In this paper, we present a broadband flexible RFID sensor tag antenna to detect the concentration of aqueous solutions. The proposed RFID tag antenna sensor with a T matching network is based on a printed dipole whose arms are loaded with circular disk patches. The structure is printed on a Kapton polyimide flexible substrate. The sensing mechanism of the RFID tag antenna is based on the change of sensitivity of the RFID tag antenna that occurs with the variation of aqueous solution concentration. The proposed sensor is designed using CST Microwave studio, and its various parameters are optimized in order to have a broadband impedance matching that covers the entire RFID band (860-960 MHz). The experimental setup is small, rapid, contactless, and inexpensive. Results are presented for NaCl and sugar aqueous solutions with concentrations ranging from 0% to 80%.
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