Mixture-Based Dielectric Permittivity Measurements Through Gallium-Excited Cavities

In dielectric measurements within resonant cavities, analytical perturbation methods encounter limitations, particularly with nonstandard cavity shapes and lossy materials under test (MUTs) having high dielectric constant. In such cases, the demand for iterative techniques to improve accuracy and flexibility is evident, but the efficiency of the existing iterative techniques, relying on numerical electromagnetic solvers, is often compromised, particularly in terms of time. Therefore, we introduce a novel methodology for measuring the permittivity of dielectric materials using liquid mixtures. This novel method employs a rapid iterative technique in which effective permittivity values are reconstructed at each iteration step based on the volume fraction of liquid mixtures, thus eliminating the dependence on time-consuming 3-D numerical solvers. In addition, we aim to achieve dual-band measurements at 2.45 and 5.8 GHz, enhancing precision by separating mode frequencies. Introducing a re-entrant cavity-like structure, we position the first mode at 2.45 GHz and the second at 5.8 GHz, effectively mitigating intermodal crosstalk and ensuring measurement accuracy. Also, for the first time in the literature, determining which mode will be excited in a cavity by the coupler probe made of gallium can be achieved through the displacement of the liquid metal, which enables measurements to be taken exclusively at the desired frequency.