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EP1097438A1 - Circuit de transpondeur sans pile - Google Patents

Circuit de transpondeur sans pile

Info

Publication number
EP1097438A1
EP1097438A1 EP99933028A EP99933028A EP1097438A1 EP 1097438 A1 EP1097438 A1 EP 1097438A1 EP 99933028 A EP99933028 A EP 99933028A EP 99933028 A EP99933028 A EP 99933028A EP 1097438 A1 EP1097438 A1 EP 1097438A1
Authority
EP
European Patent Office
Prior art keywords
circuit
resonant
transponder
inductance
transponder circuit
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP99933028A
Other languages
German (de)
English (en)
Inventor
Anthony Clan Holdings Ltd. PARFITT
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Clan Holdings Ltd
Original Assignee
Clan Holdings Ltd
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 Clan Holdings Ltd filed Critical Clan Holdings Ltd
Publication of EP1097438A1 publication Critical patent/EP1097438A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/22—Electrical actuation
    • G08B13/24—Electrical actuation by interference with electromagnetic field distribution
    • G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
    • G08B13/2405—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting characterised by the tag technology used
    • G08B13/2422—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting characterised by the tag technology used using acoustic or microwave tags
    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; 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
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B13/00—Burglar, theft or intruder alarms
    • G08B13/22—Electrical actuation
    • G08B13/24—Electrical actuation by interference with electromagnetic field distribution
    • G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
    • G08B13/2428—Tag details
    • G08B13/2431—Tag circuit details

Definitions

  • This invention relates to a battery-less transponder circuit for use in an Electronic Article Surveillance system (EAS system).
  • the circuit is typically provided in a tag which is detected by the EAS system and which is attached to an article to prevent unauthorised removal thereof from the premises in which the system is installed.
  • EAS systems are usually installed in clothing, book, pharmacy, hi-fi, white good, and some music retail outlets to prevent unauthorised removal of articles therefrom.
  • the systems typically comprise one or more transmitters and detectors in the form of pedestals located at the customer entry/exit points of a retail outlet. These pedestals transmit a signal to a tag, provided internally with a transponder circuit, the tag being attached to the article.
  • the transponder circuit responds to a transmitted magnetic signal by re-radiating a second signal which is detected by the said pedestals thus triggering an alarm to indicate an attempt at unauthorised removal of articles.
  • the tags may be permanently or releasably attached to the article. At the point of sale of the article, the tag is either removed from the article, or is deactivated if permanently attached thereto.
  • EAS tags and systems are designed around different operating parameters, and the primary systems currently in use are Split Frequency (SF), Radio Frequency (RF), Acousto-magnetic (AM), Microwave Frequency (MF), Electromagnetic (EM).
  • SF Split Frequency
  • RF Radio Frequency
  • AM Acousto-magnetic
  • MF Microwave Frequency
  • EM Electromagnetic
  • This invention is primarily concerned with a transponder circuit which may be incorporated within a tag used in SF and EM systems in which the tag is releasably attached to an article such that it can be reused after removal therefrom.
  • an alternating magnetic field is transmitted between the pedestals and the tag is typically provided with a transponder circuit comprising, in its simplest form, a pair of LC resonant circuits which are electrically and/or magnetically coupled such that the second resonant circuit re- radiates a signal at a different frequency to that transmitted by the pedestals.
  • a transponder circuit comprising, in its simplest form, a pair of LC resonant circuits which are electrically and/or magnetically coupled such that the second resonant circuit re- radiates a signal at a different frequency to that transmitted by the pedestals. This allows the pedestals to detect an active tag on an article as it passes therebetween.
  • tags may be attached to a large number of articles within the retail premises where the EAS system is installed, there is a requirement that the tags are inexpensive, and therefore the inclusion of complex transponder circuitry or the provision of a battery powered transponder circuit are precluded.
  • the signal re-radiated by the transponder circuit must be of sufficient strength to induce a current in an inductance coils which forms the detection circuit of the pedestals. If this does not occur, then the tag escapes detection, and the article to which it is attached may be removed without authority.
  • transponder circuits employed within modern EAS tags, but in general there are two resonant circuits comprising at least one inductance in each circuit, and a reactance element such that the impedance of the overall circuit is miriimised at a particular frequency.
  • the magnitudes of the inductive and reactive elements of each circuit are specifically chosen such that the one of the transponder resonant circuits resonates at a first frequency which is identical to the frequency of the magnetic signal transmitted by the pedestals.
  • the second circuit resonates at a second frequency, which is usually half that of the first frequency, by means of the magnetic and/or electric coupling that may exist in the transponder circuit as a whole.
  • the inductances of the first and second resonant circuits are generally disposed on a core of a ferromagnetic material to enhance the mutual coupling therebetween, and allow the self-inductance values of each inductance to be varied (and thus the transponder circuit as a whole to be "tuned") by displacing the inductance coil such that its core is only partially filled with the ferromagnetic core.
  • the mutual coupling between the inductance coils of a resonant circuit affects the resonant frequency of each of said resonant circuits because the mutual inductance between the coils is reflected as an additional impedance in each of the resonant circuits.
  • the extent to which the inductance coils are disposed on a ferromagnetic core linking the two coils can affect both the mutual inductance between the coils and the self-inductance value within a resonant circuit.
  • the inclusion of a ferromagnetic core aids the ability of the transponder circuit to concentrate the magnetic flux of the magnetic transmitted signal, but has a sensitising effect on the transponder circuit.
  • the circuits can be tuned to provide a maximum response characteristic to magnetic radiation transmitted by the pedestal and received by the tag at a first frequency.
  • a transponder circuit comprising first and second resonant circuits, said first resonant circuit comprising at least a first inductance, a reactive component and at least one other impedance component, said second resonant circuit comprising at least a second inductance mutually coupled to the first inductance and a reactive component, characterised in that the first and second resonant circuits are electrically coupled across a circuit component common to both resonant circuits which may be the said reactive component, and in that the resonant frequencies of the said electrically coupled circuits are different.
  • first and second resonant circuits are electrically coupled across the reactive component which is thus shared betwixt the first and second resonant circuits.
  • the transponder circuit is preferably battery-less.
  • the at least one other impedance component is a reactive component, and further preferably being a capacitor.
  • the component with reactance is a diode.
  • the mutual coupling between the first and second inductances is enhanced by disposing said inductances on a common ferromagnetic core.
  • the transponder of the invention is comprised of a first inductance, a capacitance and a diode
  • the second resonant circuit comprises a second inductance mutually coupled to the first inductance and a diode, the said first and second resonant circuits being electrically coupled across and sharing said diode.
  • the simple circuit described above is inexpensive as the components comprised therein are freely available and are also inexpensive, and when the inductances are mutually coupled and disposed on a ferromagnetic core as disclosed, the tuning requirements of the transponder circuit are minimised, if not eradicated.
  • Figure 1 shows a schematic electrical circuit diagram for a transponder circuit according to the invention.
  • a transponder circuit 2 is provided with a first resonant circuit shown enclosed in the dotted lines at 4, and a second resonant circuit shown enclosed by the dotted lines at 6. It will be instantly seen from the schematic that a diode DI is shared by both resonant circuits, and that both resonant circuits 4, 6 are electrically coupled across said diode.
  • the first resonant circuit indicated at 4 comprises an inductance coil LI which is provided around a core FI of a ferromagnetic material, and also a capacitance Cl.
  • the combination of these inductive and reactive elements ensures that the circuit 4 resonates at a particular frequency.
  • the second circuit 6 comprises only an inductance L2 in series with the common diode DI, and as the diode is essentially a reactive component, the second circuit will also have a frequency at which it resonates.
  • the resonant frequency of the second circuit will be different from that of the first circuit, because the impedance of both circuits is different.
  • the magnitudes of the various inductive and reactive components should be chosen to ensure that the resonant frequency of the second circuit 6 is approximately half the resonant frequency of the first circuit.

