Method and System for Obtaining Information about RFID-Equipped Objects

Abstract

Method and arrangement for obtaining information about a radio-frequency identification (RFID) device or an object on which the RFID device is mounted when the RFID device is in a space defined by a frame includes arranging a plurality of antennas on the frame to enable transmission of signals into the space and reception of signals from the space, controlling transmission of signals by the antennas by means of an interrogator, and directing radio frequency signals from at least one of the antennas into the space to cause a RFID device in the space to return a signal if it receives any signal from any of the antennas. The return signals from the RFID device are received, e.g., by the interrogator or an associated receiver, and information about the RFID device or object to which the RFID device is attached is derived based on the return signals.

1 . A method for obtaining information about an object on which a radio-frequency identification (RFID) device is mounted when the RFID device is in a space defined by a frame, comprising: 
 arranging a plurality of antennas on the frame to enable transmission of signals into the space and reception of signals from the space;    controlling transmission of radio frequency signals by the antennas by means of at least one interrogator;    directing radio frequency signals from at least one of the antennas, controlled by the at least one interrogator, into the space to cause a RFID device in the space, when present, to return a signal if and when it receives any signal from any of the antennas;    receiving any return signals from the RFID device; and    deriving information about the object on which the RFID device is mounted based on the return signals, the information being a location of the object, motion of the object and/or identification of the object.    
   
   
       2 . The method of  claim 1 , further comprising: 
 arranging a communications device on the frame;    coupling the communications device to each of the at least one interrogator; and    transmitting the information about the device to a remote site using the communications device.    
   
   
       3 . The method of  claim 1 , wherein the frame is interposed between the at least one interrogator and the space, further comprising arranging at least one RF window on the frame to enable passage of signals between the at least one interrogator and the space.  
   
   
       4 . The method of  claim 1 , wherein each of the at least one interrogator is separate and apart from the frame, further comprising: 
 coupling the antennas to an antenna multiplexer;    coupling the antenna multiplexer to an external antenna extending outside of the frame and which communicates with the at least one interrogator; and    controlling transmission and reception of signals by the antennas via the multiplexer.    
   
   
       5 . The method of  claim 4 , further comprising associating each of the antennas with a defined portion of the space, the step of deriving information about the RFID device or object to which the RFID device is attached comprising determining the location of the RFID device by analyzing strength of return signals to all of the antennas to determine which antenna provides the largest return signal whereby the RFID device is considered to be located in that portion of the space associated with the antenna which provides the largest return signal.  
   
   
       6 . The method of  claim 5 , further comprising partitioning the space into a plurality of discrete longitudinal portions, each antenna being associated with only a single one of the portions.  
   
   
       7 . The method of  claim 1 , further comprising: 
 arranging an electricity-generating system on the frame; and    coupling the electricity-generating system to the at least one interrogator and antennas to provide electricity for operation thereof.    
   
   
       8 . The method of  claim 1 , further comprising: 
 providing the at least one interrogator and the RFID device with a clock;    arranging the RFID device to synchronize its clock upon reception of any signal from any of the antennas relative to the at least one interrogator's clock; and    arranging the RFID device to return the signal if it receives any signal from any of the antennas only after synchronization of its clock to the at least one interrogator's clock; and    arranging the interrogator to predict a transmit time at which the RFID device will return a signal after reception of a signal from one of the antennas whose transmission is controlled by the at least one interrogator;    the step of deriving information about the RFID device or the object to which the RFID device is attached comprising analyzing an arrival time of the return signal from the RFID device and the predicted transmit time to enable a measurement of a distance between the RFID device and the antenna to be determined.    
   
   
       9 . The method of  claim 8 , wherein the step of arranging the RFID device to return the signal only after synchronization of its clock to the interrogator's clock comprises arranging the RFID device to return the signal at a specific time relative to the reception of the signal from the antenna, at a specific time relative to a time when the signal from the antenna was sent or at a predesignated time.  
   
   
       10 . The method of  claim 1 , wherein the step of directing radio frequency signals from at least one of the antennas into the space comprises directing radio frequency signals from a plurality of antennas into the space, further comprising arranging the RFID device to provide information in the return signal indicative of a phase or relative time of reception of signals from multiple antennas.  
   
