## Re: surface roughness modelling Groisse model

Volker, excellent reference! I read through it and it presents a nice summary of Groisse model that is hard to find through searches (unless several papers are read ;) ) However, it is of note that HFSS14 (and maybe CST, I do not know from my own experience on that) indeed includes two separate models for surface roughness that are a surface impedance approximation as done in Planar 2D MoM tools. The default surface roughness uses the Groisse model (excellent for low RMS surface roughness, or as the paper alludes to "smooth" metal surfaces) and the Huray model which is highly applicable to higher frequencies as in incorporates the mean radius and spatial densities of the 'blobs' that tend to be artifacts of sputtering and evaporation techniques. The other advantage to HFSS14 is that it incorporates a 'DC Thickness' determination to ensure that the DC point (or equivalent spectral regions where there is substantial field distribution in the trace cross section) is correct as per 'back of the envelope calculations :) Hope this helps!

Have Fun!

1 members found this post helpful.