Acceleration of the Computation of the Method of Moments EFIE Impedance Matrix From an Updated Fraunhofer Criterion

This communication deals with the acceleration of the computation of the impedance matrix obtained from the electric field integral equation (EFIE) discretized by the Galerkin method of moments (MoM) with Rao-Wilton-Glisson basis functions. The elements of the impedance matrix need to calculate a double integral (quadruple integral) over two planar triangles, which is typically done from two numerical Gauss-Legendre integrations. For far-field interactions, this integration can be done analytically by introducing a criterion for which the resulting closed-form expression is valid. This approximation is tested on a sphere and a concave cavity-shaped object, for which the results show that the time saving factor is about 20, with a mean difference of 0.1-0.5 dB on the radar cross section (RCS) compared to that obtained from two numerical integrations.