Accurate Evaluation of Green´s Functions for a Lossy Layered Medium by Fast Extraction of Surface- and Leaky-Wave Modes

In this paper, a method based on consecutive perturbation for the fast and accurate extraction of all useful surface- and leaky-wave modes for a lossy layered medium is proposed. The algorithm consists of two perturbation stages. In the first stage, according to the relationship for the frequency variation between the surface- and leaky-wave modes, the leaky-wave modes for a lossless medium can be tracked by consecutive frequency perturbation, with the surface-wave modes at a proper high frequency as starting points. All the surface-wave modes are extracted by a modified dichotomy method. In the second stage, a consecutive loss perturbation is performed, in which the medium´s loss is increased step by step. In each perturbation step of both of the two stages, Newton-Raphson iterations are employed to update the modes on the corresponding Riemann sheet. With these discrete modes accurately extracted, a combination of the Discrete Complex-Image Method (DCIM) and the All-Modes Method can be realized for accurate evaluation of the Green´s functions in the near-field and non-near-field regions, respectively. Several numerical examples demonstrated the high accuracy and efficiency of this method.