WO2014155204A1 - Rfid reader and method for discriminating rfid tags installed on adjacent container units or the likes - Google Patents

Rfid reader and method for discriminating rfid tags installed on adjacent container units or the likes Download PDF

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Publication number
WO2014155204A1
WO2014155204A1 PCT/IB2014/000710 IB2014000710W WO2014155204A1 WO 2014155204 A1 WO2014155204 A1 WO 2014155204A1 IB 2014000710 W IB2014000710 W IB 2014000710W WO 2014155204 A1 WO2014155204 A1 WO 2014155204A1
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WO
WIPO (PCT)
Prior art keywords
rfid tag
reader
elevation
rfid
array
Prior art date
Application number
PCT/IB2014/000710
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French (fr)
Inventor
Pierre DUPRÉ
Original Assignee
International Rfid Solutions Sas
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Publication date
Application filed by International Rfid Solutions Sas filed Critical International Rfid Solutions Sas
Publication of WO2014155204A1 publication Critical patent/WO2014155204A1/en

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Classifications

    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
    • G06K7/0008—General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K17/00—Methods or arrangements for effecting co-operative working between equipments covered by two or more of main groups G06K1/00 - G06K15/00, e.g. automatic card files incorporating conveying and reading operations
    • G06K17/0022—Methods or arrangements for effecting co-operative working between equipments covered by two or more of main groups G06K1/00 - G06K15/00, e.g. automatic card files incorporating conveying and reading operations arrangements or provisions for transferring data to distant stations, e.g. from a sensing device
    • G06K17/0029—Methods or arrangements for effecting co-operative working between equipments covered by two or more of main groups G06K1/00 - G06K15/00, e.g. automatic card files incorporating conveying and reading operations arrangements or provisions for transferring data to distant stations, e.g. from a sensing device the arrangement being specially adapted for wireless interrogation of grouped or bundled articles tagged with wireless record carriers
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
    • G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
    • G06K7/10009—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves
    • G06K7/10019—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves resolving collision on the communication channels between simultaneously or concurrently interrogated record carriers.
    • G06K7/10079—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves resolving collision on the communication channels between simultaneously or concurrently interrogated record carriers. the collision being resolved in the spatial domain, e.g. temporary shields for blindfolding the interrogator in specific directions
    • G06K7/10089—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves resolving collision on the communication channels between simultaneously or concurrently interrogated record carriers. the collision being resolved in the spatial domain, e.g. temporary shields for blindfolding the interrogator in specific directions the interrogation device using at least one directional antenna or directional interrogation field to resolve the collision
    • G06K7/10099—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves resolving collision on the communication channels between simultaneously or concurrently interrogated record carriers. the collision being resolved in the spatial domain, e.g. temporary shields for blindfolding the interrogator in specific directions the interrogation device using at least one directional antenna or directional interrogation field to resolve the collision the directional field being used for pinpointing the location of the record carrier, e.g. for finding or locating an RFID tag amongst a plurality of RFID tags, each RFID tag being associated with an object, e.g. for physically locating the RFID tagged object in a warehouse
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
    • G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
    • G06K7/10009—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves
    • G06K7/10366—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves the interrogation device being adapted for miscellaneous applications
    • G06K7/10376—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves the interrogation device being adapted for miscellaneous applications the interrogation device being adapted for being moveable
    • G06K7/10386—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves the interrogation device being adapted for miscellaneous applications the interrogation device being adapted for being moveable the interrogation device being of the portable or hand-handheld type, e.g. incorporated in ubiquitous hand-held devices such as PDA or mobile phone, or in the form of a portable dedicated RFID reader
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q1/00—Details of, or arrangements associated with, antennas
    • H01Q1/12—Supports; Mounting means
    • H01Q1/22—Supports; Mounting means by structural association with other equipment or articles
    • H01Q1/2208—Supports; Mounting means by structural association with other equipment or articles associated with components used in interrogation type services, i.e. in systems for information exchange between an interrogator/reader and a tag/transponder, e.g. in Radio Frequency Identification [RFID] systems
    • H01Q1/2216—Supports; Mounting means by structural association with other equipment or articles associated with components used in interrogation type services, i.e. in systems for information exchange between an interrogator/reader and a tag/transponder, e.g. in Radio Frequency Identification [RFID] systems used in interrogator/reader equipment
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q21/00—Antenna arrays or systems
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01Q—ANTENNAS, i.e. RADIO AERIALS
    • H01Q25/00—Antennas or antenna systems providing at least two radiating patterns
    • H01Q25/02—Antennas or antenna systems providing at least two radiating patterns providing sum and difference patterns

Definitions

  • the present disclosure relates to the use of a mono-pulsed antenna on an RFID reader and methods to discriminate one RFID tag over a plurality of RFID tags being in the radio field at the same moment.
  • the present disclosure also relates to the UHF RFID ISO18000 standard.
  • UHF RFID has the advantage of allowing reading all the RFID tags that are present in the electromagnetic field of a reader's antennas.
  • that UHF RFID advantage become an inconvenient.
  • operators in non-automated station typically have to identify a single pack, container, bin or pallet for grading, calibrating, certifying, auditing or simply track the products that they contain. These tasks are conventionally accomplished by identifying the product or a group of products, one by one. To add to the challenge, in most processes, the containers are combined into greater units.
