WO1999038109A1 - Systeme de transaction - Google Patents

Systeme de transaction Download PDF

Info

Publication number
WO1999038109A1
WO1999038109A1 PCT/GB1999/000244 GB9900244W WO9938109A1 WO 1999038109 A1 WO1999038109 A1 WO 1999038109A1 GB 9900244 W GB9900244 W GB 9900244W WO 9938109 A1 WO9938109 A1 WO 9938109A1
Authority
WO
WIPO (PCT)
Prior art keywords
token
terminal
voltage
controller
token according
Prior art date
Application number
PCT/GB1999/000244
Other languages
English (en)
Inventor
Melvin Paul Clarkson
Neil Andrew Mcdonald
Original Assignee
Marconi Communications Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from GB9801442A external-priority patent/GB2333493B/en
Application filed by Marconi Communications Limited filed Critical Marconi Communications Limited
Priority to AU21795/99A priority Critical patent/AU2179599A/en
Publication of WO1999038109A1 publication Critical patent/WO1999038109A1/fr

Links

Classifications

    • 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
    • G06K19/0701—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 at least one of the integrated circuit chips comprising an arrangement for power management
    • G06K19/0715—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 at least one of the integrated circuit chips comprising an arrangement for power management the arrangement including means to regulate power transfer to the integrated circuit
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K19/00—Record carriers for use with machines and with at least a part designed to carry digital markings
    • G06K19/06—Record carriers for use with machines and with at least a part designed to carry digital markings characterised by the kind of the digital marking, e.g. shape, nature, code
    • G06K19/067—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components
    • G06K19/07—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components with integrated circuit chips
    • G06K19/0723—Record carriers with conductive marks, printed circuits or semiconductor circuit elements, e.g. credit or identity cards also with resonating or responding marks without active components with integrated circuit chips the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs

