Flexible Chipless RFID Sensor for Permittivity Sensing of Cylindrical Impedance Surface

Abstract

This paper presents the chipless RFID sensor characteristics when placed on the cylindrical impedance surface. The chipless RFID sensor is designed based on the multiple resonant printed on the flexible substrate of Polyimide <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\varepsilon_{\mathrm{r}}=3.5$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\tan 6=0.0027)$</tex>. The humidity of the material under test is identified using the chipless RFID sensor based on the multi-resonators. This chipless sensor can be generated 5 bits of identification (ID). Furthermore, the orientation effect of the plane wave is studied. The results shows that the flexible chipless RFID sensor can be identified the different dielectric constant that related with the water content in the material. Therefore, this sensor can be applied to recognize the humidity state of material under test.