A DIELECTRIC RESONATOR FOR MEASUREMENTS OF COMPLEX PERMITTIVITY OF LOW-LOSS DIELECTRIC MATERIALS AS A FUNCTION OF TEMPERATURE

An application of a TE01 delta mode dielectric resonator is described for precise measurements of complex permittivity and the thermal effec ts on permittivity for isotropic dielectric materials. The Rayleigh-Ri tz technique was employed to find a rigorous relationship between perm ittivity, resonant frequency, and the dimensions of the resonant struc ture, with relative computational accuracy of less than 10(-3). The in fluence of conductor loss and its temperature dependence was taken int o account in the dielectric loss tangent evaluation. Complex permittiv ities of several materials, including cross-linked polystyrene, polyte trafluoroethylene, and alumina, were measured in the temperature range of 300-400 K. Absolute uncertainties of relative permittivity measure ments were estimated to be smaller than 0.2%, limited mainly by uncert ainty in the sample dimensions. For properly chosen sample dimensions, materials with dielectric loss tangents in the range of 5 x 10(-7) to 5 x 10(-3) can be measured using the TE01 delta mode dielectric reson ator.