Imaging Radars: System Architectures and Technologies

1. Imaging Radars: system architectures and technologiesG. Angino, A. Torre Frascati, INFN, 2011, November 28th

2. Scope The potentiality of multichannel SAR to provide wide-swath and high resolution at the same time, has attracted increased interest among remote sensing community • The scope of this paper is to address some of the architectural and technological aspects related to the implementation of a multichannel receiver for a multi-beam SAR, with the objective to provide some solutions for different configurations with increased complexity • A further point is the exploitation of the multichannel configuration for the implementation of very high resolution modes

3. Next Generation SAR Challenges • Spaceborn SAR systems are now no more “experiments” but are fielded for operational use. • Specialized systems optimized for different application: • Earth Resource Exploitation • Ship Traffic Monitoring • Land Use • Disaster Prevention and Management • Security/Intelligence • and many others… • Sophisticated features required • Polarimetry • MTI • Very wide swath • Very high resolution

4. Space-based observationThe applications Civilianapplications Risk Management Environment Landscape ecology Land use monitoring Science Homeland security Cartography Digital Elevation Modelling Defence applications Territory Surveillance Intelligence Target detection, classification and recognition Decision making support (C4I) Mission preparation 4

5. SAR allows quick detection of metallic artifacts, ships, and docking infrastructures High resolution applications Cranes Optical Image Multi-temporal observation (one more ship) Railway 5

6. Wide Area applications

7. User Needs Very High Geometric Resolution Wider bandwidths to achieve range resolution r = c/2B sin q Larger Synthetic Aperture for azimuth resolution Spotlight Multi-beam Increased swath coverage Swath width is limited by range ambiguity SCANSAR mode allows to enlarge the swath at the expense of azimuth resolution These two performances impose contrasting requirements to the SAR system. The usage of multiple receive beams is a promising technique which can solve this contrast, at the expenses of system complexity

8. User needs – Imaging Modes satellite velocity (v) Along track Scansar mode Along track Spotlight mode satellite velocity (v)

9. Imaging Radar Performance

10. Digital Beam Forming • Capability to synthesize several simultaneous beams in the azimuth direction by means of digital beam-forming (DBF) allows to couple the high azimuth resolution typical of the spotlight mode with the continuous coverage of the stripmap operation. • DBF for future SAR payloads requires an advanced architectural design assuring with a modular architecture • On-board data processing and storage • Modular HW & SW partitioning • Multichannel digital core • Multi-Gbps I/F (ASIC,FPGA,DSP,RAM)

11. DBF for Spaceborne SAR The Elevation DBF compensates the reduced transmit-gain with a large receive-gain The Azimuth DBF allows for a fine azimuth resolution at a reduced PRF by means of Multi-Channel Sampling of the signal-phase azimuth-spectrum

12. Multichannel Architecture • A multi-channel receiver is needed to handle multiple beams and offers the potential two handle very high bandwidth in frequency displaced mode • This architecture offers the advantage that the same standard building blocks can be used in different quantities and mix to fit a wide range of applications. • Multi-channel architecture can operate either in • frequency displaced mode (each channel handles a share of the overall bandwidth, merged afterwards in on-ground processing), or in • space displaced mode for multi-beam application

13. Multichannel Architecture • Single conversion, sampling at S-band IF • Optical data link with digital backend (digital filtering and decimation) • Flexible LO generator and Flexible Switch Matrix to allow reconfiguration

14. DBF processing • The DPE shall receive the individual receive channels from the antenna (following digitization and first level processing performed by dedicated Integrated Pre-Processing Modules (IPP)) • The Integrated Pre-Processing consists of a building block housed in a dedicated mechanical module performing the following functions: • Digitalisation of the incoming IF echo • Extraction of the I/Q channels • Band-limiting filtering and (if needed) data decimation

15. Integrated Pre-Processing Section • Pre processing section in charge of: • Echo Digitisation • Extraction of baseband components • Bandpass filtering and decimation • Data compression and formatting

16. Digital processing element (DPE) DPE main processing task is beam synthesis

17. DPE Implementation: Integrated Digital Core • The processing nodes are fully programmable and can perform virtually any computation function running application-specific software. • Required processing power can be achieved by simply using more or less modules. • Integrated Pre-Processors based (for the development phase) on Xilinx Virtex-5 FPGAs • HIGH-Performance processing nodes based on PowerPC 7448 CPUs • 16 to 32 GByte DRAM mass memory

18. THANK YOU FOR YOUR ATTENTION !