WO2006065157A1 - Systeme d'identification optimisee de portee - Google Patents

Systeme d'identification optimisee de portee Download PDF

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Publication number
WO2006065157A1
WO2006065157A1 PCT/NZ2005/000331 NZ2005000331W WO2006065157A1 WO 2006065157 A1 WO2006065157 A1 WO 2006065157A1 NZ 2005000331 W NZ2005000331 W NZ 2005000331W WO 2006065157 A1 WO2006065157 A1 WO 2006065157A1
Authority
WO
WIPO (PCT)
Prior art keywords
assembly
impedance
transmitter
identification system
receiver
Prior art date
Application number
PCT/NZ2005/000331
Other languages
English (en)
Inventor
Gordon Douglas Irving
Christopher Lewis Anderson
Murray Greenman
Alfred Nassenstein
Original Assignee
Edit Id Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Edit Id Limited filed Critical Edit Id Limited
Publication of WO2006065157A1 publication Critical patent/WO2006065157A1/fr

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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
    • G06K19/00—Record carriers for use with machines and with at least a part designed to carry digital markings
    • G06K19/06—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code
    • G06K19/067—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components
    • G06K19/07—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components with integrated circuit chips
    • G06K19/0723—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components with integrated circuit chips the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs

Definitions

  • This invention relates to improvements in or associated with identification systems.
  • the present invention may provide improvements with respect to radio frequency identification devices or tags (RFID tags) and preferably may improve or increase the range at which such tags may be interrogated by a reader component.
  • RFID tags radio frequency identification devices or tags
  • Reference through out this specification will also be made in particular to RFID tags and range sensing improvements in relation to same. However those skilled in the art should appreciate that other applications are also envisioned.
  • Radio frequency identification devices have been used in a wide variety and number of applications. Comparatively small tags may be applied to stock items, to animals (injected subcutaneously or attached via external piercing or other means) or used in security applications as pass key or authorisation identifiers.
  • the tags involved are capable of being interrogated by a reader component or device which can extract a unique identification code from each and every tag interrogated.
  • Passive RFID tags have been developed which are relatively small and which do not require their own power source. Passive tags are excited by the energy present in an initial reader/transmitter electromagnetic field and are used to encode a return echo from the tag back to the reader where the return echo has the identification information of the tag encoded into it.
  • the range or distance from which a tag can be read is an important fact to be considered when a system that uses such tags is designed or built. Some physically small passive tags may only be read by readers that must be placed in close proximity to the tag, and therefore cannot be interrogated effectively or safely in many RFID applications. In general it will be preferable to increase or improve the range at which such tags may be read to in turn give greater design flexibility in the implementation/operation of a system which uses such tags in combination with either hand held or fixed installation readers.
  • the range at which a passive RFID tag can be read is influenced by the power of the original interrogating reader transmission signal.
  • the transmitter power of a reader element is normally limited with respect to both the signal frequency range used and also the power of any initial interrogation signal emitted.
  • Government regulations generally control both the frequency band available for transmitters and also the power levels at which transmitters can operate without forming a health hazard to persons in the general vicinity of the transmitter, and to manage the potential conflict between various users of the radio spectrum. These regulations are normally defined through examining a maximum power value to be experienced at set distances from a transmitter.
  • transmitter signal power may not necessarily result in intelligible or valid signals being received at greater ranges.
  • transmitter power also generally comes an increase in radio frequency noise generated through the identification system's circuitry, or the excitation from other external noise sources nearby. These noise sources are separate to environmental or far field radio frequency noise sources which exist and also cause interference to RFID identification systems and lead to a reduction in their performance.
  • the read range for a tag will also be affected by the spatial orientation of the tag.
  • these passive RFID tags have an optimum axis of orientation with respect to any incident excitation field flux lines.
  • the tags involved will extract the greatest amount of power or energy from the reader's initial excitation field if the tag is placed or moved with its optimum axis parallel to the field's lines of flux. This optimum orientation of a tag will in turn generate the highest possible power return echo signal, thereby potentially resulting in the reader obtaining a valid identification signal.
  • the tag Conversely if the tag is presented or moved with its optimum axis more perpendicular to the excitation field's lines of flux the amount of energy extracted from the field reduces. This in turn may result in the generation of a return echo from the tag with insufficient signal to noise ratio or power to be detected by the reader, or no signal at all if the interrogation field is not sufficient to excite the tag.
  • an electromagnetic identification system which includes a transmitter assembly, antenna assembly and receiver assembly, the method including the steps of:
  • This embodiment of the present invention provides improved range of operation for electromagnetic identification systems because of mitigation of noise effects through independent impedance matching of the transmitter assembly and the antenna assembly to the impedance of the receiver assembly.
  • Preferably forming the transmitter assembly includes arranging the impedance of the transmitter assembly to be optimal for loading a given antenna assembly to provide conditions for optimum bandwidth for the receiver assembly.
  • Preferably arranging the impedance of the transmitter assembly includes adjusting the Q characteristic of the impedance.
  • Preferably forming the antenna assembly includes providing at least one electrically conductive coil and includes adjusting the impedance of the antenna assembly by modifying the mechanical characteristics of said at least one electrically conductive coil.
