Microwave Resonator Based Blood Glucose Sensor

The pursuit of non-invasive glucose monitoring has remained central to biomedical research over the past three decades. Despite notable advancements in sensor and RF circuit design, conventional techniques often face limitations in accuracy, real-time performance, and hardware complexity. Recent trends emphasize microwave and electromagnetic sensing techniques, particularly within the ISM band, to exploit dielectric property variations of blood and interstitial fluids influenced by glucose concentration. In this study, we present a microstrip ring resonator (MRR)-based sensor engineered for biomedical applications, operating at 1.25 GHz, tailored for high sensitivity and compact integration. The sensor leverages its S-parameter response (S21) to detect frequency shifts induced by varying glucose concentrations in aqueous media. The proposed resonator achieves a sensitivity of 3 MHz/100 mg/dL, with a quality factor (Q) of 40, enabling accurate detection at low glucose levels. Optimized coupling geometry enhances electric field confinement and coupling capacitance (Cg), leading to improved insertion loss characteristics. The sensor demonstrates excellent impedance matching, with a VSWR of 1.1012 and return loss of -27 dB, translating to a power transmission efficiency of 99.97%.This work integrates principles of microwave engineering, RF sensors, and dielectric spectroscopy, offering a compact, cost-effective, and reliable solution for continuous glucose sensing. The improved sensitivity, low-loss performance, and compatibility with planar circuit technologies make this resonator design highly suitable for IoT-enabled biomedical sensing platforms.