A GroundBased ArcScanning Synthetic Aperture Radar Arc SAR

A Ground-Based Arc-Scanning Synthetic Aperture Radar (Arc. SAR) System and Focusing Algorithms Hoonyol Lee Department of Geophysics, Kangwon National University, Chuncheon, Republic of Korea (hoonyol@kangwon. ac. kr) Seong-Jun Cho and Kwang-Eun Kim Korea Institute of Geosciences and Mineral Resources, Daejeon, Republic of Korea (mac, kimke@kigam. re. kr) Abstract - KNU and KIGAM are developing a ground-based Arc-scanning SAR system (Arc. SAR) mounted on a truck. The system achieves a coherent integration of radar returns from ground targets by the circular motion of the antennae attached to the end of an extendable arm. Precise control of antenna position and the extended coherent-integration-length enable the formation of high-resolution, highprecision and phase-preserving SAR images. Deramp-FFT algorithm was used for Arc. SAR Spot Mode focusing while Range-Doppler algorithm was implemented for Arc. SAR Scan Mode, both in polar format. Arc. SAR Spot Mode has 3. 14 times higher resolution than GB-SAR, while Arc. SAR Scan Mode can obtain omnidirectional image with reduced resolution but still has 11 times higher resolution than a conventional real aperture radar. 1

GB-SAR DIn. SAR tested: Phase stability of 1° (0. 1 mm range) was achieved for several hours for stable reflectors, rendering phase change of 10 ° to be assured (1 mm accuracy). PSIn. SAR displacement measurement: R 2=0. 9999 achieved. GB-SAR can be used for various applications such as: Safety monitoring of natural or anthropogenic structures Microwave backscattering properties of target New SAR system concept design 2

Arc. SAR System 3

Arc. SAR Imaging Modes Spot Mode Dual rotational motion (boom and antenna) Coherent Integration Arc can be 180 degree maximum. High resolution Limited azimuth coverage Scan Mode Single rotational motion (boom only) Coherent Integration Arc is the width of the antenna beam. Low resolution Full azimuth coverage 4

Arc. SAR Focusing SPOT Mode : Deramp-FFT Algorithm in Polar Format Range Compressed Signal: Deramp Function: Coherent Integration Arc: Azimuth Compression: IFFT Range Function: Focused Image: Taylor’s Expansion at : Azimuth (angular) Resolution: Phase: 5

Arc. SAR Focusing SCAN Mode : Range-Doppler Algorithm in Polar Format Range Compressed signal: Matched Filter: Coherent Integration Arc: Azimuth Compression: Matched Filtering Focused Image: Range Function: Taylor’s Expansion at : Azimuth (angular) Resolution: Phase: 6

Arc. SAR Focusing Flowchart Raw Data Range Hamming Filter Range Compression Azimuth FFT Range Migration Multiply Deramp function Azimuth Matched Filter Azimuth Hamming Filter Azimuth FFT Azimuth i. FFT Geometric Correction Output SPOT: Deramp-FFT SCAN: Range-Doppler 7

Azimuth Resolutions 8

Simulation: Arc. SAR Spot Mode 9

Simulation: Arc. SAR Scan Mode 10

Arc. SAR Scan Mode Experiment 11

Conclusions A novel Arc. SAR system is developed and mounted on a truck. Deramp-FFT algorithm was used for the Arc. SAR Spot Mode. Range-Doppler algorithm was implemented for the Arc. SAR Scan Mode. Comparisons of image resolutions between various ground-based radar systems confirmed the advantages of Arc. SAR: Arc. SAR Spot Mode > Linear-scanning GBSAR > Arc. SAR Scan Mode > Arc. RAR 167. 2 53. 4 11. 0 1 Arc. SAR Spot Mode has 3. 14 times higher resolution than GB-SAR. Arc. SAR Scan Mode can obtain omnidirectional image with reduced resolution, but still has 11 times higher resolution than a conventional real aperture radar. The system will provide a rapid response tool for various applications such as regional mapping and environmental hazard monitoring. 12