Dual-Band Metamaterial Structure for High-Loss Liquid Sensing

This paper introduces a dual-band RF planar sensor designed for the detection of sucrose solutions at varying concentrations. The sensor is composed of a microstrip line and complementary split-ring resonators (CSRR), with each CSRR unit demonstrating band-stop characteristics at resonant frequencies of 2.45 GHz (ISM) and 4.9 GHz. CST simulation results indicate that changes in the liquid concentration placed on the CSRR result in corresponding changes to its resonant center frequency and amplitude response. By utilizing data derived from CST simulations, a relationship between the complex dielectric constant and the resonant center frequency can be fitted. When compared with reference dielectric constants measured by a commercial coaxial probe, this method yields maximum relative errors of 3.6% for the real part and 9% for the imaginary part of the dielectric constant, respectively. The measured dielectric constants also validate the applicability of the proposed method.