Small Conformal UHF RFID Tag Antenna for Labelling Fruits

A label-type ultra-high frequency (UHF) radio frequency identification (RFID) antenna for tagging apple fruits is presented. The proposed tag consists of a hybrid structure, which is a composed of eye-shaped rectangular nested slots, a loop and dipole like strips. The loop was placed for impedance match of the chip, while the rectangular nested slots further help to provide imaginary impedance match on high permittivity surface such as fruits. The dipole like strips assists in reducing the increase in loss resistance due to the high permittivity of fruits. The measured read range of the tag is 3 m, when attached to apple and can work well in whole US RFID band. Moreover, an automatic billing and weight calculating experiment is conducted by placing the tagged apples inside a refrigerator. Overall, the tag antenna performance after testing on different apple fruits indicates its robustness and makes it suitable for automatic billing and weighting of fruits in future perspective vending machines and departmental stores.