NUMERICAL ANALYSIS OF COMBINED FIELD INTEGRAL EQUATION FORMULATIONS FOR ELECTROMAGNETIC SCATTERING BY DIELECTRIC AND COMPOSITE OBJECTS

Numerical analysis of a generalized form of the recently developed electric and magnetic current combined field integral equation (JM-CFIE) for electromagnetic scattering by homogeneous dielectric and composite objects is presented. This new formulation contains a similar coupling parameter α as CFIE contains in the case of perfectly conducting objects. Two alternative JM-CFIE(α) formulations are introduced and their numerical properties (solution accuracy and convergence of iterative Krylov subspace methods) are investigated. The properties of these formulations are found to be very sensitive to the choice of α and to the permittivity of the object. By using normalized fields and currents the optimal value of α minimizing the number of iterations becomes only weakly dependent on the permittivity object. Using linear-linear basis functions instead of the more conventional constant-linear (RWG) basis functions the solution accuracy can be made less dependent on the choice of α.