A new approach for obtaining the time samples of the retarded-time scalar and vector potentials due to an impulsively excited Schaubert-Wilton-Glisson (SWG) basis function is presented. The approach is formulated directly in the time domain without any assumptions regarding the temporal behavior of the currents represented by the SWG bases. It is shown that the aforementioned potentials are related to the solid angle formed by the intersection of the tetrahedral supports of the SWG basis and the "hyper-cone" that is centered at the observation point and that has a radius = , where is the speed of light. In particular, the scalar potential is directly proportional to the total solid angle, and the vector potential is a function of the area centroid vector of this solid angle. The validity of the obtained time-domain formulas is demonstrated through comparison of results to those obtained in the frequency domain by using numerical quadrature and transformed into time domain. IndexTerms-Marching-on-in-time (MOT) method, Schaubert-Wilton-Glisson (SWG) basis, time-domain analysis, volume integral equations (VIEs).

Implementation of the shooting and bouncing rays (SBR) method for radar cross section or scattering center prediction of complex electrically large objects is studied with a focus on the computational efficiency. A triangulated CAD model is assumed and SBR is processed by a ray-triangle intersection algorithm. An octree space partitioning, which might be based on either rectangular boxes or spheres as bounding volumes, is used to speedup the intersection decision. The effect of proper implementation and choice of the bounding volume to reduce ''the constant in front'' of the leading order complexity is demonstrated. It is shown that the required computer resources can be reduced drastically using the techniques outlined in this article.

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