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Title: SAR polar format implementation with MATLAB.

Abstract

Traditional polar format image formation for Synthetic Aperture Radar (SAR) requires a large amount of processing power and memory in order to accomplish in real-time. These requirements can thus eliminate the possible usage of interpreted language environments such as MATLAB. However, with trapezoidal aperture phase history collection and changes to the traditional polar format algorithm, certain optimizations make MATLAB a possible tool for image formation. Thus, this document's purpose is two-fold. The first outlines a change to the existing Polar Format MATLAB implementation utilizing the Chirp Z-Transform that improves performance and memory usage achieving near realtime results for smaller apertures. The second is the addition of two new possible image formation options that perform a more traditional interpolation style image formation. These options allow the continued exploration of possible interpolation methods for image formation and some preliminary results comparing image quality are given.

Authors:
;
Publication Date:
Research Org.:
Sandia National Laboratories
Sponsoring Org.:
USDOE
OSTI Identifier:
877139
Report Number(s):
SAND2005-7413
TRN: US200606%%712
DOE Contract Number:
AC04-94AL85000
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; EXPLORATION; INTERPOLATION; PERFORMANCE; RADAR; IMAGE PROCESSING; Image analysis.; Synthetic Aperture Radar.; Image processing.

Citation Formats

Martin, Grant D., and Doerry, Armin Walter. SAR polar format implementation with MATLAB.. United States: N. p., 2005. Web. doi:10.2172/877139.
Martin, Grant D., & Doerry, Armin Walter. SAR polar format implementation with MATLAB.. United States. doi:10.2172/877139.
Martin, Grant D., and Doerry, Armin Walter. Tue . "SAR polar format implementation with MATLAB.". United States. doi:10.2172/877139. https://www.osti.gov/servlets/purl/877139.
@article{osti_877139,
title = {SAR polar format implementation with MATLAB.},
author = {Martin, Grant D. and Doerry, Armin Walter},
abstractNote = {Traditional polar format image formation for Synthetic Aperture Radar (SAR) requires a large amount of processing power and memory in order to accomplish in real-time. These requirements can thus eliminate the possible usage of interpreted language environments such as MATLAB. However, with trapezoidal aperture phase history collection and changes to the traditional polar format algorithm, certain optimizations make MATLAB a possible tool for image formation. Thus, this document's purpose is two-fold. The first outlines a change to the existing Polar Format MATLAB implementation utilizing the Chirp Z-Transform that improves performance and memory usage achieving near realtime results for smaller apertures. The second is the addition of two new possible image formation options that perform a more traditional interpolation style image formation. These options allow the continued exploration of possible interpolation methods for image formation and some preliminary results comparing image quality are given.},
doi = {10.2172/877139},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Tue Nov 01 00:00:00 EST 2005},
month = {Tue Nov 01 00:00:00 EST 2005}
}

Technical Report:

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  • SAR phase history data represents a polar array in the Fourier space of a scene being imaged. Polar Format processing is about reformatting the collected SAR data to a Cartesian data location array for efficient processing and image formation. In a real-time system, this reformatting or ''re-gridding'' operation is the most processing intensive, consuming the majority of the processing time; it also is a source of error in the final image. Therefore, any effort to reduce processing time while not degrading image quality is valued. What is proposed in this document is a new way of implementing real-time polar-format processingmore » through a variation on the traditional interpolation/2-D Fast Fourier Transform (FFT) algorithm. The proposed change is based upon the frequency scaling property of the Fourier Transform, which allows a post azimuth FFT interpolation. A post azimuth processing interpolation provides overall benefits to image quality and potentially more efficient implementation of the polar format image formation process.« less
  • We present a MATLAB toolbox on multiresolution analysis based on the W-transform introduced by Kwong and Tang. The toolbox contains basic commands to perform forward and inverse transforms on finite 1D and 2D signals of arbitrary length, to perform multiresolution analysis of given signals to a specified number of levels, to visualize the wavelet decomposition, and to do compression. Examples of numerical experiments are also discussed.
  • Wavefront curvature defocus effects occur in spotlight-mode SAR imagery when reconstructed via the well-known polar-formatting algorithm (PFA) under certain imaging scenarios. These include imaging at close range, using a very low radar center frequency, utilizing high resolution, and/or imaging very large scenes. Wavefront curvature effects arise from the unrealistic assumption of strictly planar wavefronts illuminating the imaged scene. This dissertation presents a method for the correction of wavefront curvature defocus effects under these scenarios, concentrating on the generalized: squint-mode imaging scenario and its computational aspects. This correction is accomplished through an efficient one-dimensional, image domain filter applied as a post-processingmore » step to PF.4. This post-filter, referred to as SVPF, is precalculated from a theoretical derivation of the wavefront curvature effect and varies as a function of scene location. Prior to SVPF, severe restrictions were placed on the imaged scene size in order to avoid defocus effects under these scenarios when using PFA. The SVPF algorithm eliminates the need for scene size restrictions when wavefront curvature effects are present, correcting for wavefront curvature in broadside as well as squinted collection modes while imposing little additional computational penalty for squinted images. This dissertation covers the theoretical development, implementation and analysis of the generalized, squint-mode SVPF algorithm (of which broadside-mode is a special case) and provides examples of its capabilities and limitations as well as offering guidelines for maximizing its computational efficiency. Tradeoffs between the PFA/SVPF combination and other spotlight-mode SAR image formation techniques are discussed with regard to computational burden, image quality, and imaging geometry constraints. It is demonstrated that other methods fail to exhibit a clear computational advantage over polar-formatting in conjunction with SVPF. This research concludes that PFA in conjunction with SVPF provides a computationally efficient spotlight-mode image formation solution that solves the wavefront curvature problem for most standoff distances and patch sizes, regardless of squint, resolution or radar center frequency. Additional advantages are that SVPF is not iterative and has no dependence on the visual contents of the scene: resulting in a deterministic computational complexity which typically adds only thirty percent to the overall image formation time.« less
  • DOE 5480.22 (Technical Safety Requirements) and DOE 5480.23 (Nuclear Safety Analysis Reports) impose requirements for submittal of implementation plans (IPs). This standard provides guidance on the contents of IPs, including plans for managing the upgrade process; the submittal, review, approval, and revision of IPs; and the basis for interim operation during the upgrade process. Guidance is also provided on techniques of preliminary hazards analysis and on the development of site-wide and activity-specific safety documentation.