Download - Sar Presegntation
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Synthetic Aperture Radar Synthetic Aperture Radar (SAR)(SAR)
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Ground RegionGround Region
We took a small sample of a SAR image to use as test data
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Flight SimulationFlight SimulationRealistic
Parameters◦ Beam angle◦ Beam squint◦ Platform velocity ◦ Platform altitude◦ Pulse duration◦ Ground pixel resolution◦ Sampling frequency◦ Number of samples◦ Carrier frequency◦ Transmit/Receive switching
delay
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Beam ShapeBeam ShapeOne of the sub-
functions we wrote calculates the beam pattern for any horizontal and vertical beam angle
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ROI ClosureROI ClosureAll of the ground points that
affect the data points which give information about the ROI
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ROI ClosureROI ClosureUnion of intersections of the
beam pattern and a radius for which ground pixel reflections are being sampled
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Data from ground pixelData from ground pixelEach ground pixel affects a certain set of data points
Figure 3 shows nulls in the data sets that are due to nulls in the beam pattern
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Closure for a data pointClosure for a data pointEach data point represents a sample taken at a certain time, so each data point collects reflectivity data from ground pixels in an area that is roughly the shape of the beam pattern
Data PointCorresponding Ground Pixels
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FFHHFFThe data gathered is a linear
combination of different ground reflectivities
F is a matrix that explains the mixing going on in the data◦ Each column holds data for a ground pixel◦ Each row is a different data sample mixed
with information about the ground pixel it relates to
d=Fg+nFHd=FHFg
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SAR Possibilities SAR Possibilities Optimum ML change detection:
◦ d1 = F1 g + n1 d2 = F2 (g + δ) + n2
◦ Can obtain both g and the change δ in closed form.
GMTI: Incorporate moving targets into signal model. Can estimate target position, direction, and velocity vector.
Motion compensation:◦ Allow for errors in both data d and regressors F
using weighted total least-squares techniques.◦ Estimate SAR trajectory using known strong
targets of opportunity.
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SAR Possibilities SAR Possibilities Ground elevation estimation.Extend to bistatic SAR.Extend to continuous wave signaling
(will improve rank of F ).
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Future WorkFuture Work Imposing Block Structure
◦ If the structure of FHF could be made to be Toeplitz, or have a block diagonal structure with small diagonal blocks, then inversion of FHF would be easy.
Signal Design◦ Design the signal waveform to make FHF have a structure
that is easily invertible. This may require transmitting a different pulse signal at each azimuth position. It may also require using pulse coded waveforms instead of chirps.
Antenna design◦ Suppose an antenna array is used. Then the array
weights could be designed and made to vary with time in a fashion that imposes structure on FHF that makes it easy to invert.