Measurement and Analysis of Scattering From Slightly Rough Dielectric Surfaces in 100- and 300-GHz Bands

Due to the extremely short wavelengths of terahertz waves, even slight surface roughness on everyday dielectric materials can significantly influence future terahertz-wave propagation and communication systems. To investigate this scattering effect, we conducted scattering measurements at 100 GHz and 300 GHz on four typical surfaces: wood, concrete, wallpaper, and granite. We analyzed the angular scattering distributions and compared the measured results with two analytical models: the Beckmann–Kirchhoff approximation and a stochastic function approach. While the Beckmann–Kirchhoff approximation is widely adopted in classical electromagnetic scattering theory, it has limited capability in accounting for multiple scattering and polarization coupling effects. In contrast, the stochastic function approach employs stochastic integral theory, enabling more precise modeling of complex scattering phenomena. Our results quantitatively indicate that the stochastic function approach agrees well with experimental data when the normalized surface roughness is less than approximately one-tenth of the wavelength, whereas the Beckmann–Kirchhoff approximation becomes more suitable for relatively rougher surfaces. Furthermore, we propose a simplified model to compensate for scattering-induced reflection loss. The results indicate that scattering loss can exceed 1 dB when surface roughness is considerable, particularly at higher frequencies. These insights highlight the necessity of incorporating scattering effects into terahertz-wave propagation modeling. Our outcomes contribute to the refinement of theoretical models for terahertz-wave propagation and communication systems.