Design and characterization of a small encapsulated UHF RFID tag for wood log monitoring

In this work, a small encapsulated planar dipole antenna is designed and characterized for an UHF RFID tag. In the envisaged application, the RFID tag is applied to the front or back ends of wood logs loaded on a truck for monitoring purposes in logistics, where the tag size and form factor are crucial parameters. It is shown that the antenna needs to be designed considering the dielectric loading of the encapsulation and wood in proximity for achieving satisfactory impedance matching at 868 MHz and, hence, high read-range. The designed linear polarized antenna has the dimensions 6.5 mm × 70 mm (0.02 λ × 0.2 λ), a radiation efficiency of 55 % and a gain of 0 dBi. The antenna is screen-printed on paper (substrate) with a conductive polymer paste. The transponder integrated circuit (IC) is assembled in flip-chip technology with anisotropic conductive adhesive (ACA). The assembled tag is finally encapsulated with a material, which is preferably compatible with paper manufacturing processes.