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, July, Vancouver, Canada

Microwaves and Radar Institute 2 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)

Microwaves and Radar Institute 3 Displaced Phase Center Antenna >> high spatial resolution Multichannel Antenna Wide transmit pattern >> wide swath R(t) nadir H orb Digital Beamforming SCORE algorithm >> high gain HRWS (High-Resolution Wide-Swath) SAR System The 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)

Microwaves and Radar Institute 4 Monostatic System Planar phased array antenna HRWS Reference System Parameters 2 Tile 1 Tile 12 Tile... Panel 1 Panel 7 Panel ,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 km Antenna Tilt Angle: 34,3 deg RF Center Frequency: 9,6 GHz Pulse Bandwidth: 408 ÷ 194 MHz Processed Doppler bandwidth: 5950 Hz (stripmap) Averaged Tx Power: 2171 W Fully Polarimetric SCORE operation Tx patterns in az. and elev. by Phase Spoiling

Microwaves and Radar Institute 5 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: km o Spatial resolution: 1 m x 1 m o NESZ < dB o RASR: < - 28 dB o AASR < - 26 dB How performs the HRWS in Quad-Pol, ScanSAR Modes?

Microwaves and Radar Institute 6 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 m Nr. Subswaths: 12 Swath width smaller: km Spatial resolution: 1 m x 1 m Nr. Subswaths: 6 Subswath width: km PRF: 1650 – 1780 HzPRF double: 3400 – 3800 Hz

Microwaves and Radar Institute 7 Requirements & Constraints 2)Multichannel: Less degrees of freedom in the PRF choice (PRF uniformity*)  AASR (particularly low)  NESZ (multichannel processing)  Flexibility Design Elevation Patterns  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

Microwaves and Radar Institute 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

Microwaves and Radar Institute 9 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)

Microwaves and Radar Institute 10 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

Microwaves and Radar Institute 11 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 km Spatial resolution: 1m x ?m

Microwaves 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

Microwaves and Radar Institute 13 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)

Microwaves and Radar Institute 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

Microwaves and Radar Institute 15 Summary and Conclusions o Quad-Pol, Stripmap Mode o 12 subswaths, swath width: km o Spatial resolution: 1 m x 1 m o NESZ < dB o RASR: Cross-Pol < - 19 dB, Co-Pol < - 27 dB o AASR < dB o ScanSAR Mode: Ultra-Width Swath o 1 swath, swath width 375 km o Spatial resolution: 1 m x 9 m o NESZ < dB o RASR < - 28 dB o AASR < - 24 dB o Scalloping < 2.1 dB