`(12) Patent Application Publication (10) Pub. No.: US 2010/0207738 A1
`Bloy
`(43) Pub. Date:
`Aug. 19, 2010
`
`US 2010020773 8A1
`
`(75)
`
`Inventor:
`
`(54) STEERABLE PHASE ARRAY ANTENNA RFID
`TAG LOCATER AND TRACKING SYSTEM
`AND N“? THODQ
`‘
`‘
`Graham P. Bloy, St. Louis, MO
`US
`(
`)
`Correspondence Address:
`BABCOCK 11’: PLLC
`1’-0-BOX 433
`BRIDGMAN, MI 49106 (Us)
`
`Related U.S. Application Data
`
`Provisional application No. 60/993,418, filed on Sep.
`11, 2007.
`
`Publication Classification
`
`Int CL
`H04Q 5/22
`H01Q 3/00
`
`(2006.01)
`(2006.01)
`
`Assignee;
`
`R1: CONTROLS, LLC, st. Louis,
`MO (US)
`
`(52) U.S. Cl.
`
`...................................... .. 340/10.3; 342/368
`
`Appl. No.2
`
`12/675,527
`
`(57)
`
`ABSTRACT
`
`PCT Filed:
`
`PCT NO .3
`
`§ 37] (c)(1),
`(2), (4) Date;
`
`Sep_ 9, 2008
`
`PC T/[B03/53 643
`
`Feb, 26, 2010
`
`A system for and method oftracking 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.
`
`RFC - Exhibit 1011
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`STEERABLE PHASE ARRAY ANTENNA RFID
`TAG LOCATER AND TRACKING SYSTEM
`AND METHODS
`
`CROSS REFERENCE TO RELATED
`APPLICATIONS
`
`[0001] This application claims the benefit of U.S. Provi-
`sional Patent Application No. 60/993,418, titled “Steerable
`Phase Array Antenna RFID Tag Locator and Tracking Sys-
`tem”, filed by Graham P. Bloy on Sep. 11, 2007 and Interna-
`tional Patent Application No.: PCT/IB2008/053643, titled
`“Steerable Phase Array Antenna RFID Tag Locater and
`Tracking System and Methods”, filed by Graham P. Bloy on
`Sep. 9, 2008, both applications hereby incorporated by refer-
`ence in their entirety.
`
`FIELD OF THE INVENTION
`
`[0002] The present invention relates to a steerable phase
`array antenna RFID tag locater and tracking system. More
`particularly, the system comprising at least one steerable
`phase array antenna, RFID reader and a controller to acquire,
`locate and track RFID tags.
`
`BACKGROUND OF THE INVENTION
`
`[0003] Conventional RFID readers can read tags at dis-
`tances less than desired by the RFID tag user. Multiple RFID
`tags in a particular location or volume, such as a warehouse,
`are inherently difficult to locate or track. When RFID tags are
`in proximity to one another (the proximity varying, for
`example, due to RFID tag type or conditions within the space
`in which they are located or conditions in the surrounding
`space or both), that is a multipath environment, conventional
`RFID readers cannot locate the RFID tags with acceptable
`precision. Furthermore, conventional systems cannot track
`the three dimensional movement of RFID tags with any pre-
`cision, if at all.
`[0004] Therefore, it is an object of the invention to provide
`a system and method(s) that overcomes deficiencies in the
`prior art.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0005] The accompanying drawings, which are incorpo-
`rated in and constitute a part of this specification, illustrate
`embodiments of the invention and, together with a general
`description of the invention given above, and the detailed
`description of the embodiments given below, serve to explain
`the principles of the invention.
`[0006]
`FIG. 1 is an exemplary top level system block dia-
`gram of an ITCS with a single SASL.
`[0007]
`FIG. 2 is an alternative exemplary system diagram
`illustrating communications and or signal interconnections of
`an ITCS including two SASL. One of the SASL showing
`exemplary internal connections, the other provided in only
`block form.
