Double Loop Inductive Feed Patch Antenna Design for Antimetal UHF RFID Tag

Planar UHF RFID antimetal tag can be widely used for the metallic products or packages with metal material inside. A double loop inductive feed planar patch antenna is proposed for UHF RFID tag mounted on metallic objects. Compared to conventional microstrip antennas or PIFA antennas used for UHF RFID tags, the double loop inductive feed patch antenna has a planar structure, with no short via or short wall, which could decrease the manufacturing cost of the tags. The double loop inductive feed structure also increases the radiation performance of the planar antenna. Moreover, the double loop inductive feed structure makes the impedance of the patch antenna be tuned easily for conjugate impedance matching.