Definitions

  • This invention relates to a transaction system in which a portable token, for example a
  • a card is used in conjunction with a device, often termed a terminal, to perform a
  • the invention is particularly, but not exclusively, related to
  • Contactless tokens work on, or close to, a terminal which provides power. This power is supplied via a RF (radio frequency) induction field which is referred to as a carrier field. Power is transferred from an aerial in the terminal to an aerial on the token and is akin to the terminal being a primary coil of a transformer and the token being a secondary coil. In particular embodiments both the terminal and the token each have a single aerial each of which may comprise a coil having one or more turns.
  • RF radio frequency
  • the terminal modulates it onto the carrier field.
  • the token switches an impedance to modulate the
  • the token receives a variable AC voltage supply. Rectification of the AC voltage supply provides the token with an unregulated DC voltage supply which is
  • Token controllers require a reasonably steady voltage supply to give reliable performance. For this reason a regulator is usually incorporated into circuitry connected to the token aerial in order to regulate the unregulated voltage supply.
  • voltages supplied to it must be within maximum and minimum values.
  • the voltage supply to a controller should not vary by more than 10%. Although variation of ⁇ 20% might be tolerated, the controller might become unreliable in operation.
  • Typical operating voltages are 3 V or 5V with a variation of ⁇ 10%. If less voltage than the minimum operating value is supplied the controller will not work reliably. If more voltage than the maximum operating value is supplied circuits in the controller could be damaged. The maximum value is limited by the characteristics of circuits on a controller silicon die and the
  • the token sends data to the terminal by altering the effect of its load on the carrier field of the terminal. Conveniently this is achieved by changing the impedance of the token in the carrier field as perceived by the terminal. Since the shunt regulator compensates for any changes in load, changes in current drawn by the controller due to different instructions or changes in clock speed are compensated for by the shunt regulator and so do not perturb the carrier field and thus do not appear as data from the token.
  • amplitude modulation is preferred because it is a simple and
  • the token will operate at larger separations from the terminal because it consumes less power (and the power available from carrier field decreases with increasing token separation from the terminal).
  • a small current is available from the current source only a small current can be supplied to the controller.
  • a series regulator has a voltage dropout and so its use will restrict the input voltage range available to the controller.
  • the invention provides a contactless token for communicating with a terminal of a transaction system the token and the terminal communicating via
  • the terminal Preferably the terminal generates a carrier field. Preferably the excess voltage is highest when a large carrier field is present and lowest when a small carrier field is present. 5
  • the regulator is a shunt regulator.
  • the load impedance is a resistor.
  • it could be an active load
  • resistance value may be set so that the breakdown voltage of the controller is not exceeded when the token is close to the terminal.
  • the load impedance can be modified by switching in an extra component, circuit or sub-circuit so as to cause modulation of the carrier field at the terminal aerial.
  • the extra component, circuit or sub-circuit may be an impedance.
  • the extra component, circuit or sub-circuit is switched in in parallel. Alternatively, it may be switched in in series.
  • the load impedance is an active load its value can be set, and possibly altered, by a control circuit.
  • the token transmits data to the terminal by altering its own impedance in the carrier field. This may be detected by the terminal as data represented by amplitude modulation.
  • the load impedance drops less voltage across itself at low voltages.
  • low voltages are in the range 3 to 6V. Most preferably a low voltage is substantially 3 or 5V.
  • high voltages are in the range 15 to 21V. Most preferably a high voltage is 18V. 6
  • the invention provides a transaction system comprising a
  • Figure 1 shows a schematic representation of a transaction system
  • Figure 2 shows a schematic representation of the electrical circuitry of a contactless token
  • Figure 3 shows voltage and current characteristics of a token at a number of different separations from a terminal.
  • Figure 1 shows a transaction system 110 comprising a terminal 112 and a token, such as a smart card, 114.
  • the terminal 112 has a carrier source 116 and a modulation source 118.
  • the modulation source 118 produces a modulation signal 120 which is a data signal.
  • the modulation signal 120 may contain raw data 122 such as transaction related information and instructions. It may also contain a clock signal 124.
  • a carrier modulator 126 uses the modulation signal 120 to modulate a carrier source signal 128 produced by
  • the carrier modulator 126 produces a modulated
  • the token 114 has an aerial 134 and an interface 136 which is connected to a controller
  • the aerial 134 receives the modulated carrier signal 130 and from it the interface 136, and thus the controller 138, extracts a clock and a data 7 signal 140 and power 142.
  • the controller 138 processes the data signal 140 to produce its own data to be transmitted to the terminal 112 to conduct a transaction.
  • Transmission of data from the token to the terminal is carried out by switching an impedance 143 across the aerial 134 and thus changing the amount of power drawn by
  • the terminal 112 receives a signal representative of the impedance switching and detects the token data in data receiving means or a detector 144. Extracted data 146 is then processed by the terminal 112.
  • FIG. 2 shows a token 10 in a schematic representation and, more particularly, shows its power supply circuit for its electronic controller or processor.
  • the token 10 has an aerial 12 which is tuned by a capacitor 14. This makes power extraction more efficient at large separations of the token and a terminal (for example 10cm) because it amplifies induced voltage.
  • AC power induced in the aerial 12 and capacitor 14 is converted to DC power by a rectifier 16. In the present embodiment this is a full bridge rectifier.
  • the output of the rectifier 16 is smoothed by a capacitor 18 to reduce voltage ripple.
  • rectifier 16 produces an unregulated voltage supply 44 which is connected to a shunt regulator 20 via a load resistor 42.
  • the shunt regulator 20 regulates voltage supply 22
  • the shunt regulator 20 which is supplied to a controller 26, such as a microprocessor.
  • the shunt regulator 20 is supplied to a controller 26, such as a microprocessor.
  • controller voltage supply 22 operates by comparing the controller voltage supply 22 to a reference voltage 24.
  • controller voltage supply 22 is scaled to a voltage 28 typically in
  • the voltage 28 is compared to the reference voltage 24 which is also typically in the region of 1.25V.
  • the reference voltage is 8 supplied by a bandgap circuit.
  • the token may use a Zener
  • the difference between voltages 24 and 28 is amplified by an operational amplifier 32 to provide a control signal 34 which controls operation of a transistor 36, which is typically a FET.
  • the transistor 36 takes a proportion of current (I) from the current
