Designing Highly Sensitive Microwave Antenna Sensor with Novel Model for Noninvasive Glucose Measurements

—The concentration induced permittivity change involves a dispersion which occurs at the resonant frequency and is often not predictable by simulation using the traditional Cole-Cole model. To overcome this problem, a new Lorentz’s model is proposed as a substitute for the Cole-Cole model. Under this new model, the glucose concentration is expected to be measured at the contact interface in the form of a resonant frequency shift. With the help of the model, a contact-based meander-line antenna sensor (CMS) is realized with a high sensitivity of 1.3158 dB/(mmol/L) in terms of d|S₁₁ |/dC, or of 17 ∼ 18 MHz/(mmol/L) in terms of dω/dC. The model has been experimentally validated with in-vitro measurements and for proof-of-concept with in-vivo clinical investigations in the microwave frequency. Consistent with the predictions of model, a linear correlation is observed not only between the resonant frequency shift and the glucose concentration, but also between the S-parameters magnitude and glucose concentration.