Terahertz Dielectric Characterization of Low-Loss Thermoplastics for 6G Applications

Common thermoplastics, namely, polycarbonate (PC), poly (methyl methacrylate) (PMMA), and acrylonitrile butadiene styrene (ABS) are low-cost materials with potential applications in emerging 6G communications systems, ranging from microelectronics packaging to metasurfaces for reflectors and filters. In addition, low-loss materials are also needed for more pedestrian applications, such as packaging for entire handheld devices, subassemblies, and high-frequency windows where low-cost is key and long lifetime might not be a requirement. In this work, we utilize terahertz time-domain spectroscopy from 500 GHz to 2 THz to characterize the dielectric properties and loss tangent for each thermoplastic above. The plastics investigated have refractive index (similar to 1.6-1.7) in the 6G band with low dispersion. The absorption, however, increases at high frequencies as is common in disordered materials, highlighting a key challenge for 6G. Nonetheless, in absolute terms, all the thermoplastics studied present low-loss performance compared with (higher-index) common glasses and ceramics within the entire frequency range, suggesting that they are promising candidates for selected applications for future 6G systems.