WO2023121548A1 - Communication arrangement and method of controlling communication in a smartcard comprising a fingerprint sensor module - Google Patents

Communication arrangement and method of controlling communication in a smartcard comprising a fingerprint sensor module Download PDF

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Publication number
WO2023121548A1
WO2023121548A1 PCT/SE2022/051209 SE2022051209W WO2023121548A1 WO 2023121548 A1 WO2023121548 A1 WO 2023121548A1 SE 2022051209 W SE2022051209 W SE 2022051209W WO 2023121548 A1 WO2023121548 A1 WO 2023121548A1
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WO
WIPO (PCT)
Prior art keywords
inductive coil
communicate
antenna loop
frequency
wireless communication
Prior art date
Application number
PCT/SE2022/051209
Other languages
French (fr)
Inventor
Johan Hammersberg
Mats Slottner
Erik NAESLUND
Anton LANDBERG
Original Assignee
Fingerprint Cards Anacatum Ip Ab
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Filing date
Publication date
Application filed by Fingerprint Cards Anacatum Ip Ab filed Critical Fingerprint Cards Anacatum Ip Ab
Publication of WO2023121548A1 publication Critical patent/WO2023121548A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/58—Structural electrical arrangements for semiconductor devices not otherwise provided for, e.g. in combination with batteries
    • H01L23/64—Impedance arrangements
    • H01L23/66—High-frequency adaptations
    • 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
    • G06K19/0716—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 a sensor or an interface to a sensor
    • G06K19/0718—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 a sensor or an interface to a sensor the sensor being of the biometric kind, e.g. fingerprint sensors
    • 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
    • G06K19/0724—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 the arrangement being a circuit for communicating at a plurality of frequencies, e.g. for managing time multiplexed communication over at least two antennas of different types
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/58—Structural electrical arrangements for semiconductor devices not otherwise provided for, e.g. in combination with batteries
    • H01L23/64—Impedance arrangements
    • H01L23/645—Inductive arrangements
    • H04B5/26—
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2223/00—Details relating to semiconductor or other solid state devices covered by the group H01L23/00
    • H01L2223/58—Structural electrical arrangements for semiconductor devices not otherwise provided for
    • H01L2223/64—Impedance arrangements
    • H01L2223/66—High-frequency adaptations
    • H01L2223/6644—Packaging aspects of high-frequency amplifiers
    • H01L2223/665—Bias feed arrangements
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L2223/00—Details relating to semiconductor or other solid state devices covered by the group H01L23/00
    • H01L2223/58—Structural electrical arrangements for semiconductor devices not otherwise provided for
    • H01L2223/64—Impedance arrangements
    • H01L2223/66—High-frequency adaptations
    • H01L2223/6661—High-frequency adaptations for passive devices
    • H01L2223/6677—High-frequency adaptations for passive devices for antenna, e.g. antenna included within housing of semiconductor device

Definitions

  • the present invention relates to an integrated biometric sensor module.
  • the invention relates to a smartcard comprising an integrated biometric sensor module and a method for manufacturing a smartcard comprising a biometric sensor module.
  • fingerprint sensing has been adopted more and more in for example consumer electronic devices due to small form factor, relatively beneficial cost/performance factor and high user acceptance.
  • Capacitive fingerprint sensing devices built based on CMOS technology for providing the fingerprint sensing elements and auxiliary logic circuitry, are increasingly popular as such sensing devices can be made both small and energy efficient while being able to identify a fingerprint with high accuracy.
  • capacitive fingerprint sensors are advantageously used for consumer electronics, such as portable computers, tablets and mobile phones.
  • fingerprint sensors in smartcards to enable biometric identification in a card such as a bank card where other types of biometric systems are not applicable.
  • a smartcard often contains a contact plate for physically connecting the card to a terminal as well as a wireless interface for contactless operation.
  • an object of the present invention to provide an improved smartcard comprising an integrated fingerprint sensor.
  • a smartcard comprising: a fingerprint sensor module comprising a first inductive coil; a microcontroller module; a contact plate comprising externally accessible contacts configured to communicate with a terminal, the contact plate being galvanically connected to the microcontroller module; a first inductively coupled wireless communication interface between the microcontroller module and the fingerprint sensor module; and a second inductively coupled wireless communication interface enabling communication between the microcontroller module and an external terminal, wherein the first wireless communication interface is configured to operate at a first frequency and the second wireless communication interface is configured to operate at a second frequency different from the first frequency.
  • the fingerprint sensor module comprises at least a fingerprint sensor having an active sensing surface, and the fingerprint sensor may advantageously be a capacitive fingerprint sensor comprising an array of electrically conductive sensing elements.
  • a capacitive fingerprint sensor should be understood to further comprise sensing circuitry connected to sensing elements for reading a signal from the sensing elements.
  • the sensing circuitry may in turn comprise or be connected to readout circuitry for providing a result of the sensing device to an external device for further processing, which in the present case may be included in the fingerprint sensor module.
  • the fingerprint sensor module may also comprise additional passive or active components.