`
`FIG. 3 is an alternative exemplary system diagram
`[0008]
`illustrating communications and or signal interconnections of
`an ITCS including two SASL with direct interconnection
`between the RFID reader and the control computer. One of
`the SASL showing exemplary intemal connections, the other
`provided in only block form.
`[0009]
`FIG. 4 is an exemplary block diagram of a multiple
`SASL configuration.
`
`FIG. 5 is an exemplary diagram showing multiple
`[0010]
`SASL oriented to face a common operating environment.
`[0011]
`FIG. 6 is an exemplary method diagram for RFID
`location using an ITCS with at least two SASL.
`
`DETAILED DESCRIPTION OF THE INVENTION
`
`[0012] The inventor has developed an RF signal intelligent
`tracking and control system (ITCS) 10, for example as gen-
`erally shown in FIG. 1 and in higher detail in FIGS. 2 and 3,
`including a phase array steerable antenna 15; an RFID reader
`20 in operative communication with the phase array steerable
`antenna 15; a beam steering unit (BSU) 25, in operative
`communication with the phase array steerable antenna 15; a
`BSU controller 30 in operative communication with the BSU
`25; and a control computer 35 in operative communication
`with the BSU controller 30. An operator interface 37, such as
`a display and or control panel may be coupled to the control
`computer 35. The operator interface 37 may be local to the
`installation or remotely coupled, via a proprietary network
`and or the internet.
`
`[0013] The phase array steerable antenna 15 is comprised
`of at least one antenna element 65, for example a circularly
`polarized patch antenna element 65, and preferably includes
`a plurality of circularly polarized patch antenna element(s)
`65, for example 32 antenna element(s) 65. At least one of the
`antenna element(s) 65 is configured as an independently con-
`trollable channel.
`
`[0014] An amplification sub system 40 including, for
`example, an amplifier 45, attenuator 50 and circulator 55 may
`be applied between the RFID reader 20 and a power splitter
`60 coupled to the individual antenna element(s) 65 of the
`phase array steerable antenna 15 to drive the interrogation
`signal at a desired power level and wave format.
`[0015] The BSU 25 may include control circuitry driving a
`plurality of individual phase shifter(s) 70,
`the individual
`phase shifter(s) 70 coupled in-line between the power splitter/
`combiner 60 and the individual antenna elements 65 and or
`
`groups of the antenna elements 65, enabling antenna beam
`steering from the phase array steerable antenna 15 surface via
`purely electrical means.
`[0016] The BSU 25 and the BSU controller 30 indepen-
`dently control the beam direction of each independently con-
`trollable channel, for example in more than one axis, and
`preferably the BSU 25 and the BSU controller 30 cooperate
`and control the phase array steerable antenna 15 in two axes.
`[0017] The RFID reader 20 may be a single channel RFID
`reader. The RFID reader 20 generates a RF beam comprised
`of the independently controllable channel(s) capable of
`obtaining a response from or otherwise interrogating an RFID
`tag 85, such as via back scatter modulation, and thereby
`reading the RFID tag 85.
`[0018] The RFID reader 20 generates the RF beam to
`obtain the response from the RFID tag 85 so as to calculate
`one and or each of a distance between the RFID tag 85 and a
`reference point; to calculate a direction between the RFID tag
`85 and the reference point; to calculate and track a location
`relative to the RFID tag 85 and the reference point.
`signifi-
`[0019]
`To improve manufacturing efiiciencies,
`cantly simplify system installation and or for ease of system
`configuration, elements of the system may be integrated to
`form a signal acquisition and source location module (SASL)
`75 that incorporates the phase array steerable antenna 15,
`beam steering unit 25 and beam steering controller 30 into a
`single module. Alternatively, the SASL 75 may also include
`
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`the RFID reader 20 operative to transmit an interrogation
`signal beam on a desired frequency or frequency band and to
`receive one or more response signals on a desired frequency
`or frequency band via the phase array steerable antenna. The
`interrogation signal and response signal frequency(s) and or
`frequency band(s) may be configured to a common frequency
`or frequency band according to the signal parameters the
`system is configured for use with.
