EP2465103A1 - A method and device for identification purpose - Google Patents

A method and device for identification purpose

Info

Publication number
EP2465103A1
EP2465103A1 EP10808422A EP10808422A EP2465103A1 EP 2465103 A1 EP2465103 A1 EP 2465103A1 EP 10808422 A EP10808422 A EP 10808422A EP 10808422 A EP10808422 A EP 10808422A EP 2465103 A1 EP2465103 A1 EP 2465103A1
Authority
EP
European Patent Office
Prior art keywords
scattering
magnetic element
magnetic field
alternating
magnetic
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Withdrawn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
EP10808422A
Other languages
German (de)
French (fr)
Inventor
Carl Tyrén
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.)
Svenska Realvaerden AB
Original Assignee
SARCI AG
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 SARCI AG filed Critical SARCI AG
Publication of EP2465103A1 publication Critical patent/EP2465103A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/74—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
    • G01S13/75—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems using transponders powered from received waves, e.g. using passive transponders, or using passive reflectors
    • G01S13/751—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems using transponders powered from received waves, e.g. using passive transponders, or using passive reflectors wherein the responder or reflector radiates a coded signal
    • G01S13/753—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems using transponders powered from received waves, e.g. using passive transponders, or using passive reflectors wherein the responder or reflector radiates a coded signal using frequency selective elements, e.g. resonator
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/74—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
    • G01S13/75—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems using transponders powered from received waves, e.g. using passive transponders, or using passive reflectors
    • G01S13/751—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems using transponders powered from received waves, e.g. using passive transponders, or using passive reflectors wherein the responder or reflector radiates a coded signal
    • G01S13/756—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems using transponders powered from received waves, e.g. using passive transponders, or using passive reflectors wherein the responder or reflector radiates a coded signal using a signal generator for modifying the reflectivity of the reflector
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
    • G01V15/00—Tags attached to, or associated with, an object, in order to enable detection of the object
    • 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
    • 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
    • G06K19/077—Constructional details, e.g. mounting of circuits in the carrier
    • G06K19/07749—Constructional details, e.g. mounting of circuits in the carrier the record carrier being capable of non-contact communication, e.g. constructional details of the antenna of a non-contact smart card
    • 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
    • G08B13/2408—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 ferromagnetic tags
    • 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
    • G08B13/2414—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 inductive tags
    • 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
    • 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
    • G08B13/2437—Tag layered structure, processes for making layered tags
    • G08B13/2442—Tag materials and material properties thereof, e.g. magnetic material details