  • a smartcard can be considered to be any card comprising functionality such as biometric sensing, and smartcards may be used as payment cards, identification cards, access cards and in other applications where a card with built-in functionality is desirable.
  • the smartcard comprises a fingerprint sensor module which communicates with the microcontroller module via an inductively coupled communication interface.
  • An inductively coupled wireless communication interface comprises two inductive coils which are arranged so that a change of current in one of the coils is detected by the other coil, thereby enabling wireless communication between the two coils.
  • Inductive coils can also be referred to as inductive antennas.
  • the present invention is based on the realization that the risk of damage to the microcontroller control module, to the contact plate and to a card reader can be significantly reduced by providing an inductively coupled wireless communication interface between the microcontroller module and the fingerprint sensor module.
  • the fingerprint sensor module is thus galvanically isolated from the microcontroller module and subsequently from a card reader terminal. To comply with the safety requirements of major card manufacturers, only a small portion of the energy of an electrostatic discharge (ESD) is allowed to reach a reader terminal.
  • ESD electrostatic discharge
  • a fingerprint sensor often comprises a conductive structure such as a bezel to be touched by the finger of the user in order to control the potential of a finger in contact with the sensor. Such a conductive structure may also guide a discharge to other components in the smartcard through galvanic connections.
  • the smartcard according to the present invention provides significantly improved ESD-protection by galvanically isolating the fingerprint sensor module from the contact plate.
  • the first inductively coupled wireless communication interface is here an internal interface on the smartcard between the microcontroller module and the fingerprint sensor module and the second inductively coupled wireless communication interface is an external interface for communication between the smartcard and an external terminal, for example using conventional NFC and or RFID protocols.
  • the first and second interfaces are configured to operate at different frequencies.
  • the present invention is further based on the realization that it is desirable to reduce the number of galvanic contacts on the card, thereby simplifying manufacturing of the smartcard.
  • the conductive inlays in a smartcard used to form the wireless interface are easily patterned during manufacturing of the smartcard.
  • forming a galvanic contact between components on the smartcard requires both proper alignment and often also a heating step for forming the electrical contact, which may complicate the manufacturing process since plastic layers of the smartcard typically are sensitive to heat. Accordingly, the suggested implementation using wireless interfaces instead of galvanic connections will facilitate an increased yield in smartcard manufacturing and assembly.
  • the first inductively coupled wireless communication interface comprises a first antenna loop connected to the microcontroller module, the first antenna loop comprising a second inductive coil arranged to communicate with the first inductive coil of the fingerprint sensor module; and the second communication interface comprises a second antenna loop connected to the microcontroller module, the second antenna loop comprising a third inductive coil arranged to communicate with an external terminal, wherein the first antenna loop is configured to communicate at the first frequency and the second antenna loop is configured to communicate at the second frequency.
  • An antenna loop is here described as a conductive wire or pattern which forms at least one inductive coil acting as an antenna for communication internally between components on the card or externally with an external device.
  • the antenna loop can be formed from a conductive wire arranged in a desired pattern or by pattering a conductive foil and/or layer of the smartcard.
  • different antenna loops may be formed in several different layers of a smartcard.
  • each inductively coupled wireless interface comprises a respective antenna loop which enables galvanic isolation of the fingerprint sensor module from the microcontroller module.
  • the microcontroller module is galvanically connected to each of the first and second antenna loop, while the fingerprint sensor module is inductively coupled to the first antenna loop to galvanically isolate the fingerprint sensor module from other components of the smartcard.
  • the first inductively coupled wireless communication interface comprises a first antenna loop comprising a second inductive coil arranged to communicate with the first inductive coil of the fingerprint sensor module and a third inductive coil configured to communicate with a fourth inductive coil of the microcontroller module; and the second inductively coupled wireless communication interface comprises a second antenna loop connected to the microcontroller module and comprising a fifth inductive coil arranged to communicate with an external terminal, wherein the first antenna loop is configured to communicate at the first frequency and the second antenna loop is configured to communicate at the second frequency.
  • an additional layer of ESD protection is achieved by forming two galvanically isolated inductive couplings between the fingerprint sensor module and the microcontroller module by means of the second and third inductive coils of the first antenna loop, thereby further reducing the risk of transferring a discharge current from the fingerprint sensor module to the microcontroller.
  • Such additional protection is for example advantageous when a card is inserted into a terminal so that there is physical and galvanic contact between the contact plate and the terminal.
  • the microcontroller module comprises a second inductive coil and a third inductive coil
  • the first communication interface comprises a first antenna loop comprising a fourth inductive coil arranged to communicate with the first inductive coil of the fingerprint sensor module and a fifth inductive coil arranged to communicate with the second inductive coil of the microcontroller
  • the second communication interface comprises a second antenna loop comprising a sixth inductive coil arranged to communicate with the third inductive coil of the microcontroller module and a seventh inductive coil arranged to communicate with an external terminal.
  • the microcontroller module is galvanically isolated from each of the first and second antenna loop.
  • using an inductive coupling instead of a galvanic coupling simplifies manufacturing of the card to thereby provide an improved yield.