`[0020] An ITCS 10 may include one or more spaced apart
`SASL 75 arranged, for example at a ceiling or other elevated
`location, to face a desired target area, as shown for example in
`FIG. 4, each of the SASL 75 communicating with and being
`controlled by the control computer 35 over a control and or
`data communications link. Where multiple SASL 75 are used,
`the communications link with the control computer 35 may
`be established with the assistance of a network switch 77 or
`router, such as an Ethernet 10/100/1000 MB network switch.
`[0021] A power supply 70 configured to supply desired
`power levels to individual power consumers of the system
`may be integrated within the SASL or alternatively remotely
`mounted. The power supply 70 may be applied as a single
`centralized unit providing a range of different voltages to the
`various consumers or alternatively as a plurality of discrete
`power supplies each dedicated to generating a desired power
`level for each consumer.
`
`[0022] The phase array steerable antenna 15 launches a
`steerable signal beam that may be configured for a narrow and
`or focused beam pattern. Once an ITCS 10 is calibrated for a
`specific installation configuration and operating environ-
`ment, the three dimensional coordinates of the signal beam
`are known. Via location triangulation, measurement of return
`signal strength indication and or response times between
`launching of the interrogation signal(s) and detecting a back-
`scatter modulation signal or other response from an RFID tag
`85, the ITCS permits the operator thereof to find RFID tag(s)
`85 in three dimensions, in time.
`[0023]
`In one embodiment of the system of the present
`invention, a single channel RFID reader 20 interrogates the
`RFID tag(s) 85 via a directional beam of the phased array
`steerable antenna 15 while a BSU 25 controls the beam direc-
`
`tion. The beam may be controlled in two axes by an array of
`antenna elements 65 such as, for example, circularly polar-
`ized patch antennas. The direction of the beam being formed
`may be based on the general orientation of the phase array
`steerable antenna 15 and more finely via a relative phase of
`each signal from the RFID reader 20 to the various individual
`antenna element(s) 65 ofthe phase array steerable antenna 15,
`and each ofthe charmels is independently controllable via the
`BSU 25. The BSU Controller 30 commands the RFID reader
`
`20 to interrogate the RFID tag(s) 85 by generating the proto-
`col specific for the particular RFID radio frequency wave-
`form of the target RFID tag(s) 85. The waveform may be
`transmitted through an attenuator 50 and or power amplified
`via an amplifier 45 to provide a predetermined power level to
`each phase array steerable antenna 15.
`[0024] The control
`instructions for and or signal data
`received by the RFID reader 20 may be communicated via a
`network data communications link such as Ethernet or and a
`
`direct connection serial communication protocol such as
`RS-232 directly between the RFID reader 20 and the control
`computer 35 or alternatively between the RFID reader 20 and
`the control computer 35 via the BSU controller 30.
`[0025] Capabilities and or applications of the ITCS 10
`include the three dimensional spatial location of one or more
`
`RFID tag(s) 85; tracking of RFID tag(s) 85 via two or more
`antennas; tracking RFID tag(s) 85 in motion, for example
`along a moving conveyor belt; and, track and triangulate tags
`throughout a space, for example throughout an office or pub-
`lic space, backroom area of a warehouse, retail establishment
`or the like.
`
`[0026] An ITCS 10 including at least first and second SASL
`75, as shown for example in FIG. 5, may be operated accord-
`ing to an exemplary method as shown in FIG. 6. After con-
`figuration to the operating environment 90 for example by
`recording signal responses from sample RFID tags positioned
`at a range ofknown locations and distances across the desired
`operating environment 90, the operating environment 90 may
`be divided into a matrix of antenna beam direction vectors
`
`which when successively stepped through one after another
`results in a full scan of the operating environment 90.
