Transcript GB-SAR 시스템의 개발과 응용

The 9th Workshop on Subsurface Electromagnetic Measurement
KIST, Seoul, 25 October 2007.
Development of a Ground-based Synthetic Aperture Radar System
for Highly Repeatable Measurements
Hoonyol Lee, Seong-Jun Cho, Nak-Hoon Sung and Jung-Ho Kim
Kangwon National University
KIGAM
Contents






Introduction
GB-SAR System
Gb-SAR Focusing
GB-SAR Interferometry
Measurement of Target Displacement
Conclusion
Introduction

GB-SAR: Ground-Based Synthetic Aperture Radar

Synthetic Aperture Radar



Imaging Radar
Azimuth aperture synthesis
Ground-Based

Fairly versatile system configuration



Ultimate SAR focusing






Multiple frequency (L, C, X, Ku, Ka, etc)
Full Polarization (VV, VH, HV, HH)
Zero Doppler centroid (stationary vehicle during Tx/Rx)
Accurate estimation of Doppler rate from geometry
Topography Mapping: Cross-Track InSAR or Delta-K InSAR
Surface Motion: Zero-baseline and short atmospheric path for Temporal Coherency,
DInSAR and PSInSAR
Useful for new SAR concept design
Previous Works


LISA (EU) for Avalanche and landslide monitoring
Other laboratory or field tests (UK, Japan)
GB-SAR System
System Configuration
Rx V-pol
Rx H-pol
Tx V-pol
Tx H-pol
GPIB
Motion
Control
TX RX
IN
OUT
SAR Focusing Algorithms
Algorithms
Advantange
Disadvantage
Usage
Range-Doppler
or ω-k
Widely used for
SAR
Memory
inefficiency for
partial-focusing
Near Range
(full-focusing)
Deramp-FFT
Efficient in
Far Range
Distortion in near
memory and CPU
range
(partial-focusing)
time
Time Domain
Exact everywhere
Time consuming
Everywhere
DF vs RD (Indoor)
(a) DF algorithm
(b) RD algorithm
DF vs RD (outdoor)
(a) DF algorithm (2MB Memory)
(b) DF algorithm (geocoded)
(b) RD algorithm (128MB Memory)
GB-SAR Resolutions
Range Resolution
c
R 
2B
(25 cm for B  600 MHz)
AzimuthResolution
Azimut hResolut ion
L
x  a
2
(a) Full Focusing
x 
R
,  

2X
2X
(0.3 for X  5 m, C - band)
(b) Partial Focusing
GB-InSAR Configuration




DInSAR, PSInSAR
Cross-Track
InSAR
Delta-f InSAR
Cross-Track and
Delta-f InSAR
DInSAR with target
displacement in range
direction
Cross-Track InSAR
for DEM Generation
GB-InSAR Phases
Change
DInSAR
Range
displacement
Cross-Track
InSAR
Vertical
baseline
Delta-f
InSAR
Frequency
shift
Cross-Track
and Delta-f
InSAR
and
Phase Difference
Range phase
ramp
Sensitivity
Displacement:
none
Height
 4Bv

h
R
none
Height
 4Bv

h
R
KIGAM Roof-Top Test

T1
Range:
Center frequency=5.3GHz
Bandwidth=200MHz
Sample=1601
Power=33dBm (2W)
Azimuth:
Scan length=5m
Step=5cm
Sample=101

T2: Temporal baseline of 20minutes
(DInSAR)

T3: Spatial baseline of -30cm
vertical (InSAR DEM)

T4: Frequency shift of -10MHz
(Delta-K InSAR)
Image Area
VV
T1
VH
T1
HH
T1
DInSAR (T2-T1):
Temporal baseline of 20 minutes
VV
Cross-Track InSAR (T3-T2)
Vertical baseline of 30cm
VV
Delta-f InSAR (T4-T3)
Frequency shift of -10MHz
VV
VV
Cross-Track and Delta-f InSAR (T4-T2)
Vertical baseline of 30cm, Frequency shift of -10MHz
VV
VV
Automatic Acquisition
with 2cm Step, 2007. 3. 19 7:22pm- 4:20am, A1~A9
VV
HH
Phase Errors
Ideal Case
A6-A5, HH
Azimuth scan shift
of 2cm. A9-A1, HH
Range System
Shift of 2mm
PSInSAR – Temporal Coherence
TC of 9 acquisitions for 2 hours.
Color scheme: black(0) to white(0.9) and blue (0.9) to red(1)
Measurement of Target Displacement
2007. 7. 18
Movements of the reflector (150m away from the system)
↑ Radar
direction
A trihedral corner reflector on top of an
Displacement from the origin:
acrylic plate with rulers on both sides
1, 2, 6, 10, 30, 40mm
Comparisons – Original (ground range)
HH
VH
VV
HV
Comparisons – Original (slant range)
HH
VH
VV
HV
Comparisons – After system correction
HH
VV
VH
HV
Conclusion

A GB-SAR system was developed, tested, and waiting for applications.

Optimal GB-SAR focusing algorithms were tested.

Cross-Track and Delta-f InSAR were tested.

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
More robust GB-SAR system optimized to a specific application will be developed.
Thank You,
and
Welcome to
Korea.