Design and Experimental Evaluation of Miniaturized Monopole UHF RFID Tag Antennas

This letter reports the design and experimental evaluation of three compact printed monopole antennas for UHF RFID applications. The antennas that include folded, 2-D meander, and 3-D meander monopole designs are inductively coupled to RFID chips and are fabricated using a 1.524-mm-thick Rogers RB4350B substrate with the relative permittivity of 3.66. Experimental results reveal that these tags cover the worldwide UHF RFID operation band (860-960 MHz) with a maximum readable range of 6.3 m for the folded monopole, 5.39 m for the 2-D meander, and 5.24 m for the 3-D meander monopole designs with an effective isotropic radiated power of 3.28 W. A method for measuring the radiation pattern of an assembled UHF RFID tag without the use of any additional matching circuits or feeding wires is presented. This method is used to measure the radiation pattern of the fabricated 3-D meander monopole tag antenna.