Small-sized spiral dipole antenna for RFID transponder of UHF band

In this paper, the small-sized spiral dipole antenna for UHF RFID transponder is proposed. For the expected application of the UHF RFID systems, such as a supply chain integration, industrial automation, track and trace, and so on, the small and efficient printed antenna is required. To reduce the antenna size and to minimize the efficiency lowering due to small size, the proposed antenna is designed to have the spiral structure rather than the meander structure. In this structure, the current cancellation on the antenna is much less than in the meander structures, and the total current induces an identical magnetic dipole, which makes the omni-directional radiation pattern. The proposed antenna is designed for UHF RFID systems of Korea, to have the operating frequency bandwidth of 908 MHz similar to 913 MHz for VSWR < 2. The antenna has the physical size of 15.5 mm by 14.8 mm, which is about lambda over 16 in electrical length. This antenna is fabricated on the PET dielectric, to be utilized as an antenna of the transponder for the application of the UHF RFID systems.