  • a simple solution to the above-described problems is to move the reader, or the reader's antenna, toward the targeted RFID tag until it is the only tag that the reader sees. Also, the use of a near field antenna allows to reduce the proximity of the antenna required to isolate a single RFID tag. Sometimes a combination of decreased distance or power and the change of antenna type is used to have a faster and more accurate RFID tag discrimination.
  • connection should be construed herein and in the appended claims broadly so as to include any cooperative or passive association between mechanical parts or components.
  • such parts may be connected together by direct coupling, or indirectly coupled using further parts therebetween.
  • Elevation should be construed broadly herein and in the appended claims so as to include “altitude or height above a fixed reference such as the ground” and the position along the conventional Y axis in mathematic.
  • the problem of discriminating from a distance a RFID tag among a plurality of other RFID tags is solved by providing a mono pulsed operating antenna array that operates within a predetermined angle range relative to the RFID tag and alternating a RFID module connected to the antenna array between mono and bi-static modes.
  • a UHF RFID (Ultra-High Frequency Radio-Frequency identification) tag reader that discriminates, from a distance, a selected RFID tag among a plurality of other RFID tags, the reader comprising:
  • a mono pulsed operating antenna array that operates within a predetermined angle range relative to the selected RFID tag
  • a RFID module coupled to the antenna array that alternates between mono and bi-static modes.
  • UHF RFID Ultra-High Frequency Radio-Frequency identification
  • an array of mono pulse antennas that generates elevation and transverse signals when the array of mono pulse antennas is oriented in a detecting direction relative to a RFID tag from a detecting distance therefrom; [0019] a coupler that is connected to the array of mono pulse antennas for receiving the elevation and transverse signals therefrom and for computing a sum and a difference thereof; and
  • a RFID module for operating alternatively between mono static and bi static modes for collecting the sum and difference of the elevation and transverse signals from the coupler and for generating a power signal indicative of the RFID tag.
  • a method for discriminating from a distance a selected UHF RFID (Ultra-High Frequency Radio-Frequency identification) tag among a plurality of other RFID tags comprising:
  • Embodiments of RFID tag discriminating method and system allow: • discriminating UHF RFID tags that are distanced from 0 mm to 5000 mm from the RFID reader, proportional with the distance between the RFID tags;
  • Figure 1 is a block diagram of a reader for discriminating a specific RFID tag among a plurality of RFID tags according to a first illustrated embodiment
  • Figure 2 is a schematic perspective view illustrating a typical use of the reader from Figure 1 ;
  • Figure 3 is a schematic perspective view illustrating the angles relation between the RFID reader from Figure 1 and a RFID tag targeted thereby;
  • Figure 4 is a block diagram illustrating the coupling of the antennas array to the micro ribbon coupler, both parts of the reader system from Figure 1 ;
  • Figure 5 is a schematic perspective view illustrating the radiation of a four-lobes mono-pulsed antenna used in conventional radar system ;
  • Figure 6 is a schematic perspective view illustrating the radiation of the four-lobe mono-pulsed antennas of the RFID reader from Figure 1 and a targeted RFID tag;
  • Figure 7 is a schematic view of the micro ribbon PC board, part of the reader from Figures 1 and 2;
  • Figure 8 is a graph illustrating the sum and difference responses of the output of the coupler from Figure 4.
  • Figure 9 is a schematic view illustrating the micro-ribbon coupler from Figure 4 coupled to the RFID module, both parts of the reader from Figures 1 and 2.
  • UHF RFID Ultra-High Frequency Radio-Frequency identification
  • the reader 10 is in the form of a handheld device embodying an array of mono pulse antennas 12, a coupler 14 that is coupled to the array of mono pulse antennas 12 for receiving elevation and transverse signals therefrom and for computing a sum and a difference thereof, and a bi-static UHF RFID tag reader module 16 for operating alternatively between mono static and bi static modes for collecting the sum and difference of the elevation and transverse signals from the coupler 14 and for generating a power signal indicative of the RFID tag 18.
  • the handheld device 10 further comprises an aiming device in the form of a laser pointer 20, a manual trigger 22, an orientation-determining device 24 and input/output devices 26.
  • Figure 2 illustrates, as a typical application of the reader 10, the use thereof for discriminating the RFID tag 18 affixed to one of many container bins 28, each having a RFID tag 30 secured thereto.
  • distances between the RFID tags 30 present in the matrix can be as low as 30 mm.
  • the operating distance between the targeted RFID tag 18 and the RFID reader 10 is directed by the ISO-18000-6 standard and can be up to 4000 mm in Europe and 5000 mm in America.
  • the handheld device 10 is further configured to inform the user when operational limitations are reached and to give instructions or provide feedback to the user to re-enter operational specifications.
  • the example shown in Figure 2 illustrates that the reader 10 allows discriminating, in Europe, a targeted tag 18 at a distance of 4000 mm from the RFID reader, if the tags 18 and 30 present in the matrix are separated by a minimum distance of 750 mm. This is considering that RFID tags 30 having a sensibility of -15dbm.
  • a further limitation relates to the angles in the x and y axis between the RFID reader 10 and the targeted RFID tag 18.
  • the array of antennas 12 includes four (4) mono pulsed antennas 32.
  • the choice of a four antennas array results from the type of RFID tag used.
  • another array of RFID antennas is used which includes another number of antennas, such as more than four antennas.