`[0027] With configuration to the operating environment 90
`completed, the operating environment 90 may be scanned by
`a first steerable signal beam interrogation signal from a first
`SASL 75. To perform a scan, the antenna signal beam is
`stepped incrementally through each of the direction vectors,
`in step 100. Any RFID tag response signals received at each
`direction vector is stored in a data matrix including, for
`example, a direction vector (thetal, phil) ofthe first steerable
`signal beam when each response signal is received, an iden-
`tification of the RFID tag providing the response signal and a
`return signal strength indicator (RSSI), at step 110. Altema-
`tively and or additionally, the data matrix may include signal-
`timing data, such as a time delay between launch of the
`interrogation signal and reception of each response signal.
`[0028] Calculations based upon the data matrix received
`signal data enables generation of an estimated location of
`each RFID transponder, for example in global coordinates, at
`step 120, also stored in the data matrix. For example, where
`the direction vector ofthe interrogation signal that resulted in
`the strongest RSSI from a single RFID tag is known, the RSSI
`associated with that direction vector for the single RFID tag
`may be compared to values obtained during system configu-
`ration to identify a distance along the direction vector from
`the antenna, where the RFID tag is expected to be. Signal
`timing data, if available, can be similarly applied to estimate
`the position of the RFID tag along the direction vector.
`[0029]
`For each estimated location of an RFID tag obtained
`in step 120, a second SASL 75 may be directed to scan a
`subset area ofthe second SASL 75 operating environment 90,
`in step 130, the selected subset centered, for example, upon
`the estimated location translated to the second SASL 75
`
`direction vector(s) by conjugate pairing upon the global co-
`ordinates defined with respect to the first SASL 75 in step
`120. Alternatively, the selected scan subset area may be along
`a widened path of the associated direction vector of the first
`SASL 75, or a portion thereof guided by the RSSI value
`distance from antenna estimation. The scan results of the
`
`subset area are similarly processed into a data matrix in step
`140.
`
`[0030] Because the second SASL 75 scans a subset of its
`operating environment 90, guided by the first SASL 75 result,
`the number of direction vectors stepped through and thus the
`overall scan time is significantly reduced.
`[0031] After each ofthe RFID tag estimated location subset
`scans of step 130 are completed, two estimated locations for
`each RFID tag have been stored into a data matrix. Triangu-
`lation calculations based upon the positions of each SASL 75
`and the direction vector of each when obtaining the highest
`
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`RSS1 may be performed to obtain another estimated location
`of each RFID tag, at step 150.
`[0032] A comparison between the three calculated posi-
`tions of each RFID tag that has been obtained may be used to
`generate a reliability factor for the position result and or
`generate a final averaged position of each RFID tag for output
`to the user and or further processing, at step 160, whereupon
`the system returns to step 100 to perform another scan
`sequence.
`[0033] The results of further scan sequences may be
`applied wherein the interrogation signal(s) are simulta-
`neously directed at global coordinates of likely RFID tag
`response signal origin locations to confirm projected tag loca-
`tions with the benefit of a focused interrogation beam from
`each of the multiple SASL 75.
`[0034] As the data matrix is updated and projected tag
`locations stored with respect to ongoing scans, changes in
`projected tag locations may be analyzed to identify RFID tags
`that are in motion, including speed and direction. Error cor-
`rection may be applied to the data matrix origin location
`patterns, such as iterative weighted robust least squares esti-
`mation to improve the accuracy of traj ectory estimates, from
`which directional tracking may be derived via derivatives of
`the trajectory results.
`[0035] Analysis of the results stored in the data matrix may
`be performed, for example with respect to maximum RSS1
`value and or a time of signal reception associated with each
`response signal having the same RFID tag identifier that is
`received, to identify and flag pseudo emitter signal responses,
`for example generated by reflections of the actual signal
`response that travel farther and thus arrive later and with a
`lower RSS1, within the operating environment 90.
`[0036] By focusing the directional antenna signal bearn(s),
`including applying interrogation signals from multiple SASL
`(s) 75 upon a common coordinate in space, the RFID tag(s)
`can also be communicated with at increased distances, with-
`out exceeding allowable power levels.