  • Capacitor 38 is used to decouple the power supply of the controller. It supplies the current for any current spikes required by the controller which the regulator is not fast enough to provide and so helps provide a stable voltage supply for the controller 26. Current spikes normally occur on clock edges due to the way the controller logic works, which is usually synchronous logic.
  • the power drawn by the token 10 from the carrier field of a terminal depends on various factors
  • the unregulated voltage supply provided by the rectifier changes as the impedance in the token is switched for the token to transmit data, but the shunt regulator stops the impedance 9 change affecting the controller voltage supply 22 of the controller 26 and inhibits data transmission from the token.
  • the unregulated voltage supply provided by the rectifier changes as the impedance in the token is switched for the token to transmit data, but the shunt regulator stops the impedance 9 change affecting the controller voltage supply 22 of the controller 26 and inhibits data transmission from the token.
  • the unregulated voltage supply provided by the rectifier changes as the impedance in the token is switched for the token to transmit data, but the shunt regulator stops the impedance 9 change affecting the controller voltage supply 22 of the controller 26 and inhibits data transmission from the token.
  • the unregulated voltage supply provided by the rectifier changes as the impedance in the token is switched for the token to transmit data, but the shunt regulator stops the impedance 9 change affecting the controller voltage supply 22 of the controller 26 and inhibits data transmission from the token.
  • voltage supply 44 also changes when data is transmitted by the token but this does not
  • the impedance 40 and the load resistor 42 are the same type of component, for example both impedances and preferably both resistors, they can be different.
  • Component 40 does not have to be an impedance, but could be a weak current sink or a voltage clamp. The only requirement of component 40 is that it is able to alter the impedance of the token in the carrier field of the terminal.
  • the load resistor typically has a resistance of 500 ⁇ .
  • the effect of the load resistor is best explained with reference to Figure 3.
  • Figure 3 is a graph showing unregulated voltage supply in the token against current drawn by the token. As is explained above in relation to Figure 2, the unregulated voltage supply and current are DC supplies provided by the rectifier 16.
  • a number of characteristic lines 50 are shown each indicating current (I,) against unregulated voltage provided by the rectifier 16. Each line represents a specific
  • the characteristic lines 50 have a negative gradient because the DC power supplied by the rectifier 16 is equivalent to a supply provided by a voltage 10 source which has a resistance.
  • the characteristic lines 50 can be determined empirically or by analytical methods. As can be seen in this case, they are fairly horizontal so the terminal inductive coupling and the token rectifier are acting like a current source.
  • the graph shows a number of power lines 52 each of which shows how values of voltage and current vary in providing a fixed value of power to the token.
  • the lines 52 show the variation with received power values of 200, 250 and 300mW.
  • controller or more particularly the silicon die in the controller, can only dissipate a certain amount of power. If the controller receives more power than this, it may
  • a typical maximum power for a controller is 250mW.
  • the power lines 52 define upper operating characteristics for the token. For example a silicon die capable of working up to +125 °C in an ambient temperature of 75 °C which
  • the maximum power dissipation (effectively the relative amounts of voltage and current) is not always at 0cm separation between the token and the terminal. In some cases this may be at greater separations, for example 1.5cm. This is because the maximum power dissipation in the token occurs at a critical coupling point which depends on the Q-factors of the aerials of the token and the terminal. If the critical coupling point is exceeded beyond a separation of 0cm power dissipation will fall as the token becomes closer to the terminal than the critical coupling point.
  • Minimum voltage limit 54 is set by the shunt regulator 20 which
  • Limit 56 shows a typical breakdown
  • Line 60 is the load characteristic imposed by having the load resistor 42 inserted between the rectifier 16 and the regulator 20. One end of the line 60 is point 62 which
  • the gradient of line 60 is determined by the resistance of the load resistor 42. If the impedance 40 is switched in parallel with the load resistor 42, the combined resistance of resistors 40 and 42 in parallel is lower than the resistance of the load resistor 42 and so load characteristics of the token change from line 60 to line 64. It should be noted that line 64 also originates from point 62.
  • the characteristic of the load resistor 42 changes from that of load line 60 to that of load line 64. Therefore, the overall load of the token changes which affects the voltage in the aerial in the terminal.
  • the change may be detected by the terminal as amplitude modulation. More importantly this switching in of impedance 40 does not affect the performance of the shunt regulator 20 at any separation. Therefore the voltage supply to the controller remains stable.
  • the change in loading due to data transmission compensates with separation, for example it is weaker at larger
  • AM amplitude modulation
  • the load resistor 42 allows AM to be received without affecting
  • the operation of the shunt regulator 20 Furthermore, it allows the rectifier to be used to AM demodulate the carrier as well as provide power supply to the token.
  • the signal at 44 is removed from the influence of the clamping of the shunt regulator 20, therefore 13 the signal AM modulated on the carrier now appears on the DC power supply at 44 with the carrier ripple reduced by the capacitor 18.
  • Data can be extracted by a detector AC
  • This signal could be data or a tone for use in providing a controller clock or both.
  • the resistance of the load resistor is chosen so that both the unregulated voltage limit 56 and the maximum power dissipation are not exceeded at the critical coupling point. Usually this is at a small separation, for example 0cm.
  • the load resistor 42 dissipates excess power across itself. The closer the token is to the terminal, the more voltage it drops across itself. The shunt regulator 20 does not drop any voltage.
  • the presence of the load resistor 42 means that the operating point is defined by line 60 and is at point 66.
  • the token still works and provides more than the minimum necessary current for the controller. This is because less voltage is dropped across the load resistor 42. Therefore, the presence of the load resistor 42 maximises the separation at which the token and the terminal can operate.
  • the load resistor 42 fixes the maximum current available at any separation so if a token
  • the token may take, for example, 1mA at 10cm which allows it to work at 10cm and may also take 15mA at 0cm. Therefore this allows it to 14 make maximum use of current available to it, and so the token is not restricted to operation at small separations. Clearly this provides an advantage over a token with a low constant current supply.
  • the controller 26 can take any value up to the maximum permitted by the load resistor 42 at a particular separation because the shunt regulator 20 takes any excess. Therefore
  • I z controller current
  • I y +I Z I x (where I x is the maximum permitted current via the load resistor 42). Therefore controller load variations are not transmitted to the terminal and therefore are not detected as data transmissions from the token.
  • I x remains constant if the separation is constant although it does change with changing separation.

