Quadruple-feed beam-controlled antenna array for the localisations of ultra-high-frequency radio-frequency identification tags

Item-level tagging has been required to the retail market with densely placed items as well as the production line. Owing to the multi-path fading, the blind spots where the tag is non-responsive can be created. Furthermore, in case of the indoor radio-frequency identification (RFID) localisation system, additional circuits and localisation algorithms are indispensable for accurate localisation of RFID tags. In this study, in order to solve this problem, the beam-controlled antenna array with a quadruple beamforming network which generates multiple beams is presented for ultra-high-frequency (UHF) RFID systems. The proposed quadruple-feed antenna array can cover the wide spatial coverage, and the main beam directions of the proposed array can be controlled by selecting the appropriate input port of the quadruple network. The fabricated antenna array with the quadruple-feed network operates at the 902-928 MHz band and produces scannable multiple beams for UHF RFID localisation system within the wide interrogation zone.