Limitation of Asymptotic RF Simulation Method in Presence of Periodic Structures of Close-to-Wavelength Size

Ray Launching Geometrical Optics (RL-GO) technique is known for reliable and accurate results including those in the automotive radar related field. However, the high frequency approximation can be expected to reveal inaccuracies when applied to periodical structures consisting of close-to-wavelength structure sizes. This paper investigates the limitations of RL-GO for objects or arrangements that possess dimensions below or close to the radiation wavelength
$\lambda_{g}$
inside the material. Here, Multilevel Fast Multipole Method (MLFMM) which is a full wave technique provides the benchmark for accuracy verification. The expected accuracy impact has been investigated in this work for periodic structures with dimensions between 1.5
$\lambda_{g}$
and 0.15
$\lambda_{g^{*}}$
In the scope of this work for RL-GO, accuracy condition are found and formulated.