A silk-screen printed RFID tag antenna

In this work, a dipole antenna with bent ends printed on hydrophobic paper as flexible substrate using conductive ink for passive UHF RFID tags operating at 915 MHz center frequency is presented. A conductive ink prepared with silver particles was used in a silk-screen printing technique to build the conductive elements of the antenna. The technique of depositing a high viscosity conductive ink on paper through a twisted-wires screen, is a very practical method for printing any type of geometric forms, enabling fast production of patch antennas for RFID tags. Measurements were taken to verify the feasibility of using tags printed with conductive ink regarding operation, reliability of the stored information, and data exchange with the reader, via air interface. Practical results were compared with those obtained for commercial tags. For this purpose, a technique to determine the minimum power necessary to turn on passive tags is also presented. The setup includes a small, low-cost GTEM cell which is immune against electromagnetic radiation.