Evaluation of a printed patch antenna for robust microwave RFID tags

Antennas in RFID tags have often been designed in a single layer with copper as conductor and plastic foils as substrate. There is currently a large interest in roll to roll production of RFID tags and silver based inks have been developed for use in printed RFID antennas. Silver ink based single layer antennas works well and is providing 70% to 80% of the reading range compared to copper solutions. However, more advanced antennas are needed to provide less sensitivity to the environment of RFID tags .i.e. need for placing tags on metal or near water. In this work we present a study of multilayered antennas so called patch antennas, for 2.45 GHz RFID tags. The advantage of the patch antenna is that it can be applied to any kind of material, reflecting or lossy material, and still provide good antenna function. However, the patch antenna efficiency is strongly dependent on the material used. For low cost RFID tags in logistics there is a need to manufacture the antenna as a part of the packaging process. In the current work we have investigated the possibility to manufacture printed patch antennas of common packaging materials.
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