Open-ended coaxial probe permittivity measurements on pulverized materials

The open-ended coaxial probe technique can be used to obtain estimates of the permittivities of some solid dielectrics over broad ranges of frequency by measurements on powdered or pulverized samples, but certain problems must be resolved. 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 measurement 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 to 20 GHz were then estimated by computations based on the Landau & Lifshitz, Looyenga dielectric mixture equation and solid material densities