Experimental Study of Meniscus Effect on Broadband Permittivity Measurements of Liquids in a Semi-Open Coaxial Test Cell

We present results of broadband permittivity measurement of distilled water with a calibrated vector network analyzer using a semi-open, vertically-oriented test cell. We determine this permittivity with the Nicolson-Ross-Weir method and a novel technique, developed recently at the Warsaw University of Technology, which is capable of meniscus effect removal. In particular, we study how the meniscus affects the reflection coefficients at the boundaries of the water sample, since accuracy of liquid column height determination vitally depends on them. Although, we have not discerned any clear symptom of the meniscus effect in the frequency range from 0.5 to 18 GHz, our comparison of the permittivity characteristics obtained with the different methods with the reference data available for distilled water shows supremacy of the meniscus-effect removal method.