  • Preferably forming the transmitter assembly includes providing at least one selected reactive component to match the electrical impedance of the transmitter assembly with the electrical impedance determined for the receiver assembly.
  • Preferably forming the antenna assembly includes providing at least one pair of balanced counter-wound conductive coils.
  • Preferably forming a transmitter assembly includes providing at least one Royer circuit as part of the transmitter assembly.
  • forming the transmitter assembly and/or forming the receiver assembly includes adapting the transmitter assembly and/or the receiver assembly for use with radio frequency identification tags. Suitable adaptions will be apparent to those skilled in the art.
  • Preferably forming the antenna assembly includes adapting the antenna for use with radio frequency identification tags.
  • the method of manufacturing an electromagnetic identification system includes the step of forming a second receiver assembly so as to substantially match the impedance of the first receiver assembly.
  • an electromagnetic identification system manufactured according to the method disclosed in one of the preceding paragraphs.
  • an electromagnetic identification system which includes:
  • a receiver assembly having an impedance said receiver being adapted to receive at least one response signal elicited from an identification tag;
  • a transmitter assembly having an impedance said transmitter assembly adapted to provide an interrogation signal for an identification tag
  • an antenna assembly having an impedance said antenna assembly being adapted to radiate the interrogation signal to provide an interrogation field to elicit a response signal from an identification tag;
  • respective impedances of the transmitter assembly and antenna assembly each independently substantially matches the impedance of the receiver assembly.
  • transmitter assembly impedance is optimal for loading the antenna assembly to arrange an optimal band width of the receiver assembly.
  • Those skilled in the art will be familiar with the reference to an optimal transmitter impedence that provides an optimal receiver assembly bandwidth.
  • the antenna assembly includes at least one electrically conductive coil and the impedance of the antenna is determined by the mechanical characteristics of said electrically conductive coil.
  • the coil is adapted so that the mechanical characteristics are adjustable to adjust the impedance of the antenna assembly.
  • the transmitter assembly includes at least one reactive component selected to match the transmitter assembly impedance to the receiver assembly impedance.
  • the antenna includes at least one pair of balanced counter-wound conductive coils.
  • the transmitter assembly includes at least one Royer circuit.
  • the transmitter assembly is adapted for radio frequency identification tags.
  • the electromagnetic identification system includes a second receiver assembly additional to the first receiver assembly wherein the impedance of the second receiver assembly matches the impedance of the first receiver assembly.
  • the present invention relates to improvements in and modifications made to identification systems.
  • the present invention may be implemented as a radio frequency identification tag reading system which can interrogate RFID tags within a detection zone or region in the vicinity of such a reader system.
  • an identification reader system may include a transmitter assembly, antenna assembly, and receiver assembly.
  • the transmitter assembly may be adapted to generate an interrogation signal which, when transmitted via the antenna assembly, results in the generation of an electromagnetic interrogation field in the vicinity of the reader system.
  • the reader system can employ the receiver assembly to detect at least one response signal elicited from an RFID tag within the readers interrogation field.
  • a response signal can be detected by a receiver assembly and interpreted or decoded to provide an intelligible identification code using techniques and practises again well known in the art.
  • the transmitter, antenna and receiver assemblies may be designed and preferably formed so as to substantially match the electrical impedances of these assemblies with one another.
  • the receiver's electrical impedance may be substantially the same as that of the antenna, which in turn may be substantially the same as that of the transmitter. Matching the impedances of these three systems implements a design optimisation which maximises the power transfer characteristics of the reader system, sets the system bandwidth, and also preferably minimises the noise generated by the operation of the system.
  • the read range of the system may preferably be increased through increasing the overall power of the signals transmitted by the antenna to in turn increase the volume of space within the vicinity of the system within which a tag's response signal may be generated. Furthermore through the matching of impedances, the noise experienced by a reader assembly from both the internal workings of the reader system, and also from remote external noise sources may be mitigated. Those skilled in the art should appreciate that a reduction in the noise experienced by the reader assembly will result in a greater signal to noise ratio, allowing the range of the system to be increased until noise levels involved again become unacceptable.
  • each of the antenna, transmitter and receiver assemblies may be adjusted independently of each other.
  • This independent adjustment scheme will allow each impedance to be set or fixed independently, thereby ensuring that each of the assemblies may be substantially matched with one another.
  • the assemblies of the reader system may be designed initially to have their impedances match with one another. Each assembly may then be manufactured or formed and subsequently integrated into a single reader system.
  • the receiver assembly may be implemented through any form of appropriate radio frequency signal detection circuitry know in the art.
  • the circuitry employed to implement the receiver assembly may function effectively for the appropriate frequency ranges and power levels employed in the operation of the present invention.
  • Such receiver assembly circuitry may be employed as a reference or static impedance to which the impedances of the antenna and transmitter assemblies are matched. Once the impedance of the receiver assembly circuitry has been determined appropriate adjustments or changes can be made in the design or formation of the transmitter and antenna to match all three impedances involved together.
  • an antenna assembly may include at least one conductive coil. Conductive coil based antennas are well known in the art and are widely used in numerous forms of antenna systems.
  • the impedance of the antenna assembly may be adjusted or modified through modifying the physical characteristics of the conductive coil or coils integrated within the antenna assembly.
  • the type of conductor employed, number of turns provided in the coil, the width of the conducting wire and/or its length may all be factors or parameters modified to in turn modify the impedance of the antenna assembly to preferably match that of the receiver assembly.