`[0037]
`It is known and understood by those ofordinary skill
`in the art that, as used herein, references to the tracking of
`RFID tag(s) 85 encompasses the tracking of items, including
`retail items, which have been afiixed with or otherwise physi-
`cally associated with an RFID tag 85.
`[0038] An alternative method of locating and tracking an
`RFID tag 85 includes, the following steps: providing a phase
`array steerable antenna 15; providing an RFID reader 20 in
`operative communication with the phase array steerable
`antenna 15 and capable of generating a protocol specific
`RF1D RF waveform; providing a BSU 25 in operative com-
`munication with the phase array steerable antenna 15; pro-
`viding a beam steering unit controller 30 in operative com-
`munication with the beam steering unit 25; providing a
`control computer 35 in operative communication with the
`beam steering unit controller 30; generating a RF beam; and,
`generating a response, reading and or interrogating an RFID
`tag 85.
`Further additional and or alternative steps that may
`[0039]
`each be separately included in the above method may include
`transmitting the protocol
`specific RF1D RF waveform
`through an attenuator 50 and or power amplifier 45; creating
`an RF beam, the RF beam preferably having maximum allow-
`able power at the phase array steerable antenna 15. Queries
`may be made via RFID reader 20 under the control of the
`control computer 35; controlling at least one operative con-
`trollable channel independently; operating the beam steering
`
`unit 25 and the beam steering unit controller 30 cooperatively
`to direct the signal beam of the phase array steerable antenna
`15 in more than one axis, and preferably comprises control-
`ling the phase array steerable antenna 15 in two axes.
`[0040] Additional steps related to locating the RFID tag 85
`based upon the response may include calculating a distance
`between the RFID tag 85 and the reference point and or
`tracking sequential location(s) of the RFID tag 85 relative to
`the reference point.
`[0041] Additional steps related to directionality of the RF
`beam may include controlling the BSU 25 with the BSU
`controller 30; controlling the RF beam with the BSU 25 so as
`to control the direction ofthe RF beam; controlling the physi-
`cal orientation of the phase array steerable antenna 15; pro-
`viding communication between the beam steering unit con-
`troller 30 and the control computer 35 via Ethernet; and or
`providing communication between the beam steering unit
`controller 30 and the RFID reader 20 via a serial communi-
`
`cations protocol such as RS-232.
`[0042] Additional steps related to an at least two phased
`array steerable antenna 15 embodiment wherein RFID tag
`data is associated with Electronic Price Codes (EPC’s)
`includes: calibrating the at least two phase array steerable
`antennas 15 to optimally align the antennas 15 with known
`global coordinates; configuring an RFID reader 20 to the
`nature of its working environment; performing a two-dimen-
`sional raster scan of a visible area with one antenna 15;
`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 one antenna to determine if one or more
`RFID tags are present in the beam areas; saving a list of
`EPC’s; estimating an expected location for at least one RFID
`tag in the one or more beam areas; 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 the other 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 other antenna; reading with the other antenna in the direc-
`tion indicated by a plane point projection of PGPt2; triangu-
`lating any RFID tag seen by the other antenna using PGPt1
`and PGPt2; triangulating using PGPt1 and PGPt2 ifthe 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.
`[0043] The above embodiment may further comprise post-
`processing with respect to stored intermediate and or histori-
`cal data as needed, such as: 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 con-
`jugated raster scans using, for example, 1terative 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.
`[0044]
`1n an embodiment ofthe present invention the phase
`array steerable antenna(s) 15 and RFID tag may communi-
`cate at a distance of over twenty feet, preferably at a distance
`of over forty feet, more preferably at a distance of over fifty
`feet, and even more preferably at a distance of over sixty feet.