  • the microcontroller module comprises a second inductive coil
  • the smartcard further comprising an antenna loop comprising a third inductive coil arranged to communicate with the first inductive coil of the fingerprint sensor module, a fourth inductive coil arranged to communicate with the second inductive coil of the microcontroller module and a fifth inductive coil configured to communicate with an external terminal.
  • the first inductively coupled wireless communication interface between the microcontroller module and the fingerprint sensor module is thereby formed by the first, second, third and fourth inductive coils and the second inductively coupled wireless communication interface is formed by the fifth inductive coil.
  • the microcontroller module comprises a second inductive coil
  • the smartcard further comprising an antenna loop comprising a third inductive coil arranged to communicate with the first inductive coil of the fingerprint sensor module, a fourth inductive coil arranged to communicate with the second inductive coil of the microcontroller module and a fifth inductive coil configured to communicate with an external terminal.
  • a single antenna loop can be used both for internal communication between the fingerprint sensor module and the microcontroller module, and for external communication where the fifth inductive coil enables communication with an external reader.
  • the first frequency is higher than second frequency, meaning that communication between the microcontroller module and the fingerprint sensor module is performed at a higher frequency than the communication between the microcontroller and an external terminal.
  • the first frequency may for example be in the range of 30 MHz to 900 MHz (VHF/UHF range) and the second frequency is 13.56 MHz which is the common frequency for NFC.
  • NFC operates at 13.56 MHz with a bandwidth slightly lower than 1 MHz.
  • the bandwidth increases by the same factor which is desirable to achieve the bandwidth required in the communication between the microcontroller module and the fingerprint sensor which is substantially higher than the bandwidth for standard NFC-communication at 13.56 MHz.
  • the second antenna loop is configured to harvest energy from an external electromagnetic field, for example using standardized NFC protocols.
  • the microcontroller module is configured to transfer energy from the second antenna loop to the first antenna loop.
  • the first antenna loop or the components connected thereto to harvest energy from an external source which further simplifies the overall layout of the smartcard.
  • energy is transferred via the first inductively coupled wireless communication interface at the first frequency.
  • the fingerprint sensor module it would in principle be possible for the fingerprint sensor module to harvest energy from an external source operating at the first frequency.
  • the microcontroller module comprises a secure element, SE, and the microcontroller module may also be configured to control communication to and from the fingerprint sensor module.
  • the microcontroller module may thus be either a singlepurpose or multi-purpose module comprising the functionality of one or more processing devices needed for the desired smartcard functionality.
  • the second frequency is different from an overtone of the first frequency. Using two frequencies where the higher frequency is not an overtone of the lower frequency reduces the risk of cross-talk and other disturbances between the two wireless interfaces operating at the different frequencies.
  • the first frequency is preferably at least ten times higher than the second frequency in order to provide a data transfer rate required for communication between the fingerprint sensor module and the microcontroller module.
  • a method of controlling communication in a smartcard comprising: a fingerprint sensor module comprising a first inductive coil; a microcontroller module; a contact plate comprising externally accessible contacts configured to communicate with a terminal, the contact plate being galvanically connected to the microcontroller module; a first inductively coupled wireless communication interface between the microcontroller module and the fingerprint sensor module; and a second inductively coupled wireless communication interface enabling communication between the microcontroller module and an external terminal, wherein the first wireless communication interface is configured to operate at a first frequency and the second wireless communication interface is configured to operate at a second frequency different from the first frequency.
  • the method comprises controlling wireless communication between the microcontroller module and the fingerprint sensor module by load modulation.
  • Load modulation can be described as data transmission back to the carrier source component by back scattering of carrier power through the mutual transmission line by the load component.
  • the back scattering can be achieved by mismatching the end of the transmission line by load modulation.
  • a transmission line can be designed as a resonance circuit and by changing the load of the resonance circuit, the resonance frequency of the circuit is changed and the power is reflected by to the source, where it can be detected as a digital data signal.
  • the inlay of the smartcard will then need to include the resonance circuit.
  • the microcontroller includes the carrier frequency source with a detector of the backscattering power and the fingerprint sensor module includes the energy harvest and load modulation.
  • NFC near field communication
  • the wireless communication between the microcontroller module and the fingerprint sensor module is performed using a self-clocked signal scheme such as Manchester coding or similar coding.
  • Fig. 1 schematically illustrates a smartcard comprising a fingerprint sensor module according to an embodiment of the invention
  • FIG. 2A-B schematically illustrates a smartcard according to an embodiment of the invention
  • Figs. 3A-B schematically illustrates a smartcard according to an embodiment of the invention
  • Figs. 4A-B schematically illustrates a smartcard according to an embodiment of the invention
  • Figs. 5A-B schematically illustrates a smartcard according to an embodiment of the invention
  • Figs. 6A-B schematically illustrates a smartcard according to an embodiment of the invention.
  • Figs. 7A-B schematically illustrates a smartcard according to an embodiment of the invention.
  • Fig. 1 schematically illustrates a smartcard 100 comprising a fingerprint sensor module 102 according to an embodiment of the invention.
