Design of a spherical-shaped, UHF RFID tag antenna with 3-axes polarization

In this paper, a spherical-shaped, UHF RFID tag antenna with 3-axes polarization is proposed to detect information of the status of a liquid container by inserting it inside the liquid container, which would be beneficial for a patient management in a hospital. Fig. 1 shows an example of reading environment of RFID tag for liquid detection. Typically, it is hard for a tag antenna to be identified in liquid solutions since the efficiency of the antenna is degraded significantly and the matching problem occurs. If liquid solution becomes empty, however, the RFID tag in the solution starts working. Then the RFID reader can identify the RFID tag signal about replacement information of the intravenous solution. The designed antenna had -lOdB bandwidth of 8MHz(0.88%) and maximum readable range of 132cm. Return losses of the antenna are measured in several different types of liquid.