A Novel Permittivity Measurement Method Using Multiple TM_mn0 Modes of Cylindrical Cavity

In this article, a novel permittivity measurement method utilizing multiple TMmn0 modes of the cylindrical cavity is proposed. Compared with the traditional TMmn0 modes, the TMmn0 modes have more degrees of freedom, which is beneficial for multifrequency measurement employing a single cavity. The loading position of the substrate is properly designed to simultaneously perturb the TM220 mode, TM430 mode, TM540 mode, and TM460 mode of the cavity, thus realizing multifrequency measurement. To achieve the high-precision measurement, a numerical method derived from the perturbation theory is presented. Three different samples are tested for demonstration, thus showing competitive accuracy compared with the traditional method.