Characterization of the complex permittivity of glucose/water solutions for noninvasive RF/Microwave blood glucose sensing

摘要

This paper presents an accurate and low-cost method for measuring complex permittivity of various concentrations of glucose/water solutions utilizing an open-ended coaxial probe. An accurate complex permittivity model for varying concentrations of glucose/water solutions is needed for the simulation and validation of RF glucose sensors for the purpose of noninvasive blood glucose measurement. Liquids can be modeled in terms of their dielectric properties by the Cole-Cole or Debye model when several parameters are known for a specific sample. These parameters are addressed in this paper for the glucose/water solutions of 100mg/dl to 500mg/dl. An open-ended coaxial probe was designed and validated in CST Microwave Studio (MWS) and was manufactured for measuring the complex permittivity values. The values were extracted in MATLAB from the S-parameters obtained on the Vector Network Analyzer (VNA) using the equations published in the open literature with subsequent use of artificial neural networks to further improve the results. A new set of Debye parameters were proposed for glucose/water solutions for 1 GHz-8 GHz range. A compact RF/Microwave sensor for noninvasive glucose measurement was also designed, simulated, fabricated and tested with results briefly reported in this paper.