   
       11 . An asset with an integral system for obtaining information about a radio-frequency identification (RFID) device or an object on which the RFID device is mounted when the RFID device or object is in or in connection with the asset, comprising: 
 a frame defining an interior space of the asset;    a plurality of antennas arranged on said frame and enabling transmission of radio frequency signals into the space and reception of signals from the space;    an interrogator coupled to said antennas and arranged to control transmission of signals by said antennas whereby when a RFID device in the space receives a transmitted signal, it generates a return signal, said antennas being arranged to receive the return signals generated by any RFID devices in the space; and    a processor coupled to said antennas and said interrogator for receiving and analyzing the return signals received by said antennas to derive information about the RFID device or object on which the RFID device is mounted based on the return signals.    
   
   
       12 . The asset of  claim 11 , wherein said antennas comprise at least three antennas and said processor is arranged to determine a location of the RFID device based on measurements of a distance between each of said antennas and the RFID device.  
   
   
       13 . The asset of  claim 11 , further comprising a communications device arranged on said frame and coupled to said interrogator, said communications device being arranged to transmit the information about the RFID device obtained by said processor a remote site.  
   
   
       14 . The asset of  claim 11 , wherein said frame is interposed between said interrogator and the space, said frame including at least one RF window which enables passage of signals between said interrogator and the space.  
   
   
       15 . The asset of  claim 11 , wherein said frame is interposed between said interrogator and said space, further comprising: 
 an antenna multiplexer coupled to said antennas; and    an external antenna coupled to said antenna multiplexer and extending outside of said frame and communicating with said interrogator, transmission and reception of signals by said antennas being effected through said multiplexer.    
   
   
       16 . The asset of  claim 11 , wherein each of said antennas are spaced from one another along one dimension of said frame, said processor being arranged to determine the location of the RFID device by analyzing strength of return signals to all of said antennas to determine which of said antennas provides the largest return signal whereby the RFID device is considered to be located in a portion of the space associated with said antenna which provides the largest return signal.  
   
   
       17 . The asset of  claim 11 , further comprising an electricity-generating system arranged on said frame and coupled to said interrogator and said antennas to provide electricity for operation thereof.  
   
   
       18 . The asset of  claim 11 , wherein said interrogator has a clock and the RFID device has a clock, the RFID device being arranged to synchronize its clock upon reception of any signal from any of said antennas relative to said clock of said interrogator and return the signal if it receives any signal from any of said antennas only after synchronization of its clock to said clock of said interrogator, said processor being arranged to predict a transmit time at which the RFID device will return a signal after reception of a signal from one of said antennas whose transmission is controlled by said interrogator and analyze an arrival time of the return signal from the RFID device with the predicted transmit time to enable a measurement of a distance between the RFID device and said antenna to be determined.  
   
   
       19 . A monitoring system for monitoring objects in an asset, comprising: 
 a frame defining an interior space of the asset;    a plurality of antennas arranged on said frame and enabling transmission of radio frequency signals into the space and reception of signals from the space;    a radio-frequency identification (RFID) device arranged in connection with each object to be monitored;    at least one interrogator coupled to said antennas and arranged to control transmission of signals by said antennas whereby when one of said RFID devices present in the space receives a transmitted signal from said at least one interrogator, it generates a return signal, said antennas being arranged to receive the return signals generated by any of said RFID devices in the space; and    a processor coupled to said antennas and said at least one interrogator for coordinating transmission of signals by said antennas under control of said at least one interrogator, and for receiving and analyzing the return signals received by said antennas to derive information about said RFID device or object on which said RFID device is mounted based on the return signals.    
   
   
       20 . The system of  claim 19 , wherein said interrogator has a clock and each of said RFID devices has a clock and is arranged to synchronize its clock upon reception of any signal from any of said antennas relative to said clock of said interrogator and return the signal if it receives any signal from any of said antennas only after synchronization of its clock to said clock of said interrogator, said processor being arranged to predict a transmit time at which each of said RFID devices will return a signal after reception of a signal whose transmission is controlled by said interrogator and analyze an arrival time of the return signal from any of said RFID devices with the predicted transmit time to enable a measurement of a distance between said RFID device and said interrogator to be determined.