Estimation of the complex permittivity of liquids by means of complementary split ring resonator (CSRR) loaded transmission lines

Abstract

This paper presents a method to estimate the complex permittivity of liquids. The sensor consists of an embedded microstrip line with a complementary split ring resonator (CSRR) etched in the ground plane, beneath the conductor strip. A liquid container, surrounding the CSRR, is added to the structure in order to load the sensing element (CSRR) with the liquid under test (LUT). The complex permittivity of the LUT is inferred from the frequency response of the structure, particularly from the notch frequency and depth, without the need of reference samples for calibration. The proposed method is validated by measuring the dielectric constant and loss tangent of deionized (DI) water.