Compact size flexible UHF RFID tag antenna for racing pigeon ring applications

A very small size radio frequency identification (RFID) tag antenna specifically designed for racing pigeon ring applications is proposed. The structure of this UHF tag is a closed-loop type printed on a 30 x 8 mm(2) polyimide film of thickness 0.063 mm. Thus, it can be wrapped into a double layer plastic cylindrical ring of size similar to those used for racing pigeon. By simply tuning the inner width of the loop, good conjugate matching between the tag chip input impedance and the tag antenna can be achieved. When mounted onto a real preserved dried pigeon feet specimen, the measured impedance bandwidth of the tag antenna was 901-929 MHz. Further experimental results have also shown that the proposed antenna has a maximum reading range of up to 50 cm.