Research on U-shaped tuning stub RFID tag on different objects

Abstract

A new ultra-high frequency radio frequency identification (RFID) tag antenna, which is comprised a U-shaped tuning stub and a dipole radiator for different permittivity surfaces is investigated, fabricated, and measured. For a conjugate match to the NXP G2XM chip impedance of 29–j137 at 915 MHz, a dipole tag antenna with U-shaped stubconnected to dipole arms was designed. Simple size adjustments of the U-shaped tuning stub and dipole radiator of the antenna allow for easy control of the antenna resistance and inductive reactance, from which the chip impedance requirement may be readily satisfied. The read range of the prototype antenna attached on a different permittivity surfaces (εr= 1–4) can reach more than 4.5 m, which has been tested for an RFID reader with 4.0 W of effective isotropic radiated power. The antenna structure consists of two dipole load bars and two loop electrically connected. The design offers more choice of freedom to tune the input impedance of the proposed antenna. Measurement data are presented which are in good agreement with simulation results. The design is suitable for mounting on all kinds of objects. The fabricated tag sensitivity of −3 dBm, read range of 7 m on the x–z and y–z planes, and the measured orientation radiation patterns were obtained in the desired frequency band.