Two-dimensional scanning antenna array for UHF radio frequency identification system application

This study presents a two-dimensional (2D) scanning antenna array of ultra high frequency radio frequency identification system with high stability and reliability in metal cavity. The antenna array is composed of nine elements and a feeding network. The two-shorting-plate planar inverted-F antenna is designed as antenna element with small dimension 10 × 10 × 1.5 cm3. The bandwidth of element is about 72 MHz (840–912 MHz) under the condition of voltage standing wave ratio (VSWR) <2. The feeding network consists of a butler matrix and three three-way power dividers. Both the nine antenna elements and a feeding network are specified within 33 × 30 × 20 cm3 areas, where switches are used to change the connection of feeding network to obtain 2D scanning beam. The measured bandwidth is about 30 MHz (845–875 MHz) under the condition of VSWR <2, which covers Europe standard (865–868 MHz) completely. The scanning beam directions are ±60° with 10 dBi gain at the xz-plane and ±50° with 10 dBi gain at the yz-plane. The read rate of the proposed antenna array achieves 100% in the metal cavity with 18 dBm input power.