  • the smartcard 100 is provided with means for wireless communication with a reader terminal such as a point-of-sale (POS) terminal 104.
  • POS point-of-sale
  • FIGs. 2A-B schematically illustrate a smartcard 100 according to an embodiment of the invention
  • Fig. 2A is a circuit schematic describing components of the smartcard 100
  • Fig. 2B is an exemplary illustration of how an electrically conductive inlay of the smartcard 100 can be configured to achieve the described functionality.
  • the smartcard 100 can be considered to be formed as a laminate structure comprising a plurality of layers, such as one or more core layers and outer layers on respective sides of the core layer(s).
  • the smartcard 100 will also comprise one or more electrically conductive layers embedded within the smartcard 100 to route signals between different parts of the card and to form antennas for energy harvesting and communication.
  • An electrically conductive layer of the smartcard can also be referred to as an inlay or a conductive inlay.
  • the smartcard 100 comprises a fingerprint sensor module 102 comprising a first inductive coil 201 , a microcontroller module 214, and a contact plate 216 comprising externally accessible contacts configured to communicate with a terminal, the contact plate being galvanically connected to the microcontroller module 214.
  • the first inductive coil 201 of the fingerprint sensor module 102 may be arranged on an outer surface of the fingerprint sensor module 102 on either side of the fingerprint sensor module 102 or it may be embedded within the fingerprint sensor module 102, allowing the fingerprint sensor module 102 to communicate wirelessly with other components using the first inductive coil 201.
  • the contact plate 216 may be of the type commonly used in credit cards having contact pads configured according to ISO/IEC 7816-2 where the contact plate is capable of communicating with a reader terminal when in physical contact with the reader terminal.
  • the contact plate, contact pads and /or the contact area may also be referred to as an “ISO-plate”.
  • the microcontroller module 214 may further comprise a secure element, SE, used in fingerprint authentication and the microcontroller module 214 may also be configured to control communication with and/or operation of the fingerprint sensor module 102.
  • SE secure element
  • the microcontroller module 214 may also be configured to control communication with and/or operation of the fingerprint sensor module 102.
  • the microcontroller module 214 may include a microprocessor, microcontroller, programmable digital signal processor or another programmable device.
  • the control unit may also, or instead, include an application specific integrated circuit, a programmable gate array or programmable array logic, a programmable logic device, or a digital signal processor.
  • the processor may further include computer executable code that controls operation of the programmable device.
  • the smartcard 100 further comprises a first inductively coupled wireless communication interface between the microcontroller module 214 and the fingerprint sensor module 102 which in Figs.2A-B is embodied by the first inductive coil 201 of the fingerprint sensor module 102 and a first antenna loop 211 connected to the microcontroller module 214, the first antenna loop 211 comprising a second inductive coil 202 arranged to communicate with the first inductive coil 201 of the fingerprint sensor module 102.
  • the fingerprint sensor module 102 is thereby galvanically isolated from the microcontroller module 214, and also from the contact plate 216 which means that there is no galvanic connection between the fingerprint sensor module 102 and a reader terminal when the smartcard 100 is arranged so that the contact plate has galvanic contact with the reader terminal, thereby reducing or eliminating the risk of an electrostatic discharge going from the finger sensor module to the reader terminal.
  • that a component is connected to another component should be interpreted as a galvanic connection unless stated otherwise.
  • components and antennas which are described as inductively coupled are galvanically separated from each other, i.e. there galvanic isolation between inductively coupled antennas.
  • the smartcard 100 further comprises a second inductively coupled wireless communication interface which in Figs. 2A-B is embodied by a second antenna loop 212 connected to the microcontroller module 214, the second antenna loop 212 comprising a third inductive coil 203 arranged to communicate with an external terminal. That the second antenna loop 212 is connected to the microcontroller module 214 here refers to a galvanic connection unless specified otherwise.
  • Fig. 2B illustrates an example of how a conductive inlay layer of the smartcard 100 can be configured to form the first and second antenna loops 211 , 212.
  • the second inductive coil 202 is arranged to overlap with the fingerprint sensor module 102 in order to communicate with the first inducive coil (not shown) 201 of the fingerprint sensor module 102. It is also possible to form the different antenna loops and inductive coils in different layers of the smartcard.
  • each of the first and second antenna loop, 211 , 212 is physically connected to the microcontroller module 214 by means of soldering, bonding, a conductive adhesive or the like.
  • soldering bonding
  • a conductive adhesive or the like.
  • the described physical connection could be replaced by a capacitive coupling.
  • the first antenna loop 211 is configured to communicate at a first frequency and the second antenna loop 212 is configured to communicate at a second frequency, where the first frequency is higher than second frequency.
  • the first frequency may for example be in the range of 30 MHz to 900 MHz while the second frequency is 13.56 MHz which is a standardized frequency for NFC communication. It is course possible to use other frequencies as long as there is a sufficient separation between the first and second frequency.
  • the second antenna loop 212 which comprises the antenna 203 for commination with an external reader is preferably also configured to harvest energy from an external electromagnetic field, for example provided by an NFC reader terminal.
