Characteristic mode analysis of PEC bodies using combined field integral equation

Characteristic mode (CM) theory for perfectly electrically conducting (PEC) bodies was initially developed from the electric field integral equation (EFIE). Alternatively, it was reported that the CM theory for PEC bodies could be also formulated from the magnetic field integral equation (MFIE). As an extension to those earlier developments, this paper is devoted to the development of CM theory for PEC bodies using a combined field integral equation (CFIE). This newly developed CM formulation further increases the flexibility of implementing the CM theory with different integral equations. Numerical examples are given to validate the CFIE based CM formulation. It is found that the EFIE, MFIE, and CFIE based CM formulations result in the same eigenvalues and eigenvectors.