Synthetic aperture RFID handheld with tag location capability

• US 9,176,215 B2
• Filed: 03/14/2013
• Issued: 11/03/2015
• Est. Priority Date: 03/22/2012
• Status: Active Grant

• Current Assignee: Intermec IP Corporation (Honeywell International Inc.)
• Original Assignee: Intermec IP Corporation (Honeywell International Inc.)
• Inventors: Nikitin, Pavel, Rao, KVS, Brueckmann, Rainer, Leland, Hunter, Kelly, Stephen
• Primary Examiner(s): NWUGO, OJIAKO K
• Application Number:
  US13/826,758
• Publication Number:
  US 20130249736A1
• Time in Patent Office: 964 Days
• Field of Search: 235375-385
• US Class Current: 1/1
• CPC Class Codes: G01S 13/74 Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
• CPC Class Codes: G01S 5/0249 Determining position using measurements made by a non-stationary device other than the device whose position is being determined
• CPC Class Codes: G01S 5/02585 at least one of the measurements being a non-radio measurement
• CPC Class Codes: G01S 5/0284 Relative positioning
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence
• CPC Class Codes: G01S 5/12 by co-ordinating position lines of different shape, e.g. hyperbolic, circular, elliptical or radial

Abstract

A system for determining a bearing or location of a radio frequency identification (RFID) tag using a handheld RFID reader is described. In one embodiment, the reader is equipped with an accelerometer. A user moves the reader while the reader receives the tag'"'"'s signal and determines the tag signal'"'"'s phase at multiple locations. The locations of the reader antenna can be reconstructed using the accelerometer data. By using the phase determined at multiple locations in conjunction with the location of the reader antenna, the reader can determine the bearing of the tag. For an RFID reader not equipped with an accelerometer, the sign and ratio of the rate of change in the phase of a tag'"'"'s signal to the distance traveled by the reader antenna can be used to determine the location of the tag relative to the reader.

Claims

1. An RFID (radio frequency identification) reader comprising:

a location or movement determination component configured to measure location or acceleration of the reader in three dimensions;

at least one RFID radio having a first antenna;

at least one data memory component;

at least one input/output component configured to prompt a user to move the reader; and

at least one processor coupled among the location or movement determination component, the RFID radio, the data memory component, and the input/output component, wherein the processor is configured to;

transmit a first RF (radio frequency) query using the RFID radio;

calculate a first phase and a second phase for a tag signal sent by a tag in response to the first RF query, wherein a first phase corresponds to the tag signal received at a first position of the first antenna, and wherein the second phase corresponds to the tag signal received at a second position of the first antenna;

calculate a trajectory or positions of the moving reader using data from the location or movement determination component; and

determine a bearing for the tag using the calculated trajectory or positions and the calculated first phase and second phase for the tag,

wherein the input/output component is further configured to;

prompt the user when to move the reader to synchronize with received tag signals;

display progress in determining the bearing for the tag; and

display the determined bearing for the tag.

2. The RFID reader of claim 1, wherein the at least one RFID radio has a second antenna, and wherein the processor is further configured to calculate a third phase and a fourth phase corresponding to the tag signal received at the second antenna, and wherein determining the bearing for the tag further uses the calculated third phase and fourth phase for the tag.

3. The RFID reader of claim 1, wherein the first antenna is motorized.

4. The RFID reader of claim 1, wherein the location or movement determination component comprises a trajectory tracker.

5. The RFID reader of claim 4, wherein the location or movement determination component provides angular acceleration data for the moving reader, and wherein the processor is further configured to determine from the angular acceleration data a location of the tag relative to the moving reader, and further wherein the input/output component is configured to display an indication of a direction of the tag relative to the moving reader.

6. The RFID reader of claim 1, wherein the system determines whether to take more tag signal readings based on whether a minimum level of confidence has been reached, and wherein the RFID radio transmits on a different frequency when the minimum level of confidence is not achieved within a predetermined time period.

7. An RFID (radio frequency identification) reader comprising:

at least one RFID radio having a first antenna;

at least one data memory component;

at least one input/output component configured to prompt a user to move the reader in a first direction; and

at least one processor coupled among the RFID radio, the data memory component, and the input/output component, wherein the processor is configured to;

transmit a first RF (radio frequency) query using the RFID radio;

calculate a first phase and a second phase for a tag signal sent by a tag in response to the first RF query, wherein a first phase corresponds to the tag signal received at a first position of the first antenna, and wherein the second phase corresponds to the tag signal received at a second position of the first antenna, and wherein the first and second positions correspond to movement of the reader in the first direction;

calculate a change of phase of the tag signal as a function of time using the first phase and the second phase; and

determine a location of the tag relative to the movement direction of the reader based on the calculated change of phase as a function of time;

wherein the RFID reader is configured to determine when the RFID reader is in motion, further wherein data from the RFID reader is used to determine the change of phase of the tag as a function of time.

