Evaluation of a high sensitivity radiofrequency inductive probe for the non-contact sensing of dielectric properties of organic media

Abstract

The sensing of dielectric properties of organic media is required in various fields such as agriculture, food industry or human health. Indeed these properties are related to the state of the organic media, and may be used as relevant indicators, especially in the radiofrequencies (RF), to either assess the quality of food in food industry or the physiopathological state of tissues in medical applications. As opposed to some conventional dielectric measurement techniques, the technique proposed in this study is contactless, easy to implement, and sensitive to both the conductivity and the permittivity of the media under investigation. The sensing technique lies in the distant monitoring of a high-quality factor inductive RF resonator, electromagnetically coupled to the investigated medium. In this study, the authors aim at assessing the feasibility and accuracy of dielectric media sensing by means of their contactless and easy-to-implement method. To that purpose, a wireless cylindrical inductive RF resonator inductively coupled to a monitoring bobbin coil is considered. It constitutes a radiating transmit and receive inductive sensor electromagnetically interacting with its direct environment (e.g. organic material). The dielectric properties of this environment are sensed through the impedance changes of the resonator, which is remotely monitored by a distant bobbin coil. In this study, the resonator is implemented for the distant sensing of organic material phantoms constituted of solutions featuring tabulated dielectric properties. A lumped element modeling of the RF probe interacting with the medium is proposed. Preliminary results open the way to the development of easy-to-implement dielectric characterization techniques of organic media, such as contactless medical sensing devices.