Localization of passive UHF RFID tagged goods with the Monopulse principle for a logistic application

By now RFID technology is an integral part of logistics and logistic applications, because of the advantage of contactless identification of tagged objects even without line of sight. With standard RFID technology, it is only possible to identify objects, but the actual position within the reading range is unknown. Many applications in logistics require a more precise localization of the tagged goods. There are several scenarios where the knowledge of the actual position of an object could improve the process and even avoid mistakes. We designed a system for localization for the application “logistic supermarket”, where one has to know, which objects are put in which gate. We use the so-called Monopulse principle to estimate the relative position of a transponder together with an algorithm to eliminate constant reflections and to improve the angle measurement. The first prototype shows very good results: we performed more than 500 tests in a complex logistic supermarket environment with two adjacent gates. In 97 % the position of the tag was correctly detected. In this paper we focus on the calculation of the Direction of Arrival (DoA) of a transponder and the evaluation of this step in a logistic supermarket.