Patch-Type Microwave Resonant Sensor Based on a Complementary Split-Ring Resonator for Monitoring Glucose Concentration Under Static and Dynamic Conditions

This study designs a complementary split-ring resonator (CSRR)-based 5 GHz patch-type microwave resonant sensor for measuring the concentrations of glucose solutions under static and dynamic conditions. Circulating glucose solutions were used to simulate blood glucose, and the CSRR sensor was operated over a frequency range of 4.8–5.0 GHz. The planar microstrip configuration of the CSRR creates a highly confined electric field within the sensing area. When glucose solution covers or flows through the sensing region, the dielectric loading changes, altering the resonance condition and inducing perturbations. Identifiable measurement features can be extracted from data on the scattering parameter S11. Glucose solutions with concentrations ranging from 5% to 65% were used to examine the response of the proposed sensor. The concentrations of these solutions were estimated on the basis of resonant frequency shifts, and variation in S21 at the CSRR’s resonant frequency (or at a fixed frequency corresponding to the maximum slope) was also analyzed.