mailobe @ subswath width (RASR, NESZ)
Low sidelobe level (RASR)
Severe requirements and constraints characterize the Quad-pol mode
1) Quad-pol: High PRF
RASR (critical especially in Cross-Pol)
*PRF matched to the antenna length and No. of apertures > regular sampling in azimuth results
8Microwaves and Radar Institute
- 19 dB
RASR Cross-pol < - 19 dB
Elev. pattern design crucial to meet the RASR requirements in Cross-Pol
Hamming vs. Uniform:
improvement in far range - 4 dB
near range
far range
Tx Phase Spoiling and uniform tapering (mainlobe subswath width)
- - - Rx Hamming window ( side lobe level)NESZ RASR
Pattern Design & RASR in Cross-Pol
9Microwaves and Radar Institute
Stripmap Quadpol: RASR in Co-Pol & NESZ
-27 dB- 19,5 dB
RASR Co-Pol < - 27 dB NESZ < - 19,5 dB
Range Ambiguity Signal Ratio: Co-Pol
Noise Equivalent Sigma Zero
(spatial resolution: 1 m x 1m)
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Stripmap Quadpol: Azimuth Performance
1,1 m
- 30,5 dB
Az. Res. < 1,1 m AASR < - 30,5 dB
Azimuth Resolution
Azimuth Ambiguity Signal Ratio
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Swath width of 375 km complete imaging of the Earth with a repeat time of 8 days
Ultra-Wide ScanSAR
375 km
Imaging of the complete acces range (375 km) in a single pass
6 bursts // 6 subswaths
Swath width: 375 kmSpatial resolution: 1m x ?m
12Microwaves and Radar Institute
- - - Rx Patt.___ Tx Patt.___ 2-way Patt.
Pattern Design & Performance
Azimuth pattern shape key influence on ScanSAR performance
The Phase Spoiling technique is used to obtain the Tx pattern
Ripple: Scalopping
Mainlobe-width: azimuth resolution
Side Lobe Level: AASR
Mainlobe-level: NESZ
Ripple: Scalopping
Mainlobe-width: azimuth resolution
Side Lobe Level: AASR
Mainlobe-level: NESZ
13Microwaves and Radar Institute
UW ScanSAR: Azimuth Performance
-24 dB
8,7 m
2,1 dB
Az. Res. < 8,7 m AASR < - 24 dB Scalloping < 2,1 dB
Azimuth Resolution
Azimuth Ambiguity Signal Ratio
Scalloping Stripmap: 1 m
Scansar: 7 m gives high scalloping (>3.5dB)
14Microwaves and Radar Institute
- 28 dB
UW ScanSAR: NESZ & RASR
- 22,6 dB
NESZ < - 22,6 dB RASR < - 28 dB
Noise Equivalent Sigma Zero
Range Ambiguity Signal Ratio
ground range resolution: 1 m
15Microwaves and Radar Institute
Summary and Conclusionso Quad-Pol, Stripmap Mode
o 12 subswaths, swath width: 20 - 50 km
o Spatial resolution: 1 m x 1 m
o NESZ < - 19.5 dB
o RASR: Cross-Pol < - 19 dB, Co-Pol < - 27 dB
o AASR < - 30.5 dB
o ScanSAR Mode: Ultra-Width Swath
o 1 swath, swath width 375 km
o Spatial resolution: 1 m x 9 m
o NESZ < - 22.6 dB
o RASR < - 28 dB
o AASR < - 24 dB
o Scalloping < 2.1 dB