Definitions

  • TITLE A METHOD AND DEVICE FOR IDENTIFICATION PURPOSE
  • the present invention relates to a device for identification of objects, for example goods to be sold or identified in an inventory system.
  • Such means of identification may be a tag attached to the goods, such as RFID tags.
  • Identification of articles is desired in many applications.
  • the goods to be sold may be marked with tags.
  • the tag may be read at passage out of the store for different purposes. Such purpose may be to charge payment for the goods and/or for inventory purpose.
  • An identification system is shown, for example, in document WO 00/75894, which discloses a tag for electronic article identification.
  • the tag has several magnetic elements, which represent an identify of the tag, or the identity of an article to which the tag is attached.
  • the magnetic elements may be electromagnetically detected and are formed of wires made from an amorphous or nano-crystalline magnetic metal alloy.
  • the magnetic elements are arranged at predetermined angles to each other. At least one of the magnetic elements has a length, which is different from the length of the other magnetic elements of the tag.
  • At least one of the magnetic elements has a diameter, which is different from the diameter of the other magnetic elements of the tag.
  • the lengths and diameters of the magnetic elements, and the angles between them, jointly form the identity of the tag.
  • the magnetic field may be modulated by a low frequency signal.
  • the permeability of the element will change with the low frequency signal. If the element is exposed to an electromagnetic detection signal, such as a microwave signal, the reflectance properties of the element change with the magnetic field and the reflected microwave signal will be amplitude modulated with the low frequency signal. In this way, the length, the diameter and the angular direction of the element can be determined.
  • Document WO 93/14478 discloses a method and a device for remote sensing of objects.
  • the object is provided with a label comprising an electrical resonant circuit.
  • the resonant circuit is excited to resonance at a resonance frequency.
  • the resonance frequency of the resonant circuit is determined based on the electromagnetic energy transmitted from said resonant circuit.
  • An element of a magnetic material having a varying permeability is coupled inductively to an induction element of the resonant circuit.
  • the resonant frequency of said resonant circuit is affected by the permeability of said element of magnetic material.
  • the element of magnetic material is exposed to an external and spatially
  • Document WO 99/66466 A2 discloses a method for remote detection of objects, each object being provided with a sensor comprising at least two magnetic elements arranged in a predetermined mutual relationship representing an identity of the sensor. Electromagnetic signals are generated for exciting the sensor elements to produce electromagnetic reply signals. An amplitude of the electromagnetic reply signal from each sensor element is modulated by a first magnetic field having a magnitude-variant and a magnitude-invariant component. A second magnetic field is generated with rotating field vector.
  • a frequency shift is detected in a component of said reply signal, when a magnitude-invariant component of said second magnetic field balances the magnitude-invariant component of said first magnetic field, wherein the respective sensor element is momentarily exposed to a resulting magnetic field with essentially no magnitude-invariant component.
  • An orientation of the respective sensor element is determined from the orientation of the magnitude-invariant component of said second magnetic field, when said frequency shift occurs.
  • All the above-mentioned systems require that the tag enters a magnetic field with certain properties.
  • the influence of the magnetic field on a magnetic element in the tag is monitored, for example by a microwave system.
  • the monitoring can take place at a long distance of several tenths of meters or even 100 meters, but the magnetic field cannot be generated at such a distance. If the system should be made operative at larger distances, large magnets are required.
  • the system comprises a transponder comprising a retroreflecting arrangement and a modulation arrangement.
  • the modulating arrangement is arranged to apply a predetermined typ of patter of modulation to incident microwave radiation passing therethrough and reflected back to the source by the retroreflecting arrangement.
  • the modulation is obtained by passing the radiation through a varying magnetic field.
  • this system requires that the transponder is arranged in a specific manner in relation to the microwave source.
  • the modulation obtained by the varying magnetic field is weak, making the system difficult to detect.
  • the tag may be active, i.e. comprise a power source on-board, or passive, i.e. operable without an on-board power source.
  • an object of the present invention is to mitigate, alleviate or eliminate one or more of the above-identified deficiencies and disadvantages singly or in any combination.
  • a device for identification of an object comprising a magnetic element attached to the object, said magnetic element having a permeability, which is dependent on a magnetic field exposed to the magnetic element; a source of an alternating magnetic field for exposure of said magnetic element; and a microwave transmitter for exposing said magnetic element for microwaves and a microwave receiver for receiving microwaves reflected and/or retransmitted from said magnetic element and modulated by said alternating magnetic field; characterized in that said source of an alternating magnetic field is arranged on-board of the object.
  • the source of an alternating magnetic field may comprise an LC-circuit having a resonance frequency and wherein said magnetic element may be arranged adjacent an symmetry axis of a L-member of said LC-circuit.
  • the source of an alternating magnetic field may comprise a source of an alternating voltage or current having the same frequency as said resonance frequency and being powered by an energy source.
  • the energy source may be a battery.
  • the energy source may be energy which has been wirelessly transmitted to the object, and being electromagnetic radiation, ultrasound, or induction.
  • the source of an alternating magnetic field may comprise an oscillator circuit, the output of which may be connected to the ends of the magnetic element in order to pass an electric alternating current through the magnetic element.
  • the oscillator circuit may be arranged to generate several discrete frequencies in a time sequence, which frequencies form an identity of the object.
  • the magnetic element may be an amorphous or nano-crystalline magnetic wire.
  • the length of the magnetic wire may be half the wavelength of the microwaves.
  • the said source of an alternating magnetic field may comprise an oscillator circuit, the output of which is connected to the ends of a wire arranged adjacent and extending in parallel with the magnetic element in order to pass an electric alternating current through the wire for generating said alternating magnetic field.
  • Fig. 1 is a schematic diagram of a first embodiment.
  • Fig. 2 is a schematic diagram of a second embodiment including a circuit diagram of an oscillator.
  • Fig. 3 is a schematic diagram of a third embodiment.
  • Fig. 4 is a schematic diagram of a fourth embodiment.
  • Fig. 5 is a schematic diagram of a fifth embodiment.
  • Fig. 6 is a circuit diagram of an oscillator intended to be used in the fifth
  • Such a magnetic element is made of an amorphous or nano-crystalline magnetic wire for example as disclosed in WO 97/24734A1, the contents of which is incorporated in the present specification by reference.
  • This material may exhibit Giant Magnetoresistive properties or even Colossal Magnetoresistive properties, which might explain why a small magnetic field may cause a large change of permeability.
