Advanced Material-Based Chipless RFID Sensor for Multiparameter Sensing

This article investigates a low-cost FR4-based 8-bit chipless radio frequency identification (CRFID) tag sensor with a multifunctional sensing application and the operating frequency range for the proposed sensor varies from 800 MHz to 5 GHz. The tag’s design is based on a complimentary C-shaped resonator with dimensions $50\times 50\times 0.75$ mm3. A material-based sensing method has been adopted to sense the multiple environmental parameters. Advanced materials such as Kapton HN and graphene are embedded between the gaps of the copper slot and used as dedicated moisture and temperature sensing. The Kapton and graphene were tested through Fourier transform infrared spectroscopy (FTIR) spectroscopy to determine its absorption rate. The method of excitation for the proposed sensor is linear-polarized plane wave excitation. Here, two standardized horn antennas have been used for plane wave excitation. This research work proposes two specific sensor performance measurement setups to sense the environmental parameters: the moisture test box (MTB) and the greenhouse test box (GTB). The sensing is achieved by a maximum frequency shift of 300 MHz. The amplitude, resonant frequency, and variance are three major parameters extracted from the moisture and temperature sensor as a function of frequency. Lorentz second-order polynomial equations are used to fit the nonlinear, frequency variant sensor response to an optimal value along with the variance analysis techniques to interpret the sensing data for extracting the features in the CRFID system. The reversible behavior of the tag sensor on the low-cost FR4 substrate concerning moisture and temperature sensing is a better substitute for the other commercial environmental sensors.