  • the microcontroller module 214 is advantageously configured to wirelessly transfer energy from the second antenna loop 212 to the first antenna loop 211 at the first frequency, thereby powering the fingerprint sensor module 102 without the need for a galvanic connection between the fingerprint sensor module 102 and a power source.
  • Figs 3A-B schematically illustrate an embodiment of the smartcard 100 where the first inductively coupled wireless communication interface comprises a first antenna loop 311 comprising a second inductive coil 302 arranged to communicate with the first inductive coil 201 of the fingerprint sensor module and a third inductive coil 303 configured to communicate with a fourth inductive coil 304 of the microcontroller module 214.
  • the first antenna loop 311 further comprises a capacitor 320 for tuning the frequency of the first antenna loop 320.
  • the capacitor can be referred to as a tuning capacitor which is formed by the parasitic capacitance between adjacent wires of the conductive inlay.
  • the second inductively coupled wireless communication interface comprises a second antenna loop 312 connected to the microcontroller module 214, the second antenna loop comprising a fifth inductive coil 305 arranged to communicate with an external terminal.
  • the first antenna loop 311 is configured to communicate at the first frequency and the second antenna loop 312 is configured to communicate at the second frequency.
  • Fig. 3B illustrates an example configuration of a conductive inlay showing the first and second antenna loops 311 , 312 and inductive coils 302, 303 and 305 of the smartcard 100.
  • Figs. 4A-B schematically illustrate an embodiment of the smartcard where the microcontroller module 214 comprises a second inductive coil 402 and a third inductive coil 403.
  • the second and third inductive coils 402, 403 may be integrated within the microcontroller module 214 or they may be arranged on a surface of the microcontroller module 214.
  • the first inductively coupled wireless communication interface comprises a first antenna loop 411 comprising a fourth inductive coil 404 arranged to communicate with the first inductive coil 201 of the fingerprint sensor module 102 and a fifth inductive coil 405 arranged to communicate with the second inductive coil 402 of the microcontroller module 214.
  • the second inductively coupled wireless communication interface comprises a second antenna loop 412 comprising a sixth inductive coil 406 arranged to communicate with the third inductive coil 403 of the microcontroller module 214 and a seventh inductive coil 407 arranged to communicate with an external terminal.
  • Each of the first and second antenna loops 411 , 412 comprise a respective capacitor 420, 422 for providing the desired resonance frequency of the respective antenna loop 411 , 412.
  • the first antenna loop 411 is configured to communicate at the first frequency and the second antenna loop 412 is configured to communicate at the second frequency.
  • Fig. 4B illustrates an example configuration of a conductive inlay showing the first and second antenna loops 411 , 412 and inductive coils 404, 405, 406 and 407 of the smartcard 100.
  • Figs. 5A-B schematically illustrate an embodiment of the smartcard 100 where the microcontroller module 214 comprises a second inductive coil 502, and where the smartcard further comprises an antenna loop 511 comprising a third inductive coil 503 arranged to communicate with the first inductive coil 201 of the fingerprint sensor module, a fourth inductive coil 504 arranged to communicate with the second inductive coil 502 of the microcontroller module 214 and a fifth inductive coil 505 configured to communicate with an external terminal.
  • the first inductively coupled wireless communication interface between the microcontroller module 214 and the fingerprint sensor module 102 is formed by the first, second, third and fourth inductive coils 201 , 502, 503 ,504 and the second inductively coupled wireless communication interface is formed by the fifth inductive coil 505 which is configured to communicate with an external reader.
  • the fingerprint sensor module 102 may communicate directly with an external reader by means of the inductive coupling between the first inductive coil 201 of the fingerprint sensor module and the third inductive coil 503 of the antenna loop 511. It is also possible to configure communication so that all communication with an external reader is handled by the microcontroller module 214 in which case the fingerprint sensor module 102 communicates with the microcontroller module 214 via the first, second, third and fourth inductive coils 201 , 502, 503, and 504.
  • Figs. 6A-B schematically illustrate an embodiment of the smartcard 100 where the first inductively coupled wireless communication interface comprises a first antenna loop 611 connected to the fingerprint sensor module 102, the first antenna loop 611 comprising the first inductive coil 201 of the fingerprint sensor module 102 arranged to communicate with the second inductive coil 602 of the microcontroller module 214.
  • the first inductive coil 201 is formed in the first antenna loop 611 which is part of the smartcard inlay, and the first antenna loop 611 is in turn connected to the fingerprint sensor module 102.
  • the first inductive coil 201 overlaps the second inductive coil 602 of the microcontroller module 214 to enable communication with the microcontroller module 214.
  • the second inductively coupled wireless communication interface comprises a second antenna loop 612 which is connected to the microcontroller module 214.
  • the second antenna loop 612 comprises a third inductive coil 603 arranged to communicate with an external terminal.
  • the first antenna loop 611 is configured to communicate at the first frequency and the second antenna loop 612 is configured to communicate at the second frequency.
