A Novel Broadband Antenna Design for UHF RFID Tags on Metallic Surface Environments

In this letter, a novel ultrahigh-frequency radio frequency identification (UHF RFID) tag antenna is proposed. Suitable for metallic objects, this broadband antenna can cover the three major UHF RFID bands. A modified folded dipole and a meander bar have been implemented on the upper substrate, while the second substrate is a double face with parallel bars printed on the top face and a metal plane on the bottom to isolate the antenna from metallic surfaces. The bars are used as parasitic elements to excite multiresonant modes and enhance the antenna bandwidth. To improve the gain of the antenna, the two substrates have been speared by an air layer. Furthermore, the proposed design is cost-effective since it does not require metallic vias. Mounted on a metallic plate of 300 × 250 mm2, the proposed antenna covers the targeted UHF RFID bands with a return loss better than 10 dB and a maximum outdoor measured reading range of 14.6 m at 905 MHz.