  • permeability is defined as the degree of magnetization of a material that responds to an applied magnetic field. Magnetic permeability is typically represented by the Greek letter ⁇ . The permeability is measured in Henry per meter (H/m), or Newton per ampere squared (N/A A 2). The permeability of the magnetic material influences directly upon the reflectivity of the magnetic material when exposed to electromagnetic radiation, such as microwaves. Thus, a variation of the permeability of the material will cause an amplitude modulation of the microwaves, which are scattered, reflected and/or retransmitted from the magnetic material.
  • the magnetic wire acts as a receiving antenna, which receives the microwaves directed towards the magnetic wire.
  • the energy received by the antenna is immediately retransmitted in all directions.
  • a part of the received energy is retransmitted towards a receiver.
  • the magnetic wire is seen by a receiver as an element, which scatters the microwave radiation, and thus, the expression "scattering magnetic element" will be used below.
  • the element should be arranged as a wire, which may act as an "antenna".
  • the wire may be made of an electrically conducting material.
  • the antenna may have a length corresponding to half the wavelength of the microwave radiation.
  • the wire may have a permeability and/or resistivity, which is variable and may be modulated by a magnetic field. Without being bound by a theory, it is believed that the magnetic field influences upon both the permability and the resistivity of the wire, which causes a variable scattering.
  • Fig. 1 shows a first embodiment of the invention, which comprises a tag 11 provided with a scattering magnetic element 12, an inductor 13 and a capacitor 14.
  • the tag and the circuit are similar to the tag shown in WO 93/14478.
  • the first embodiment comprises in addition a source 15 of an alternating current or voltage.
  • the inductor 13 is a coil of wires forming a cylinder.
  • the magnetic element 12 may be arranged outside the cylinder in close relationship to the cylinder and with the magnetic element 12 extending parallel with an axis of the coil, as schematically shown in Fig. 1.
  • the magnetic element 12 may be arranged inside the cylinder adjacent or at the axis thereof, as
  • the voltage source 15 is arranged to produce an alternating voltage with a low frequency.
  • the resonance circuit 13 and 14 is tuned to said low frequency.
  • the inductor 13 generates an alternating magnetic field, which is parallel with the scattering magnetic element 12 and modulates the permeability of the scattering magnetic element with the low frequency.
  • a microwave transmitter 16 transmits microwaves towards the scattering magnetic element and receives microwaves scattered by the scattering magnetic element 12 by a microwave receiver 17.
  • the tag itself comprises an on-board circuit 13, 14, 15 for producing an alternating magnetic field at the magnetic element 12.
  • Another difference in relation to WO 93/14478 is that in the present embodiment, the magnetic element is monitored by a microwave transceiver 16, 17.
  • the microwave transmitter 16 and receiver 17 can be arranged at a distance of several tenths of meters, or even 100 meters from the tag and will still be able to detect the low frequency modulation of the scattered or reflected microwaves.
  • a power source 15 with low energy contents can be used in the tag, which makes the tag light and cheap.
  • an alternating voltage source 15 is shown.
  • Such voltage source may be driven by a small battery arranged at the tag.
  • the alternating voltage may be obtained by a conventional oscillator circuit, such as a Hartley oscillator, a Colpitts oscillator, an Armstrong oscillator etc.
  • Fig. 2 shows a second embodiment comprising a conventional Hartley oscillator comprising a FET transistor 18 and a battery 19.
  • a switch 28 is arranged in the battery circuit and normally prevents current from passing out of the battery 19.
  • the switch 28 comprises an insulating material 29 normally arranged between two contacts. When the insulating material 29 is removed, the switch is closed and the circuit starts to oscillate at a frequency determined by the inductor 13 and the capacitor 14. The circuit oscillates until the battery is out of energy or the switch is opened.
  • the material 29 may be removed, for example manually, when the goods is taken from the shelf. If the battery time is sufficient for 6 hours, there is ample time for the buyer to pass the cost charging system.
  • the insulating material 29 can be removed in many different ways.
  • the material may include a substance that absorbs energy when passing an induction field so that the material melts.
  • the material may be an optical material that conducts current when exposed to light. The material may be removed manually, etc.
  • the tag may be used for identification purpose.
  • the tag may indicate a number associated with the goods, for example as used in an EAN system.
  • the number may be arranged in a memory arranged at the tag.
  • An output of the memory may interact with the capacitor 14, which may be a variable capacitor, the capacitance of which is altered by an external voltage.
  • the capacitor 14 which may be a variable capacitor, the capacitance of which is altered by an external voltage.
  • the tag may alternatively or additionally be used for a theft protection system.
  • the oscillator may have a fixed frequency. When said fixed frequency is sensed by sensor in an outpassing device from the shop, an alarm may be triggered.
  • the magnetic element is arranged parallel with a symmetry axis of the inductive coil element, which may have the same or larger length compared to the magnetic element.
  • the magnetic field should be directed in parallel with the magnetic element in order to influence as efficiently as possible on the permeability of the magnetic element.
  • the modulating magnetic field may be produced by exposing the LC-circuit for an electromagnetic radiation from a radio wave transmitter 36.
  • the LC-circuit may be tuned to a frequency of 200 kHz and an electromagnetic radiation with this frequency is directed towards the LC- circuit 13, 14.
  • the radiation will cause a current in the LC-circuit.
  • the current will be amplified.
  • the current in the L-element, i.e. the coil will produce a magnetic field inside the coil, which is amplified in relation to the free (electro-) magnetic field of the radiation, because of the Q-value of the LC-circuit.
  • the amplified magnetic field influences upon the scattering magnetic element 12 inside the coil and changes the permeability of the magnetic material.
  • the magnetic material is in addition exposed to microwaves from the transmitter 16, which are modulated by the changes in the permeability.
  • the modulated microwaves can be detected at a large distance by the receiver 17.
  • the tag according to the second embodiment can be considered to be a semi-passive tag. Since there is no power source on-board, the tag will operate at any time.
  • the on-board voltage source may include a capacitor, which is charged from a distance and then forms a voltage source when needed.
  • Wakeup circuitry is known in the prior art for producing an oscillating signal when activated by an electromagnetic signal.
  • the operation according to the second embodiment is different from the operation described in the publication WO 93/14478. It was unexpected to find that electromagnetic radiation, having low frequency, could change the magnetic properties of the scattering magnetic element 15 to such a degree, that it was detectable at a large distance by
  • the low frequency may be a few kHz up to several MHz. see further below.
  • the scattering magnetic element 12 should have certain properties.
  • the magnetic material may be an amorphous or nano-crystalline magnetic wire for example as disclosed in WO 97/24734A1, the contents of which is incorporated in the present specification by reference.
  • This material may exhibit Giant Magnetoresistive properties or even Colossal Magnetoresistive properties, which might explain why such a small magnetic field may cause such a large change of permeability.
