Scattering in RL-GO

Luke Jacobs

As I was using the RL-GO solver in a radar application, I noticed that it casts rays from the source that do not end at the "receiver" (the near field sampler). Instead, the end of a ray is denoted with an "S," which the documentation describes as an "observation point." Here is a picture of one ray:

My source is the dipole in free space above the dielectric cuboid. My near field sampler is co-located with my source, and I have checked the setting to "calculate only the scattered part of the field."

There is no description of this "observation point" concept in the documentation. I am curious how a ray like the one above contributes to the final electric field observed by the receiver. Is RL-GO considering scattering from each observation point? If so, how does the solver calculate the portion of energy that returns to the receiver?

Torben Voigt

Hi Luke,

The RL-GO solver does not generate rays that lead from the source (e.g. mesh elements) to the target (e.g. near field request). The rays end on the surfaces of the geometry, where they generate so-called Huygens sources. If the geometry is represented by Huygens sources at sufficiently small distances, the results (e.g. nearfield) are calculated on the basis of the actual source and Huygens sources.

I have attached a small overview of how the different solvers in Feko work. The description is very superficial, but should provide a good introduction.

Best regards,
Torben