Specular Reflections from Finite Sheet

[rscheeler]

I am looking for clarification and perhaps what would be the correct way to model a finite reflecting sheet.

I have a screen with a reflector orthogonal to the screen to provide a not line-of-sight reflected path. The way I would think to model this is to consider the area of the reflector and treat it like a bi-static radar and account for the RCS of the sheet. Thus, I would expect to see less received power if I change the size of this finite reflecting sheet. However, I observe the same received power regardless of the sheet size. Optically this would make sense when the reflector is very large with respect to a wavelength, but at RF frequencies it may be less than 10 wavelengths. My intuition says this would be incorrect and possibly off by many orders of magnitude. What could be the steps to correct for this, or is my intuition wrong? If the result is wrong - I guess that would mean reflections off of smaller structures would be highly inaccurate too?

[faycalaa]

Specular reflection is modeled in Sionna by assuming that the size of the reflecting surface is large compared to the wavelength, allowing it to be treated as if it were infinite. Note that Sionna RT currently does not support the modeling of objects using RCS.

You could try enabling diffuse reflection with a directive scattering pattern. Then the reflected energy captured at the receiver depends on the surface area of the reflector. However, there are significant differences between the modeling of specular reflection and diffuse reflection in Sionna. For more details, see the primer.