Measurement of adulterated freeze-dried fruits using a highly sensitive transmission line sensor

Abstract This article presents a highly sensitive sensor for real permittivity measurement, based on a single transmission line where the differential line method is applied to extract the differential phase. In this transmission line configuration, the material under test (MUT) can be positioned between the signal trace and the ground plane, enhancing the interaction between the MUT and the electromagnetic fields. In this study, the method is validated using known commercial substrates, and its application is demonstrated in detecting sugar adulteration in freeze-dried fruits. The method was validated within a measurement range of 0.6 GHz–5.8 GHz. Additionally, the reference substrate can be adjusted according to the permittivity range required for the specific application. The sensor exhibits superior performance compared to traditional phase-variation methods in transmission lines and is proposed as an alternative to conventional permittivity measurement techniques used in food analysis.