Liquids Characterization Using A Dielectric Resonator-Based Microwave Probe

A dielectric resonator-based microwave probe for low loss and lossy liquids characterization is presented in this paper. When the probe is operated under in-situ conditions, improvement of the probe sensitivity to variations in the permittivity of the liquid was observed. Measurements of the quality factor of the resonator reveal that the probe is able to resolve variations around 0.04 in epsilon' for low loss liquids. The spatial resolution of the probe is 10 mu m, and was experimentally verified by scanning a MMIC detector covered with a 30 mu m thick layer of mineral oil, at a standoff distance of 10 mu m. Scanning results confirm that the presence of the mineral oil layer on top of the circuit improves the sensitivity of the probe without degrading the spatial resolution. Simulated data using a lumped-element model of the probe and sample support the measured results.