Abstract
In RFID systems, how to detect the position precisely is an important and challenging research topic. In this paper, we propose a range-free 2D tag localization method based on phased array antenna, called PATL. This method takes advantage of the adjustable radiation angle of the phased array antenna to scan the surveillance region in turns. By using the statistics of the tags’ number in different antenna beam directions, a weighting algorithm is used to calculate the position of the tag. This method can be applied to real-time location of multiple targets without usage of any reference tags or additional readers. Additionally, we present an optimized weighting method based on RSSI to increase the locating accuracy. We use a Commercial Off-the-Shelf (COTS) UHF RFID reader which is integrated with a phased array antenna to evaluate our method. The experiment results from an indoor office environment demonstrate the average distance error of PATL is about 21 cm and the optimized approach achieves an accuracy of 13 cm. This novel 2D localization scheme is a simple, yet promising, solution that is especially applicable to the smart shelf visualized management in storage or retail area.
Highlights
In Radio Frequency Identification (RFID) systems, how to detect the position precisely is an important and challenging research topic
Considering the feature of the 2D phased array antenna where the beam direction is known and adjustable, we propose a range-free weighting method PATL to calculate the two-dimensional coordinates of the tag
We firstly propose a method PATL based on two-dimensional phased array antenna for the RFID system
Summary
Comparing to other positioning technologies, angle of arrival based localization can provide a higher positioning accuracy and multipath anti-interference capability for UHF RFID9. Considering the feature of the 2D phased array antenna where the beam direction is known and adjustable, we propose a range-free weighting method PATL to calculate the two-dimensional coordinates of the tag. If the antenna beam can precisely modify its beam direction to scan the entire two-dimensional plane and the radiation lobe is enough narrow, when the antenna receives the tag’s backscatter signal on a certain angle, we can directly consider that the coordinate of the tag as calculated by formula [5]. The beam directions generated by phased array antenna has been divided into K quadrants and we eliminate the multipath effect by comparing the beams number that can read the tag in each quadrant. After eliminating the misreading measurements introduced by multipath interference, we use the reads number ni of the filtered M beams to provide the weighting factor and calculate the tag’s 2D coordinate based on PATL. EPATL algorithm to detect and calculate the locating results for these two cases, and compare the results.We investigated the performance of the algorithm from two aspects: the average distance error and time consumption. lated
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