Divergence-conforming discretization of second-kind integral equations for the RCS computation in the Rayleigh frequency region

Abstract

The divergence-conforming discretization in method of moments of the magnetic field integral equation (MFIE) shows huge inaccuracies in the computed radar cross section (RCS) at the very low or extremely low frequency regime. We justify theoretically that the presence of this error in the computed RCS can be mitigated to some extent for some sharp-edged objects, where this discrepancy is most evident, through the adoption of uniformly triangular or quadrangular meshings. Moreover, we present two discretizations in method of moments of second-kind integral equations that are free from these huge RCS inaccuracies: (1) a modified implementation of the conventional Rao-Wilton-Glisson (RWG) discretization of the MFIE that provides in two steps the static and dynamic current components so that the nonsolenoidal static contribution can be discarded in the far-field computation; and (2) the loop-star discretization in method of moments of the novel electric-magnetic field integral equation (EMFIE) which provides inherently a null static nonsolenoidal current contribution whereby a static-dynamic decomposition of the current is not required. Copyright © 2011 by the American Geophysical Union.