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 x 10 x 1.5 cm(3). 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 x 30 x 20 cm(3) 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 degrees with 10 dBi gain at the xz-plane and +/- 50 degrees 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.