System and method of estimating true bearings of radio frequency identification (RFID) tags associated with items located directly underneath an overhead antenna array in a controlled area

摘要

An RFID tag reading system and method estimate true bearings of RFID tags associated with items located in a scan zone directly underneath an overhead array of antenna elements. A controller energizes a plurality of diametrically opposite antenna elements to yield electric fields having polarizations, and switches each antenna element between mutually orthogonal polarizations. A primary transmit beam and a primary receive beam are steered at a primary steering angle over the scan zone, and a plurality of secondary receive beams are steered over the scan zone at different secondary steering angles that are offset from the primary steering angle by receiving secondary receive signals from each tag, and by processing the secondary receive signals to estimate a true bearing for each tag.

主权项

1. A radio frequency (RF) identification (RFID) tag reading system for estimating true bearings of RFID tags associated with items in a controlled area, comprising:
an RFID reader having an overhead array of antenna elements arranged about a vertical axis, and a plurality of RF transceivers; and a controller operatively connected to the transceivers, and operative for controlling the transceivers by executing an antenna processing module operative for energizing a plurality of the antenna elements at opposite sides of the vertical axis to yield electric fields having polarizations, and for switching each antenna element between mutually orthogonal polarizations, the controller being further operative for controlling the transceivers by executing a tag processing module operative for steering a primary transmit beam throughout the controlled area, including a scan zone directly underneath the overhead array, by transmitting a primary transmit signal via the plurality of the antenna elements to each tag, and for steering a primary receive beam throughout the controlled area, including the scan zone, at a primary steering angle by receiving a primary receive signal via the plurality of the antenna elements from each tag, the controller being further operative for controlling the transceivers by executing a bearing processing module operative for steering a plurality of secondary receive beams throughout the controlled area, including the scan zone, at different secondary steering angles that are offset from the primary steering angle by receiving a plurality of secondary receive signals via the first and second pairs of the antenna elements from each tag, and by processing the secondary receive signals to determine a true bearing for each tag throughout the controlled area, including the scan zone.