Measurement of liquids dielectric property using monopole probes operating at microwave frequencies

Determination of the dielectric properties of liquids has high practical potential in many industrial, medical, as well as environmental sectors. With the increasing demand for efficient measurement systems, the need arises for a reliable, inexpensive, hand-held, battery operated, and user-friendly system for liquids dielectric properties measurement. In this paper, a microwave nondestructive evaluation (NDE) system that is intended to meet these requirements is proposed. This system utilizes a monopole antenna to transmit microwave signals into the liquid and monitors the reflected waves in the feeding coaxial line. The functional dependence of the reflection coefficient on the dielectric property of the liquid surrounding the monopole will be employed in our measurement schema - i.e. we will be measuring the reflection coefficient and then solving the inverse problem. In general, this dependence is nonlinear in nature and requires sophisticated algorithm to be inverted. To this end, we will introduce a Fuzzy-Maximum-Likelihood (FML) hybrid algorithm to be applied in conjunction with multi-frequency measurements to solve the inverse problem.