Performance of the Normally-Integrated Magnetic Field Integral Equation for Fla Faceted Surfaces

The “normally-integrated” magnetic field integral equation (NIMFIE) formulation was introduced in [1] and used to analyze scattering from toroidal targets in [2]. The traditional MFIE has several limitations that the NIMFIE approach attempts to ameliorate. By incorporating integrals in directions that are both tangential and normal to the target surface, the NIMFIE formulation produces a true “weak” form of the MFIE where all derivatives are absorbed by testing integrals. In [1–2] the approach was used to simplify the matrix entry calculations associated with higher order representations and curved models of surfaces. It was demonstrated in [1] that the approach is easily modified to enable it to suppress internal resonances. Although one of the limitations of the traditional MFIE is that it can become unstable when applied to a multiply-connected geometry [3–4], the NIMFIE approach was shown to be stable for thick and thin loop targets [2]. The primary limitation of the NIMFIE formulation is shared with the traditional MFIE: targets under investigation must be closed bodies that are not too electrically thin (since one of the testing integrals follows a path into the target).