A novel design for UHF near-field RFID reader antenna based on traveling wave

A novel planar antenna is presented for ultra high frequency (UHF) near-field radio frequency identification (RFID) applications. The antenna is composed of grounded coplanar waveguide, coplanar stripline, a lumped balun, multiple resistances and a finite-size ground plane. The load impedance is equal to the characteristic impedance of the coplanar stripline, so traveling wave can transmit along the coplanar stripline. The proposed structure can make large currents along the coplanar stripline so that a strong and uniform magnetic field distribution is excited in the region around the antenna. The antenna geometry, design concept, simulated and measured results are carefully discussed throughout the paper. Measurements show that the antenna operating with a commercial reader demonstrates good performance of tag identification with inductive coupling for near-field RFID applications.