  • the mono pulsed antenna principles come from radar detection of objects. Such antennas work in the micro-wave frequency range.
  • Figure 5 illustrates such an antenna where the four (4) lobes (A, B, C and D) can target a plane many kilometers from the antennas.
  • Math and principles of mono pulsed antennas will now be described briefly. With reference to lobes positioning in Figure 6, the sum (S) of the lobes is given by the following equation:
  • the mono pulse principles are based on the fact that if we have two lobes slightly separated and a target 34 is placed exactly at the center of the lobes, that target will reflect the two lobes' signals equally. Therefore the difference of the two reflected signals will be 0. Using four lobes allows obtaining the elevation and transverse signals. Having the two signal differences at 0 allows to establish the actual position of the object 34. That relation is given by the following equation where d e i represent the elevation:
  • the two pairs of signals for the elevation can be expressed as:
  • d tr represents the transverse: 710
  • Each pair of antennas 32 is connected to the coupler 14 via a
  • Wilkinson divider 40 allow providing a suitable division of power radiation between each pair of antennas. Power lost induced by the Wilkinson divider 40 can be compensated by the static gain of the antennas 32 or/and the power of the RFID reader module 16.
  • the Wilkinson dividers 40 are omitted and the coupler 14 is configured to provide an equivalent division of power radiation between each pair of antennas.
  • the coupler 14 is in the form of a micro-ribbon coupler that meets mono pulsed antennas principles.
  • the micron ribbon coupler 14 includes an RF (Radio Frequency) circuit that allows to generate the sum and the difference signals from Si and S 2 .
  • RF couplers are normally designed with passive elements.
  • the RFID tag discriminating system 10 includes a network of capacitors and inductors so as to reduced the dimensions of the coupler 14.
  • micro ribbon coupler 14 is showed schematically in
  • Figure 7 includes the S1 input signal 2, the S2 input signal 4, the sum output 3 and the difference output .
  • the graphs from Figure 8 show the sum and difference curves depending on the variation of Dx or Dy.
  • Dx and Dy are near zero, the difference is very low and the sum is high. Such results are for an ideal operation.
  • Dx and Dy are never zero in typical operation of the system according to the first illustrated embodiment.
  • Figure 8 which results from operating the system 10 in a white room, shows that it is practically impossible to discriminate tags for values for Dx and Dy higher than ⁇ 40 degrees.
  • those angle limitations are of ⁇ 32 degrees for the best module and ⁇ 23 degree for the less preferred. This variation comes from a low power accuracy on Tx (transmission power) and a low precision in reading Rx (reception power) of theses UHF RF modules.
  • the handheld device 10 is configured to help the user positioning the device 10 relative to the RFID tag 18 so that the device 10 is within its operational range as described hereinabove.
  • the device 10 includes a conventional laser pointer 20 that is mounted to the device 10 so as to emit a laser beam in the center of the antennas array 12. That laser 20 allows the user pointing the RFID tag 18 that has to be discriminated in the matrix of tags 30 present in the antennas array field.
  • the laser pointer 20 can be actuated by the trigger 22 and is controlled by the software/firmware present in the handheld device 10 so that it stops at the moment the targeted RFID tag 18 has been discriminated.
  • the aiming device takes another form or is omitted.
  • the reader 10 further includes an output device 26 in the form of a two-tone beeper that is provided to indicate to the user when the reader 10 is out of its operational range.
  • a low tone is emitted by the beeper to indicate to the user that he/she is using the reader 10 out of its range of operation with regards to the angles Dx and/or Dy, such as when they are over ⁇ 36 degrees.
  • the reader 0 is also configured to emit a high tone when it is too far from the targeted tag 18 and that the user should reduce that distance.
  • the two-tone beeper is controlled by the software/firmware's provided in the PDA handheld.
  • the reader 10 further includes another output device in the form of a screen 42 to allow providing futher feedback to the user to help him position the reader 10 within operational range relative to the RFID tag 18 to discriminate.
  • buttons, dials, light-emitting diodes, etc. can also be provided on the device 10 to provide feedbacks or allow control thereof.
  • the reader 10 is also configured for storing information relative to the RFID tags read, and for communicating such information to a computer or another device.
  • the reader 10 further includes an orientation-determining system or mechanism 26.
  • Such system or mechanism allows detecting the values Dx and Dy, as illustrated in Figure 6 and includes, for example, a MEMS (micro-electromechanical system) gyroscope or/and accelerometer or/and magnetic compass or/and inclinometer.
  • MEMS micro-electromechanical system
  • gyroscope or/and accelerometer or/and magnetic compass or/and inclinometer.
  • Those devices are implemented in the reader 10 to evaluate angles of the RFID reader 10 in relation with the ground, in order to assess limitations of the reader 10 and to provide feedback to the user thereabout as mentioned hereinabove.
  • the values determined by the orientation- determining system 26 does not consider the orientation of the RFID targeted tag 18 in relation to the ground. Those angles, in certain case, can increase or decrease the performances of the RFID tag discriminating system. If fact the 36 degrees limitations for Dx and Dy relate to the angles between the RFID readers and the RFID tag ( Figure 6) and not with the ground.
  • the reader 10 embeds a software/firmware to further manage the operation of the MEMS detectors. Dx and Dy limitations are considered as post references in case of incapacity of the sum/difference outputs of the micron ribbon coupler 14 to discriminate the targeted tag 8 and that, after the power algorithms have been applied, which will be described hereinbelow in more detail.
