EFFICIENT NUMERICAL COMPUTATION OF THE SPECTRAL TRANSVERSE DYADIC GREENS-FUNCTION IN STRATIFIED ANISOTROPIC MEDIA

Several new ideas are provided for computing the spectral transverse d yadic Green's function (STDGF) of a stratified anisotropic medium in a n accurate and efficient way. A modified version of the equivalent bou ndary method is developed which makes it possible to compute the asymp totic values of the aforementioned. STDGF without employing exponentia l terms. This new technique for the computation of the STDGF of a stra tified anisotropic medium has more numerical stability than the other techniques proposed so far, in which the use of exponential terms for the computation of the STDGF in all the range of variation of the spec tral variables unavoidably leads to numerical problems for high values of the spectral variables. Also in this paper, it is shown how a two- step interpolation approach can be used for obtaining simple closed-fo rm expressions of the STDGF of a stratified anisotropic medium in wide ranges of the spectral variables. It is expected that the use of this interpolation approach will introduce important CPU time savings in t he spectral domain analysis of planar microwave circuits and printed a ntennas, where the STDGF of the substrate has to be calculated a large number of times.