Complex Permittivity Extraction of Building Materials from Transmission/Reflection Measurements at Sub-THz Band

The Terahertz (THz) band, spanning over 0.1-10 THz, is generally envisioned as a promising candidate for the next generation mobile communication, which has the potential to meet the demands for terabit-per-second data rates and facilitate network densification. Specifically, the sub-THz band (100-300 GHz) is currently a prominent area of research. In order to as-sess sub-THz propagation characteristics and establish accurate channel model, it is crucial to determine the complex permittivity of common building materials present in propagation links. This paper focuses on extracting the complex permittivity of five common building materials at frequencies ranging from 282 to 290 GHz, including glass, polyvinyl chloride board, marble, plaster and raw wood. Firstly, we propose a complex permittivity extraction method suitable for board-shaped building materials. Then, the rationality and accuracy of the proposed method are validated through FEKO simulations. Furthermore, an extensive measurement campaign based on free-space method is conducted at 282-290 GHz to obtain the reflection and transmission coefficients of the measured materials. The results demonstrate that the measured reflection coefficients have minimal dependency on frequency but exhibit a strong correlation with incident angle, polarization, and materials. Finally, in light of the measured results, the complex permittivity is effectively extracted. In general, this work holds significant value for channel modeling and system design of indoor sub-THz communications.