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 ε
r
and loss tangent tanδ), 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 TM
010
and TM
020
modes. Measured results were compared with ones for the conventional perturbation method and the accuracy is discussed. As a result, the measurement accuracy of ε
r
and tanδ was improved within 2 and 5 percents by the present method, respectively.