Measurement of woods complex permittivity in 220-325 GHz band

In this paper, the S-parameters of 2mm silicon wafer, 14.345mm wood I, 14.215mm wood II and 13.80mm wood III were measured based on 220-325 GHz quasi optical Vector Network Analyzer measurement system. Basic theory based on free space electromagnetic component equations, boundary conditions and S parameters. The electromagnetic field of "air-MUT-air" three-layer structure between calibrated reference planes is analyzed in detail, and the formula of complex permittivity is derived. The results of complex permittivity of silicon wafer extracted by this method are basically consistent with those in the literature. The measurement of woods can accurately distinguish heartwood from sapwood. This study is helpful for us to better understand the interaction mechanism between terahertz waves and wood media, and can lay a foundation for the identification of woods.