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WO1998011504A1 - Passive transponder - Google Patents

Passive transponder

Info

Publication number
WO1998011504A1
WO1998011504A1 PCT/DE1996/001761 DE9601761W WO9811504A1 WO 1998011504 A1 WO1998011504 A1 WO 1998011504A1 DE 9601761 W DE9601761 W DE 9601761W WO 9811504 A1 WO9811504 A1 WO 9811504A1
Authority
WO
Grant status
Application
Patent type
Prior art keywords
transponder
circuit
modulation
voltage
station
Prior art date
Application number
PCT/DE1996/001761
Other languages
German (de)
French (fr)
Inventor
Pourang Mahdavi
Original Assignee
Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.
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

Links

Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01SRADIO 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
    • G01S13/00Systems 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
    • G01S13/74Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
    • G01S13/75Systems 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
    • G01S13/751Systems 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
    • G01S13/758Systems 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 powered by the interrogation signal
    • GPHYSICS
    • G06COMPUTING; CALCULATING; COUNTING
    • G06KRECOGNITION OF DATA; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K19/00Record carriers for use with machines and with at least a part designed to carry digital markings
    • G06K19/06Record 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
    • G06K19/067Record 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
    • G06K19/07Record 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
    • G06K19/0723Record 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

Abstract

The invention deals with a passive transponder, which has a resonant circuit (LT, CT) having a transponder coil (LT), a control logic (20), a switching device (S) controlled by the control logic, a supply voltage capacitor (CS), a resistor (RL) lying parallel to the supply voltage capacitor (CS) and a rectifier circuit (D) to load the supply voltage capacitor (CS) as a function of the voltage induced by the transponder coil (LT) at the resonant circuit. The switching device (S) connects the resistor (RL) and the supply voltage capacitor (CS) through the rectifier circuit (D) to the resonant circuit (LT, CT) when closed, and it disconnects the resistor (RL) and the supply voltage capacitor (CS) from the resonant circuit (LT, CT) when open.

Description

passive transponder

description

The present invention relates to a transponder and more particularly to a passive transponder and a modulation method for modulating the data sent from the transponder to a reading station.

In the field of microelectronics and microsystems technology used and the micro transponder technology is used increasingly. Transponder with an offset spatially from a base unit system is generally referred to receive the data, send, store and possibly can also be processed. Microtransponder are spatially remote System components, ie microelectronics or microsystems technology, are realized by microtechnology. The distance between the transponder and the base unit can be divided into ranges from a few millimeters, a few meters and even a few hundred meters. The different distance ranges are referred to short-range, mid-range and long-range. A micro transponder may include a memory with an identification code and / or sensors for various physical and / or chemical parameters as sources of information.

A schematic representation of an arrangement consisting of a reading station and a transponder is shown in Fig. L. There are transponders which have no internal energy source and its energy by means of a resonant circuit Lr, C τ from an incident interrogation field 10 that relate through an antenna to the reading station, which is caused by a coil L s of particular interest. In this case it is called passive transponders. Passive transponders can be made very small and have a theoretically unlimited life. The application areas of passive transponders are extremely widely diversified, ranging from medical technology, for example implants with RF data link over which safety technology, such as access control with contactless smart card to CIM applications (CIM = com puterized integrated manufacturing = computer-integrated manufacturing ), such as a workpiece identification.

A more accurate representation of the typical arrangement of the known transponder in the interrogation field of a reader station is shown in Fig. 2. The read station generates via the antenna Lg a high-frequency interrogation field 10. The transponder comprises a tuned to the frequency of the interrogation field resonant circuit L T / C τ on, the energy removes from the high-frequency interrogation field 10, and thereby generates a voltage. The voltage is the diode D, and further rectified by a capacitor C s connected in parallel with the resonant circuit is smoothed by a rectifying means in the representation in Fig. 2. The voltage U thus obtained from the interrogation field then provides the supply voltage for the actual transponder circuit 20, which may comprise for example a read only memory and a control circuit. The resistance of the transponder circuit may be modeled by the dashed lines shown working resistance R L.

