A technique which combines the finite element and boundary integral formulations along with the conjugate gradient method (CGM) and fast Fourier transform (FFT) was proposed for the electromagnetic characterization of infinitely long slots in a thick conducting plane filled with an inhomogeneous composite material (see J. M. Jin and J. L. Volakis, 1989). In the present work, the authors extend the technique to treat three-dimensional problems. Specifically, they consider the problem of scattering by a three-dimensinal cavity in an infinite conducting plane.
