Computation of Sommerfeld integrals via rational function fitting

A new methodology is proposed for the robust computation of the Sommerfeld integrals encountered in evaluating the electromagnetic Green's function in planar layered media. The key attribute of the proposed methodology is that it yields a closed-form expression for the Green's function in terms of both spherical waves and cylindrical waves. The former, representing the source and quasi-static terms, provide for the accurate description of the singularity and the near-field physics in the vicinity of the source, while the latter capture correctly the surface wave behavior that dominates in the far field.