Accordingly, the overlay set a voltage in the form of a reflected wave is produced at the read station then through the transponder coil CIV, wherein the amount of the voltage generated at the read station to the current flowing through the transponder coil L τ is proportional.

The data transmission from the transponder to the reading station is performed by the switching on or off a plane parallel to the resonant circuit L τ, C τ, additional modulation resistor R M by an electronic switch S. This switch is controlled by the actual transponder circuit 20th By switching the switch S to the L s by the antenna radiated interrogation field in the rhythm of the switch S is removed more or less energy, which is generated at the antenna of the read station an AC signal voltage u signaled. The transponder data which are for example stored in the ROM, the switch S is controlled by the control circuit the actual transponder circuit 20, by the processing of this signal U S i gna; Li determined. This process of transferring data from the transponder to the reading station is known as absorption modulation and, for example, in P. Neukomm, H. Baggentos, "Passive telemetry absorption modulation", ETH Zurich, Design & Elektronik, 09.18.1990, described in detail.

The method of the absorption modulation has the disadvantage of the additional expense of the power source of the transponder, namely the resonant circuit L τ, τ C, by the modulation resistance R M. Thereby a reduction of the supply voltage U c and thus a reduction in reading distance is effected. Minimum modulation losses are when the modulation resistance R M in comparison to the working resistance, which is modeled by the resistor R L, the transponder circuit is large. the incoming signals in the reading station Usignall 'whereby the noise sensitivity of the system is increased, which in turn results in a reduction of the reading distance result, however, the larger the working resistance RL, the weaker.

Regardless of the carried out in the last paragraph considerations the process of the absorption modulation remains disadvantageous in that valuable energy in the modulation resistance R M is destroyed by the absorption modulation, with the result that the range of the transponder system is always less than pure at a energy transfer would be possible.

Starting from the aforementioned prior art the present invention has for its object to provide a passive transponder which allows a transfer of data from the transponder to a reading station with a reduced susceptibility to interference and an increased read distance.

This object is achieved by a passive transponder according to Claim. 1

Another object of the present invention is to provide a modulation method for data transmission from a transponder to a reading station with a reduced susceptibility to interference and an increased read distance.

This object is achieved by a modulation method according to claim. 6

The present invention provides a passive transponder with a transponder coil having resonant circuit, a control logic, an controlled by the control logic switch, a power supply capacitor, a plane parallel to the supply voltage generator load and a rectifier circuit for charging the supply voltage capacitor as a result of the of the transponder coil in resonant circuit induced voltage, wherein the switch in its closed state connects the load and the supply voltage capacitor via the rectifier circuit to the resonant circuit and the load in its opened state of the resonance circuit separates.

The inventive passive transponder, the problem of additional energy dissipation in the modulation resistance R jf according to the prior art and the low efficiency of the modulation is achieved in the case of the conventional absorption modulation.

The modulation method according to the invention for data transmission from a transponder to a reading station is DA characterized by that the modulation of the transmitted from the transponder to the reading station data by switching between a payload of the transponder and a with respect to the payload higher impedance load is. This switching is in the preferred embodiment of the present invention carried out by the opening of a switch which is connected between the resonant circuit of the transponder and the payload. Due to the effect produced by this switching process of the invention may be referred to as an idle modulation.

By the method of idle modulation for the transponder, the modulation losses of the transponder are minimized. Thereby, since the power consumption of the transponder and the necessary strength of the interrogation field are reduced, the reading distance of the transponder system increased. Furthermore, the incoming in the reading station transponder signals when using the idle modulation are stronger than is the case when using the absorption modulation method. This has a greater noise immunity and a smaller error rate of the transmission result. In the same range can thus the antennas, that is, the coils, which constructed according to the invention, the transponder can be realized less. This in turn means that the transponder can be made smaller and cheaper.

