Fast Fourier-domain modelling for a SAS simulator with application to time-variant targets, aspect-dependent occlusions, and Doppler effects

This paper presents a new technique for the rapid computation of the far-field beampattern for the field scattered from a facet. We show how an affine transform and application of the warping property of the Fourier transform can be used to calculate the beampattern of an arbitrary triangular facet from the beampattern of a unit right-angle triangular facet. Thus, only a single beampattern needs to be calculated and stored; this is then interpolated as required. We describe how this technique can be applied to efficiently model time-variant facets, for example, the facets of a moving sea surface, or the visible region of a partially occluded facet. We also describe the incorporation of temporal Doppler effects. The fast Fourier-domain technique described in this paper has significantly improved the computational performance and memory footprint of our synthetic aperture sonar simulator.