The read range limitations of passive UHF-RFID tags based on electric dipole antennas have
been studied in this work. A 1.25 wavelength long linear wire has been proposed as a tag antenna
which maximizes the gain while maintaining acceptable dimensions and radiation pattern. Based
on this result, a tag prototype has been designed by matching the antenna impedance to the Alien
Higgs-3 chip input impedance by means of a shunt inductance. The presented tag antenna length and
diameter are 400 mm and 0.8 mm, respectively, and a 4 ˆ 14.6 mm2
rectangular substrate, holding
the chip and the inductive matching network, is located at the center of the tag. The measured read
range exhibits a maximum value of 17.5 m at the 902–928 MHz band, representing an important
improvement as compared to the best general purpose commercial passive UHF-RFID tags. Moreover,
several simulations predict that the tag can be implemented in planar technology (i.e., inlay) while
maintaining high values of radiation efficiency. The application of this type of antennas to RFID tags is
the main novel aspect of this paper.