Tackling the slow attenuation of the spectral-domain Green´s function in Sommerfeld integrals

The improved GE method has been used to evaluate the spatial-domain Green´s function of the shielded structures. However, for some cases, the spectral-domain Green´s function decays slowly and is very difficult to be accurately approximated by the GPOF used in the improved GE method. This subsequently deteriorates the accuracy and stability of this method. In this paper, we devise a scheme that the GPOF is applied for multiple times to approximate the spectral-domain Green´s function. Numerical results have shown that the spectral-domain Green´s function can be better approximated and thus the accuracy of spatial-domain Green´s function is improved.