Determining the complex permittivity of powder materials from l-40GHz using transmission-line technique

In this paper, the method is proposed to determine the complex permittivity of powder materials form 1 -40GHz using the transmission-line technique. In the entire frequency range, it´s impractical to use only one type transmission-line filled with power materials. Therefore, 7mm coaxial transmission-line is used for 1-18GHz, regular waveguide BJ220 transmission-line is used from 17.6-26.5GHz and regular waveguide BJ320 transmission-line is used from 26.5-40GHz. Different from the measurements of solid materials in a two-port transmission-line, two Teflon solid spacers are used to house the powder materials. After obtaining the scattering parameters at the reference plane of the powder materials using an improved TRL calibration method, then reconstruct the complex permittivity based on the traditional transmission-line method. Before filling the transmission-line with power materials, the complex permittivity of air is measured as verifiable. Finally the results of the measurements of two powder materials: loess and thin sand are shown.