  • the RFID tag discriminating system 10 allows Dx and a Dy deviation angles between -36 degrees and +36 degrees between the antennas 32 and the targeted tag 18. When those angles are exceeded, the system is configured to provide feedback to the user, for example via the display screen 42, as to how to realign the reader within the limitation angles.
  • the reader 10 further comprises a bi-static UHF RFID reader module 16.
  • the reader module 16 is coupled to the array of mono pulse antennas 12 via the micro ribbon coupler 14.
  • the module 16 operates alternatively between mono static and bi static modes for collecting the sum and difference of the elevation and transverse signals from the coupler and for generating a power signal indicative of the RFID tag 18.
  • the mono static mode is defined by the use of a single antenna port for the Tx (transmission) and Rx (reception) signals.
  • Mono static mode implies the use of an RF circulator that is normally not accessible.
  • Bi static mode includes the use of a first port for Tx and a second port for Rx. In order to collect the difference signal, which is the returning power from micro ribbon coupler output, only the Rx signal is collected from the RFID RF module 16. The sum of the micro ribbon coupler 14 outputs is read by a mono static RF port.
  • FIG. 9 illustrates how the RFID RF module 16 according to the first illustrated embodiment is connected.
  • the module 16 is configured to switch from mono static to bi static mode and inversely in less than 30 ms.
  • the RFID RF module 16 allows monitoring values of powers returned by the RFID tag 18.
  • RFID RF modules being commercially distributed, any RFID RF modules that respect the above specifications can be used.
  • RFID tag discriminating reader implement software/firmware algorithms that allow: • initiating the above-described RFID tag discriminating process:
  • the reader 10 is described as being in the form of a handheld device, it can take other forms more or less compact than the reader 10. Also, according to other embodiments (not shown), the UHF RFID tag reader is in the form of a system including a plurality of interconnected devices.

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Abstract

A UHF RFID (Ultra-High Frequency Radio-Frequency identification) tag reader, that operates under the ISO-18000-6 (EpcGlobal) RFID standard, includes an array of four mono frequency pulse antennas that generates elevation and transverse signals when it is oriented in a detecting direction relative to a RFID tag within a detecting distance therefrom. The UHF RFID tag reader further includes a micro ribbon coupler that receives the elevation and transverse signals from the antenna array and that computes a sum and a difference thereof. The reader also includes a RFID module that operates alternatively between mono static and bi static modes for collecting the sum and difference of the elevation and transverse signals from the coupler and for generating a power signal indicative of the RFID tag.

Description

TITLE
RFID READER AND METHOD FOR DISCRIMINATING RFID TAGS INSTALLED ON ADJACENT CONTAINER UNITS OR THE LIKES
FIELD
[0001] The present disclosure relates to the use of a mono-pulsed antenna on an RFID reader and methods to discriminate one RFID tag over a plurality of RFID tags being in the radio field at the same moment. The present disclosure also relates to the UHF RFID ISO18000 standard.
BACKGROUND
[0002] As the RFID technology penetrates the supply chain management industry, some utilization problems emerge when that technology is used in day to day processes. This is true for all RFID technologies and more specifically for the ISO-18000-6 (EpcGlobal) RFID standard, to which the present disclosure pertains.
[0003] The UHF RFID (Ultra- High Frequency Radio Frequency
Identification) technology is increasingly replacing the optical bar code technology in warehouses, logistics platforms, packing stations and packaging facilities. In such sites, many processes have been developed considering the limitations and the advantages of the bar code technology. UHF RFID has the advantage of allowing reading all the RFID tags that are present in the electromagnetic field of a reader's antennas. However, in processes where the operator has to pin point and read a single RFID tag that is among many others, that UHF RFID advantage become an inconvenient. [0004] Indeed, operators in non-automated station typically have to identify a single pack, container, bin or pallet for grading, calibrating, certifying, auditing or simply track the products that they contain. These tasks are conventionally accomplished by identifying the product or a group of products, one by one. To add to the challenge, in most processes, the containers are combined into greater units.
[0005] A simple solution to the above-described problems is to move the reader, or the reader's antenna, toward the targeted RFID tag until it is the only tag that the reader sees. Also, the use of a near field antenna allows to reduce the proximity of the antenna required to isolate a single RFID tag. Sometimes a combination of decreased distance or power and the change of antenna type is used to have a faster and more accurate RFID tag discrimination.
[0006] However, this last problem is not easily solved when a fork lift driver is at four (4) meters from container-bin piles facing a 3 by 3 matrix and he has to identify the containers-bins one by one. Currently, the driver simply grabs his bar code reader and flashes each container one by one. Considering the above-noted constrains, doing that same task using UHF RFID technology is currently very fastidious. For example, if the driver cannot move his forklift in close proximity, he has no other choice than getting out of his forklift and try to use one or all of the above-described methods in order to discriminate the nine (9) containers-bins. Even if the driver could move the forklift nearby the container matrix, isolating each RFID tag remain complicated for a driver that remains sitting in his forklift. Either ways, the conventional use of UHF RFID technology in those cases represents a production lost. This lost represents a barrier to RFID technology adoption for such applications. SUMMARY
[0007] The use of the word "a" or "an" when used in conjunction with the term "comprising" in the claims and/or the specification may mean "one", but it is also consistent with the meaning of "one or more", "at least one", and "one or more than one". Similarly, the word "another" may mean at least a second or more.
