Abstract
Abstract: This study investigates the optimization of non-invasive blood glucose sensors by analyzing the impact of substrate thickness on the transmission characteristics of microwave resonators. Using Rogers 4003C (ε= 3.38), two H-shaped slot sensors were compared at thicknesses of 0.813 mm and 1.524 mm. The electromagnetic interaction was characterized using the Cole-Cole model, correlating glucose-induced dielectric shifts with variations in the transmission coefficient (S21).The results reveal that the 1.524 mm substrate significantly enhances sensor performance. It achieved a more pronounced S21 magnitude shift of 1.1101 dB across the physiological glucose range, compared to only 0.9871 dB for the 0.813 mm substrate. Power budget analysis showed that the thicker design optimized the energy flow by reducing the reflection coefficient S11 to 0.1544, thereby allowing a higher total power loss (absorption) of 0.5021. This increased absorption facilitates a stronger coupling between the fringing fields and the blood sample, directly improving the S21 resonance depth sensitivity.Furthermore, real-time measurements demonstrated that the 1.524 mm configuration provides superior stability and robustness, maintaining consistent S21 profiles across different subjects, whereas the thinner substrate exhibited significant interpersonal deviations. These findings confirm that optimizing substrate thickness to maximize S21 sensitivity and energy absorption is vital for developing reliable, non-invasive glucose monitoring technologies.Keywords: Non-invasive Glucose Monitoring, S21 Transmission Coefficient, Substrate Thickness, Cole-Cole Model, Power Loss, Rogers 4003C.