mo3.l09.2 - bistatic sar based on terrasar-x and ground based receivers
TRANSCRIPT
Dept. Signal Theory & Communications RemoteSensing Laboratory (RSLab) 1
BISTATIC SAR BASED ON TERRASAR-X AND BISTATIC SAR BASED ON TERRASAR-X AND GROUND BASED RECEIVERSGROUND BASED RECEIVERS
A.Broquetas, M.Fortes, M.A.Siddique, S.Duque, J.C.Merlano, P.López-Dekker, J.J.Mallorquí, A.Aguasca
Remote Sensing Laboratory (RSLab)
Universitat Politècnica de Catalunya, Barcelona
Dept. Signal Theory & Communications RemoteSensing Laboratory (RSLab) 2
Introduction: Fixed receivers bistatic SAR
SABRINA-X Receiver design & implementation
Bistatic SAR Processing
Results
Conclusions
ContentsContents
2005
2006
2007
2008
2009
2010
• Firs
t BiS
AR Imag
es
• Sing
le-pa
ss fri
nges
.
• Sing
le-pa
ss DEM
• Rep
eat-p
ass
InSAR
• Firs
t Exp
erim
ents
(C-B
and)
• ATI,
Tomog
. , X-B
and
Dept. Signal Theory & Communications RemoteSensing Laboratory (RSLab) 3
IntroductionIntroduction : Fixed receivers bistatic SAR : Fixed receivers bistatic SAR
WHY?•Wide angle bistatic scattering understanding•SAR raw data in flexible RX configurations: InSAR, PolSAR, Tomography•Training covering the whole SAR chain: systems/processing/new applications
Dept. Signal Theory & Communications RemoteSensing Laboratory (RSLab) 4
Bistatic SAR Spatial ResolutionBistatic SAR Spatial Resolution
Bistatic Resolution:
For the monostatic case, the ground range resolution depends inversely to the sine of the transmitter local incidence angle.
For the bistatic case, the ground range resolution depends inversely to both sines of the transmitter and the receiver local incidence angles.
In the bistatic case, the azimuth resolution is slightly worse than monostatic, due to the one-way path
TX
RX
α
( ) ( )( )αθαθ −+−⋅∆=∆
rtcbistaticg f
cr
sinsin
( )αθ −⋅∆⋅=∆
tcmonostaticg f
cr
sin2
2monostatic
lz∆ =
2bistatic
lz∆ =rθ
tθ
Dept. Signal Theory & Communications RemoteSensing Laboratory (RSLab) 5
SABRINA-X: Channel Block DiagramSABRINA-X: Channel Block Diagram
Homodyne configuration for simplicity and low cost/size/weight/consumption
Initially designed with 2 channels, now 3, channel 4 is being implemented
Multiple channels needed for Interferometry, Polarimetry, MSAR
Dept. Signal Theory & Communications RemoteSensing Laboratory (RSLab) 6
SABRINA-X: L.O. SynthesizerSABRINA-X: L.O. Synthesizer
Dept. Signal Theory & Communications RemoteSensing Laboratory (RSLab) 7
SABRINA-X: Subsystem design & development (I)SABRINA-X: Subsystem design & development (I)
LNA: 9 -18 GHz, G = 19 dB, NF = 2 dB
RF Filter: 9.5-9.8 GHz, I.Loss = 3 dB
Horn Antennas G = 18 dB
Dept. Signal Theory & Communications RemoteSensing Laboratory (RSLab) 8
SABRINA-X: Subsystem design & development (II)SABRINA-X: Subsystem design & development (II)
I/Q DET.: RF 7.1-13.5 GHz, IF:DC-3.5 GHz, CL= 9 dB
BB Amp. & LP Filter G =16.5 dB
RF Amp. 6.5 a 13.5 GHz G=14 dB NF= 4.5dB
1/4 Freq. Synthesizer X4 Freq. Multiplier
Dept. Signal Theory & Communications RemoteSensing Laboratory (RSLab) 9
4 Acquisition Modes: I/Q BB: 4 Acquisition Modes: I/Q BB: 2 A/D x RF channel. Fs = 200/100 MS/s 2 A/D x RF channel. Fs = 200/100 MS/s
Bandwidth retained < Fs MHz
200 Ms/s example with low-pass filter 70 MHz cut-off
Dept. Signal Theory & Communications RemoteSensing Laboratory (RSLab) 10