Landscapes

  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Automation & Control Theory (AREA)
  • Computer Security & Cryptography (AREA)
  • Electromagnetism (AREA)
  • Acoustics & Sound (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Theoretical Computer Science (AREA)
  • Burglar Alarm Systems (AREA)
  • Radar Systems Or Details Thereof (AREA)

Abstract

On décrit un circuit de transpondeur sans pile destiné à être utilisé dans une étiquette de surveillance électronique d'articles. Le transpondeur est constitué de premier et deuxième circuits résonants qui sont électriquement couplés au niveau d'un constituant commun mais qui résonnent cependant à des fréquences différentes. Le premier circuit résonnant comprend idéalement une bobine d'inductance, un condensateur et une diode, et le deuxième circuit résonant n'est constitué que d'une bobine d'inductance qui est mutuellement couplée à la bobine d'inductance du premier circuit résonant mais connectée au niveau de la diode du premier circuit résonant. Cette connexion a pour effet de produire un deuxième circuit résonant qui est couplé à la fois électriquement et magnétiquement au premier circuit résonant. Ceci permet d'obtenir un circuit de transpondeur extrêmement peu coûteux mais véritablement efficace.
EP99933028A 1998-07-14 1999-07-13 Circuit de transpondeur sans pile Withdrawn EP1097438A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB9815120 1998-07-14
GBGB9815120.2A GB9815120D0 (en) 1998-07-14 1998-07-14 Battery-less transponder circuit
PCT/GB1999/002250 WO2000004520A1 (fr) 1998-07-14 1999-07-13 Circuit de transpondeur sans pile

Publications (1)

Publication Number Publication Date
EP1097438A1 true EP1097438A1 (fr) 2001-05-09

Family

ID=10835390

Family Applications (1)

Application Number Title Priority Date Filing Date
EP99933028A Withdrawn EP1097438A1 (fr) 1998-07-14 1999-07-13 Circuit de transpondeur sans pile

Country Status (5)

Country Link
EP (1) EP1097438A1 (fr)
AU (1) AU4920599A (fr)
GB (1) GB9815120D0 (fr)
TW (1) TW445436B (fr)
WO (1) WO2000004520A1 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
USRE47599E1 (en) 2000-10-20 2019-09-10 Promega Corporation RF point of sale and delivery method and system using communication with remote computer and having features to read a large number of RF tags
JP4074518B2 (ja) 2000-10-20 2008-04-09 プロメガ・コーポレーション 扉を有するキャビネット内の複数の製品を管理する方法
US20020183882A1 (en) 2000-10-20 2002-12-05 Michael Dearing RF point of sale and delivery method and system using communication with remote computer and having features to read a large number of RF tags

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
NL8204802A (nl) * 1982-12-10 1984-07-02 Nedap Nv Detectieplaatje met niet-lineair circuit voor een detectiestelsel.
NL8701541A (nl) * 1987-07-01 1989-02-01 Nedap Nv Identificatiesysteem voor de veehouderij.
US5241298A (en) * 1992-03-18 1993-08-31 Security Tag Systems, Inc. Electrically-and-magnetically-coupled, batteryless, portable, frequency divider
US5517179A (en) * 1995-05-18 1996-05-14 Xlink Enterprises, Inc. Signal-powered frequency-dividing transponder

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO0004520A1 *

Also Published As

Publication number Publication date
WO2000004520A1 (fr) 2000-01-27
GB9815120D0 (en) 1998-09-09
AU4920599A (en) 2000-02-07
TW445436B (en) 2001-07-11

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