Transcript Development of Focusing Algorithms for Arc

A Ground-Based Arc-Scanning Synthetic Aperture Radar
(ArcSAR) System and Focusing Algorithms
Hoonyol Lee
Department of Geophysics, Kangwon National University, Chuncheon, Republic of Korea ([email protected])
Seong-Jun Cho and Kwang-Eun Kim
Korea Institute of Geosciences and Mineral Resources, Daejeon, Republic of Korea (mac, [email protected])
Abstract - KNU and KIGAM are developing a ground-based Arc-scanning SAR
system (ArcSAR) 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
ArcSAR Spot Mode focusing while Range-Doppler algorithm was implemented for
ArcSAR Scan Mode, both in polar format. ArcSAR Spot Mode has 3.14 times higher
resolution than GB-SAR, while ArcSAR Scan Mode can obtain omnidirectional image
with reduced resolution but still has 11 times higher resolution than a conventional
real aperture radar.
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GB-SAR
DInSAR tested: Phase stability of 1° (0.1mm range) was achieved for several hours for
stable reflectors, rendering phase change of 10 ° to be assured (1mm accuracy).
PSInSAR displacement measurement: R2=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
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ArcSAR System
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ArcSAR 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
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ArcSAR Focusing
SPOT Mode : Deramp-FFT Algorithm
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:
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ArcSAR Focusing
SCAN Mode : Range-Doppler Algorithm
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:
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ArcSAR Focusing Flowchart
Raw Data
Range Hamming Filter
Range Compression
Azimuth FFT
Range Migration
Range Migration
Multiply Deramp function
Azimuth Matched Filter
Azimuth Hamming Filter
Azimuth Hamming Filter
Azimuth FFT
Azimuth iFFT
Geometric Correction
Geometric Correction
Output
Output
SPOT: Deramp-FFT
SCAN: Range-Doppler
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Azimuth Resolutions
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Simulation: ArcSAR Spot Mode
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Simulation: ArcSAR Scan Mode
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ArcSAR Scan Mode Experiment
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Conclusions
A novel ArcSAR system is developed and mounted on a truck.
Deramp-FFT algorithm was used for the ArcSAR Spot Mode.
Range-Doppler algorithm was implemented for the ArcSAR Scan Mode.
Comparisons of image resolutions between various ground-based radar systems confirmed the
advantages of ArcSAR:
ArcSAR Spot Mode > Linear-scanning GBSAR > ArcSAR Scan Mode > ArcRAR
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53.4
11.0
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ArcSAR Spot Mode has 3.14 times higher resolution than GB-SAR.
ArcSAR 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.
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