A boundary-element solution of the Leontovitch problem

A boundary-element method is introduced for solving electromagnetic scatter ing problems in the frequency domain relative to an impedance boundary cond ition (IBC) on an obstacle of arbitrary shape. The formulation is based on the field approach; namely, it is obtained by enforcing the total electroma gnetic field, expressed by means of the incident field and the equivalent e lectric and magnetic currents and charges on the scatterer surface, to sati sfy the boundary condition. As a result, this formulation is well-posed at any frequency for an absorbing scatterer. Both of the equivalent currents a re discretized by a boundary-element method over a triangular mesh of the s urface scatterer. The magnetic currents are then eliminated at the element level during the assembly process. The final linear system to be solved kee ps all of the desirable properties provided by the application of this meth od to the usual perfectly conducting scatterer; that is, its unknowns are t he fluxes of the electric currents across the edges of the mesh and its coe fficient matrix is symmetric.