  This paper presents a new single-source surface integral equation (SS-SIE) to
model composite penetrable objects. In the proposed formulation, the surface
electric and magnetic fields on all interior boundaries are first eliminated
through combining integral solutions inside each object. Then, by enforcing the
surface electric fields in the original and equivalent configurations are equal
to each other, an equivalent model with only the electric current density on
the outermost boundaries is derived. Compared with other SIEs, like the PMCHWT
formulation, all unknowns are residing on the outermost boundaries in the
proposed formulation and therefore, less count of unknowns can be obtained.
Finally, two numerical examples are carried out to validate the effectiveness
of the proposed SS-SIE.
