Anti-Water UHF RFID Tag Antenna with Multi-Loop Structure for Impedance Matching

An anti-water UHF RFID tag antenna with multi-loop structure for impedance matching is proposed. Conformal design is adopted to make the antenna suitable for the bottle surface. To obtain wideband performance, a multi-loop impedance matching structure is designed, which can double the band of that by the traditional T-match structure. Besides, the proposed antenna has a vertically omnidirectional radiation pattern when attached to bottle surface, so that it will be less shaded by water bottles around it. The dimension of the antenna design is 44 mm × 20 mm, the -6 dB bandwidth is 100 MHz at around 915 MHz, and the maximum gain is -5.54 dBi.