High-Resolution Glucose Microwave Sensor Based on Amplified Asymmetric Plasmon Mode

Microwave sensors are one of the candidates for continuous glucose monitoring (CGM), with the advantages of high sensitivity and non-invasion. However, the losses caused by microwave sensors and the glucose solution impair the quality factor (Q) of the microwave sensor and significantly limit their performance. In this paper, a high-resolution glucose microwave sensor based on amplifying the asymmetric plasmon mode (ASM) is proposed. Firstly, a dual-channel injection-locked oscillator (ILO) is implemented, where two amplification circuits (ACs) are incorporated into a spoof localized surface plasmon (LSP) resonator with two split modes. By fine-tuning the phases of the two ACs to the optimum phase, both ASM and symmetric plasmon mode (SM) are simultaneously amplified. The unloaded Q value achieves 5656.8 for the ASM and 548.01 for the SM. Furthermore, it is theoretically and experimentally confirmed that the sensing performance of the ASM surpasses that of the SM by varying the glucose concentrations (GCs). When GCs range from 40 to 150 mg/dL, the resolution of the sensor based on the ASM reaches 5 mg/dL. It is believed that active microwave sensors based on the ASM hold significant promise for the high-sensitivity sensing applications.