Bistatic scattering characterization of complex objects

Discusses the bistatic scattering nature of complex metal objects and assesses the accuracy of several common bistatic scattering prediction techniques: a common physical optics/physical theory of diffraction (PO/PTD) based simulation package, Kell´s (1965) scattering center-derived monostatic-to-bistatic equivalence theorem (MBET), and Crispin´s (Crispin and Siegel 1968) PO-based MBET. Monostatic and bistatic measured and simulated data are gathered and compared for three test objects of increasing complexity. Delineation between specular and nonspecular effects is highlighted to help explain when prediction techniques fail. The PO code proves erroneous at low grazing angle receive antenna positions and does not predict nonspecular type scattering well. Interestingly, however, it does accurately compute specular reflections from electrically small surface features. Kell´s and Crispin´s MBETs are also studied. For simple objects (e.g., flat plate) both MBETs predict scattering fairly well for bistatic angles of 30-40°, with Kell´s having a slight edge at larger angles. As the complexity of the object increases, MBET accuracy decreases. Neither MBET is particularly capable at bistatic angles greater than 15° for objects whose scattered field is primarily comprised of specular interactions (minimally complex). Both tend to predict lower returns at larger bistatic angles. MBET accuracy holds for smaller bistatic angles with increasing geometrical complexity. The object whose geometry contains large shadowing features and a cavity supports multi-bounce, diffraction, and surface wave phenomena. The accuracy of both MBETs is limited to bistatic angles of only 5-10° in this case. Each tends to predict higher than measured scattering at larger bistatic angles