SYSTEM FOR, AND METHOD OF, ACCURATELY AND RAPIDLY DETERMINING, IN REAL-TIME, TRUE BEARINGS OF RADIO FREQUENCY IDENTIFICATION (RFID) TAGS ASSOCIATED WITH ITEMS IN A CONTROLLED AREA

摘要

A radio frequency identification (RFID) tag reading system and method accurately and rapidly determine, in real-time, true bearings of RFID tags associated with items in a controlled area. Primary transmit and receive beams are steered over the area, and multiple secondary receive beams are substantially simultaneously steered to a plurality of bearings in the area. The highest signal strength of secondary receive signals from the secondary receive beams determines an approximate tag bearing of each tag. Two secondary receive beams at opposite sides of the approximate tag bearing in elevation are selected to obtain a pair of elevation offset signals, and two secondary receive beams at opposite sides of the approximate tag bearing in azimuth are selected to obtain a pair of azimuth offset signals. The elevation offset signals and the azimuth offset signals are processed to determine a true bearing for each tag in real-time.

主权项

1. A radio frequency (RF) identification (RFID) tag reading system for accurately and rapidly determining, in real-time, true bearings of RFID tags associated with items in a controlled area, comprising:
an RFID reader having an array of antenna elements and a plurality of RF transceivers; and a controller operatively connected to the transceivers, and the controller configured to control the transceivers by steering a primary transmit beam over the controlled area by transmitting a primary transmit signal via the antenna elements to each tag, and for steering a primary receive beam at a primary steering angle by receiving a primary receive signal via the antenna elements from each tag, the controller being further configured to control the transceivers by substantially simultaneously steering a plurality of secondary receive offset beams to a plurality of bearings in the controlled area at a plurality of different secondary steering angles that are offset from the primary steering angle by receiving a plurality of secondary receive offset signals via the antenna elements from each tag, and the controller being further configured to process the secondary receive offset signals to determine a true bearing for each tag in real-time, wherein the controller is further configured to determine an approximate tag bearing by selecting the secondary receive offset signal that has a peak processing signal strength from among all the secondary receive offset signals, and wherein the controller is further configured to: select a first pair of the secondary receive offset beams at opposite sides of the approximate tag bearing in elevation to obtain a pair of elevation offset signals, for selecting a second pair of the secondary receive offset beams at opposite sides of the approximate tag bearing in azimuth to obtain a pair of azimuth offset signals; and process the elevation offset signals and the azimuth offset signals to determine a true bearing for each tag in real-time.