A novel RFID-enabled strain sensor using the double power measurement technique

This paper studies a novel RFID-enabled strain sensing approach using the radar cross-section measurement technique and taking advantage of the nonlinearity properties of the RFID chip. As a proof of concept, we applied the method for the measurement of an RFID-enabled strain sensor that was realized on fabric using electro-textiles in order to observe large variations of peak-power frequencies and corresponding strain levels. We carried out the radar measurements first applying the three-target calibration technique and then using the novel double-power-detection method, which relies upon the detection of the backscattered response for two distinct transmitting power levels and then calculating the difference of these two responses. The nonlinearity of the chip causes a large variation of its impedance value and thus a large difference of RCS values for carefully chosen power levels, allowing for the elimination of the need for calibration. Practical measurements have validated the method and the reliability of the technique.