Design of a novel ultra-high frequency radio-frequency identification reader antenna for near-field communications using oppositely directed currents

The authors propose a novel ultra-high frequency (UHF) near-field reader antenna that produces a strong and uniform magnetic near field over a broad region to detect radio-frequency identification (RFID) tags attached to various target objects consistently. The concept of two closely spaced oppositely directed currents (ODCs) is used to obtain a strong magnetic near field, and a symmetrical inverted-L structure fed by a coaxial feed with a parasitic patch is employed as the antenna body to realise the ODCs without any additional feed network. The design parameters were optimised using the Pareto genetic algorithm (GA) in conjunction with the FEKO EM simulator. The optimised antenna had an average magnetic near field of -20-dBA/m in the reading region (30-30-10-cm³), which is suitable for commercial smart-shelf applications. Finally, we examined the effect on our proposed antenna of placing objects in the reading region. The results show that our antenna is appropriate for smart shelves with item-level tagging.