A Consideration of Signal Processing for Spotlight Synthetic Aperture Radar (Ambiguity Functions)
O'brien, James Dennis
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https://hdl.handle.net/2142/69268
Description
Title
A Consideration of Signal Processing for Spotlight Synthetic Aperture Radar (Ambiguity Functions)
Author(s)
O'brien, James Dennis
Issue Date
1984
Department of Study
Electrical Engineering
Discipline
Electrical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Electronics and Electrical
Abstract
An analysis of spotlight mode synthetic aperture radar (SAR) imaging was carried out using a model based solely on the recognizable similarity it shares with tomographic reconstruction. Doppler effects were relegated to a pre-processing step. Results of this investigation included a determination of the importance of: (1) rectangular versus polar formatting of data for imaging, (2) limited time-bandwidth of chirp signals if stretch processing is employed, (3) residual Doppler effects, and (4) spherical wavefront curvature. Furthermore, the applicability of the convolution back-projection algorithm for imaging spotlight SAR data was established.
A second part of the thesis was concerned with the design of two-dimensional tapers, or windows, for Fourier transformation of data collected over arbitrarily shaped apertures. If the intent is to minimize sidelobe energy, the generalized prolate spheroidal eigen-equation of Slepian can be solved in a simple iterative manner using a digital computer to obtain the taper. Computer solutions for several aperture shapes of interest were presented.
A novel analysis of interpolation artifacts was given to explain the appearance of defocused, spurious targets which appear from digital processing of data which has been interpolated from a partial polar raster onto a rectangular raster. The polar raster arises, in the context of the SAR application, from the manner of data collection, whereas digital processing is facilitated using data sampled on a rectangular raster.
Finally, the bi-static SAR problem was examined in its relation to other forms of near-field imaging and direct parallels were drawn. With less restrictive geometries, the optimal processor was again seen to be the spatially varying matched filter.
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