LAUSR

The diffraction mechanisms of electromagnetic (EM) transient scattering from large scatterers are examined by applying a general time-domain aperture integration (TD-AI) technique when the scatterer is illuminated by an incident EM field. This incident field exhibits a transient-step field response and can be the radiation from a relatively arbitrary EM source located at any place. The mechanism is interpreted by considering an equal time-delay curved aperture (ETDCA) where a set of EM equivalent current sources are defined to radiate the scattering field. The transient responses at any instant time are then found by considering the effects of equal net time-delay in propagation when the incident wave propagates to the field point via EM scattering from the scatterer. A contributing contour in the radiation integral of the equivalent currents define on the ETDCA by its intersection with a time-varying equal path-length sphere defined by the field point is therefore extracted to reduce the surface integral into a line one. The characteristics of this contributing contour are employed to interpret the EM scattering mechanisms. Practical numerical examples are presented to demonstrate the validity and feasibility of this general TD-AI technique.