Development of a Phased Array Antenna for Universal UHF RFID Reader

摘要

Radio frequency identification (RFID) is an emerging technology for automatic identification, asset tracking, security surveillance and authentication of items, animals and personnel. RFID has been classified according to the frequency of operation-low frequency (LF), high frequency (HF), ultra high frequency (UHF) and microwave. UHF RFID tags dominate the market due to their salient features of long distance and high speed reading, more data storage capability and being more immune to environmental factors such as liquids and human presence. However, the operation of the UHF RFID system spreads over a wide frequency band starting from 860 MHz and ending at 960 MHz. This constitutes approximately 11% bandwidth at the centre frequency of 910 MHz. It is not a trivial task to design broadband antennas for both tags and readers. The specification poses a tremendous challenge to design broadband antennas. The design needs not only to meet stringent electrical requirements but also needs compact design to fit into the available space. Researchers take a short cut by designing narrowband antennas for individual frequency spectra for individual regions or countries. In this paper a unified approach is taken to address the design of a broadband antenna for the reader so that although tags are designed in discrete narrow bands, the reader can be universal to read all tags anywhere in the world. Moreover, increasing reading rates, mitigating anti-collision in multiple tag reading, and consequently improving the throughput in the RFID system are imperative in the current business climate. A UHF RFID phased array smart antenna controlled by a field programmable gate array (FPGA) and switching electronics are developed and presented in this paper. The antenna with its capabilities of steering the beam in 3D space will help to solve many problems in high speed multiple tag reading.