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  • Engineering & Computer Science (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Dc Digital Transmission (AREA)
  • Near-Field Transmission Systems (AREA)

Abstract

On décrit un jeton sans contact (10) qui permet de communiquer avec un terminal à travers un couplage inductif. Le terminal radiodiffuse une porteuse radioélectrique reçue par une antenne (12) dans le jeton (10) puis convertie en puissance et en données. La puissance reçue par l'antenne (12) est redressée par un redresseur (16) pour fournir une alimentation en continu (22), puis régulée par un régulateur de haute tension (20). Une résistance de charge (42) est disposée entre le redresseur (16) et le régulateur (20) pour baisser la surtension provoquée par le redresseur (16), afin d'optimiser la portée de la distance d'exploitation entre le terminal et le jeton (10).
PCT/GB1999/000244 1998-01-24 1999-01-22 Systeme de transaction WO1999038109A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU21795/99A AU2179599A (en) 1998-01-24 1999-01-22 Transaction system

Applications Claiming Priority (4)

Application Number Priority Date Filing Date Title
GB9801442.6 1998-01-24
GB9801442A GB2333493B (en) 1998-01-24 1998-01-24 Transaction system
GB9803381.4 1998-02-19
GB9803381A GB2333495B (en) 1998-01-24 1998-02-19 Transaction system

Publications (1)

Publication Number Publication Date
WO1999038109A1 true WO1999038109A1 (fr) 1999-07-29

Family

ID=26313005

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1999/000244 WO1999038109A1 (fr) 1998-01-24 1999-01-22 Systeme de transaction

Country Status (2)

Country Link
AU (1) AU2179599A (fr)
WO (1) WO1999038109A1 (fr)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5045770A (en) * 1988-02-04 1991-09-03 Magellan Corporation (Aust.) Pty. Ltd. Shunt regulator for use with resonant input source
US5479172A (en) * 1994-02-10 1995-12-26 Racom Systems, Inc. Power supply and power enable circuit for an RF/ID transponder
GB2307379A (en) * 1995-11-20 1997-05-21 Sony Corp Transponder device with overvoltage protection
GB2307364A (en) * 1995-11-20 1997-05-21 Sony Corp Voltage clamp circuit; non-contact type information card

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5045770A (en) * 1988-02-04 1991-09-03 Magellan Corporation (Aust.) Pty. Ltd. Shunt regulator for use with resonant input source
US5479172A (en) * 1994-02-10 1995-12-26 Racom Systems, Inc. Power supply and power enable circuit for an RF/ID transponder
GB2307379A (en) * 1995-11-20 1997-05-21 Sony Corp Transponder device with overvoltage protection
GB2307364A (en) * 1995-11-20 1997-05-21 Sony Corp Voltage clamp circuit; non-contact type information card

Also Published As

Publication number Publication date
AU2179599A (en) 1999-08-09

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