STEERABLE PHASE ARRAY ANTENNA RFID TAG LOCATER AND TRACKING SYSTEM AND METHODS

• US 20100207738A1
• Filed: 09/09/2008
• Published: 08/19/2010
• Est. Priority Date: 09/11/2007
• Status: Active Grant

• Current Assignee: RF Controls LLC
• Original Assignee: RF Controls LLC
• Inventors: Bloy, Graham P.
• Granted Patent: US 8,344,858 B2
• Time in Patent Office: Days
• US Class Current: 340/10.300
• CPC Class Codes: G01S 13/76 wherein pulse-type signals are transmitted
• CPC Class Codes: G01S 13/878 Combination of several spaced transmitters or receivers of known location for determining the position of a transponder or a reflector G01S13/874 takes precedence
• CPC Class Codes: G01S 5/0218 Multipath in signal reception
• CPC Class Codes: G01S 5/04 Position of source determined by a plurality of spaced direction-finders
• CPC Class Codes: G01S 5/12 by co-ordinating position lines of different shape, e.g. hyperbolic, circular, elliptical or radial
• CPC Class Codes: G06K 7/01 Details
• CPC Class Codes: G06K 7/10079 the collision being resolved in the spatial domain, e.g. temporary shields for blindfolding the interrogator in specific directions
• CPC Class Codes: G08B 13/2462 Asset location systems combined with EAS inventory, tracking, logistic G06Q10/00; entrance control systems G07C9/00
• CPC Class Codes: H01Q 1/2216 used in interrogator/reader equipment
• CPC Class Codes: H01Q 3/36 with variable phase-shifters

Abstract

A system for and method of tracking and locating RFID tags, including where at least one steerable phase array antenna may locate the tags associated with items in three dimensions in real time, through the use of a beam steering unit and controller therewith to control the direction of a beam launched by the at least one steerable phase array antenna.

Claims

1. An RFID tag locater and tracking system, comprising:

a phase array steerable antenna provided with a plurality of antenna elements;

an RFID reader in operative communication with the phase array steerable antenna;

a beam steering unit in operative communication with the plurality of antenna elements;

a beam steering unit controller in operative communication with the beam steering unit; and

a control computer in operative communication with the beam steering unit controller.

2. An RFID tag locater and tracking system as claimed in claim 1 wherein the plurality of antenna elements includes at least one circularly polarized patch antenna;

and

the phase steerable antenna having at least one independently controllable channel.

3. An RFID tag locater and tracking system as claimed in claim 2 wherein the phase array steerable antenna, the RFID reader, the beam steering unit and the beam steering unit controller are integrated into a module having a common enclosure.

4. An RFID tag locater and tracking system as claimed in claim 1 wherein the beam steering unit and the beam steering unit controller cooperate and control the phase array steerable antenna in more than one axis.

5. An RFID tag locater and tracking system as claimed in claim 1 wherein the RFID reader generates an RF beam to obtain a response from the RFID tag so as to calculate a distance between the RFID tag and a reference point.

6. An RFID tag locater and tracking system as claimed in claim 1 wherein the RFID reader generates an RF beam to obtain a response from the RFID tag so as to calculate a direction between the RFID tag and a reference point.

7. An RFID tag locater and tracking system as claimed in claim 1 wherein the RFID reader generates an RF beam to obtain the response from the RFID tag to calculate and track a real time location of the RFID tag relative to a reference point.

8. An method of locating and tracking an RFID tag, the steps comprising:

providing a phase array steerable antenna;

providing an RFID reader in operative communication with the phase array steerable antenna;

providing a beam steering unit in operative communication with the phase array steerable antenna;

providing a beam steering unit controller in operative communication with the beam steering unit;

providing a control computer in operative communication with the beam steering unit controller;

generating a protocol specific RFID RF waveform and launching it via the phase array steerable antenna; and

interrogating the RFID tag.