[0008] As used in this specification and claim(s), the words
"comprising" (and any form of comprising, such as "comprise" and "comprises"), "having" (and any form of having, such as "have" and "has"), "including" (and any form of including, such as "include" and "includes") or "containing" (and any form of containing, such as "contain" and "contains"), are inclusive or open-ended and do not exclude additional, unrecited elements or process steps.
[0009] The expression "connected" should be construed herein and in the appended claims broadly so as to include any cooperative or passive association between mechanical parts or components. For example, such parts may be connected together by direct coupling, or indirectly coupled using further parts therebetween.
[0010] The word "elevation" should be construed broadly herein and in the appended claims so as to include "altitude or height above a fixed reference such as the ground" and the position along the conventional Y axis in mathematic.
[0011] The word "transverse" should be construed broadly herein and in the appended claims so as to include "the angular position from a fixed reference after pivoting about a reference axis". [0012] An object of the illustrated embodiments is therefore to provide improved method and system for discriminating RFID tags when the RFID reader's antenna is not in close proximity from the RFID tags.
[0013] The problem of discriminating from a distance a RFID tag among a plurality of other RFID tags is solved by providing a mono pulsed operating antenna array that operates within a predetermined angle range relative to the RFID tag and alternating a RFID module connected to the antenna array between mono and bi-static modes.
[0014] More specifically, in accordance with an illustrated embodiment herein, there is provided a UHF RFID (Ultra-High Frequency Radio-Frequency identification) tag reader that discriminates, from a distance, a selected RFID tag among a plurality of other RFID tags, the reader comprising:
[0015] a mono pulsed operating antenna array that operates within a predetermined angle range relative to the selected RFID tag; and
[0016] a RFID module coupled to the antenna array that alternates between mono and bi-static modes.
[0017] In accordance to another illustrative embodiment, there is provided UHF RFID (Ultra-High Frequency Radio-Frequency identification) tag reader comprising:
[0018] an array of mono pulse antennas that generates elevation and transverse signals when the array of mono pulse antennas is oriented in a detecting direction relative to a RFID tag from a detecting distance therefrom; [0019] a coupler that is connected to the array of mono pulse antennas for receiving the elevation and transverse signals therefrom and for computing a sum and a difference thereof; and
[0020] a RFID module for operating alternatively between mono static and bi static modes for collecting the sum and difference of the elevation and transverse signals from the coupler and for generating a power signal indicative of the RFID tag.
[0021] According to a further illustrative embodiment, there is provided a method for discriminating from a distance a selected UHF RFID (Ultra-High Frequency Radio-Frequency identification) tag among a plurality of other RFID tags, the method comprising:
[0022] generating elevation and transverse signals from a detecting direction relative to the selected UHF RFID tag from a detecting distance therefrom;
[0023] computing a sum and a difference of the elevation and transverse signals; and
[0024] using the sum and difference of the elevation and transverse signals for generating a power signal indicative of the RFID tag.
[0025] Embodiments of RFID tag discriminating method and system allow: • discriminating UHF RFID tags that are distanced from 0 mm to 5000 mm from the RFID reader, proportional with the distance between the RFID tags;
• a reading distance of up to 4000 mm in Europe and up to 5000 mm in America such as within the ISO-1800-6 power limitations;
• the operators in logistic and supply chain processes to continue operating similarly than before the implementation of RFID technologies into the sites process;
• an angle of ±36 degrees between the RFID reader and the targeted RFID tag on the two axes.
[0026] Other objects, advantages and features of the method and system according to illustrated embodiments will become more apparent upon reading the following non restrictive description of preferred embodiments thereof, given by way of example only with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS [0027] In the appended drawings:
[0028] Figure 1 is a block diagram of a reader for discriminating a specific RFID tag among a plurality of RFID tags according to a first illustrated embodiment; [0029] Figure 2 is a schematic perspective view illustrating a typical use of the reader from Figure 1 ;
[0030] Figure 3 is a schematic perspective view illustrating the angles relation between the RFID reader from Figure 1 and a RFID tag targeted thereby;
[0031] Figure 4 is a block diagram illustrating the coupling of the antennas array to the micro ribbon coupler, both parts of the reader system from Figure 1 ;
[0032] Figure 5 is a schematic perspective view illustrating the radiation of a four-lobes mono-pulsed antenna used in conventional radar system ;
[0033] Figure 6 is a schematic perspective view illustrating the radiation of the four-lobe mono-pulsed antennas of the RFID reader from Figure 1 and a targeted RFID tag;
[0034] Figure 7 is a schematic view of the micro ribbon PC board, part of the reader from Figures 1 and 2;
[0035] Figure 8 is a graph illustrating the sum and difference responses of the output of the coupler from Figure 4; and
[0036] Figure 9 is a schematic view illustrating the micro-ribbon coupler from Figure 4 coupled to the RFID module, both parts of the reader from Figures 1 and 2. DETAILED DESCRIPTION
[0037] With references to the appended drawings, and more specifically to Figure 1 , a UHF RFID (Ultra-High Frequency Radio-Frequency identification) tag reader 10 will now be described. It is to be noted that the expressions handheld device, reader and system will be used interchangeably with reference to the UHF RFID tag reader 10.