  • the material may be for example an amorphous magnetic wire comprising a metallic amorphous core with a diameter ranging between 5 and 25 ⁇ m and of a composition based on Co containing 20 atomic % or less Si, 7 up to 35 atomic % B and 25 atomic % or less of one or more metals selected from the group Fe, Ni, Cr, Ta, Nb, V, Cu, Al, Mo, Mn, W, Zr, Hf and a glass cover with the thickness ranging between 1 and 15 ⁇ m, for example an alloy of composition Co70Fe5B15SilO.
  • the wire may be thin, such as below 25 ⁇ m, and may have a length adapted to the microwave frequency, such as about 49 mm for a microwave frequency of 2.45 GHz, which corresponds to half the wavelength of the microwaves. In another embodiment, the length is selected to correspond to the full wavelength or any length between the full wavelength and half the wavelength.
  • the tag may be exposed to a low frequency electromagnetic field, which is picked up by the coil of the resonance circuit, whereby a current is generated and a magnetic field is formed inside the inductor.
  • the low frequency field may be an electromagnetic field, for example in the long-wave range at about 200 kHz.
  • the transmitter 36 for such a long- wave electromagnetic field can be arranged at any distance from the tag, which is mainly only determined by the power of the source of long-wave radiation.
  • the resonance circuit will amplify the long-wave energy and produce a magnetic field, which is sufficient for influencing upon the permeability of the wire and cause amplitude modulation of the microwaves.
  • the long-wave radiation source may send radio waves at different frequencies and detect possible magnetic elements by the modulation of magnetic properties of the magnetic element.
  • a tag having a frequency resonance at frequency 220 kHz and a tag having a frequency resonance at 625 kHz are present, there will be microwave modulation signals at these frequencies, and the corresponding goods may be identified.
  • the on-board voltage source may include a capacitor, which is charged from a distance and then forms a voltage source when needed.
  • Wakeup circuitry is known in the prior art for producing an oscillating signal when activated by an electromagnetic signal.
  • the magnetic field is parallel with the length direction of the wire, and an inductor 13 and a capacitor 14, tuned to a low frequency, are used for generating a low-frequency, alternating magnetic field.
  • an inductor 13 and a capacitor 14, tuned to a low frequency are used for generating a low-frequency, alternating magnetic field.
  • such components may become relatively cumbersome at low frequencies.
  • the inductor 13 and the capacitor 14 has been replaced by a single wire 23 extending in parallel with the scattering magnetic element 22.
  • the voltage source may for example be said piezo-electric ultrasound transducer 25 or a separate oscillator driven by an on-board battery, such as for example the circuit shown in Fig. 6.
  • the magnetic field influencing upon the magnetic element 22 will be perpendicular to the longitudinal direction of the magnetic element.
  • the magnetic field is circular around the conductor 23.
  • the circuit produced a pronounced change of permeability of the magnetic element 22. This effect cannot be readily explained, but it is believed that it has something to do with the Giant Magnetoresistive properties of the magnetic material in the magnetic element.
  • the single wire 23 may have a predetermined resistivity, which is adapted to the power source.
  • the single wire 23 is arranged as close as possible to the scattering magnetic element 22.
  • Fig. 5 shows a fifth embodiment, wherein the alternating voltage source 25 is connected directly to the scattering magnetic element 32 so that an alternating current passes through the magnetic element 32, which acts as a conductor.
  • the alternating current produces a circular magnetic field.
  • still better performance may be obtained compared to the forth embodiment shown in Fig. 4. Again, this surprising effect cannot be easily explained.
  • the embodiments according to the invention can be used in many applications.
  • the frequency of the voltage source 15 can be set to a predetermined value, which is an identification of the tag.
  • n is a number between 1 and 1000, which gives 1000 identities.
  • 10 ⁇ 6 different identities may be coded.
  • n is a number between 100 and 1100.
  • the circuit 35 may be arranged to produce a series of frequencies, which are repeated until the battery power has been consumed. These frequencies may form the identity of the tag.
  • the tag is triggered to start producing said series of frequencies by an external signal, for example as mentioned above in connection with Fig. 2.
  • the oscillator may be an astabile multivibrator having several capacitors connected one after the other in time sequence to produce several frequencies after each other. Such a circuit is shown in Fig. 6.
  • the circuit of Fig. 6 is built around a circuit 61, a so called 555-IC, which is well known.
  • the 555-IC produces a square wave output signal, with a frequency defined by a capacitor at the input thereof.
  • a first capacitor 62 is always connected to the circuit 61.
  • the circuit produces a square wave signal at an output 67, which has a high frequency, determined by the capacitor value.
  • a counter 68 is arranged to produce a binary signal at two output contacts connected to two switch members 65, 66, in the nature of MOSFET transistors, for adding capacitors 63 and 64 to the circuit 61.
  • the counter is arranged to produce the following sequence of signals:
  • both the switch members 65, 66 are switched off and only the first capacitor determines the frequency, which becomes high, for example 550 kHz.
  • the second capacitor 63 is connected in parallel with the first capacitor 62 and the frequency becomes lower, for example 320 kHz.
  • the third capacitor 64 is connected in parallel with the first capacitor 62 and the frequency becomes still lower, for example 260 kHz.
  • both the second capacitor 63 and the third capacitor 64 are connected in parallel with the first capacitor 62 and the frequency becomes still lower, for example 210 kHz.
  • the output signal is fed to the wire 32 of Fig. 5, or to the magnetic member of any of the embodiments. These four frequencies form an identity for the tag and the goods at which the tag is attached.
  • the frequencies are detected by the microwave transceiver 16, 17.
  • the stability of the circuit 61 is sufficient for defining for example 100 different frequencies, whereby the number of combination of four frequencies becomes 10 ⁇ 8. Further frequencies may be added for increased number of combinations, for example 6 or 10 frequencies.
  • the multivibrator circuit may be based on a crystal oscillator oscillating at a high frequency of for example 100 MHz and divided down by a counter to a range of 100 kHz to 1100 kHz. Such a multivibrator will be very stable.
  • 13, 14 may be square wave signals or sinusoidal signals or any other suitable wave-shape, such as triangular.
  • a battery may power the circuit 61 in the same manner as shown in Fig. 2.
  • the magnetic material will change its permeability at frequencies up to several MHz and down to zero Hz.
  • the circuit may comprise means for charging an on-board power source.
  • the power source When the power source has been charged, for example by ultrasound energy or induction or any other means, the circuit will be producing said series of frequencies.
  • the tag In this case, the tag is self-supporting and may operate at any time the energy is supplied.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Remote Sensing (AREA)
  • Radar, Positioning & Navigation (AREA)
  • Automation & Control Theory (AREA)
  • Computer Security & Cryptography (AREA)
  • Electromagnetism (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Theoretical Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Computer Hardware Design (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geophysics (AREA)
  • Burglar Alarm Systems (AREA)
  • Geophysics And Detection Of Objects (AREA)

