Reconfigurable Multimode Microwave Sensor With Resonance and Transmission Sensing Capabilities for Noninvasive Glucose Monitoring

This article proposes a novel reconfigurable multimode microwave sensor integrating with resonance-and transmission-sensing capabilities for real-time noninvasive glucose monitoring. The sensor is initiated by utilizing a dynamic controllable spoof surface plasmon polariton (SSPP) transmission line (TL) and a multimode array resonator based on spoof localized surface plasmon (SLSP). This sensor possesses multiple resonance modes with high Q-factors, and its working characteristic can be flexibly manipulated by tuning the bias voltage applied to the loaded varactor diodes. Glucose monitoring is accomplished by analyzing the changes in the shift of multiple resonance frequencies and the amplitude of transmission coefficient within a specific operating band. Furthermore, an effective joint sensing method is developed by combining the results obtained from different resonance modes and various working characteristics of the sensor, which can greatly enhance sensitivity and the ability to correct errors. The experimental results demonstrate that, within a valuable glucose concentration range of 0–800 mg/dL, the presented sensor realizes a high sensitivity of 9.86$\times$10$^{\mathbf{-2}}$MHz/(mg/dL) for resonance sensing and 2.00$\times$10$^{\mathbf{-2}}$dB/(mg/dL) for transmission sensing. Also, the resonance sensing and transmission sensing exhibit an ultrahigh linear correlation, enabling the glucose sensor to possess robust crosschecking capability. Moreover, the results demonstrate that this sensor has a strong error correction function.