MFIE-Based Formulation Using Double-Layer Modeling for Perfectly Conducting Objects

We present resonance-free solutions of scattering problems involving closed conductors using the magnetic field integral equation (MFIE). In the literature, MFIE is often combined with the electric-field integral equation (EFIE) to avoid internal resonances that can significantly contaminate solutions especially when scatterers become electrically large. The resulting combined-field integral equation (CFIE), however, possesses the disadvantages of EFIE, e.g., ill-conditioning for dense discretizations. We show that placing an interacting inner surface inside the given object and enforcing internal fields to be zero can mitigate internal resonances, making MFIE resonance free without employing EFIE. Using an arbitrary inner surface can significantly suppress internal fields; but, as also shown in this contribution, the size of the inner surface, i.e., the distance between inner and outer surfaces, can be critical to obtain accurate results that are comparable to those obtained with the conventional CFIE.