Chipless RFID Sensor on Paper Substrate

This paper proposes a chipless RFID sensor to detect permittivity changes in the Material Under Test (MUT) that is placed in a small container. The proposed design comprises an interrogator antenna and a miniaturized aluminium tag that is shaped as a meander line to reduce size and ensure high Q-factor. The detection of material is through the observation of the frequency peaks in the reflected signal <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S₁₁</tex> , which corresponds to the resonating frequency of the tag modulated by the material inside the container. Experimental verification uses air and ice as MUT, due to the intended application in frozen food monitoring. Measurement of the proposed design shows that the resonating peaks of air and ice are 5.3 and 4.2 GHz, respectively, and are similar to the simulation results.