Design of near‐field ultra‐high frequency radio‐frequency identification antenna with fragmented wires for electrically‐large coverage

Abstract

Design of ultra-high frequency radio-frequency identification (UHF RFID) reader antenna covering electrically-large near-field area is still challenging for near-field UHF RFID applications. In such design, magnetic field distribution on a large coverage area is required to be as uniform as possible. Fragment-type wire antennas are quite suitable for such demand because distribution of fragmented wires in a designated electrically-large area can be optimised to counterpoise the magnetic fields generated by non-uniform current distribution. By optimisation searching with multiobjective evolutionary algorithm based on decomposition combined with enhanced genetic operators, fragment-type RFID reader antenna is designed to provide uniform magnetic field distribution within dynamic range of 4 dB in an electrically-large near-field coverage of 320 × 320 mm at 915 MHz. The designed antenna is fabricated and tested. Both simulation and measurement results show good impedance matching, satisfactory near-field coverage, and desirable omni-directional pattern.