[0038] The reader 10 is in the form of a handheld device embodying an array of mono pulse antennas 12, a coupler 14 that is coupled to the array of mono pulse antennas 12 for receiving elevation and transverse signals therefrom and for computing a sum and a difference thereof, and a bi-static UHF RFID tag reader module 16 for operating alternatively between mono static and bi static modes for collecting the sum and difference of the elevation and transverse signals from the coupler 14 and for generating a power signal indicative of the RFID tag 18.
[0039] The handheld device 10 further comprises an aiming device in the form of a laser pointer 20, a manual trigger 22, an orientation-determining device 24 and input/output devices 26.
[0040] Figure 2 illustrates, as a typical application of the reader 10, the use thereof for discriminating the RFID tag 18 affixed to one of many container bins 28, each having a RFID tag 30 secured thereto.
[0041] It is to be noted that the distances specified in the drawings are not restrictive and are provided for illustrative purposes only. For example, distances between the RFID tags 30 present in the matrix can be as low as 30 mm. The operating distance between the targeted RFID tag 18 and the RFID reader 10 is directed by the ISO-18000-6 standard and can be up to 4000 mm in Europe and 5000 mm in America.
[0042] The handheld device 10 is further configured to inform the user when operational limitations are reached and to give instructions or provide feedback to the user to re-enter operational specifications. The example shown in Figure 2 illustrates that the reader 10 allows discriminating, in Europe, a targeted tag 18 at a distance of 4000 mm from the RFID reader, if the tags 18 and 30 present in the matrix are separated by a minimum distance of 750 mm. This is considering that RFID tags 30 having a sensibility of -15dbm.
[0043] In addition to the limitation of the reader 0 that relates to the
ISO-18000-6 power limitation, a further limitation relates to the angles in the x and y axis between the RFID reader 10 and the targeted RFID tag 18.
[0044] ARRAY OF ANTENNAS
[0045] As illustrated in Figure 4, the array of antennas 12 includes four (4) mono pulsed antennas 32. The choice of a four antennas array results from the type of RFID tag used. According to another embodiment (not shown) another array of RFID antennas is used which includes another number of antennas, such as more than four antennas.
[0046] The mono pulsed antenna principles come from radar detection of objects. Such antennas work in the micro-wave frequency range. Figure 5 illustrates such an antenna where the four (4) lobes (A, B, C and D) can target a plane many kilometers from the antennas. [0047] Mathematics and principles of mono pulsed antennas will now be described briefly. With reference to lobes positioning in Figure 6, the sum (S) of the lobes is given by the following equation:
Figure imgf000011_0001
[0048] The ½ factor in the above equation results from the fact that the signals are sinusoidal. Therefore, it is the near RMS value that is considered. That equation also takes into account that the coupling of the devices is ideal i.e. that it does not generate lost.
[0049] The mono pulse principles are based on the fact that if we have two lobes slightly separated and a target 34 is placed exactly at the center of the lobes, that target will reflect the two lobes' signals equally. Therefore the difference of the two reflected signals will be 0. Using four lobes allows obtaining the elevation and transverse signals. Having the two signal differences at 0 allows to establish the actual position of the object 34. That relation is given by the following equation where dei represent the elevation:
{04 + C) - (5 + D)}
[0050] The two pairs of signals for the elevation can be expressed as:
(B + D)
and S2 =
V2 V2
[0051] dtr represents the transverse: 710
11 dtr = - {{C + D) - (A + B)}
[0052] where the two pairs of signals for the transverse can be expressed as:
C + A C ^ + fl)
S = —— ana S2 = 7=—
V2 V2
[0053] The sum (S) and the difference (d) can be expressed as:
Figure imgf000012_0001
[0054] Each pair of antennas 32 is connected to the coupler 14 via a
Wilkinson divider 40. Wilkinson dividers allow providing a suitable division of power radiation between each pair of antennas. Power lost induced by the Wilkinson divider 40 can be compensated by the static gain of the antennas 32 or/and the power of the RFID reader module 16.
[0055] According to another embodiment (not shown), the Wilkinson dividers 40 are omitted and the coupler 14 is configured to provide an equivalent division of power radiation between each pair of antennas.
[0056] COUPLER
[0057] The coupler 14 is in the form of a micro-ribbon coupler that meets mono pulsed antennas principles. [0058] According to the first illustrated embodiment, the micron ribbon coupler 14 includes an RF (Radio Frequency) circuit that allows to generate the sum and the difference signals from Si and S2.
[0059] RF couplers are normally designed with passive elements.
However, the dimensions of the coupler are inversely proportional to the operational frequency. This results that a passive coupler reaches approximately 90 mm square in the UHF RFID ISO-18000-6 frequency band. The RFID tag discriminating system 10 according to the first illustrative embodiment includes a network of capacitors and inductors so as to reduced the dimensions of the coupler 14.
[0060] The micro ribbon coupler 14 is showed schematically in
Figure 7, and includes the S1 input signal 2, the S2 input signal 4, the sum output 3 and the difference output .
[0061] Typical response from the reader 10, including the antennas 32, Wilkinson dividers 40 and micro ribbon coupler 14, is shown in Figure 8. The graphs from Figure 8 show the sum and difference curves depending on the variation of Dx or Dy. One can see that when Dx and Dy are near zero, the difference is very low and the sum is high. Such results are for an ideal operation. However, Dx and Dy are never zero in typical operation of the system according to the first illustrated embodiment.
