MICROWAVE MEASUREMENT OF DIELECTRIC PROPERTIES OF LOW-LOSS MATERIALS BY THE DIELECTRIC ROD RESONATOR METHOD.

Improvements in both accuracy and speed are described for the technique of measuring the microwave dielectric properties of low-loss materials by using a dielectric rod resonator short-circuited at both ends by two parallel conducting plates. A technique for measuring the effective surface resistance R//s of the conducting plates is proposed to allow the accurate measurement of the loss tangent tan delta . By means of a first-order approximation, expressions are analytically derived for estimating the errors of the measured values of relative permittivity epsilon //r , tan delta , and R//s , for measuring the temperature coefficient of epsilon //r , and for determining the required size of the conducting plates. Computer-aided measurements are realized by using these expressions. It is shown that the temperature dependence of R//s should be considered in tan delta measurements. Experimental results are given for a 99. 9-% alumina ceramic rod sample.