Further developments of the present invention are set out in the dependent claims.

Preferred embodiments of the present invention are explained in detail below with reference to the accompanying drawings. Show it:

Figure 1 is a rough schematic representation of an arrangement of write station and the transponder.

Figure 2 is a schematic illustration of a reading station and a transponder, which operates according to the method of the waste Sorptionsmodulation.

Figure 3 is a schematic illustration of a reading station and a transponder according to the invention.

Fig. 4 is a diagram showing the characteristics of the power drawn by the resonant circuit to the interrogation field reactive power P L c "of the received from the transponder active power Pip, and the voltage produced by the transponder to the reading station U R, depending on the working resistance R L of the transponder; and

Fig. 5 diagrams the "Transponder-supply voltage" U c and the voltage applied to the reading station signals u and u Signall Signal2-

Will be explained below with reference to FIGS. 3 to 5, a preferred embodiment of the present invention. Elements of Lesesta- tion / transponder arrangement shown in Fig. 3 corresponding to those of the arrangement shown in Fig. 2 are identified by the same reference numerals as in Fig. 2.

The reading station of the arrangement shown in Fig. 3 corresponds to the reading station of Fig. 2 and generated by means of the coil L s, a high-frequency interrogation field 10..

The transponder comprises according to the preferred embodiment of the present invention, a parallel resonance circuit consisting of an inductor Lr and a capacitor C τ on. An output of the resonant circuit is connected to the input terminal of a rectifier device which is formed in the preferred embodiment by a diode D,. The second terminal of the diode D is connected to the first terminal of a switch S. The second terminal of the switch S is connected via a capacitor C s to the second output of the tank circuit Lp, C τ. The capacitor C s is used as a supply voltage ponders capacitor of the transport. As shown in Fig. 3 by dashed lines, the payload of the transponder can be represented as a resistance R L which is connected in parallel with the capacitor C s.

The transponder further comprises an actual transponder circuit 20, which substantially corresponds to the transponder circuitry described above with reference to FIG. 2. Such circuits are well known in the art.

Missing compared with the example shown in Fig. 2 known transponder in the illustrated in Fig. 3 according to the invention the transponder the modulation resistance R M. Further, the switch S is no longer parallel to the resonant circuit L τ, connected Cm, but serially connected thereto.

Based on the characteristic field, which is shown in Fig. 4, the difference of the known absorption is hereinafter described modulation method and the idle modulation method of the invention. The characteristics shown in Fig. 4 are each shown as a function of the working resistance of the transponder circuit R L in normalized form.P corresponds to the LC withdrawn from the interrogation field reactive power in the resonant circuit of the transponder, P τ corresponds to the power absorbed by the transponder active power, and U R corresponds to the amplitude of the voltage generated by the transponder to the reading station in the reading direction. The operating point of the transponder is typically chosen close to the point (A), since a power adjustment for the transponder circuit is present.

Starting from the operating point (A), in the prior art in accordance with the transponder shown in Fig. 2, the switch S is open, closing the switch in the known transponder has a switch from operating point (A) to that shown in Fig. point shown in Figure 4 (B) the effect thereby at the read station generates a signal U s ^ gnall. The signal S j U "na ιι is transmitted through the absorption modulation from the transponder to the reading station DA is ten.

In the inventive transponder according to Fig. 3, the switch S is closed in the initial state, so that the transponder through the interrogator high-frequency field and the resonant circuit m, τ C can be supplied with power. At the beginning of the modulation phase, the switch S is in the rhythm of the data to be transmitted through the circuit 20 which contains, for example a read only memory and a control circuit on and off. In the characteristic curve of the voltage U R, which is shown in Fig. 4, this means a shift from the operating point (A) to operating point (C). In contrast to the known method of absorption modulation no attenuation of the transponder resonant circuit thus occurs. Much more can swing up and an open switch S until the open circuit voltage thus take the maximum energy from the interrogation field, the resonant circuit. When the switch S is closed from this state, this energy is in the form of the voltage of the capacitor C τ tor in the Versorgungsspannungskondensa- C reloaded s. Over a Modulationszyklusses only capacitive Umladeverluste and no ohmic losses thus incurred in the inventive transponder. Therefore, the efficiency of energy transfer in this circuit is higher than in the known circuit of FIG. 2.

