Investigation of UHF Circular Loop Antennas for RFID

In radio frequency identification (RFID), the design and investigation of ultra-high-frequency (UHF) circular loop antennas used as reader antennas as well as tag antennas is of growing importance. Since these antennas are electrically short, a 2-D finite-element method (FEM) analysis using a single-component magnetic vector potential together with perfectly matched layers (PMLs) at the boundary is proposed in this paper in order to perform very fast and accurate axisymmetric simulations compared to very time-consuming 3-D calculations. In addition, the capacitances of the tag loops have been calculated using a 3-D quasi-static electric approach taking the gap of the loops into account.