Evaluation of a printed patch antenna for robust microwave RFID tags

Antennas in Radio frequency identification (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 work well and provide 70-80 of the reading range compared to copper solutions. However, more advanced antennas are needed to provide less sensitivity to the environment of RFID tags that is need for placing tags on metal or near water. In this work, a study of multilayered antennas so called patch antennas, for 2.45GHz RFID tags, is presented. 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, the possibility of manufacturing printed patch antennas of common packaging materials is investigated.