As a result of the more favorable energy balance in the inventive method, the point to be selected (C) at a greater distance from the point (A). For this reason, the incoming at the read station voltage u Signal2 'd ^ - e corresponding to the transmitting from the transponder to the reading station data, more than with the known method of absorbing modulation in which the modulation is caused by an attenuation of the transponder resonant circuit.

A comparison of these voltages is shown in Fig. 5. . In the upper left graph of Figure 5, the voltage u Siqnall '^ - is produced by the conventional absorption modulation is illustrated. In the lower left diagram, the voltage at the transponder circuit U c is shown in the known transponder. In the upper right diagram of the voltage generated by the inventive idle modulation method at the read station is shown Usi q nal. 2 In the lower right graph of Fig. 5, the present invention at the transponder voltage U c is shown. Further, in the lower diagrams in each case the modulation frequency is shown, which controls the switching of the switch S. This modulation frequency is that for the same component values, the minimum allowable voltage at the respective transponder circuit, for example, 9 volts, does not fall below chosen so.

The diagrams illustrated determined show in Fig. 5 that the transponder signal at the reading station in the inventive method the idle modulation about a factor of four greater than the signal that is generated in the known method the absorption modulation.

Claims

claims
1. The passive transponder with
a transponder coil (L τ) comprising resonant circuit (L τ, c τ), a control logic (20), a controlled by the control logic switch (S), a power supply capacitor (C s), a (parallel to the supply-voltage capacitor C s ) load applied (R L) and a rectifier circuit (D) for charging the power supply capacitor (C s) due to a (by the transponder coil L τ) in the resonant circuit induced voltage, characterized in that
that the switch (S) in its closed state, the load (R L) and the power supply capacitor (C s) via the rectifier circuit (D) to the resonant circuit (L τ, C τ) connects, and the load (R L) and the supply voltage capacitor (C s) separated into its opened state of the resonant circuit (L τ, τ C).
2. The passive transponder according to claim 1, characterized in that
that the rectifier circuit (D) is a diode.
3. The passive transponder according to claim 1 or 2, characterized in that
that the resonant circuit (L τ, τ c) is a parallel resonance circuit consisting of the parallel circuit of a transponder coil (L τ) and a capacitor (C τ).
4. The passive transponder according to any one of claims 1 to 3, characterized. that the load (RL) is formed by the working resistance of the passive transponder.
5. The passive transponder according to any of claims 1 to 4, characterized in that
that the switch (S) in series with the resonant circuit (L τ, τ C) is connected.
6. modulation method for data transmission from a transponder to a reading station, characterized in that
that the modulation of the transmitted from the transponder to the reading station data by switching between a payload of the transponder and a payload with respect to the higher impedance load is.
7. modulation method according to claim 6, characterized in that
that the switching between the normal load of the transponder and with respect to the normal load higher impedance load by the opening of a switch (S) coupled between a resonant circuit (L τ, c τ) of the transponder and the load (RL) of the transponder is connected, is carried out ,
PCT/DE1996/001761 1996-09-12 1996-09-12 Passive transponder WO1998011504A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/DE1996/001761 WO1998011504A1 (en) 1996-09-12 1996-09-12 Passive transponder

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/DE1996/001761 WO1998011504A1 (en) 1996-09-12 1996-09-12 Passive transponder

Publications (1)

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WO1998011504A1 true true WO1998011504A1 (en) 1998-03-19

