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Abstract In the problem of spotlight mode airborne synthetic aperture radar (SAR) image formation, it is well-known that data collected over a wide azimuthal angle violate the isotropic scattering property typically assumed. Many techniques have been proposed to account for this issue, including both full-aperture and sub-aperture methods based on filtering, regularized least squares, and Bayesian methods. A full-aperture method that uses a hierarchical Bayesian prior to incorporate appropriate speckle modeling and reduction was recently introduced to produce samples of the posterior density rather than a single image estimate. This uncertainty quantification information is more robust as it can generate a variety of statistics for the scene. As proposed, the method was not well-suited for large problems, however, as the sampling was inefficient. Moreover, the method was not explicitly designed to mitigate the effects of the faulty isotropic scattering assumption. In this work we therefore propose a new sub-aperture SAR imaging method that uses a sparse Bayesian learning-type algorithm to more efficiently produce approximate posterior densities for each sub-aperture window. These estimates may be useful in and of themselves, or when of interest, the statistics from these distributions can be combined to form a composite image. Furthermore, unlike the often-employed ℓ p -regularized least squares methods, no user-defined parameters are required. Application-specific adjustments are made to reduce the typically burdensome runtime and storage requirements so that appropriately large images can be generated. Finally, this paper focuses on incorporating these techniques into SAR image formation process, that is, for the problem starting with SAR phase history data, so that no additional processing errors are incurred. The advantage over existing SAR image formation methods are clearly presented with numerical experiments using real-world data.
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Modeling frequency dependent scattering models for SAR Image Spectrum Extrapolation
The wavelength used for illumination dictates the scale of the mechanisms that interact with the incident electromagnetic (EM) energy. We model the synthetic Aperture Radar Image of a target as a superposition of the returns from scattering mechanisms that depend on the wavelength of the illuminating waveform and the viewing angle. In this work, we present a method to jointly model the scattering responses of the target over a wide aperture of measurements and a wide swath of frequencies spanning the C to X Band. Specifically, we estimate the location of the scattering centers and their azimuth-dependent responses normalized by the wavelength, jointly for low and high bands. We verify the validity of the proposed model using simulated data from a backhoe and Civilian vehicle data domes dataset over two non-overlapping frequency bands centered at 7GHz and 12 GHz.
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- Award ID(s):
- 2037398
- PAR ID:
- 10491303
- Publisher / Repository:
- IEEE
- Date Published:
- Journal Name:
- Proceedings of 2023 IEEE Radar Conference (RadarConf23)
- ISBN:
- 978-1-6654-3669-4
- Page Range / eLocation ID:
- 1 to 5
- Subject(s) / Keyword(s):
- Frequency band extrapolation augmentation wide-band scattering model
- Format(s):
- Medium: X
- Location:
- San Antonio, TX, USA
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1109/RadarConf2351548.2023.10149732
