A UHF omni-directional RFID antenna

Radio frequency identification (RFID) is a technology that provides wireless identification and tracking capability, it is more robust than the bar code system [1]. A typical RFID system consists of at least a reader, a reader antenna, a host computer, a software system, and a tag (transponder) attached item. Recently the item-level RFID receives much attention for the applications of tagging small and high volume items - retail apparel, jewelry, rented apparel/laundry, aircraft parts, drugs and postal packages, books, documents - at the request of retailers, military forces, postal authorities, libraries, museums, art galleries, hospitals, and so on [2]. The challenges in designing the antenna for item-level RFID applications include controlling reading zone of the reader antenna, alleviating the effect of the platform on tag antenna (as the tags are always attached to specific objects which may be lossy material or metal), and maintaining tag performance with serious multi-coupling between the tag antennas (as the tags are placed in very close proximity with objects which exhibit distinct RF properties).