Dielectric characterization based on a printable resonant stub in air and a liquid environment

This paper develops a new approach for in situ characterization of specific dielectric-based products that are located in complex geometric containers. The method uses a resonant T-topology of microstrip lines realized on a flexible substrate. This narrowband interferometric technique consists of determining the dielectric properties via the resonance characteristics of a flexible band-stop filter. The system is designed for the application of RFID (Radio-Frequency IDentication) traceability. The proof of principle is validated experimentally and a complete comparison between an analytical approach and electromagnetic simulations are presented. The flexibility of the proposed solution allows the characterization of the liquid and container in the final form. This study highlights several measurement optimization strategies that can be combined when a material is loaded with a constituent containing alcohol concentrations ranging from 0 to 37%. The parameters extracted for the loss tangent and the relative permittivities demonstrate an accurate technique with a precision better than 5%.