In FEKO, we can model planar multilayer substrate using Green's function in layered media. I'm interested in the fast solution of FEKO when modeling PEC scatter residing in a multilayer substrate.
I know that FEKO calculates Green's function in layered media (LMGF) using the interpolation table. But I'm not sure which method it uses to evaluate the Sommerfeld integral which is essential to the calculation of LMGF. There are several methods available in academic research, such as the discrete complex image method (DCIM), numerical integration with the extrapolation method, singularity subtraction method. I am using the numerical integration with the extrapolation method and singularity subtraction method. However, my Fortran code is very slow compared to FEKO even I also use the interpolation table.
I hope to receive some comments on my problem and the LMGF.