Air to Ground Signature Database Development Technologies for Combat Identification

The physics-based scattering phenomena from general targets can be very complex and occur in many different forms such as: a) specular reflection, b) creeping waves, c) traveling waves, d) slow moving surface waves, e) edge diffraction, f) singular currents at surface discontinuities, g) resonating gaps and cavities, and h) general material response. While in vacuum Maxwell’s equations representing the coupling between electric and magnetic fields are linear, it is still a formidable challenge to be able to accurately simulate the various scattering phenomena. Especially for waves traveling over long distances, the relationship between the phase and amplitude of various scattered waves and the incident illumination is very critical for accurate representation of the near fields and the resulting farfield. While it is of great interest to solve physics-based scattering from electrically large problems very accurately, it may not be efficient to solve the whole problem using one single full-wave solver. To obtain relatively fast turnaround, it is potentially efficient to combine the virtues of different approaches in a hybrid fashion to solve such large problems. For example, to solve a full size aircraft (Figure 1) at X-band range, one could use high frequency approximation for the exterior surfaces and use a full-wave solver for the long engine interior ducts, while taking into account the interaction between the ducts and the exterior. In this way, full target RCS accurate to a fraction of a dB can be obtained in a day turnaround using a 64-128 node PC cluster.