High-sensitivity narrow-band CSRR-based Microwave Sensor for Monitoring Glucose Level

In this paper, a high-sensitivity narrow-band microwave sensor based on a complementary split-ring resonator (CSRR) to detect glucose concentrations in an aqueous solution is presented. The sensor consists of three CSRR cells engraved on the bottom level of a 59 mm x 20 mm x 0.8 mm FR4 (εr=4.3) dielectric substrate with a sensing area of 36 x 20 mm2. The cells operate over the 2.3 - 2.4 GHz band and are powered by a 50 Ω microstrip waveguide at the bottom of the substrate. A sensitivity analysis, starting from an optimization of the thickness of the glass layer added to the cells to avoid short circuits between the sample solution and the CSRRs rings, is performed. The sensitivity analysis is carried out by varying the concentration of glucose in the range of 40-150 mg/dl dissolved in aqueous solution. The simulations performed by 3D CST Studio Suite 2021 with an optimum value of the glass layer thickness of 10 µm and a 38 x 20 mm2 area show a sensitivity value equal to 5.72 MHz/mg/dl which represents the highest sensitivity value compared to previously published works.