Analysis and Design of a Microwave Coplanar Sensor for Non-Invasive Blood Glucose Measurements

In this paper a design for a microwave sensor for the non-invasive measurement of blood glucose concentrations is proposed. The sensor is intended for usage as part of a non-invasive glucose-quantifying device. With this aim, three different microwave resonator structures are analyzed as possible candidates, and strengths and weaknesses are highlighted in each case. The chosen resonator is an open structure in which a finger of the patient is placed, fulfilling the role of a sample to be characterized by the sensor. The shape and size of the finger thus condition those of the resonator. Variations in the concentration of blood glucose modify the dielectric properties of the tissue, which is part of the microwave resonator-finger system, and as such, the changes translate to the resonance frequency of the whole structure. Among the three studied topologies, it was found that a single resonator designed using a coplanar structure with a ground plane showed the best trade-off in frequency sensitivity, stability and repeatability of the measurements. A notable correlation, between the resonance frequency of the proposed sensor and the blood glucose levels measured with a traditional glucometer, was found. This highlights a potential interchangeability of both glucose measurement methods.