Low Profile Compact-Slot Antenna Array for RFID Applications: Backscatter-Tag Identification and Localization

摘要

A recent application of radio frequency identication (RFID) systems consists, besides identification, in the localization of backscatter-tags. This can be performed through estimation of the direction of arrival (DOA) of the signal backscattered from the tag and incident on an antenna array. In this paper, we propose an antenna array dedicated to such applications in the european UHF RFID band (868-870 MHz). The system is designed to operate in a warehouse. The reader array is designed to be fixed horizontally on the ceilling and, the tag antennas are put on stacks all along the alleys. Hence, the antenna array communicates with tags located sideways. The antenna array shape has been studied to meet good performances in terms of DOA estimation accuracy and robustness to noise. It is found that a Y-shape array presents good performances. The antenna-array element (see Fig.1) consists of a miniaturized slot antenna printed on a non-resonating metallic box, fed by a stripline and backed by a ground plane. A compact antenna element having a low back radiation level and occupying a volume of (0.25λ{sub}0×0.25λ{sub}0×0.03λ{sub}0) is achieved exploiting to the slot miniaturization technique introduced by R. Azadegan et al. [1]. The antenna geometry, design concept, simulated and measured results are discussed in this paper. As well as the impact of the antenna thickness on its bandwidth and radiation efficiency.