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Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1999060509A1 (en) * 1998-05-15 1999-11-25 Infineon Technologies Ag Device for the contactless transmission of data
EP0974798A2 (en) * 1998-07-20 2000-01-26 Liebherr-Hausgeräte Gmbh Freezer
FR2787655A1 (en) * 1998-12-21 2000-06-23 St Microelectronics Sa capacitive modulation in electromagnetic transponder
EP1164532A2 (en) * 1998-05-15 2001-12-19 Infineon Technologies AG Device for the contactless transmission of data
WO2002047592A2 (en) * 2000-12-12 2002-06-20 Kimberly-Clark Worldwide, Inc. Wetness signaling device
WO2005006246A2 (en) * 2003-07-02 2005-01-20 Ge Medical Systems Global Technology Company, Llc Wireless electromagnetic tracking system using a nonlinear passive transponder
EP1760639A1 (en) * 2000-11-30 2007-03-07 ZIH Corporation Input impedance arrangement for RF transponder

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0242906A1 (en) * 1986-04-22 1987-10-28 N.V. Nederlandsche Apparatenfabriek NEDAP Electromagnetic identification system
US4918416A (en) * 1987-03-18 1990-04-17 Sielox Systems, Inc. Electronic proximity identification system
EP0492569A2 (en) * 1990-12-28 1992-07-01 On Track Innovations Ltd. A system and method for the non-contact transmission of data
DE4434240C1 (en) * 1994-09-24 1995-11-30 Norbert H L Dr Ing Koster Dynamic modulation arrangement for transponder with compact structure

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0242906A1 (en) * 1986-04-22 1987-10-28 N.V. Nederlandsche Apparatenfabriek NEDAP Electromagnetic identification system
US4918416A (en) * 1987-03-18 1990-04-17 Sielox Systems, Inc. Electronic proximity identification system
EP0492569A2 (en) * 1990-12-28 1992-07-01 On Track Innovations Ltd. A system and method for the non-contact transmission of data
DE4434240C1 (en) * 1994-09-24 1995-11-30 Norbert H L Dr Ing Koster Dynamic modulation arrangement for transponder with compact structure

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6533178B1 (en) 1998-05-15 2003-03-18 Infineon Technologies Ag Device for contactless transmission of data
WO1999060509A1 (en) * 1998-05-15 1999-11-25 Infineon Technologies Ag Device for the contactless transmission of data
EP1164532A2 (en) * 1998-05-15 2001-12-19 Infineon Technologies AG Device for the contactless transmission of data
EP1164532A3 (en) * 1998-05-15 2002-01-02 Infineon Technologies AG Device for the contactless transmission of data
EP0974798A3 (en) * 1998-07-20 2000-11-02 Liebherr-Hausgeräte Gmbh Freezer
EP0974798A2 (en) * 1998-07-20 2000-01-26 Liebherr-Hausgeräte Gmbh Freezer
FR2787655A1 (en) * 1998-12-21 2000-06-23 St Microelectronics Sa capacitive modulation in electromagnetic transponder
EP1014300A1 (en) * 1998-12-21 2000-06-28 STMicroelectronics SA Capacitive modulation in a electromagnetic transponder
US6356198B1 (en) 1998-12-21 2002-03-12 Stmicroelectronics S.A. Capacitive modulation in an electromagnetic transponder
EP1760639A1 (en) * 2000-11-30 2007-03-07 ZIH Corporation Input impedance arrangement for RF transponder
WO2002047592A2 (en) * 2000-12-12 2002-06-20 Kimberly-Clark Worldwide, Inc. Wetness signaling device
WO2002047592A3 (en) * 2000-12-12 2003-04-03 Kimberly Clark Co Wetness signaling device
WO2005006246A2 (en) * 2003-07-02 2005-01-20 Ge Medical Systems Global Technology Company, Llc Wireless electromagnetic tracking system using a nonlinear passive transponder
WO2005006246A3 (en) * 2003-07-02 2006-06-08 Ge Med Sys Global Tech Co Llc Wireless electromagnetic tracking system using a nonlinear passive transponder

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