Building a Comprehensive Complex Permittivity Library for THz Radio Planning Using Quasi-Optical Measurements

The lack of an accessible comprehensive reliable dataset of material properties at terahertz (THz) frequencies is a significant roadblock for the development of accurate propagation models for THz wireless systems. To fill this gap, in this article, we extract the complex permittivity of 75 different home and commercial furnishings categorized into fabric, leather, plastic, stone, and wood from quasi-optical measurements. Given that quasi-optical transmission measurement standards are not developed yet, we utilize both vector network analysis and time-domain spectroscopy under collimated and focused beam illumination to highlight the differences and the challenges that precise material extraction faces at THz, and to compute average complex permittivities with confidence intervals.