On the near-interaction elements in integral equation solvers for electromagnetic scattering by three-dimensional thin objects

Abstract

The accuracy of near-interaction (NI) evaluation is investigated for hypersingular and strongly singular kernels in solving electromagnetic (EM) integral equations. We first define the NI between a field point and a source triangular patch using a nearness factor (N F) and show the accuracy of numerical integrations for the NI integrals with hypersingular or strongly singular kernels. It is found that there exists a transition area or turning point before and after which the convergence behaviors of those integrations are greatly different. We define the N F value at the 1% relative error as the turning point N F0 and define N F ≤ N F0 as the NI range. We find that N F0 =1.4 could be a bound of NI range for the triangles with a quality factor q > 0.35 and analytical formulas should be used in evaluating NI elements within the bound. Numerical examples for EM scattering by three-dimensional (3D) thin objects are used to demonstrate the significance of NI treatments for the accurate solutions. © 2009 IEEE.