The dual surface combined field integral equation for scattering from three-dimensional objects

Numerical solutions of electromagnetic scattering problems often use method of moments (MoM) based on a variety of integral equations. The traditional electric and magnetic field integral equations (EFIE/MFIE) fail at the resonant frequencies associated with the interior cavity modes of the closed three-dimensional (3D) bodies and several techniques have been proposed to deal with these resonances. Among these techniques, a large class of methods use dual-surfaces to create a well-conditioned problem. These methods operate with MFIE - both on the surface of the body and also on the virtual surface located inside it, and are sensitive to the location of the virtual surface. We propose an alternative form of dual-surface integral equation for computing electromagnetic scattering from perfectly conducting arbitrary three-dimensional (3-D) bodies that enforces conventional MFIE on the surface of the body and EFIE on the virtual surface. The enforcement of DS-CFIE leads to an overdetermined problem of 3N equations with 2N unknowns when solved using MoM. This over determined system is solved for a least squares solution using normal form of the conjugate gradient (CG) method. Numerical results have been presented for the case of plane wave scattering from a conducting sphere and cube to validate the present approach.