Design of a bitonal dielectric resonator for the measurement of anisotropic surface impedance

The measurement of the microwave surface impedance is a fundamental characterization tool for a wide class of conducting, semiconducting and superconducting materials. In many cases, material anisotropy can show up as an intrinsic or tailored property, and its measure is often desirable. Microwave resonators can be designed to give at the same time nondestructive and highly sensitive measurements, in particular with the surface perturbation method for planar samples. Rectangular resonators can be designed to preserve sensitivity to the anisotropy of the samples under study, since they can induce straight currents on the sample. In this manuscript we report on the design, based on finite elements electromagnetic simulations, of a rectangular dielectric resonator which induces straight currents on the sample, with the additional feature of simultaneous operation at two different resonant frequencies, to allow multifrequency study e.g., for validation of the results.