Wide-Range Permittivity Measurement With a Parametric-Dependent Cavity

This paper reports an approach that can determine a very wide-range permittivity using a parametric-dependent cavity based on the field-enhancement method. The method is superior in accuracy as compared with the traditional cavity perturbation technique, especially at high and ultra-high dielectrics. Three regions of interest will be shown. At the low dielectric region ranging from 1 to 15, the field-enhancement method agrees well with the perturbation. At the intermediate or transition region from 15 to 125, the resonant frequency gradually changes from cavity dependence to sample dependence. Beyond 125, the resonant frequency depends mainly on the properties of the sample, not the geometry of the cavity. In addition to the resonant frequencies, the quality factors allow us to determine the imaginary part of the permittivity for low-loss materials. The field-enhancement approach significantly improves the sensitivity and resolution of the measurement. Two representative samples were tested. The results show that the parametric-dependent cavity is intriguing in physics and effective in characterizing materials' complex permittivity.