Dynamic Measurement of Temperature Dependent Complex Permittivity of Material by Microwave Heating Using Cylindrical Cavity Resonator

A TM_0.10 mode of cylindrical cavity resonator and heating system in a frequency of 2.45 GHz band has been designed to measure the temperature dependent complex permittivity of dielectric materials. To measure the temperature dependent complex permittivity of material, the output power of vector network analyzer is amplified to heat materials and obtaining complex permittivity by measuring transmission coefficient with measuring the temperature of the material using an infrared thermometer. From the results, it is found that the error of the complex permittivity obtained by perturbation method is at most 1.5 % compared to the one obtained by rigorous analysis. It is confirmed that the dielectric loss of crystal organic materials increases remarkably above the glassy transition temperature. On the other hand, the dielectric loss of amorphous resin increases linearly as increasing the temperature.