  • the transmitter assembly may be implemented using a circuit or circuits which can have its impedance modified by at least one reactive component.
  • Reactive components such as capacitors or inductors can be used to modify the overall impedance of a transmitter assembly without causing heat dissipation or signal noise issues normally associated with resistive type components.
  • the use of reactive components in the transmitter assembly circuit design will also allow for the adjustment of the transmitter's impedance independent of any modifications made to the antenna's or receiver's impedances.
  • the transmitter assembly may be implemented through or use a Royer circuit to generate the interrogation signal required.
  • the output impedance of a Royer circuit may be controlled independently through the addition of reactive components.
  • a Royer circuit may work with high efficiency to maximise power transfer through to the antenna assembly while minimising the amount of internal electrical noise created through the generation of the interrogation signal required.
  • elements or components of the transmitter assembly may function as a synchronous detector to be used by the receiver assembly provided.
  • a synchronous detector can provide a frequency downshift facility with respect to a return signal elicited from a tag within the reader system's interrogation field.
  • a synchronous detector facility may be obtained through monitoring the voltage and current fluctuations present within the transmitter assembly circuitry caused by a tag's return signal impinging on the antenna assembly.
  • the present invention may provide many potential advantages over the prior art.
  • the present invention may be used to provide improvements with respect to the range at which a tag may be read by an identification reader system. Improvements with respect to the power transfer capabilities of each of the assemblies integrated into the system can be implemented independently matching the impedances of these assemblies. This can provide high levels of energy to excite an identification tag, without necessarily creating significant increases in the magnitude of internal noise sources for the read system.
  • features of the chosen Royer design allow the transmitter circuit to operate concurrently and beneficially as the receiver balanced synchronous detector, offering high dynamic range.
  • dynamic range is of great importance since the transmitter power level and tag signal power level are of such considerable difference when attempting to read RFID tags at extreme range or with non-optimum orientation.
  • Figure 1 illustrates a schematic circuit diagram of an identification system implemented in conjunction with the preferred embodiment of the present invention.
  • Figure 1 illustrates a schematic circuit diagram of an identification system implemented in conjunction with the preferred embodiment of the present invention.
  • FIG. 1 shows an identification system (1) implemented in accordance with the preferred embodiment of the present invention.
  • the identification system (1) includes three main sub-assemblies, being a transmitter assembly (2), antenna assembly (3) and receiver assembly (4).
  • the transmitter assembly (2) is adapted to generate an interrogation signal to be supplied in turn to the antenna assembly.
  • the transmission of this interrogation signal via the antenna assembly (3) will generate an electromagnetic interrogation field in the vicinity of the identification system (1) and also preferably in the area encompassing that occupied by an identification tag (5).
  • the identification tag involved is implemented through an FDX RFID tag.
  • a response signal elicited from the tag (5) is again received by the antenna assembly (3) and passed through components of the transmitter assembly (2) through to the receiver assembly (4).
  • the Identification reader system (1) is designed so as to independently match the impedances of each of the transmitter (2) and antenna (3) and receiver (4) assemblies.
  • This design approach is implemented through initially determining and optimally adjusting the impedance of the receiver assembly (4).
  • the antenna impedance is then matched to the receiver impedance through modifying the physical characteristics of a conductor coil used to implement the antenna assembly.
  • the specific physical configuration of the coil windings including the windings length, number of turns and thickness of the wire in addition to other physical parameters can be modified to match the impedance of the antenna assembly (3) with that of the receiver assembly (4).
  • the impedance of the transmitter assembly (2) is also matched to that of the receiver assembly (3) for maximum power transfer.
  • the transmitter assembly includes a Royer circuit which allows for the provision of reactive matching impedance components (2a, 2b) in the implementation of the circuit provided. These reactive components (2a, 2b) can modify the impedance of the transmitter assembly (2) without necessarily requiring the addition of resistive components which can increase the noise generated by the transmitter assembly (2) and also increase the amount of heat generated in operation.
  • Reactive components (2b) specifically allow independent adjustment of the transmitter output impedance (i.e. the impedance seen looking into the transmitter from the antenna and receiver), which allows independent adjustment of system Q.
  • This adaptation of the Royer configuration is chosen since in this embodiment output impedance is independently adjustable.
  • a further matching impedance component (4a) is also included or incorporated into the receiver assembly (4).
  • This additional matching impedance component (4a) can be used to provide flexibility in the design of the resulting identification system (1 ) if required.
  • the impedance matching components (4a) can be used to optimally and independently set the operating input impedance of the receiver, to which the antenna and transmitter assemblies are then matched.
  • the impedance matching component (4a) can be used to bring the impedance of the receiver assembly (4) to the same level or magnitude of that of the antenna and transmitter assemblies prior to modifications been made to these components to match their impedances with that of the receiver assembly.
  • An identification system implemented in conjunction with an alternative embodiment (not shown) of the present invention may include two receiver assemblies. One of these may cater for FDX RFID tags and the other may cater for HDX RFID tags. In this embodiment one of these receiver assemblies may include an additional impedence matching component (not shown) to allow the impedence of this additional receiver assembly to the other receiver assembly.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Artificial Intelligence (AREA)
  • Computer Vision & Pattern Recognition (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Near-Field Transmission Systems (AREA)

