RADIO FREQUENCY IDENTIFICATION (RFID) is a technology used for objects identification. A considerable number of studies have been conducted on RFID tag design for metallic objects in recent years. The inverted-F antenna (IFA), planar inverted-F antenna (PIFA), and patch-type antenna structures, which possess a ground plane in their structures, are commonly used in RFID metal tag designs [1]–[4]. Not all RFID metal tags are designed based on these antenna structures. Small loop antenna and double-folded dipole antenna with complementary impedance variation characteristics can also be applied to overcome the antenna near metallicobjectproblems[5],[6].TheimplementationsofRFID metal tags based on the above concepts are all workable and useful. However, in order to meet with the high inductance requirement, the sizes of these antennas are very large. Even thepreviousworkin[7]adoptsahigh-impedancesurface(HIS) unit cell as an antenna structure to achieve a slim RFID metal tag design, whose size may still restrain the use of RFID from certain practical applications. Therefore, a miniature RFID metal tag mountable on metallic object is desirable and worth developing.