Further results on a new O(N2logN) algorithm for spotlight-mode SAR
Abstract
A new algorithm has been proposed for spotlight-mode synthetic aperture radar in a recent correspondence by W. Lawton. This new processing scheme assumes that Fourier transform samples of the obtained projections lie on a trapezoidal grid. The spatial domain image is produced through a series of convolutions and DFT's, all performed using FFII's. The geometry of the trapezoidal grid makes this fast algorithm possible, which requires 0 (N2logN) multiplications for an NxN image. In this paper we show that the Lawton algorithm implements a form of trapezoidal-to-Cartesian interpolation followed by a 2-D FFT. We then derive a closed-form approximate expression for the point-target response of the algorithm with Hamming weighting of the acquired data. Next, we simulate reconstructions of point targets and of extended targets composed of groups of point targets. The effects of windowing and incorporation of a Jacobian weighting factor are deter-mined. We also consider the effect on image quality of moderate levels of sampling jitter in the A/D and of deviations of actual data collection angles from those intended. These errors serve to provide Fourier samples of the reflectivity on a grid that deviates from the assumed trapezoidal raster. Overall, the Lawton algorithm is found to be robust, and to produce high quality imagery.
- Publication:
-
Millimeter Wave and Synthetic Aperture Radar
- Pub Date:
- August 1989
- DOI:
- 10.1117/12.960511
- Bibcode:
- 1989SPIE.1101...23A
- Keywords:
-
- Microwave Imagery;
- Radar Antennas;
- Radar Data;
- Radar Targets;
- Synthetic Aperture Radar;
- Data Processing;
- Fast Fourier Transformations;
- High Resolution;
- Communications and Radar