PERFORMANCE OF VARIOUS INTEGRAL-EQUATION FORMULATIONS FOR NUMERICAL-SOLUTION OF SCATTERING BY IMPEDANCE OBJECTS

Impedance boundry conditions are used to formulate integral equations for imperfectly conducting and coated objects. Both magnetic type integral equations are obtained and used to formulate a combined integral equation. The accuracy of the solutions using these methods is studied and the superiority of the combined form is pointed out. The problem of internal resonances is also investigated. For both electric and magnetic integral equations, the inaccuracy of the solutions near the resonances increases with increasing surface impedance. The combined formulation is found to give stable solutions throughout. It is then used to generate scattering data for various objects, and the effect of the object parameters and the field polarization on the results is discussed.