Abstract

A device for identification of an object, comprising a scattering magnetic element (12, 22, 32) attached to the object. The scattering magnetic element has a permeability, which is dependent on a magnetic field exposed to the magnetic element. Moreover, there is a source (13, 14, 15; 25; 35) of an alternating magnetic field for exposure of said scattering magnetic element. A microwave transmitter (16) exposes the scattering magnetic element for microwaves and a microwave receiver (17) receives microwaves scattered or reflected from the scattering magnetic element and modulated by the alternating magnetic field. The source of an alternating magnetic field is arranged on-board of the object and is powered by a battery. In an embodiment, the source of an alternating magnetic field comprises an LC- circuit having a resonance frequency and wherein the scattering magnetic element is arranged adjacent a symmetry axis of a L-member of the LC-circuit. In another embodiment, the object comprises an oscillator, the output of which is connected to the ends of the scattering magnetic element for passing an alternating current through the magnetic element. The scattering magnetic element is of a magnetic material, such as an amorphous or nano- crystalline magnetic wire, having a length corresponding to half the wavelength of the microwaves.

Description

TITLE: A METHOD AND DEVICE FOR IDENTIFICATION PURPOSE
FIELD OF INVENTION
The present invention relates to a device for identification of objects, for example goods to be sold or identified in an inventory system. Such means of identification may be a tag attached to the goods, such as RFID tags.
BACKGROUND OF THE INVENTION
Identification of articles is desired in many applications. In a store, the goods to be sold may be marked with tags. The tag may be read at passage out of the store for different purposes. Such purpose may be to charge payment for the goods and/or for inventory purpose.
An identification system is shown, for example, in document WO 00/75894, which discloses a tag for electronic article identification. The tag has several magnetic elements, which represent an identify of the tag, or the identity of an article to which the tag is attached. The magnetic elements may be electromagnetically detected and are formed of wires made from an amorphous or nano-crystalline magnetic metal alloy. The magnetic elements are arranged at predetermined angles to each other. At least one of the magnetic elements has a length, which is different from the length of the other magnetic elements of the tag.
Furthermore, at least one of the magnetic elements has a diameter, which is different from the diameter of the other magnetic elements of the tag. The lengths and diameters of the magnetic elements, and the angles between them, jointly form the identity of the tag. When the tag enters a magnetic field, the magnetic properties of the tag change, which can be used for detection purpose. The magnetic field may be modulated by a low frequency signal. The permeability of the element will change with the low frequency signal. If the element is exposed to an electromagnetic detection signal, such as a microwave signal, the reflectance properties of the element change with the magnetic field and the reflected microwave signal will be amplitude modulated with the low frequency signal. In this way, the length, the diameter and the angular direction of the element can be determined.
Document WO 93/14478 discloses a method and a device for remote sensing of objects. The object is provided with a label comprising an electrical resonant circuit. The resonant circuit is excited to resonance at a resonance frequency. The resonance frequency of the resonant circuit is determined based on the electromagnetic energy transmitted from said resonant circuit. An element of a magnetic material having a varying permeability is coupled inductively to an induction element of the resonant circuit. The resonant frequency of said resonant circuit is affected by the permeability of said element of magnetic material. In addition, the element of magnetic material is exposed to an external and spatially
heterogeneous magnetic bias field through which the permeability of said element of magnetic material is controlled. Document WO 99/66466 A2 discloses a method for remote detection of objects, each object being provided with a sensor comprising at least two magnetic elements arranged in a predetermined mutual relationship representing an identity of the sensor. Electromagnetic signals are generated for exciting the sensor elements to produce electromagnetic reply signals. An amplitude of the electromagnetic reply signal from each sensor element is modulated by a first magnetic field having a magnitude-variant and a magnitude-invariant component. A second magnetic field is generated with rotating field vector. A frequency shift is detected in a component of said reply signal, when a magnitude-invariant component of said second magnetic field balances the magnitude-invariant component of said first magnetic field, wherein the respective sensor element is momentarily exposed to a resulting magnetic field with essentially no magnitude-invariant component. An orientation of the respective sensor element is determined from the orientation of the magnitude-invariant component of said second magnetic field, when said frequency shift occurs.
All the above-mentioned systems require that the tag enters a magnetic field with certain properties. The influence of the magnetic field on a magnetic element in the tag is monitored, for example by a microwave system. The monitoring can take place at a long distance of several tenths of meters or even 100 meters, but the magnetic field cannot be generated at such a distance. If the system should be made operative at larger distances, large magnets are required.
A system operating according to a different technique is disclosed in US
2008/0284568. The system comprisesa transponder comprising a retroreflecting arrangement and a modulation arrangement. The modulating arrangement is arranged to apply a predetermined typ of patter of modulation to incident microwave radiation passing therethrough and reflected back to the source by the retroreflecting arrangement. The modulation is obtained by passing the radiation through a varying magnetic field. However, this system requires that the transponder is arranged in a specific manner in relation to the microwave source. In addition, the modulation obtained by the varying magnetic field is weak, making the system difficult to detect.
There is a need in the art for a system that can detect a tag at a large distance. In addition, the system should be able to detect tags that are coded with information so that a great number of different articles can obtain tags with separate identities. The tag may be active, i.e. comprise a power source on-board, or passive, i.e. operable without an on-board power source. SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to mitigate, alleviate or eliminate one or more of the above-identified deficiencies and disadvantages singly or in any combination. According to an aspect of the invention, there is provided a device for identification of an object, comprising a magnetic element attached to the object, said magnetic element having a permeability, which is dependent on a magnetic field exposed to the magnetic element; a source of an alternating magnetic field for exposure of said magnetic element; and a microwave transmitter for exposing said magnetic element for microwaves and a microwave receiver for receiving microwaves reflected and/or retransmitted from said magnetic element and modulated by said alternating magnetic field; characterized in that said source of an alternating magnetic field is arranged on-board of the object.
According to an embodiment, the source of an alternating magnetic field may comprise an LC-circuit having a resonance frequency and wherein said magnetic element may be arranged adjacent an symmetry axis of a L-member of said LC-circuit. The source of an alternating magnetic field may comprise a source of an alternating voltage or current having the same frequency as said resonance frequency and being powered by an energy source.
The energy source may be a battery. Alternatively, the energy source may be energy which has been wirelessly transmitted to the object, and being electromagnetic radiation, ultrasound, or induction.
According to another embodiment, the source of an alternating magnetic field may comprise an oscillator circuit, the output of which may be connected to the ends of the magnetic element in order to pass an electric alternating current through the magnetic element. The oscillator circuit may be arranged to generate several discrete frequencies in a time sequence, which frequencies form an identity of the object.
The magnetic element may be an amorphous or nano-crystalline magnetic wire. The length of the magnetic wire may be half the wavelength of the microwaves.
According to a further embodiment, the said source of an alternating magnetic field may comprise an oscillator circuit, the output of which is connected to the ends of a wire arranged adjacent and extending in parallel with the magnetic element in order to pass an electric alternating current through the wire for generating said alternating magnetic field.
BRIEF DESCRIPTION OF THE DRAWINGS
Further objects, features and advantages of the invention will become apparent from the following detailed description of embodiments of the invention with reference to the drawings, in which:
Fig. 1 is a schematic diagram of a first embodiment.
Fig. 2 is a schematic diagram of a second embodiment including a circuit diagram of an oscillator.
Fig. 3 is a schematic diagram of a third embodiment.
Fig. 4 is a schematic diagram of a fourth embodiment.
Fig. 5 is a schematic diagram of a fifth embodiment. Fig. 6 is a circuit diagram of an oscillator intended to be used in the fifth
embodiment.
DETAILED DESCRIPTION OF EMBODIMENTS
Below, several embodiments of the invention will be described with references to the drawings. These embodiments are described in illustrating purpose in order to enable a skilled person to carry out the invention and to disclose the best mode. However, such embodiments do not limit the invention. Moreover, other combinations of the different features are possible within the scope of the invention.
