Measurement accuracy of a TM0m0 mode cavity method to measure complex permittivity of rod samples

A measurement method using the TM_0m0 mode cylindrical cavity with a dielectric rod sample inserted on the center axis is proposed to measure the accurate complex permittivity (relative permittivity epsiv_r and loss tangent tandelta), which can be obtained by the rigorous electromagnetic field analysis on the basis of the Ritz-Galerkin method. The complex permittivity of a polyethylene rod sample is measured using three cavities with different dimensions resonating in the TM₀₁₀ and TM₀₂₀ modes. Measured results were compared with ones for the conventional perturbation method and the accuracy is discussed. As a result, the measurement accuracy of epsiv_r and tandelta was improved within 2 and 5 percents by the present method, respectively.