An observation about radar imaging of re-entrant structures with implications for automatic target recognition

Abstract

The standard inverse synthetic aperture radar (ISAR) high-frequency weak-scatterer model is inappropriate to targets with inlets and cavities, and images created under this model assumption often display artifacts associated with these structures. Since inlets and cavities (typically) make a strong contribution to the radar field scattered from aircraft targets, these artifacts often confound the image interpretation process and considerable effort has been spent in recent years to model, isolate, and remove these sources of error. Many of the more complete and accurate scattering models require extensive knowledge about the cavity/inlet shape and size and, moreover, are numerically intensive - features that make them unsuitable for many imaging applications. We examine an older (and less accurate) model based on a weak-scattering modal expansion of the structure which appears to be well suited to ISAR imaging. In addition, the analysis shows how cavity/inlet shape-specific information may be estimated from an ordinary ISAR image.