Document WO 99/66466A2 mentioned above, discloses a magnetic element, which is very sensitive to an applied magnetic field. An oscillating magnetic field having a field strength, which is equal to or smaller than the earth magnetic field, may cause a change of the permeability of the magnetic element, which is possible to detect by a microwave system.
Such a magnetic element is made of an amorphous or nano-crystalline magnetic wire for example as disclosed in WO 97/24734A1, the contents of which is incorporated in the present specification by reference. This material may exhibit Giant Magnetoresistive properties or even Colossal Magnetoresistive properties, which might explain why a small magnetic field may cause a large change of permeability.
The expression "permeability" is defined as the degree of magnetization of a material that responds to an applied magnetic field. Magnetic permeability is typically represented by the Greek letter μ. The permeability is measured in Henry per meter (H/m), or Newton per ampere squared (N/AA2). The permeability of the magnetic material influences directly upon the reflectivity of the magnetic material when exposed to electromagnetic radiation, such as microwaves. Thus, a variation of the permeability of the material will cause an amplitude modulation of the microwaves, which are scattered, reflected and/or retransmitted from the magnetic material.
Without being bound by any theory, it is believed that the magnetic wire acts as a receiving antenna, which receives the microwaves directed towards the magnetic wire. The energy received by the antenna is immediately retransmitted in all directions. Thus, a part of the received energy is retransmitted towards a receiver. The magnetic wire is seen by a receiver as an element, which scatters the microwave radiation, and thus, the expression "scattering magnetic element" will be used below. In order to act as a scattering element, the element should be arranged as a wire, which may act as an "antenna". The wire may be made of an electrically conducting material.
It has also been found that if the element has a length, which is substantially longer than the cross-dimension of the wire, the scattering properies will be pronounced. In addition, the antenna may have a length corresponding to half the wavelength of the microwave radiation. The wire may have a permeability and/or resistivity, which is variable and may be modulated by a magnetic field. Without being bound by a theory, it is believed that the magnetic field influences upon both the permability and the resistivity of the wire, which causes a variable scattering.
Fig. 1 shows a first embodiment of the invention, which comprises a tag 11 provided with a scattering magnetic element 12, an inductor 13 and a capacitor 14. The tag and the circuit are similar to the tag shown in WO 93/14478. However, the first embodiment comprises in addition a source 15 of an alternating current or voltage. The inductor 13 is a coil of wires forming a cylinder. The magnetic element 12 may be arranged outside the cylinder in close relationship to the cylinder and with the magnetic element 12 extending parallel with an axis of the coil, as schematically shown in Fig. 1. Alternatively, the magnetic element 12 may be arranged inside the cylinder adjacent or at the axis thereof, as
schematically shown in Fig. 2.
The voltage source 15 is arranged to produce an alternating voltage with a low frequency. The resonance circuit 13 and 14 is tuned to said low frequency. When the alternating voltage is applied to the resonance circuit 13, 14, a resonance occurs. The inductor 13 generates an alternating magnetic field, which is parallel with the scattering magnetic element 12 and modulates the permeability of the scattering magnetic element with the low frequency.
A microwave transmitter 16 transmits microwaves towards the scattering magnetic element and receives microwaves scattered by the scattering magnetic element 12 by a microwave receiver 17.
Instead of causing the magnetic field to vary from a distance, as disclosed in
WO 93/14478, the tag itself comprises an on-board circuit 13, 14, 15 for producing an alternating magnetic field at the magnetic element 12. Another difference in relation to WO 93/14478 is that in the present embodiment, the magnetic element is monitored by a microwave transceiver 16, 17.
It has been found that the first embodiment according to Fig. 1 is very sensitive. A weak voltage source 15 is required in order to generate a low frequency magnetic field having adequate strength to modulate the scattering magnetic element 12. The microwave transmitter 16 and receiver 17 can be arranged at a distance of several tenths of meters, or even 100 meters from the tag and will still be able to detect the low frequency modulation of the scattered or reflected microwaves. Thus, a power source 15 with low energy contents can be used in the tag, which makes the tag light and cheap.
In the embodiment according to Fig. 1, an alternating voltage source 15 is shown.
Such voltage source may be driven by a small battery arranged at the tag. The alternating voltage may be obtained by a conventional oscillator circuit, such as a Hartley oscillator, a Colpitts oscillator, an Armstrong oscillator etc. Fig. 2 shows a second embodiment comprising a conventional Hartley oscillator comprising a FET transistor 18 and a battery 19. A switch 28 is arranged in the battery circuit and normally prevents current from passing out of the battery 19. The switch 28 comprises an insulating material 29 normally arranged between two contacts. When the insulating material 29 is removed, the switch is closed and the circuit starts to oscillate at a frequency determined by the inductor 13 and the capacitor 14. The circuit oscillates until the battery is out of energy or the switch is opened.
If the tag 11 is used in a shop for cost charging purpose, the material 29 may be removed, for example manually, when the goods is taken from the shelf. If the battery time is sufficient for 6 hours, there is ample time for the buyer to pass the cost charging system.
The insulating material 29 can be removed in many different ways. The material may include a substance that absorbs energy when passing an induction field so that the material melts. The material may be an optical material that conducts current when exposed to light. The material may be removed manually, etc.
The tag may be used for identification purpose. In this case, the tag may indicate a number associated with the goods, for example as used in an EAN system. The number may be arranged in a memory arranged at the tag. An output of the memory may interact with the capacitor 14, which may be a variable capacitor, the capacitance of which is altered by an external voltage. Thus, when the memory outputs a "one", the capacitance has a first value causing a first oscillation frequency, and when the memory outputs a "zero", the capacitance has a second value causing a second oscillation frequency. Thus, the memory contents can be read from a distance. Other methods may be used.
The tag may alternatively or additionally be used for a theft protection system. In this case, the oscillator may have a fixed frequency. When said fixed frequency is sensed by sensor in an outpassing device from the shop, an alarm may be triggered.
The magnetic element is arranged parallel with a symmetry axis of the inductive coil element, which may have the same or larger length compared to the magnetic element. The magnetic field should be directed in parallel with the magnetic element in order to influence as efficiently as possible on the permeability of the magnetic element.
In a third embodiment shown in Fig. 3, it has been found that the modulating magnetic field may be produced by exposing the LC-circuit for an electromagnetic radiation from a radio wave transmitter 36. For example, the LC-circuit may be tuned to a frequency of 200 kHz and an electromagnetic radiation with this frequency is directed towards the LC- circuit 13, 14. The radiation will cause a current in the LC-circuit. Because of the resonance and Q-value of the LC-circuit, the current will be amplified. The current in the L-element, i.e. the coil, will produce a magnetic field inside the coil, which is amplified in relation to the free (electro-) magnetic field of the radiation, because of the Q-value of the LC-circuit. The amplified magnetic field influences upon the scattering magnetic element 12 inside the coil and changes the permeability of the magnetic material. The magnetic material is in addition exposed to microwaves from the transmitter 16, which are modulated by the changes in the permeability. The modulated microwaves can be detected at a large distance by the receiver 17. Thus, there is no requirement for an on-board power source 15. The tag according to the second embodiment can be considered to be a semi-passive tag. Since there is no power source on-board, the tag will operate at any time.
Similar transmission of energy may be performed by other wireless methods, such as infrared light, induction, sound or ultrasound etc. The on-board voltage source may include a capacitor, which is charged from a distance and then forms a voltage source when needed. Wakeup circuitry is known in the prior art for producing an oscillating signal when activated by an electromagnetic signal.
The operation according to the second embodiment is different from the operation described in the publication WO 93/14478. It was unexpected to find that electromagnetic radiation, having low frequency, could change the magnetic properties of the scattering magnetic element 15 to such a degree, that it was detectable at a large distance by
microwaves.
The low frequency may be a few kHz up to several MHz. see further below.
The scattering magnetic element 12 should have certain properties.
The magnetic material may be an amorphous or nano-crystalline magnetic wire for example as disclosed in WO 97/24734A1, the contents of which is incorporated in the present specification by reference. This material may exhibit Giant Magnetoresistive properties or even Colossal Magnetoresistive properties, which might explain why such a small magnetic field may cause such a large change of permeability.
