New Microwave Systems for Measuring Complex Permittivity of Dielectric Materials

摘要

A nondestructive method for the non-contact characterization of non-planar dielectric objects is presented. In this study, propose a free space measurement system. Using the Michelson microwave interferometer for the measurement of material permittivity in radiofrequency nondestructive testing is analyzed experimentally. It is shown that the use of the microwave interferometer permits fairly simply to determine the permittivity of thin-layer material using a shift of one of the interferometer mirrors for various microwave radiation wavelengths. A dielectric rod resonator excited by a non-radiative dielectric waveguide is used for measuring complex permittivity of low loss dielectric materials. ε_r is determined by the TE_(0ml-)mode rod resonator. By the present method, ε_r of the sapphire crystal and two ceramic materials were measured at 60 and 77GHz. The measurement error Δε'/ε'of relative permittivityε' was within 0.1%, and Δ tanδ of dielectric loss tanδ was within 5×10~(-6), respectively.