High frequency locality embodied in terms of Fresnel zone number for matrix size reduction in method of moments

In high frequency, due to the locality of the scattering, the importance of currents is localized near the scattering centers, which correspond the stationary phase points and the edge diffraction points, as is defined by the GTD. This localization would provide the reduction of unknowns in the method of moments (MoM), though the area of importance moves with the location of the source and the observer. If this concept is extended for the observer on the surface of scatterer, the reaction matrix is transformed into the sparse band matrix. Authors have proposed the use of Fresnel zone number as the threshold for the truncation of the scatterers or the reaction matrix. This talk reviews the concept and the advancement of the high frequency technique based upon the locality of scattering in terms of Fresnel zone number.