The material may be for example an amorphous magnetic wire comprising a metallic amorphous core with a diameter ranging between 5 and 25 μm and of a composition based on Co containing 20 atomic % or less Si, 7 up to 35 atomic % B and 25 atomic % or less of one or more metals selected from the group Fe, Ni, Cr, Ta, Nb, V, Cu, Al, Mo, Mn, W, Zr, Hf and a glass cover with the thickness ranging between 1 and 15 μm, for example an alloy of composition Co70Fe5B15SilO.
The wire may be thin, such as below 25 μm, and may have a length adapted to the microwave frequency, such as about 49 mm for a microwave frequency of 2.45 GHz, which corresponds to half the wavelength of the microwaves. In another embodiment, the length is selected to correspond to the full wavelength or any length between the full wavelength and half the wavelength.
As described above in the third embodiment, the tag may be exposed to a low frequency electromagnetic field, which is picked up by the coil of the resonance circuit, whereby a current is generated and a magnetic field is formed inside the inductor. In this case, no separate voltage source 15 is required and the tag comprises only the inductor 13, the capacitor 14 and the magnetic element 12. The low frequency field may be an electromagnetic field, for example in the long-wave range at about 200 kHz. The transmitter 36 for such a long- wave electromagnetic field can be arranged at any distance from the tag, which is mainly only determined by the power of the source of long-wave radiation. The resonance circuit will amplify the long-wave energy and produce a magnetic field, which is sufficient for influencing upon the permeability of the wire and cause amplitude modulation of the microwaves.
The long-wave radiation source may send radio waves at different frequencies and detect possible magnetic elements by the modulation of magnetic properties of the magnetic element. Thus, if a tag having a frequency resonance at frequency 220 kHz and a tag having a frequency resonance at 625 kHz are present, there will be microwave modulation signals at these frequencies, and the corresponding goods may be identified.
Other manners of forming an alternating voltage without using on-board battery would be to arrange a piezoelectric crystal tuned to a frequency well above the audible range, such as about 100 kHz. An ultrasound source of the same frequency is directed towards the tag and picked up by the piezoelectric crystal acting as a microphone. The audio energy is converted to an electric voltage, which is used as the alternating voltage source 15 or as a battery source.
Similar transmission of energy may be performed by other wireless methods, such as infrared light, etc. The on-board voltage source may include a capacitor, which is charged from a distance and then forms a voltage source when needed. Wakeup circuitry is known in the prior art for producing an oscillating signal when activated by an electromagnetic signal.
In all the above embodiments, the magnetic field is parallel with the length direction of the wire, and an inductor 13 and a capacitor 14, tuned to a low frequency, are used for generating a low-frequency, alternating magnetic field. However, such components may become relatively cumbersome at low frequencies.
However, in a fourth embodiment shown in Fig. 4, the inductor 13 and the capacitor 14 has been replaced by a single wire 23 extending in parallel with the scattering magnetic element 22. The voltage source may for example be said piezo-electric ultrasound transducer 25 or a separate oscillator driven by an on-board battery, such as for example the circuit shown in Fig. 6. In this case, the magnetic field influencing upon the magnetic element 22 will be perpendicular to the longitudinal direction of the magnetic element. The magnetic field is circular around the conductor 23. Surprisingly, the circuit produced a pronounced change of permeability of the magnetic element 22. This effect cannot be readily explained, but it is believed that it has something to do with the Giant Magnetoresistive properties of the magnetic material in the magnetic element. The single wire 23 may have a predetermined resistivity, which is adapted to the power source. The single wire 23 is arranged as close as possible to the scattering magnetic element 22.
Fig. 5 shows a fifth embodiment, wherein the alternating voltage source 25 is connected directly to the scattering magnetic element 32 so that an alternating current passes through the magnetic element 32, which acts as a conductor. The alternating current produces a circular magnetic field. In this case, still better performance may be obtained compared to the forth embodiment shown in Fig. 4. Again, this surprising effect cannot be easily explained.
The embodiments according to the invention can be used in many applications. The frequency of the voltage source 15 can be set to a predetermined value, which is an identification of the tag. Thus, the frequency can be selected according to the formula below: f= n * 1000 Hz
Wherein n is a number between 1 and 1000, which gives 1000 identities. By using two such circuits at the same tag, 10Λ6 different identities may be coded.
In some cases, it might be inconvenient to use low frequencies below 20 kHz, for example if an ultrasound transducer is used. In such cases, frequencies in the range of 100 kHz to 1100 kHz may be used, i.e. n is a number between 100 and 1100.
The circuit 35 may be arranged to produce a series of frequencies, which are repeated until the battery power has been consumed. These frequencies may form the identity of the tag. The tag is triggered to start producing said series of frequencies by an external signal, for example as mentioned above in connection with Fig. 2.
The oscillator may be an astabile multivibrator having several capacitors connected one after the other in time sequence to produce several frequencies after each other. Such a circuit is shown in Fig. 6.
The circuit of Fig. 6 is built around a circuit 61, a so called 555-IC, which is well known. The 555-IC produces a square wave output signal, with a frequency defined by a capacitor at the input thereof. In the circuit of Fig. 6, there are three capacitors, 62, 63, and 64, which may be connected to the circuit 61. A first capacitor 62 is always connected to the circuit 61. When this capacitor 62 is connected, the circuit produces a square wave signal at an output 67, which has a high frequency, determined by the capacitor value.
A counter 68 is arranged to produce a binary signal at two output contacts connected to two switch members 65, 66, in the nature of MOSFET transistors, for adding capacitors 63 and 64 to the circuit 61. The counter is arranged to produce the following sequence of signals:
00, 01, 10, 11, 00 for example during one second. When the output signals become 00, both the switch members 65, 66 are switched off and only the first capacitor determines the frequency, which becomes high, for example 550 kHz. When the output signals become 01 after about 250 ms, the second capacitor 63 is connected in parallel with the first capacitor 62 and the frequency becomes lower, for example 320 kHz. When the output signals become 10 after another 250 ms, the third capacitor 64 is connected in parallel with the first capacitor 62 and the frequency becomes still lower, for example 260 kHz. When the output signals become 11 after another 250 ms, both the second capacitor 63 and the third capacitor 64 are connected in parallel with the first capacitor 62 and the frequency becomes still lower, for example 210 kHz. Then, the sequence starts from the beginning again. In this manner, four different frequencies are produced in sequence. The output signal is fed to the wire 32 of Fig. 5, or to the magnetic member of any of the embodiments. These four frequencies form an identity for the tag and the goods at which the tag is attached. The frequencies are detected by the microwave transceiver 16, 17.
The stability of the circuit 61 is sufficient for defining for example 100 different frequencies, whereby the number of combination of four frequencies becomes 10Λ8. Further frequencies may be added for increased number of combinations, for example 6 or 10 frequencies.
If better stability is desired, the multivibrator circuit may be based on a crystal oscillator oscillating at a high frequency of for example 100 MHz and divided down by a counter to a range of 100 kHz to 1100 kHz. Such a multivibrator will be very stable.
The signals fed to the scattering magnetic element 32, the wire 23 or the LC-circuit
13, 14 may be square wave signals or sinusoidal signals or any other suitable wave-shape, such as triangular.
A battery may power the circuit 61 in the same manner as shown in Fig. 2.
There are almost no limits as to what frequencies that can be used. The magnetic material will change its permeability at frequencies up to several MHz and down to zero Hz.
As mentioned above, the circuit may comprise means for charging an on-board power source. When the power source has been charged, for example by ultrasound energy or induction or any other means, the circuit will be producing said series of frequencies. In this case, the tag is self-supporting and may operate at any time the energy is supplied.
Although the present invention has been described above with reference to specific embodiment, it is not intended to be limited to the specific form set forth herein. Rather, the invention is limited only by the accompanying claims and, other embodiments than the specific above are equally possible within the scope of these appended claims.
In the claims, the term "comprises/comprising" does not exclude the presence of other elements or steps. Furthermore, although individually listed, a plurality of means, elements or method steps may be implemented by e.g. a single unit or processor.
Additionally, although individual features may be included in different claims, these may possibly advantageously be combined, and the inclusion in different claims does not imply that a combination of features is not feasible and/or advantageous. In addition, singular references do not exclude a plurality. The terms "a", "an", "first", "second" etc do not preclude a plurality. Reference signs in the claims are provided merely as a clarifying example and shall not be construed as limiting the scope of the claims in any way.