`[0045]
`It is understood by those of ordinary skill in the art
`that certain regulatory authorities have set standards and
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`regulations regarding maximum allowable power to certain
`types of antennae, such agencies including but not limited to
`the Federal Communications Commission (“FCC”). While
`the FCC promulgates such regulations, those regulations are
`not
`limiting herein, and the present
`invention explicitly
`encompasses all suitable values of power.
`[0046]
`It is known and understood by those ofordinary skill
`in the art that, as used herein, references to beam areas and or
`patterns may include ellipses, which may encompass circles.
`Further, the beam pattem(s) may have a shape other than an
`ellipse.
`[0047] One skilled in the art will recognize that the present
`invention provides numerous advantages, besides the method
`(s) of operation herein above, including the ease of installa-
`tion and greatly simplified power and or communications
`interconnection requirements provided by the SASL 75
`according to the invention.
`[0048] Another advantage of the present invention is flex-
`ibility realized by the ease with which multiple SASL 75 may
`each be utilized under the direction of a central control com-
`
`puter 35 to increase the size of the overall area being moni-
`tored, to provide additional data points for improving the
`accuracy ofthe triangulation calculations and also to increase
`the number of interrogation signals and thereby the resulting
`signal power level that may be focused upon a single point in
`space.
`Still another advantage ofthe present invention is to
`[0049]
`provide the combination of a steerable phase array antenna
`and an RFID reader to generate a radio frequency (“RF”) to
`interrogate and read RFID tags,
`to achieve significantly
`improved multipath immunity.
`
`Table of Parts
`
`intelligent tracking and control system
`phase array steerable antenna
`RFID reader
`beam steering unit
`beam steering unit controller
`control computer
`operator interface
`amplification subsystem
`amplifier
`attenuator
`circulator
`power splitter/combiner
`antenna element
`phase shifter
`signal acquisition and source location module
`network switch
`power supply
`RFID tag
`operating environment
`
`10
`15
`20
`25
`30
`35
`37
`40
`45
`50
`55
`60
`65
`70
`75
`77
`80
`85
`90
`
`[0050] Where in the foregoing description reference has
`been made to ratios, integers, components or modules having
`known equivalents then such equivalents are herein incorpo-
`rated as if individually set forth.
`[0051] While the present invention has been illustrated by
`the description of the embodiments thereof, and while the
`embodiments have been described in considerable detail, it is
`not the intention ofthe applicant to restrict or in any way limit
`the scope of the appended claims to such detail. Additional
`advantages and modifications will readily appear to those
`skilled in the art. Therefore, the invention in its broader
`aspects is not limited to the specific details, representative
`
`11
`
`apparatus, methods, and illustrative examples shown and
`described. Accordingly, departures may be made from such
`details without departure from the spirit or scope of appli-
`cant’s general inventive concept. Further, it is to be appreci-
`ated that improvements and/or modifications may be made
`thereto without departing from the scope or spirit of the
`present invention as defined by the following claims.
`What is claimed is:
`
`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 indepen-
`dently 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 com-
`munication 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.
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`Aug. 19, 2010
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`10. The method of claim 8, wherein the phase array steer-
`able antenna is comprised of at least one operative circularly
`polarized patch antenna with an independently controllable
`channel; and
`the at least one operative controllable charmel 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 refer-
`ence 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 refer-
`ence 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 refer-
`ence 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 coordi-
`nates;
`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 ofthe RFID tag into global
`coordinates;
`estimating the most probable conjugate pairing (“PGPt1”);
`calculating a most likely location of the RFID tag’s projec-
`tion 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 proj ection of PGPt2;
`triangulating any RFID tag seen by the other antenna using
`PGPt 1. and PGPt2;
`
`triangulating using PGPt1 and PGPt2 ifthe 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.
`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.
`18. A method of locating and tracking an RFID tag, com-
`prising the steps of:
`scarming 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 includ-
`ing a direction vector of the first steerable signal beam
`when each response signal is received and an identifica-
`tion of the RFID tag providing the response signal;
`scarming 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 includ-
`ing a direction vector of the second steerable signal
`beam when each response signal is received and an
`identi