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Synthetic Aperture Synthetic Aperture Radar (SAR) Radar (SAR)

Synthetic Aperture Radar (SAR)

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Synthetic Aperture Radar (SAR). Ground Region. We took a small sample of a SAR image to use as test data. Flight Simulation. Realistic Parameters Beam angle Beam squint Platform velocity Platform altitude Pulse duration Ground pixel resolution Sampling frequency Number of samples - PowerPoint PPT Presentation

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Page 1: Synthetic Aperture Radar (SAR)

Synthetic Aperture Radar Synthetic Aperture Radar (SAR)(SAR)

Page 2: Synthetic Aperture Radar (SAR)

Ground RegionGround Region

We took a small sample of a SAR image to use as test data

Page 3: Synthetic Aperture Radar (SAR)

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

Page 4: Synthetic Aperture Radar (SAR)

Beam ShapeBeam ShapeOne of the sub-

functions we wrote calculates the beam pattern for any horizontal and vertical beam angle

Page 5: Synthetic Aperture Radar (SAR)

ROI ClosureROI ClosureAll of the ground points that

affect the data points which give information about the ROI

Page 6: Synthetic Aperture Radar (SAR)

ROI ClosureROI ClosureUnion of intersections of the

beam pattern and a radius for which ground pixel reflections are being sampled

Page 7: Synthetic Aperture Radar (SAR)

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

Page 8: Synthetic Aperture Radar (SAR)

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

Page 9: Synthetic Aperture Radar (SAR)

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

Page 10: Synthetic Aperture Radar (SAR)

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.

Page 11: Synthetic Aperture Radar (SAR)

SAR Possibilities SAR Possibilities Ground elevation estimation.Extend to bistatic SAR.Extend to continuous wave signaling

(will improve rank of F ).

Page 12: Synthetic Aperture Radar (SAR)

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.