Novel RFID Conformal Tag Antennas for Liquid Level Detection Applications

Detection of liquid level in large tanks is presented in this paper. The liquid level is detected using a transmitter and RFID tag antennas as a receiver. The transmitter antenna is a Vivaldi with wide bandwidth from 0.5 GHz to 3 GHz. The Vivaldi antenna is fabricated on FR4 with 𝜀𝑟 = 4.3 and thickness of 0.8 mm. Two conformal RFID tag antennas are used as receiver antennas. The conformal antenna is placed on Rogers Ultram 3850 flexible substrates with 𝜀𝑟 = 2.9 and a thickness of 0.1016 mm. The conformal antenna is designed to set on a cylindrical tank made from PVC material. The first tag works at 0.9 GHz and the second tag works at 2.45 GHz. Water and Oil are used as liquids for testing. The antennas are simulated using CST microwave studio simulator Ver.14. The system is also fabricated and measured. Good agreement is achieved between simulated and measured results.