8-bit Chipless RFID Tag with Humidity Sensing Capability
School of ICT Convergence, Daegu University, Gyeongsan, Korea
Abstract: In this paper, an 8-bit chipless RFID tag with identification information and humidity sensing capability was proposed. A compact high-sensitivity interdigital-capacitor(IDC)-based resonator was used for humidity sensing, whereas seven electric field-coupled resonators were used for identification information. These 8 resonators were placed in a 2 by 4 array arrangement. poly(vinyl alcohol)(PVA), a hygroscopic polymer material, was coated on the IDC-based resonator with a thickness of 0.02 mm for humidity sensing. A non-reflective temperature and humidity chamber was fabricated using styrofoam, and the relative humidity(RH) was varied from 50% to 80% with a 10% interval at a temperature of 25 degrees in order to measure a bistatic radar cross section(RCS) of the proposed tag. The humidity sensing performance of the tag was measured by the shift in the resonant peak frequency and magnitude level of the RCS. Experiment results show that when RH increased from 50% to 80%, the resonant peak frequency and magnitude of the PVA-coated IDC-based resonator were only changed, whereas those of the other seven resonators without PVA coating did not change.
Keywords: chipless radio frequency identification(RFID), humidity sensing, interdigital-capacitor(IDC), poly(vinyl alcohol)(PVA), radar cross section(RCS)