Open-ended coaxial-line permittivity measurements on pulverized materials

The open-ended, coaxial-line probe technique can be used to obtain estimates of the pennittivities of some solid dielectrics over broad ranges of frequency by measurements on powdered or pulverized samples, but certain limitations must be recognized. Such a probe was used with a network analyzer to estimate the permittivities of coal and limestone from reflection coefficients measured on pulverized samples. The bulk density of the pulverized samples for the coaxial probe measurements was determined from auxiliary, single-frequency permittivity measurements on the samples at known bulk densities, and the permittivities of the solid materials over the frequency range from 0.2 GHz to 20 GHz were then estimated by computations based on the Landau and Lifshitz, Looyenga dielectric mixture equation and solid material densities.