[0062] Figure 8, which results from operating the system 10 in a white room, shows that it is practically impossible to discriminate tags for values for Dx and Dy higher than ±40 degrees. In practice, with the use of a standard ISO- 8000-6 RFID reader module, those angle limitations are of ±32 degrees for the best module and ±23 degree for the less preferred. This variation comes from a low power accuracy on Tx (transmission power) and a low precision in reading Rx (reception power) of theses UHF RF modules.
[0063] It has been found that, by implementing a power variation multi-reading algorithm, the RFID tag discriminating method and system 10 according to illustrated embodiments push up the performance limitation to between ±36 degrees. Since a power variation multi-reading algorithms is believed to be well known in the art, it will not be described herein in more detail for concision purposes.
[0064] LASER POINTER - 2 TONES BEEPER - MANUAL
TRIGGER
[0065] The handheld device 10 is configured to help the user positioning the device 10 relative to the RFID tag 18 so that the device 10 is within its operational range as described hereinabove.
[0066] For this purpose, the device 10 includes a conventional laser pointer 20 that is mounted to the device 10 so as to emit a laser beam in the center of the antennas array 12. That laser 20 allows the user pointing the RFID tag 18 that has to be discriminated in the matrix of tags 30 present in the antennas array field. The laser pointer 20 can be actuated by the trigger 22 and is controlled by the software/firmware present in the handheld device 10 so that it stops at the moment the targeted RFID tag 18 has been discriminated.
[0067] According to another embodiment (not shown), the aiming device takes another form or is omitted. [0068] The reader 10 further includes an output device 26 in the form of a two-tone beeper that is provided to indicate to the user when the reader 10 is out of its operational range. For example, according to the first illustrated embodiment, a low tone is emitted by the beeper to indicate to the user that he/she is using the reader 10 out of its range of operation with regards to the angles Dx and/or Dy, such as when they are over ± 36 degrees. The reader 0 is also configured to emit a high tone when it is too far from the targeted tag 18 and that the user should reduce that distance. The two-tone beeper is controlled by the software/firmware's provided in the PDA handheld.
[0069] The reader 10 further includes another output device in the form of a screen 42 to allow providing futher feedback to the user to help him position the reader 10 within operational range relative to the RFID tag 18 to discriminate.
[0070] Other well-known handheld device input or output means, such as a keyboard, a touch screen, buttons, dials, light-emitting diodes, etc. can also be provided on the device 10 to provide feedbacks or allow control thereof.
[0071] The reader 10 is also configured for storing information relative to the RFID tags read, and for communicating such information to a computer or another device.
[0072] Dx AND Dy DETECTION
[0073] The reader 10 further includes an orientation-determining system or mechanism 26. Such system or mechanism allows detecting the values Dx and Dy, as illustrated in Figure 6 and includes, for example, a MEMS (micro-electromechanical system) gyroscope or/and accelerometer or/and magnetic compass or/and inclinometer. Those devices are implemented in the reader 10 to evaluate angles of the RFID reader 10 in relation with the ground, in order to assess limitations of the reader 10 and to provide feedback to the user thereabout as mentioned hereinabove.
[0074] It is to be noted that the values determined by the orientation- determining system 26 does not consider the orientation of the RFID targeted tag 18 in relation to the ground. Those angles, in certain case, can increase or decrease the performances of the RFID tag discriminating system. If fact the 36 degrees limitations for Dx and Dy relate to the angles between the RFID readers and the RFID tag (Figure 6) and not with the ground.
[0075] The reader 10 embeds a software/firmware to further manage the operation of the MEMS detectors. Dx and Dy limitations are considered as post references in case of incapacity of the sum/difference outputs of the micron ribbon coupler 14 to discriminate the targeted tag 8 and that, after the power algorithms have been applied, which will be described hereinbelow in more detail.
[0076] Therefore, depending on the responses from the power algorithms, virtual angles evaluation of the targeted tag 18 can be estimated with regards to the ground. Knowing the two sets of angles, reader angles related to the ground and targeted tag angles related to the ground, Dx and Dy values are estimated. According to the first illustrated embodiment, the RFID tag discriminating system 10 allows Dx and a Dy deviation angles between -36 degrees and +36 degrees between the antennas 32 and the targeted tag 18. When those angles are exceeded, the system is configured to provide feedback to the user, for example via the display screen 42, as to how to realign the reader within the limitation angles. [0077] THE USE OF THE MONO-STATIC AND BI-STATIC MODES
[0078] As mentioned hereinabove, the reader 10 further comprises a bi-static UHF RFID reader module 16. The reader module 16 is coupled to the array of mono pulse antennas 12 via the micro ribbon coupler 14. The module 16 operates alternatively between mono static and bi static modes for collecting the sum and difference of the elevation and transverse signals from the coupler and for generating a power signal indicative of the RFID tag 18.
[0079] As can be seen in Figure 9, the mono static mode is defined by the use of a single antenna port for the Tx (transmission) and Rx (reception) signals. Mono static mode implies the use of an RF circulator that is normally not accessible. Bi static mode includes the use of a first port for Tx and a second port for Rx. In order to collect the difference signal, which is the returning power from micro ribbon coupler output, only the Rx signal is collected from the RFID RF module 16. The sum of the micro ribbon coupler 14 outputs is read by a mono static RF port.