  • Fig. 6B illustrates an example configuration of a conductive inlay showing the first and second antenna loops 611 , 612 and the first and third inductive coils 201 , 603 of the smartcard 100.
  • Figs. 7A-B schematically illustrate an embodiment of the smartcard 100 where the microcontroller module 214 comprises a second inductive coil 702 and a third inductive coil 703.
  • the first inductively coupled wireless communication interface comprises a first antenna loop 711 connected to the fingerprint sensor module 102, the first antenna loop comprising the first inductive coil 201 of the fingerprint sensor module 102 arranged to communicate with the second inductive coil 702 of the microcontroller module 214.
  • the second inductively coupled wireless communication interface comprises a second antenna loop 712 comprising a fourth inductive coil 704 arranged to communicate with the third inductive coil 703 of the microcontroller module 214 and a fifth inductive coil 705 arranged to communicate with an external terminal.
  • the first antenna loop 711 is configured to communicate at the first frequency and the second antenna loop 712 is configured to communicate at the second frequency.
  • the second antenna loop 712 further comprises a capacitance 720 for providing the desired resonance frequency of the antenna loop 712.
  • the capacitance is preferably provided as a wire capacitance between adjacent wires of the antenna loop 712 as illustrated in Fig. 7B.
  • the magnitude of the capacitance can be controlled by controlling the geometry of the wires and the distance between the wires.
  • Fig. 7B illustrates an example configuration of a conductive inlay showing the first and second antenna loops 711 , 712 and the first, fourth and fifth inductive coils 201 , 704 and 705 of the smartcard 100.
  • the general concept of using inductive communication between different modules of the smartcard can be implemented in various ways.
  • the embodiments show solutions of the integration that will solve problems associated with integrating and physically connecting active modules on the card. From a production point of view, the integration of different modules and formation of galvanic connections risk causing a yield loss.
  • the described embodiments simplify the manufacturing process by removing at least some of the galvanic contacts from the card.
  • the present invention also relates to a method of controlling communication between components of a smartcard comprising a first and a second inductively coupled wireless interface operating at different frequencies.
  • NFC typically communicates at 13.56 MHz.
  • the microcontroller module 214 and the fingerprint module 102 communicate with each other using a higher frequency, such as in the range of 30 MHz to 900 MHz, or within the UHF (Ultra High Frequency) range.
  • a higher frequency such as in the range of 30 MHz to 900 MHz, or within the UHF (Ultra High Frequency) range.
  • the communication is preferably self-clocked single wired communication that includes both SPI CLK (Serial Peripheral Interface Clock) and MOSI (Master Out Slave In) communication at half duplex.
  • SPI CLK Serial Peripheral Interface Clock
  • MOSI Master Out Slave In
  • the master in the communication channel is the microcontroller module 214 and the fingerprint sensor module 102 is the slave
  • using load modulation will require high speed load modulation by the slave in-order-to accomplish the required communication. This can be done using for example Manchester modulation.
  • the communication between the microcontroller module 214 and the fingerprint sensor module 102 takes place in the silent WTX (Waiting Time Extension) slot when the microcontroller module 214 is not load modulating the NFC communication with an external reader.

Abstract

A smartcard (100) comprising: a fingerprint sensor module (102) comprising a first inductive coil (201); a microcontroller module (214); a contact plate (216) comprising externally accessible contacts configured to communicate with a terminal, the contact plate being galvanically connected to the microcontroller module; a first inductively coupled wireless communication interface between the microcontroller module (214) and the fingerprint sensor module (102); and a second inductively coupled wireless communication interface enabling communication between the microcontroller module (214) and an external terminal, wherein the first wireless communication interface is configured to operate at a first frequency and the second wireless communication interface is configured to operate at a second frequency different from the first frequency.

Description

COMMUNICATION ARRANGEMENT AND METHOD OF CONTROLLING COMMUNICATION IN A SMARTCARD COMPRISING A FINGERPRINT SENSOR MODULE
Field of the Invention
The present invention relates to an integrated biometric sensor module. In particular, the invention relates to a smartcard comprising an integrated biometric sensor module and a method for manufacturing a smartcard comprising a biometric sensor module.
Background of the Invention
As the development of biometric devices for identity verification, and in particular of fingerprint sensing devices, has led to devices which are made smaller, cheaper and more energy efficient, the range of applications for such devices is increasing.
In particular fingerprint sensing has been adopted more and more in for example consumer electronic devices due to small form factor, relatively beneficial cost/performance factor and high user acceptance.
Capacitive fingerprint sensing devices, built based on CMOS technology for providing the fingerprint sensing elements and auxiliary logic circuitry, are increasingly popular as such sensing devices can be made both small and energy efficient while being able to identify a fingerprint with high accuracy. Thereby, capacitive fingerprint sensors are advantageously used for consumer electronics, such as portable computers, tablets and mobile phones. There is also an increasing interest in using fingerprint sensors in smartcards to enable biometric identification in a card such as a bank card where other types of biometric systems are not applicable.