9. The method of claim 8, further comprising transmitting the protocol specific RFID RF waveform from the RFID reader through an attenuator and a power amplifier.

10. The method of claim 8, wherein the phase array steerable antenna is comprised of at least one operative circularly polarized patch antenna with an independently controllable channel;

and

the at least one operative controllable channel is controlled independently.

11. The method of claim 8, further comprising controlling the phase array steerable antenna in more than one axis.

12. The method of claim 8, further comprising controlling the phase array steerable antenna in two axes.

13. The method of claim 8, further comprising:

obtaining the response from the RFID tag; and

calculating a distance between the RFID tag and a reference point.

14. The method of claim 8, further comprising:

obtaining the response from the RFID tag; and

calculating a direction between the RFID tag and a reference point.

15. The method of claim 8, further comprising:

obtaining the response from the RFID tag; and

calculating a location relative to the RFID tag and a reference point.

16. A method of locating and tracking an RFID tag in an environment in which Electronic Price Codes are used, the steps comprising:

calibrating at least two phase array steerable antennas to optimally align the antennas with known global coordinates;

configuring an RFID reader for a working environment;

performing a two-dimensional raster scan of a visible area of the working environment with a first antenna;

calculating a minimal covering of the visible area with one or more beam areas;

defining a set of steering directions for raster scans;

using the first antenna to determine if one or more RFID tags are present in the beam areas;

saving a list of electronic price codes;

estimating an expected location for at least one RFID tag in the beam area;

projecting the expected location of the RFID tag into global coordinates;

estimating the most probable conjugate pairing (“

PGPt1”

);

calculating a most likely location of the RFID tag'"'"'s projection in global coordinates relative to a second antenna (“

PGPt2”

) using an estimated random distribution of RFID tag heights and PGPt1;

calculating a projection in global coordinates inverse of PGPt2 so as to yield a most probable steering direction for the second antenna;

reading with the other antenna in the direction indicated by a plane point projection of PGPt2;

triangulating any RFID tag seen by the other antenna using PGPt 1. and PGPt2;

triangulating using PGPt1 and PGPt2 if the RFID tag is not seen by the other antenna, as this location is still highly probable as a location for the RFID tag;

and repeating these steps for each beam area.

18. A method of locating and tracking an RFID tag, comprising the steps of:

scanning an operating environment with a first steerable signal beam interrogation signal from a first phase array steerable antenna;

storing RFID tag response signals in a data matrix including a direction vector of the first steerable signal beam when each response signal is received and an identification of the RFID tag providing the response signal;

scanning a subset area of an operating environment of a second steerable signal beam interrogation signal from a second phase array steerable antenna;

storing RFID tag response signals in a data matrix including a direction vector of the second steerable signal beam when each response signal is received and an identification of the RFID tag providing the response signal; and

triangulating a response signal origin location for each response signal where the identification is the same.

17. A method according to claim 18, further comprising:

estimating a time range over which the RFID tag was seen using data collected for the RFID tag;

fitting a model to (x,y,z,t) data produced by conjugated raster scans using Iterative Weighted Robust Least Squares Estimation;

calculating an RFID tag trajectory over the time interval t using an estimated model of the RFID tag'"'"'s motion; and

tracking the RFID tag'"'"'s direction using derivatives of the RFID tag trajectory.

19. The method of claim 18, wherein the data matrix resides in a control computer.

20. The method of claim 18, wherein the data matrix for each response signal includes a time of reception.

21. The method of claim 18, wherein successive scans over time are each stored in the data matrix.

22. The method of claim 18, wherein the data matrix is analyzed to identify and flag any pseudo emitter response signals that are received;

the pseudo emitter response signals being any signal within a group of response signals having a common identification that are not the response signal with the shortest time between the interrogation signal launch and reception of the response signal.

23. The method of claim 18, wherein a return signal strength indicator associated with each response signal is stored in the data matrix.