Sensitivity evaluation of miniature microstrip line-based sensors using multiple sensing parameters for non-invasive blood glucose monitoring

Abstract

A number of high-sensitivity microwave sensors with compact resonators are designed, fabricated, and tested for non-invasive blood glucose monitoring. In the first step, a split ring resonator (SRR)-based sensor is designed, and then it’s sensing parameters, viz. the reflection coefficient magnitude and phase coupled with its input impedance, are extracted and calibrated by different glucose solutions. The results of this structure are subsequently saved as a reference sensor. During the second step, the swastika-shaped and electric-LC (ELC) geometries are substituted for the SRR to enhance the sensitivity of the reference sensor, and the sensing parameters of these structures, which are sensitive to the glucose solutions, are obtained. In the third step, the sensitivity of the three proposed designs is calculated and compared, using the reflection coefficient amplitude, phase, and input impedance. The comparisons typically demonstrate that the sensitivity of the swastika-shaped structure is equal to 148.367 (Ω/mgmL−1) if the sensitivity is acquired from the imaginary part of the input impedance, which is better than the SRR and ELC geometries. On the contrary, the sensitivity of the SRR geometry is at a maximum and equal to 16.79 (deg/mgmL−1) if the sensitivity is calculated in terms of the reflection coefficient phase.