Surface integral equations (SIEs) are promising candidates for modeling circuits because they
reduce degrees of freedom by restricting physical unknowns on the surface, which simplifies
complex structures. However, there are still challenges related to achieving stability over a broad
frequency band. Specifically, the low frequency breakdown of electrical field integral equation
(EFIE) operator is discussed in this work. In order to solve or alleviate this problem, the
separation of irrotational and solenoidal current must be accomplished. A proposed method, the
Augmented Electrical Field Integral Equation (AEFIE), is intended to separate the current
element by introducing charge as another variable and relate irrotational current and the charge
vector. Finally, the method of moments (MoM) is applied to solve the integral equation by
projecting the current onto RWG basis and performing subspace projections to fill out the
integral equation operator matrix. For complicated circuit structure, MoM can be accelerated
using the fast multipole algorithm (FMA).Ope