[0080] Figure 9 illustrates how the RFID RF module 16 according to the first illustrated embodiment is connected. The module 16 is configured to switch from mono static to bi static mode and inversely in less than 30 ms. The RFID RF module 16 allows monitoring values of powers returned by the RFID tag 18. RFID RF modules being commercially distributed, any RFID RF modules that respect the above specifications can be used.
[0081] THE POWER ALGORITHM
[0082] Illustrative embodiments of the RFID tag discriminating reader implement software/firmware algorithms that allow: • initiating the above-described RFID tag discriminating process:
• switching between bi static and mono static mode;
• adjusting RF power to yield operational conditions within the reader limitations, considering the distance between the RFID reader and the targeted RFID tag;
• detecting values of Dx and Dy greater then ±36 degree;
• detecting the use of the reader beyond its limitations;
• indicating to the user when the reader is used out of its operational limitations; and
• indicating to the user actions to take for using the reader within its limitations.
[0083] Since it is believed to be within the reach of a person of ordinary skills in the art to configure a device such as the reader 10 with software and firmware which allows the reader 10 with the above-mentioned functionalities, the actual programming of the reader 10 will not be described herein in more detail for concision purposes.
[0084] While the reader 10 according to the first illustrated embodiment is described as being in the form of a handheld device, it can take other forms more or less compact than the reader 10. Also, according to other embodiments (not shown), the UHF RFID tag reader is in the form of a system including a plurality of interconnected devices.
[0085] It is to be understood that the method and system for discriminating from a distance a selected UHF RFID tag is not limited in its applications to the details of construction and parts illustrated in the accompanying drawings and described hereinabove. The discriminating method and system are capable of other embodiments and of being practiced in various ways. It is also to be understood that the phraseology or terminology used herein is for the purpose of description and not limitation. Hence, although the method and system for discriminating from a distance a selected UHF RFID tag have been described hereinabove by way of illustrative embodiments thereof, they can be modified, without departing from the spirit, scope and nature of the subject invention.

Claims

WHAT IS CLAIMED IS:
1. A UHF RFID (Ultra-High Frequency Radio-Frequency identification) tag reader comprising:
an array of mono pulse antennas that generates elevation and transverse signals when the array of mono pulse antennas is oriented in a detecting direction relative to a RFID tag from a detecting distance therefrom;
a coupler that is connected to the array of mono pulse antennas for receiving the elevation and transverse signals therefrom and for computing a sum and a difference thereof; and
a RFID module for operating alternatively between mono static and bi static modes for collecting the sum and difference of the elevation and transverse signals from the coupler and for generating a power signal indicative of the RFID tag.
2. A UHF RFID tag reader as recited in claim 1 , wherein the array of mono pulse antennas includes two (2) pairs of antennas, each generating one of the elevation and transverse signals.
3. A UHF RFID tag reader as recited in claim 1 , wherein the coupler is a micro-ribbon coupler.
4. A UHF RFID tag reader as recited in claim 1 , wherein the coupler is connected to the array of mono pulse antennas via Wilkinson dividers.
5. A UHF RFID tag reader as recited in claim 1 , further comprising an aiming device to contribute to orienting the array of mono pulse antennas in the a detecting direction.
6. A UHF RFID tag reader as recited in claim 5, wherein the aiming device includes a laser pointer that emits a laser beam in the center of the array of mono pulse antennas.
7. A UHF RFID tag reader as recited in claim 1 , further comprising an output device to provide information indicative of at least one of the detecting direction relative to a RFID tag and the detecting distance therefrom.
8. A UHF RFID tag reader as recited in claim 7, wherein the output device includes at least one of a beeper, a display screen, a touch screen and light-emitting diodes.
9. A UHF RFID tag reader as recited in claim 1 , further comprising an orientation-determining system to determine angle values indicative of the detecting direction relative to a RFID tag.
10. A UHF RFID tag reader as recited in claim 9, wherein the orientation-determining system includes at least one of a gyroscope, an accelerometer, a magnetic compass and an inclinometer.
11. A UHF RFID tag reader as recited in claim 1 , wherein the array of mono pulse antennas has four lobes producing respective signals A, B, C and D; wherein two pairs of elevation signals being expressed by:
= —— ana
V V2
two pairs of transverse signals being expressed by:
Figure imgf000021_0001
and the sum (S) and the difference (d) difference of the elevation and transverse signals being expressed as:
Sei/tr =— γ=— and dei/tr =———
12. A UHF RFID tag reader as recited in claim 1 in the form of a handheld device.
13. A method for discriminating from a distance a selected UHF RFID (Ultra-High Frequency Radio-Frequency identification) tag among a plurality of other RFID tags, the method comprising:
generating elevation and transverse signals from a detecting direction relative to the selected UHF RFID tag and from a detecting distance therefrom;
computing a sum and a difference of the elevation and transverse signals; and
using the sum and difference of the elevation and transverse signals for generating a power signal indicative of the RFID tag.
14. A UHF RFID (Ultra-High Frequency Radio-Frequency identification) tag reader for discriminating from a distance a selected RFID tag among a plurality of other RFID tags, the reader comprising:
a mono pulsed operating antenna array that operates within a predetermined angle range relative to the selected RFID tag; and
a RFID module coupled to the antenna array that alternates between mono and bi-static modes.
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