Rfid location systems and methods

Abstract

Embodiments of the present invention include radio frequency identification location systems and methods. In one embodiment, RF signals are transmitted from one or more RFID readers, and in accordance therewith, backscattered signals are received from a tag to be located. A plurality of measured position parameters are used to determine a location of the tag. In one embodiment, one reader may transmit and three readers may receive signals to determine the position of a tag. In other embodiments, multiple readers may transmit and receive. In another embodiment, one reader may transmit from different positions to locate a tag. Embodiments of the invention may be used to track a moving tag. A reader's position may be determined using GPS, reference tags, or the reader may be positioned in a known location. A map may be provided to a user to display the location or movement of a tag or a corresponding item.

1 - 88 . (canceled) 
     
     
         89 . A method of locating radio frequency identification (RFID) tags, the method comprising:
 transmitting a radio frequency (RF) signal from a first RFID reader at a first location;   transmitting an RF signal from said first RFID reader at a second location;   transmitting an RF signal from a second RFID reader at a third location, wherein the first, second, and third locations are different locations;   receiving signals backscattered off a tag from the RF signals transmitted from the first RFID reader at the first and second locations and from the second RFID reader at the third location;   extracting at least one measured position parameter from each received signal backscattered off the tag; and   calculating a location of the tag using the extracted measured position parameters.   
     
     
         90 . The method of  claim 89  further comprising transmitting from a third RFID reader at a fourth location different from the first, second, and third locations, wherein the receiving further comprises receiving a signal backscattered off the tag from the RF signal transmitted from the third RFID reader, wherein the extracting further comprises extracting at least one measured position parameter from the signal backscattered off the tag from the RF signal transmitted from the third RFID reader. 
     
     
         91 . The method of  claim 89  further comprising transmitting the measured position parameters corresponding to the signals backscattered off the tag to a server to determine the location of the tag by the server. 
     
     
         92 . The method of  claim 89 , wherein the RF signal transmitted from the RFID readers at each of the first, second, and third locations is transmitted at a single frequency. 
     
     
         93 . The method of  claim 89  further comprising receiving measured position parameters for the signals backscattered off the tag and received at each of the first, second, and third locations at the first RFID reader, and determining the location of the tag by the first RFID reader. 
     
     
         94 . The method of  claim 89  further comprising receiving each of the first and second locations at the first RFID reader. 
     
     
         95 . The method of  claim 89  further comprising storing one or more locations corresponding to the first RFID reader. 
     
     
         96 . The method of  claim 89  further comprising determining one or more of the first, second, and third locations using a global positioning system. 
     
     
         97 . The method of  claim 89 , wherein the RF signal is transmitted by an RFID reader different from an RFID reader that receives the signal backscattered from the tag. 
     
     
         98 . The method of  claim 89 , wherein the measured position parameters comprise at least one of a power of the signal backscattered from the tag, an angle of arrival of the signal backscattered from the tag, a time difference of arrival of the signal backscattered from the tag, and a phase of the signal backscattered from the tag. 
     
     
         99 . The method of  claim 98 , wherein two or more different measured position parameters are extracted from each signal backscattered from the tag and used to determine the location of the tag. 
     
     
         100 . The method of  claim 98 , wherein the first RFID reader transmits a plurality of RF signals from each of the first and second locations and the second RDIF reader transmits a plurality of RF signals from the third location, wherein the first and second RFID readers receive a plurality of corresponding signals backscattered off the tag from each transmitted signal, wherein the first and second RFID readers extract measured position parameters from the received backscattered signals. 
     
     
         101 . The method of  claim 89  further comprising determining raw location parameters for the tag to be located, the raw location parameters representing the location of the tag as latitude and longitude, Cartesian coordinates, Polar coordinates, or as one or more vectors. 
     
     
         102 . The method of  claim 101  further comprising generating mapped position information from the raw location parameters. 
     
     
         103 . The method of  claim 89  further comprising associating a map image with the location of the tag and displaying the map image to a user. 
     
     
         104 . The method of  claim 89 , wherein the first RFID reader is embedded in a mobile device. 
     
     
         105 . A device for locating radio frequency identification (RFID) tags, the device comprising:
 a radio frequency (RF) signal transmitter for transmitting RF signals to a tag;   a receiver for receiving signals backscattered off the tag;   the device configured to:
 transmit an RF signal from the transmitter at a first location; 
 transmit an RF signal from the transmitter at a second location; 
 receive, at the receiver, signals backscattered off a tag from the RF signals transmitted at the first and second locations; and 
 receive, at the receiver, signals backscattered off the tag from RF signals transmitted at a third locations from another, wherein the first, second, and third locations are different locations; 
 extract at least one measured position parameter from each received signal backscattered off the tag; and 
 calculate a location of the tag using the extracted measured position parameters. 
   
     
     
         106 . The device of  claim 105  further configured to transmit the measured position parameters corresponding to the signals backscattered off the tag to a server to determine the location of the tag by the server. 
     
     
         107 . The device of  claim 105 , wherein the RF signal transmitted at each of the first, second, and third locations is transmitted at a single frequency. 
     
     
         108 . The device of  claim 105  further comprising receiving each of the first and second locations at the device. 
     
     
         109 . The device of  claim 105  further comprising storage, the device further configured to store the first and second locations in the storage of the device. 
     
     
         110 . The device of  claim 105  further comprising a global positioning system (GPS), the device further configured to determine one or more of the first and second locations using a global positioning system. 
     
     
         111 . The device of  claim 105 , wherein the measured position parameters comprise at least one of a power of the signal backscattered from the tag, an angle of arrival of the signal backscattered from the tag, a time difference of arrival of the signal backscattered from the tag, and a phase of the signal backscattered from the tag. 
     
     
         112 . The device of  claim 111 , wherein two or more different measured position parameters are extracted from each signal backscattered from the tag and used to determine the location of the tag. 
     
     
         113 . The device of  claim 111 , wherein the device transmits a plurality of RF signals from each of the first and second locations and the other device transmits a plurality of RF signals from the third location, wherein the device receives a plurality of corresponding signals backscattered off the tag from each transmitted signal, wherein the device is further configured to extract measured position parameters from the received backscattered signals. 
     
     
         114 . The device of  claim 105  further configured to determine raw location parameters for the tag to be located, the raw location parameters representing the location of the tag as latitude and longitude, Cartesian coordinates, Polar coordinates, or as one or more vectors. 
     
     
         115 . The device of  claim 114  further configured to generate mapped position information from the raw location parameters. 
     
     
         116 . The device of  claim 105  further configured to associate a map image with the location of the tag and displaying the map image to a user.