Two-resonator method for measurement of dielectric anisotropy in multilayer samples

A two-resonator method, based on TE₀₁₁-mode and TM₀₁₀-mode resonance cavities with a multilayer disk sample, has been developed for measurements of the longitudinal and transversal dielectric constant and dielectric loss tangent of each layer (if the other ones have known parameters) or in the whole sample averaging over the layers contribution. Dispersion equations for the considered modes in both types of cavities with three-, two-, or one-layer samples are obtained. The measurement sensitivity and errors in the dielectric constant are discussed. Analytical expressions for the computation of the dielectric loss tangent of the unknown layer in the two directions are presented for each of the considered cavities. The proposed method is applicable in simple laboratory conditions and allows an estimation of the dielectric anisotropy of multilayer materials in many practical cases. The measuring errors for one-layer artificial substrates with thicknesses of 0.25-0.5 mm are approximately 3%-6% for dielectric constants in the interval of 2.0-4.5 and 10%-15% for dielectric loss tangents in the interval of 0.002-0.010. The obtained pair of longitudinal and transversal dielectric parameters can be used in modern structure simulators for more realistic simulations of microwave components, radiating elements, antenna radomes, etc. Three practical examples for three-layer antenna radomes are given for an illustration of the dielectric anisotropy characterization of multilayer samples.