A robust and efficient algorithm to solve the scattering problems with impedance condition

We present a second-kind Fredholm equation for iterative solution of time-harmonic scattering problems by partially coated objects. After discretization, the linear system obtained is well- conditioned and few iterations of a GMRES solver are necessary to obtain the accurate solution. Moreover, this number of iterations is slightly dependent of the frequency and of the mesh refinement. Numerical results are presented that show the effectiveness of the proposed formulation.