High-frequency, complex dielectric permittivity of saline solution at elevated temperatures

The complex dielectric permittivity of saline solutions at elevated temperatures of up to 80°C has been measured at 1.1 GHz. The salinity of the solution was varied from 1000 to 5000 parts per million. The measurements were first made in a rectangular waveguide. The phase velocity and attenuation of the electromagnetic wave propagating in the waveguide were measured, and from those the real and imaginary parts of the dielectric permittivity were calculated. The complex permittivity of the heated saline solution was also measured in a parallel-plate radial waveguide. Details of the measurement techniques, together with measured data, are presented. It is found that the high-frequency conductivity and dielectric constant predicted by an empirical formula agree with the measured data in the temperature range of 20° to 40°C. However, for temperatures higher than 40°C, the measured conductivities and dielectric constant are both higher than the empirical data