Low-Profile Three-Arm Folded Dipole Antenna for UHF Band RFID Tags Mountable on Metallic Objects

A low-profile radio frequency identification (RFID) tag mountable on metallic objects is presented, which employs a multiple-arm folded dipole antenna. The proposed antenna is printed on a single-layer circuit board with an overall thickness of 1.5 mm not requiring any via or shorting plate. The presented configuration allows to match an RFID chip impedance with an imaginary part around -400 Omega. A slightly modified version of the tag that allows an easy tuning of the frequency response is illustrated as well as a more compact tag obtained by allowing the use of vias. Prototypes for the RFID UHF band allocated in Europe have been fabricated, and measurements of the impedance and read range are provided.