Localized and observer-dependent importance of currents for HF scattering and reduction of unknowns in MoM

The locality of high frequency diffraction is a base of various asymptotic methods such as Geometrical Theory of Diffraction (GTD). Scattering is determined by only local characteristics of a scattering point. In terms of current-based method, currents around scattering points contribute to the field and range of these currents is dependent on the point of observation. The locality is imported into the Method of Moments (MoM). A part of induced currents is extracted from currents solved by the MoM. The extracted currents can reproduce scattering field. The scattered field can be calculated by solving only local parts of the scatterer. This equivalent model can greatly reduce computational load of the MoM.