4 Acquisition Modes: Low-IF : 4 Acquisition Modes: Low-IF : 1 A/D x RF Channel. Fs = 200/100 MS/s 1 A/D x RF Channel. Fs = 200/100 MS/s
100 Ms/s example with low-pass filter 48.5 MHz cut-off
Bandwidth retained < 1/2 Fs MHz
Dept. Signal Theory & Communications RemoteSensing Laboratory (RSLab)
Campaign Set-upCampaign Set-up
Antennas receiving Scattered signals
Antenna receiving Direct signal
SABRINA-X
11
Dept. Signal Theory & Communications RemoteSensing Laboratory (RSLab) 12
Acquired Data & SynchronizationAcquired Data & Synchronization
Pulse-trains
Illumination envelopes • Receiver synchronization offline: preprocessing• Illumination envelope, coarse PRF and pulse replica are
obtained from direct illumination channel • From range compressed pulses accurate time
alignment of both direct and scattered signals is achieved
• The frequency offset between TSX and SABRINA is estimated from the pulse to pulse phase change
• Azimuth focusing is based on Backprojection
Direct + scattered Spectrogram
Dept. Signal Theory & Communications RemoteSensing Laboratory (RSLab) 13
Range compression with Chirp replica and receiver equalizationRange compression with Chirp replica and receiver equalization
Direct pulse compression evaluation Green: compression with linear FM chirpBlue: compression with chirp replica &RX H(f) equalization
Received spectrum Receiver H(f) Equalized Receiver H’(f)
Dept. Signal Theory & Communications RemoteSensing Laboratory (RSLab) 14
Bistatic SAR ImagesBistatic SAR Images
Dept. Signal Theory & Communications RemoteSensing Laboratory (RSLab) 15
Geocoded SAR ImageGeocoded SAR Image
Dept. Signal Theory & Communications RemoteSensing Laboratory (RSLab) 16
θr
Bn,r
A1
A2
Rr
θt
Rt
“Back”- scattering “Forward”- scattering
θt
Rt
Bistatic InSARBistatic InSAR
Acquisition scheme:
As in the monostatic case, the information resides in the difference of interferometric phase among nearby points.
( )
⋅
⋅∆⋅=∆Ψrr
rnABAB R
Bh
θλπ
sin
2 ,
Dept. Signal Theory & Communications RemoteSensing Laboratory (RSLab) 17
Preliminary geocoded InterferogramPreliminary geocoded Interferogram
Dept. Signal Theory & Communications RemoteSensing Laboratory (RSLab) 18
Geocoded Interferogram with low resolution DEM compensation Geocoded Interferogram with low resolution DEM compensation
Dept. Signal Theory & Communications RemoteSensing Laboratory (RSLab) 19
Geocoded reference imageGeocoded reference image
Dept. Signal Theory & Communications RemoteSensing Laboratory (RSLab) 20
ConclusionsConclusions
Bistatic SAR with fixed ground receivers allows to develop affordable complete SAR chains suitable for hands-on SAR training and multichannel SAR research
A multichannel X-Band SAR receiver has been designed by undergraduate students from low cost COTS monolithic devices
First results on Barcelona harbor using TSX illumination has shown the importance of acquiring clean direct channel replica and channels H(f) calibration/equalization for accurate range compression and InSAR
Metallic containers and ships produce very bright scattering centers even at wide bistatic angles
The cost of high speed digitizers is presently the main bottle-neck for budget multichannel operation. A PRF trigger is under development for longer acquisition at highest sampling rate