Measurements and simulations of scattering for propagation modeling at THz frequencies

In Piesiewicz et al., (2005), we proposed an efficient method to model reflective properties of smooth building materials at THz frequencies. It is based on Fresnel equations, which are applied to measured material parameters to account for frequency dependence. However, this technique is adequate for smooth materials only as it neglects scattering losses.The method can be extended to rough materials with Kirchoff theory of scattering from rough surfaces. In order to account for scattering losses in the specular direction, the reflection coefficient, derived from Fresnel equations can be multiplied with a Rayleigh roughness factor. This factor can be obtained from measured surface roughness data of the investigated material. Here, we show the model and direct reflection measurements for a set of angles of incidence for two common rough building materials: ingrain wallpaper and concrete plaster.