A More Accurate Measurement Method of the Dielectric Material Properties With High Tolerance Using an Overmoded Waveguide
Weijie Wang, Guo Liu, Yu Wang, Wei Jiang, Qiang Zheng, Jianxun Wang, Yong Luo
Abstract
This article proposed an overmoded waveguide method (OWM) for more accurate measurement of dielectric properties in the subterahertz and terahertz band. Compared with the traditional standard waveguide method (SWM), the OWM is beneficial to alleviate the significant error caused by the air gap. Simulation predicts that for typical medium permittivity and loss materials, the relative errors of <inline-formula> <tex-math notation="LaTeX">$\varepsilon _{r}$ </tex-math></inline-formula> and tan<inline-formula> <tex-math notation="LaTeX">$\delta $ </tex-math></inline-formula> can be reduced from 10% to below 3% using the OWM with an overmoded factor of 3 when the air gap is 0.02 mm at W-band. When extending the overmoded factor over 5, the relative error can be reduced below 1.5%. The tolerance improvement was verified by measuring a polytetrafluoroethylene (PTFE) sample through SWM and OWM. Experimental results show the relative error of <inline-formula> <tex-math notation="LaTeX">$\varepsilon _{r}$ </tex-math></inline-formula> is lower than 5% even when there exists a 0.24-mm air gap in the OWM.