Nondestructive and noncontact dielectric measurement method for high-loss liquids using free space microwave measurement system in 8 - 12.5 GHz frequency range

Nondestructive, noncontact and real time evaluation of dielectric properties of liquids is important for applications such as biomedical, remote sensing and design of radar absorbing material. Free-space methods (which are nondestructive and noncontact) were developed for accurate measurement of dielectric properties of high-loss liquids at microwave frequencies. The free space microwave measurement system (FSMM) consists of spot focusing horn lens antennas, mode transitions, coaxial cables and vector network analyzer (VNA). For high-loss liquids, namely, methanol, ethanol, ethylene glycol and N-propyl alcohol, dielectric constants and loss factors were measured using the reflection-transmission method. It is observed that the reflection-transmission method is suitable for accurate measurement of dielectric properties of high-loss liquids.