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A broadband antimetal UHF tag antenna based on symmetric resonator structures

A novel broadband ultra‐high frequency radio frequency identification (RFID) tag antenna attached to the metallic surface is proposed in this paper. A rectangular wide slot combined with a U‐shaped thin slot outside is adopted in the proposed antenna, and the size of the patch can be reduced by adjusting the length of the U‐shaped slot. Furthermore, a pair of symmetric resonator structures inside the rectangular slot are connected to both ends of the chip, which can excite a new resonant mode to broaden the frequency band. All the structures above are realized by etching rectangular slits on the same surface. The antenna has the advantages of wideband, simple processing, and good reading distance, and the 10 dB bandwidth of the antenna is 30 MHz (from 895 to 925 MHz), with a maximum directional gain of −3.5 dB. The reading distance can reach more than 5.4 m on a metallic surface.