Spectral replacement to mitigate interference for multi-pass synthetic aperture radar
First Claim
Patent Images
1. A system, comprising:
- at least one processor; and
memory comprising instructions that, when executed by the at least one processor, cause the at least one processor to perform acts comprising;
responsive to receiving a first synthetic aperture radar (SAR) phase history of a scene corresponding to a first pass of a SAR platform and a second SAR phase history of the scene corresponding to a second pass of the SAR platform, resampling the first phase history and the second phase history to a common coordinate system;
applying a spatially-variant phase correction to a first image, the first image based upon the resampled first phase history, the spatially-variant phase correction based upon a spatially-variant phase offset between a second image and a third image, wherein the second image is based upon the second resampled phase history and the third image is based upon the first resampled phase history;
applying a constant phase correction to a third phase history, the third phase history based upon the spatially-variant phase-corrected first image, the constant phase correction based upon a constant phase offset between the third phase history and the resampled second phase history; and
replacing first data in the phase-corrected third phase history with second data in the resampled second phase history.
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Abstract
Various technologies for mitigating interference artifacts in multi-pass synthetic aperture radar (SAR) imagery are described herein. First and second phase histories corresponding to first and second SAR passes over a scene are processed in image and phase-history domains to correct for spatially-variant and constant phase offsets between the phase histories that can be caused by known and unknown variations in motion of a SAR platform between passes. Data samples from one phase history can then be replaced with data samples from the other phase history to remove artifacts and distortions caused by sources of interference in the scene.
46 Citations
20 Claims
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1. A system, comprising:
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at least one processor; and memory comprising instructions that, when executed by the at least one processor, cause the at least one processor to perform acts comprising; responsive to receiving a first synthetic aperture radar (SAR) phase history of a scene corresponding to a first pass of a SAR platform and a second SAR phase history of the scene corresponding to a second pass of the SAR platform, resampling the first phase history and the second phase history to a common coordinate system; applying a spatially-variant phase correction to a first image, the first image based upon the resampled first phase history, the spatially-variant phase correction based upon a spatially-variant phase offset between a second image and a third image, wherein the second image is based upon the second resampled phase history and the third image is based upon the first resampled phase history; applying a constant phase correction to a third phase history, the third phase history based upon the spatially-variant phase-corrected first image, the constant phase correction based upon a constant phase offset between the third phase history and the resampled second phase history; and replacing first data in the phase-corrected third phase history with second data in the resampled second phase history. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method, comprising:
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responsive to receiving a first synthetic aperture radar (SAR) phase history of a scene corresponding to a first collection time and a second SAR phase history of the scene corresponding to a second collection time, resampling the first phase history and the second phase history to a common reference; applying a spatially-variant phase correction to a first image, the first image based upon the resampled first phase history, the spatially-variant phase correction based upon a spatially-variant phase offset between a second image and a third image, the second image based upon the second resampled phase history, the third image based upon the first resampled phase history; transforming the phase-corrected first image to a third phase history; applying a constant phase correction to the third phase history based upon a constant phase offset between the third phase history and the resampled second phase history, wherein applying the constant phase correction to the third phase history results in a fourth phase history; and replacing first data in the second phase history with second data in the fourth phase history to mitigate interference. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19)
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20. A computer-readable medium comprising instructions that, when executed by a processor, perform the following acts:
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responsive to receiving a first phase history corresponding to a first synthetic aperture radar (SAR) imaging scan of a scene and a second phase history corresponding to a second SAR imaging scan of the scene, resampling the first phase history and the second phase history to a common coordinate system; filtering at least a portion of the resampled first phase history based upon a filtered portion of the second phase history; forming first and second images based upon the first filtered phase history and the second resampled phase history, respectively; executing an autofocus algorithm over each of the first and second images; registering the first image to the second image; calculating a coherence estimator between the registered first image and the second image; unwrapping a two-dimensional phase of the coherence estimator; applying a phase correction to a third image, the third image based upon the first phase history, the phase correction based upon the unwrapped two-dimensional phase; executing a transform over the phase-corrected third image to generate a third phase history; applying a constant phase offset to the third phase history based upon a constant phase difference between the second resampled phase history and the third phase history; and generating an image of the scene in the first SAR imaging scan based at least in part upon the phase-offset third phase history and a value of the second resampled phase history.
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Specification