Green’s functions in lossy layered media: integration along the imaginary axis and asymptotic behavior

摘要

This paper presents an efficient technique for evaluatingGreen’s functions associated to layered media, when formulatedas Sommerfeld integrals in the space domain. The keystep in the formulation is that Sommerfeld integrals are computedchoosing a suitable integration path which is closed through theimaginary axis of the complex spectral plane. It is shown that withthis original choice of the integration contour, the numerical effortusually involved in the evaluation of Sommerfeld integrals can begreatly reduced, specially when large source-observer distances areinvolved. One asset of this technique is that it can be easily incorporatedinto integral equation based CAD packages for the efficientanalysis of complex printed microwave circuit and antennas. In addition,the theoretical developments needed to set up the numericalalgorithm throw a new light on the asymptotic behavior of the layeredmedia Green’s functions for large source-observer distances.