Design of an UHF RFID antenna on flexible substrate magnetically coupled to the tag

UHF RFID antennas that are magnetically coupled to the tag by using a transformer are designed and fabricated on flexible materials. The primary and secondary windings of the transformer are implemented on the antenna substrate and in the chip, respectively. In this way, galvanic contacts between the antenna and the tag are not required and the tag can be assembled on the antenna substrate by means of a mere placing and gluing process: the wire-bonding and the soldering processes are avoided reducing the production costs. Another important feature is the use of a flexible substrate. These features make this antenna attractive to the market of RFID and other applications, where the flexibility and the placing tolerances are mandatory. The design process of a bow-tie antenna with transformer, based on flexible substrate and operating in the UHF frequency band, is described step by step and validated by means of accurate full-wave simulations.