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A bistatic k-space imaging concept for frequency-domain (FD) electromagnetic (EM) computer codes is presented. The concept enables the computation of images without the frequency sweep required for experimental images, resulting in a significant reduction in computational effort. This analytical imaging technique uses bistatic radiation computed from a generalized radiation integral. Images permit physical insight and understanding into how a radiation or scattering pattern is produced, by decomposition of the resultant radiation into contributions from localized scattering centers, or hot spots. Knowledge of these hot spots permits a user to understand and modify the structure to obtain desired features. NoteThe bistatic k-space imaging technique is now eight years old. However, it has not had very wide dissemination. It is hoped that this presentation will make others aware of this computational technique. This article is condensed from a recent report [l], which presented much more detail on implementation, and many more examples and experimental comparisons than can be presented here. Summary bistatic k-space imaging concept for frequency-domain (FD)A electromagnetic (EM) computer Codes is presented. The concept enables the computation of images without the frequency sweep required for experimental images, resulting in a significant reduction in computational effort. This analytical imaging technique uses bistatic radiation computed from a generalized radiation integral. Images permit physical insight and understanding into how a radiation or scattering pattern is produced, by decomposition of the resultant radiation into contributions from localized scattering centers, or hot spots. Knowledge of these hot spots permits a user to understand and modify the structure to obtain desired features.The costs associated with computation of bistatic images are usually small compared with the effort required to obtain the current distribution. Bistatic k-space fields are computed from the currents by the generalized radiation integral. This is similar to the effort required to compute a bistatic radiation pattem. The computed k-space E ( k ) fields are then Fourier transformed to obtain the spatial image.The bistatic k-space: technique can be applied to both antenna and scattering problems. It can be used with any frequency-domain computer algorithm that produces a current distribution on the geometric structure. Images can be computed in one, ~WD, or three dimensions, which typically correspond to down-range, downrange/cross-range, and volumetric images, respectively.Bistatic scattering images are shown for a variety of target geometries, computed by FD EM prediction algorithms that include Method-of-Moments-patch (MOM-patch), body-of-revolution (BOR), and BOR-patch computer codes; Physical Optics (PO) computer codes; and finite-element/frequency-domain (FEFD) computer codes. Reference [ 11 shows the high-level details on how to incorporate this imaging technique into several types of computer codes. Implement...

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Recent work on Sparse MOM codes for PC applications has reduced LU matrix factorization time to significantly less than matrix fill for problem unknowns approaching 200,000. This paper reports on the use and results of applying the recently developed Adaptive Cross Approximation for significantly reducing MOM matrix fill time. Results suggest that when problem sizes approach 500,000 unknowns, matrix fill can be reduced from 100 to 10 hours on a modern PC.

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