MEASUREMENTS OF CONDUCTIVITY AND DIELECTRIC CONSTANT AT MICROWAVE FREQUENCIES AND THEIR UNCERTAINTIE

This work deals with the measurements of the conductivity and the dielectric constant of materials in the microwave frequency region and with emphasis on the uncertainty. Due to the increasing interest in the microwave conductivity and dielectric constant of fast ion conductors, a conductivity range of 10('-4) to 1/(OMEGA)-cm is considered and the effects of the negative dielectric constant are also examined.;For low and medium conductivity materials (10('-4) (LESSTHEQ) (sigma) (LESSTHEQ) 10('-1)/(OMEGA)-cm), short circuited line (SCL) method is preferred. Accurate results can be obtained by using a sample with a quarter wavelength thickness. For high conductivity ((sigma) > 10('-1)/(OMEGA)-cm) and negative dielectric constant materials, uncertainty will increase. A formula for determining the limit of applications of the SCL method is derived. For these two types of materials (high conductivity and negative dielectric constant), the transmission method is preferred. Low uncertainty in the measurement of conductivity is expected.;Two new combination methods are introduced where the conductivity and the dielectric constant are evaluated from the amplitudes of the reflection and the transmission coefficients without using the phase. The results of uncertainty analyses show that these two methods are preferred for measuring medium conductivity materials.;A new technique, the slow scan method, for measuring the resonant frequency, Q-factor and the coupling coefficient is presented. This technique is applicable to the cavity perturbation method for determining the conductivity and the dielectric constant of materials. An uncertainty analysis of the cavity perturbation method is performed for the case where a small spherical sample is placed at the electric field maximum. The uncertainties of the conductivity and the dielectric constant are calculated by analytical expressions. For highly conductive materials, the case where the sample is placed at the magnetic field maximum is also examined and compared with the result of the case where the same sample is placed at the electric field maximum.;Different conductivity samples with various dimensions are measured to verify the results of analyses.