The integration of fingerprint sensors in smartcards and the like puts new requirements on the fingerprint sensor module for example in terms of energy consumption and wear resistance. Moreover, a smartcard often contains a contact plate for physically connecting the card to a terminal as well as a wireless interface for contactless operation. With the increasing number of functions and features on a smartcard, it is becoming increasingly important to provide a smartcard which is capable of integrating the desirable component while still being commercially viable.
Accordingly, it is desirable to further facilitate integration of fingerprint sensors in smartcards.
Summary
In view of above-mentioned and other drawbacks of the prior art, it is an object of the present invention to provide an improved smartcard comprising an integrated fingerprint sensor.
According to a first aspect of the invention, there is provided a smartcard comprising: a fingerprint sensor module comprising a first inductive coil; a microcontroller module; a contact plate comprising externally accessible contacts configured to communicate with a terminal, the contact plate being galvanically connected to the microcontroller module; a first inductively coupled wireless communication interface between the microcontroller module and the fingerprint sensor module; and a second inductively coupled wireless communication interface enabling communication between the microcontroller module and an external terminal, wherein the first wireless communication interface is configured to operate at a first frequency and the second wireless communication interface is configured to operate at a second frequency different from the first frequency.
The fingerprint sensor module comprises at least a fingerprint sensor having an active sensing surface, and the fingerprint sensor may advantageously be a capacitive fingerprint sensor comprising an array of electrically conductive sensing elements. A capacitive fingerprint sensor should be understood to further comprise sensing circuitry connected to sensing elements for reading a signal from the sensing elements. The sensing circuitry may in turn comprise or be connected to readout circuitry for providing a result of the sensing device to an external device for further processing, which in the present case may be included in the fingerprint sensor module. The fingerprint sensor module may also comprise additional passive or active components.
A smartcard can be considered to be any card comprising functionality such as biometric sensing, and smartcards may be used as payment cards, identification cards, access cards and in other applications where a card with built-in functionality is desirable. In the present context, the smartcard comprises a fingerprint sensor module which communicates with the microcontroller module via an inductively coupled communication interface.
An inductively coupled wireless communication interface comprises two inductive coils which are arranged so that a change of current in one of the coils is detected by the other coil, thereby enabling wireless communication between the two coils. Inductive coils can also be referred to as inductive antennas.
The present invention is based on the realization that the risk of damage to the microcontroller control module, to the contact plate and to a card reader can be significantly reduced by providing an inductively coupled wireless communication interface between the microcontroller module and the fingerprint sensor module. The fingerprint sensor module is thus galvanically isolated from the microcontroller module and subsequently from a card reader terminal. To comply with the safety requirements of major card manufacturers, only a small portion of the energy of an electrostatic discharge (ESD) is allowed to reach a reader terminal. A fingerprint sensor often comprises a conductive structure such as a bezel to be touched by the finger of the user in order to control the potential of a finger in contact with the sensor. Such a conductive structure may also guide a discharge to other components in the smartcard through galvanic connections. Thereby, the smartcard according to the present invention provides significantly improved ESD-protection by galvanically isolating the fingerprint sensor module from the contact plate.
In order to avoid interference, it has further been realized that it is advantageous to operate the first and second inductively coupled wireless interfaces at different frequencies. The first inductively coupled wireless communication interface is here an internal interface on the smartcard between the microcontroller module and the fingerprint sensor module and the second inductively coupled wireless communication interface is an external interface for communication between the smartcard and an external terminal, for example using conventional NFC and or RFID protocols.
Thereby, to avoid that communication between the fingerprint sensor module and the microcontroller module is disturbed, the first and second interfaces are configured to operate at different frequencies.
The present invention is further based on the realization that it is desirable to reduce the number of galvanic contacts on the card, thereby simplifying manufacturing of the smartcard. The conductive inlays in a smartcard used to form the wireless interface are easily patterned during manufacturing of the smartcard. In comparison, forming a galvanic contact between components on the smartcard requires both proper alignment and often also a heating step for forming the electrical contact, which may complicate the manufacturing process since plastic layers of the smartcard typically are sensitive to heat. Accordingly, the suggested implementation using wireless interfaces instead of galvanic connections will facilitate an increased yield in smartcard manufacturing and assembly.
According to one embodiment of the invention, the first inductively coupled wireless communication interface comprises a first antenna loop connected to the microcontroller module, the first antenna loop comprising a second inductive coil arranged to communicate with the first inductive coil of the fingerprint sensor module; and the second communication interface comprises a second antenna loop connected to the microcontroller module, the second antenna loop comprising a third inductive coil arranged to communicate with an external terminal, wherein the first antenna loop is configured to communicate at the first frequency and the second antenna loop is configured to communicate at the second frequency.
An antenna loop is here described as a conductive wire or pattern which forms at least one inductive coil acting as an antenna for communication internally between components on the card or externally with an external device. The antenna loop can be formed from a conductive wire arranged in a desired pattern or by pattering a conductive foil and/or layer of the smartcard. Moreover, different antenna loops may be formed in several different layers of a smartcard.
