Generalised probe method to measure the liquid complex permittivity

A generalised probe method is proposed for fast and accurate complex permittivity measurements. The method is based on the simulated reflection coefficients using the finite difference frequency domain method. A database is set up, which consists of the simulated complex reflection coefficients of the unknown material under test. A fast searching algorithm is performed to match the measured reflection coefficients to the reference values in the database, thus the complex permittivity of the liquid can be obtained. An in-house measurement system is developed. The unique feature of this system is that it can be applied to an arbitrarily-shaped probe. Liquid samples are measured and the results are compared with that published in the literature. Good agreements are obtained. These results could be useful for liquid microwave component designs and applications.