Interaction of the Near-Field Microwave Wideband Sensor With Biological Tissues for Glucose Monitoring

In this paper, theoretical and experimental studies of physical processes occurring during the interaction of electromagnetic fields with biological tissues containing blood vessels with a small depth are given. A new approach is aimed at creating a near-field microwave sounding system for regular non-invasive monitoring of glucose levels. A feature of the proposed approach is the use of significant changes in the phase state of the near field in the vicinity of the so-called “causal surface”. At the first stage of the study, numerical simulation made it possible to obtain a picture of the interaction of near field of the wideband sensor of a special design with samples of biological tissues of various types. The most important thing in this work is that the geometry of the sensor provides the formation of an extended near-field zone with a high level of electric field near its aperture. A study of the near-field interaction of the sensor with various biological tissues was carried out on the basis of an analysis of the behavior of the real part of the radiation flux. Since a change in a blood the level of glucose leads to changes in dielectric permeability, the largest changes in signal level should be expected in the radiation passing through the blood vessels. The second stage - experimental studies of the possibility of real measurement of glucose in the phantom of biological tissue. During the experiment, the complex reflection coefficient from the sensor was measured as a function of the frequency. First, the reflection coefficient was measured for saline solutions containing dextrose. Then the same procedure was repeated for a pure saline solution. Then followed the normalization (in doing so, we fully took into account the recommendations, concerning the reduction of the influence of various negative factors). Of particular interest, in our opinion, is the signal in the range from 4.3 to 4.6 GHz. In this frequency range, a clear correlation is observed between signal magnitudes and solution concentrations.