8. The RFID reader of claim 7, wherein the first antenna is motorized.

9. The RFID reader of claim 7, wherein the at least one RFID radio has a second antenna, and wherein the processor is further configured to calculate a third phase and a fourth phase corresponding to the tag signal received at the second antenna, and wherein determining the bearing for the tag further uses the calculated third phase and fourth phase for the tag.

10. The RFID reader of claim 7, wherein the input/output component is further configured to display the determined location of the tag relative to the movement direction of the reader.

11. The RFID reader of claim 7, wherein a large positive change of phase as a function of time results when the direction of movement of the reader is toward the tag;

and a large negative change of phase as a function of time results when the direction of movement of the reader is away from the tag.

12. The RFID reader of claim 7, wherein the input/output component is configured to emit a series of sounds, wherein characteristics of the series of sounds are controlled by the processor, and further wherein the processor is configured to change a period of repetition of the sounds in the series or a frequency of the series of sounds based upon the change of phase.

13. A method of determining a location of an RFID (radio frequency identification) tag relative to an RFID reader, the method comprising:

prompting the user to move the reader in a first direction;

using an RFID transceiver having an antenna to send a first RF query;

calculating a first phase and a second phase for a tag signal sent by a tag in response to the first RF query, wherein a first phase corresponds to the tag signal received at a first location of the first antenna, and

wherein the second phase corresponds to the tag signal received at a second location of the first antenna, and

wherein the first and second locations correspond to movement of the reader in the first direction;

calculating a change of phase of the tag signal as a function of distance traveled by the reader using the first phase and the second phase;

determining a position of the tag relative to the movement direction of the reader based on the calculated change of phase as a function of time; and

displaying the position of the tag relative to the reader

emitting sounds, wherein the sounds based upon the change of phase.

14. The method of claim 13, further comprising determining a confidence level of the relative location of the tag, and if a minimum level of confidence is not satisfied, sending a second RF query using the RFID radio.

15. The method of claim 14, wherein the second RF query uses a different frequency than the first RF query.

16. An apparatus for determining a location of an RFID (radio frequency identification) tag, the apparatus comprising:

means for prompting a user to move an RFID reader, where the reader includes a module for determining a location or movement of the reader;

means for using an RFID transceiver having an antenna to transmit a first RFID interrogation signal;

means for calculating a first phase and a second phase for a tag signal sent by a tag in response to the first interrogation signal, wherein a first phase corresponds to the tag signal received at a first location of the antenna, and wherein the second phase corresponds to the tag signal received at a second location of the antenna;

means for calculating a trajectory or locations of the moving reader using data from the module for determining a location or movement of the reader;

means for determining a location for the tag using the calculated trajectory or positions and the calculated first phase and second phase for the tag.

17. An RFID (radio frequency identification) reader comprising:

a location or movement determination component configured to measure location or acceleration of the reader in three dimensions;

at least one RFID radio having a first antenna;

at least one data memory component;

at least one input/output component configured to prompt a user to move the reader; and

at least one processor coupled among the location or movement determination component, the RFID radio, the data memory component, and the input/output component, wherein the processor is configured to;

transmit a first RF (radio frequency) query using the RFID radio;

calculate a first phase and a second phase for a tag signal sent by a tag in response to the first RF query, wherein a first phase corresponds to the tag signal received at a first position of the first antenna, and wherein the second phase corresponds to the tag signal received at a second position of the first antenna;

calculate a trajectory or positions of the moving reader using data from the location or movement determination component; and

determine a bearing for the tag using the calculated trajectory or positions and the calculated first phase and second phase for the tag,

wherein the system determines whether to take more tag signal readings based on whether a minimum level of confidence has been reached, and wherein the RFID radio transmits on a different frequency when the minimum level of confidence is not achieved within a predetermined time period.

18. An RFID (radio frequency identification) reader comprising:

at least one RFID radio having a first antenna;

at least one data memory component;

at least one input/output component configured to prompt a user to move the reader in a first direction; and

at least one processor coupled among the RFID radio, the data memory component, and the input/output component, wherein the processor is configured to;

transmit a first RF (radio frequency) query using the RFID radio;

calculate a first phase and a second phase for a tag signal sent by a tag in response to the first RF query, wherein a first phase corresponds to the tag signal received at a first position of the first antenna, and wherein the second phase corresponds to the tag signal received at a second position of the first antenna, and wherein the first and second positions correspond to movement of the reader in the first direction;

calculate a change of phase of the tag signal as a function of time using the first phase and the second phase; and

determine a location of the tag relative to the movement direction of the reader based on the calculated change of phase as a function of time,

wherein the input/output component is configured to emit a series of sounds, wherein characteristics of the series of sounds are controlled by the processor, and further wherein the processor is configured to change a period of repetition of the sounds in the series or a frequency of the series of sounds based upon the change of phase.