Ray Launching Geometrical Optics (RL-GO)

The ray launching geometrical optics (RL-GO) is a ray-based method intended for modelling electrically large dielectric and perfect electrically conducting structures in applications such as lens antennas and radar cross section (RCS) analysis.

The RL-GO is formulated for use in instances where electrically very large (> 20λ) metallic or dielectric structures are modelled. RL-GO is inherently well suited to the solution of large scattering problems such as radar cross section (RCS) analysis since the shooting and bouncing rays approach are highly efficient for an arbitrary number of multiple reflections.
Figure 1. RCS of an aircraft at 1 GHz in the elevation plane: Comparison between MLFMM and RL-GO. RL-GO required 33 times less memory.

Feko integrates the RL-GO method with the current-based MoM, by launching rays from each radiating MoM element. The ray interactions with metallic and dielectric structures are then modelled using Huygens sources placed on each ray contact point (for reflected, refracted and transmitted rays) on the material boundaries. The runtime and memory requirements scale almost perfectly for parallel processing, resulting in multi-core CPUs or cluster computers operating highly efficiently while solving RL-GO problems.

A typical application of the MoM / RL-GO hybrid method is the analysis of dielectric lenses. The source structure (for example a metallic antenna under a lens), may be modelled with the MoM and the large dielectric lens may be modelled with the RL-GO.
Figure 2. Reflector near field calculated with RL-GO.