Claims

1. A device for identification of an object, comprising:
a microwave transmitter (16) for exposing the object for microwaves and a microwave receiver (17) for receiving microwaves from said object;
whereby the object comprises:
a scattering magnetic element (12, 22, 32) having scattering properties, which are dependent on a magnetic field exposed to the scattering magnetic element;
a source (13, 14, 15; 25; 35) of an alternating magnetic field arranged on-board of the object for exposure of said scattering magnetic element for the alternating magnetic field for influencing upon the scattering properties of said scattering magnetic element.
2. The device according to claim 1, wherein said source (13, 14) of an alternating magnetic field comprises an LC-circuit having a resonance frequency and wherein said scattering magnetic element is arranged adjacent an symmetry axis of an L-member of said LC-circuit.
3. The device according to claim 2, wherein said source (13, 14, 15) of an alternating magnetic field comprises a source of an alternating voltage or current having the same frequency as said resonance frequency and being powered by an energy source.
4. The device according to claim 3, wherein said energy source is a battery.
5. The device according to claim 3, wherein said energy source is energy which has been wirelessly transmitted to the object, and being electromagnetic radiation, ultrasound, or induction.
6. The device according to any of the above claims, wherein said source (35) of an alternating magnetic field comprises an oscillator circuit (61), the output (67) of which is connected to the ends of the scattering magnetic element in order to pass an electric alternating current through the scattering magnetic element.
7. The device according to claim 6, wherein said oscillator circuit is arranged to generate several discrete frequencies in a time sequence, which frequencies form an identity of the object.
8. The device according to any one of the previous claims, wherein said scattering magnetic element is an amorphous or nano-crystalline magnetic wire.
9. The device according to any one of the previous claims, wherein said scattering magnetic element is an amorphous or nano-crystalline magnetic wire made by an electrically conducting material.
10. The device according to claim 8 or 9, wherein the length of the magnetic wire is half the wavelength of the microwaves.
11. The device according to claim 1, wherein said source (35) of an alternating magnetic field comprises an oscillator circuit (61), the output (67) of which is connected to the ends of a wire (23) arranged adjacent and extending in parallel with the scattering magnetic element (22) in order to pass an electric alternating current through the wire (23) for generating said alternating magnetic field.
12. An identification object, comprising:
a scattering magnetic element (12, 22, 32) having a permeability, which is dependent on a magnetic field exposed to the magnetic element;
a source (13, 14, 15; 25; 35) of an alternating magnetic field arranged on-board of the object for exposure of said scattering magnetic element for the alternating magnetic field for influencing upon the scattering properties of said scattering magnetic element.
13. A method for identification of an object, comprising
directing microwave radiation towards the object;
detecting microwave radiation scattered by the object;
analyzing the detected microwave radiation for amplitude modulation caused by an alternating magnetic field generated by the object and influencing upon a scattering magnetic element arranged at the object and exposed to said alternating magnetic field, whereby scattering properties of said scattering magnetic element is modulated by said alternating magnetic field.
EP10808422A 2009-08-14 2010-08-14 A method and device for identification purpose Withdrawn EP2465103A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
SE0901082A SE534420C2 (en) 2009-08-14 2009-08-14 An apparatus for identification purposes
US27621809P 2009-09-10 2009-09-10
PCT/SE2010/000203 WO2011019311A1 (en) 2009-08-14 2010-08-14 A method and device for identification purpose

Publications (1)

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EP2465103A1 true EP2465103A1 (en) 2012-06-20

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SE469673B (en) * 1992-01-20 1993-08-16 Rso Corp SETTING AND DEVICE ON CONTACT-FREE SALE OF OBJECTS
GB0515523D0 (en) * 2005-07-28 2005-12-07 Bae Systems Plc Transponder

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* Cited by examiner, † Cited by third party
Title
See references of WO2011019311A1 *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2529867C2 (en) * 2013-01-10 2014-10-10 Федеральное государственное бюджетное учреждение "Арктический и антарктический научно-исследовательский институт" Method of controlling ship movement

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SE0901082A1 (en) 2011-02-15
SE534420C2 (en) 2011-08-16

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