Abstract

L'invention concerne un système d'identification électromagnétique et son procédé de fabrication. Ce procédé consiste à adapter séparément les impédances d'un émetteur et d'une antenne à l'impédance d'un récepteur. Est également décrit un procédé qui implique en outre le réglage de la caractéristique Q du système de l'impédance de l'émetteur afin d'optimiser la largeur de bande vue par le récepteur.
PCT/NZ2005/000331 2004-12-17 2005-12-16 Systeme d'identification optimisee de portee WO2006065157A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NZ535423 2004-12-17
NZ53542304 2004-12-17

Publications (1)

Publication Number Publication Date
WO2006065157A1 true WO2006065157A1 (fr) 2006-06-22

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PCT/NZ2005/000331 WO2006065157A1 (fr) 2004-12-17 2005-12-16 Systeme d'identification optimisee de portee

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WO (1) WO2006065157A1 (fr)

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5926093A (en) * 1997-08-15 1999-07-20 Checkpoint Systems, Inc. Drive circuit for reactive loads
US6307468B1 (en) * 1999-07-20 2001-10-23 Avid Identification Systems, Inc. Impedance matching network and multidimensional electromagnetic field coil for a transponder interrogator

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5926093A (en) * 1997-08-15 1999-07-20 Checkpoint Systems, Inc. Drive circuit for reactive loads
US6307468B1 (en) * 1999-07-20 2001-10-23 Avid Identification Systems, Inc. Impedance matching network and multidimensional electromagnetic field coil for a transponder interrogator
US20020053973A1 (en) * 1999-07-20 2002-05-09 Ward William H. Impedance matching network and multidimensional electromagnetic field coil for a transponder interrogator

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
STEINER ET AL: "A tuning transformer for the automatic adjustment of resonant loop antennas in RFID systems.", PROCEEDINGS OF THE IEEE INTERNAIONAL CONFERENCE ON INDUSTRIAL TECHNOLOGY., vol. 2, 10 December 2004 (2004-12-10), pages 912 - 916-8 *

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