Open-ended waveguide measurement of liquids at millimeter wavelengths

In this paper, a measurement setup applicable to characterization of liquids at millimeter wavelengths is investigated. The system is composed of a vertically-oriented open-ended waveguide section, where the liquid under test can be easily poured. It is separated from waveguide measurement equipment with a dielectric window made of either fused silica of monocrystalline quartz. The advantage of the proposed approach is in the robustness of the design consisting of off-the-shelf components and a straightforward procedure for determining complex permittivity of high loss liquids with a decent accuracy.