Tunable Matching Layer Method for Identifying Impurities on Liquids at Microwaves

The aim of the work is to develop a method for contactless identifying of impurity concentration in liquids of a given type in the microwave frequencies. The work presents the theoretical analysis of the novel method for identifying impurities in liquids at microwave frequencies, based on the use of a tunable matching layer (a dielectric layer of variable thickness). To find the reflection coefficient of an electromagnetic wave from the layered structure, a standard technique consisting of determining the electromagnetic fields in each region and imposing continuity conditions for the field components at each boundary of the layer was used. Numerical estimations of the method’s sensitivity are provided using the example of determining ethanol impurity concentrations in water. The results are compared with experimental data reported in other publications. It has been shown that this method has a high sensitivity to impurity concentration.