In the described embodiment, each inductively coupled wireless interface comprises a respective antenna loop which enables galvanic isolation of the fingerprint sensor module from the microcontroller module. Further, the microcontroller module is galvanically connected to each of the first and second antenna loop, while the fingerprint sensor module is inductively coupled to the first antenna loop to galvanically isolate the fingerprint sensor module from other components of the smartcard.
According to one embodiment of the invention, the first inductively coupled wireless communication interface comprises a first antenna loop comprising a second inductive coil arranged to communicate with the first inductive coil of the fingerprint sensor module and a third inductive coil configured to communicate with a fourth inductive coil of the microcontroller module; and the second inductively coupled wireless communication interface comprises a second antenna loop connected to the microcontroller module and comprising a fifth inductive coil arranged to communicate with an external terminal, wherein the first antenna loop is configured to communicate at the first frequency and the second antenna loop is configured to communicate at the second frequency.
In the described embodiment, an additional layer of ESD protection is achieved by forming two galvanically isolated inductive couplings between the fingerprint sensor module and the microcontroller module by means of the second and third inductive coils of the first antenna loop, thereby further reducing the risk of transferring a discharge current from the fingerprint sensor module to the microcontroller. Such additional protection is for example advantageous when a card is inserted into a terminal so that there is physical and galvanic contact between the contact plate and the terminal.
According to one embodiment of the invention, the microcontroller module comprises a second inductive coil and a third inductive coil; the first communication interface comprises a first antenna loop comprising a fourth inductive coil arranged to communicate with the first inductive coil of the fingerprint sensor module and a fifth inductive coil arranged to communicate with the second inductive coil of the microcontroller; and the second communication interface comprises a second antenna loop comprising a sixth inductive coil arranged to communicate with the third inductive coil of the microcontroller module and a seventh inductive coil arranged to communicate with an external terminal.
Thereby, the microcontroller module is galvanically isolated from each of the first and second antenna loop. As discussed above, using an inductive coupling instead of a galvanic coupling simplifies manufacturing of the card to thereby provide an improved yield.
According to one embodiment of the invention, the microcontroller module comprises a second inductive coil, the smartcard further comprising an antenna loop comprising a third inductive coil arranged to communicate with the first inductive coil of the fingerprint sensor module, a fourth inductive coil arranged to communicate with the second inductive coil of the microcontroller module and a fifth inductive coil configured to communicate with an external terminal. The first inductively coupled wireless communication interface between the microcontroller module and the fingerprint sensor module is thereby formed by the first, second, third and fourth inductive coils and the second inductively coupled wireless communication interface is formed by the fifth inductive coil.
According to one embodiment of the invention, the microcontroller module comprises a second inductive coil, the smartcard further comprising an antenna loop comprising a third inductive coil arranged to communicate with the first inductive coil of the fingerprint sensor module, a fourth inductive coil arranged to communicate with the second inductive coil of the microcontroller module and a fifth inductive coil configured to communicate with an external terminal. Thereby, a single antenna loop can be used both for internal communication between the fingerprint sensor module and the microcontroller module, and for external communication where the fifth inductive coil enables communication with an external reader.
According to one embodiment of the invention, the first frequency is higher than second frequency, meaning that communication between the microcontroller module and the fingerprint sensor module is performed at a higher frequency than the communication between the microcontroller and an external terminal. The first frequency may for example be in the range of 30 MHz to 900 MHz (VHF/UHF range) and the second frequency is 13.56 MHz which is the common frequency for NFC.
An advantage of having a higher carrier frequency is that the bandwidth scales with the carrier frequency. NFC operates at 13.56 MHz with a bandwidth slightly lower than 1 MHz. By increasing the carrier frequency by a factor of 10, the bandwidth increases by the same factor which is desirable to achieve the bandwidth required in the communication between the microcontroller module and the fingerprint sensor which is substantially higher than the bandwidth for standard NFC-communication at 13.56 MHz.
According to one embodiment of the invention, the second antenna loop is configured to harvest energy from an external electromagnetic field, for example using standardized NFC protocols.
Moreover, according to one embodiment of the invention, the microcontroller module is configured to transfer energy from the second antenna loop to the first antenna loop. There is thus no need for the first antenna loop or the components connected thereto to harvest energy from an external source which further simplifies the overall layout of the smartcard. Instead, energy is transferred via the first inductively coupled wireless communication interface at the first frequency. Even though not required in the described implementation, it would in principle be possible for the fingerprint sensor module to harvest energy from an external source operating at the first frequency.
According to one embodiment of the invention, the microcontroller module comprises a secure element, SE, and the microcontroller module may also be configured to control communication to and from the fingerprint sensor module. The microcontroller module may thus be either a singlepurpose or multi-purpose module comprising the functionality of one or more processing devices needed for the desired smartcard functionality.
According to one embodiment of the invention, the second frequency is different from an overtone of the first frequency. Using two frequencies where the higher frequency is not an overtone of the lower frequency reduces the risk of cross-talk and other disturbances between the two wireless interfaces operating at the different frequencies. Moreover, the first frequency is preferably at least ten times higher than the second frequency in order to provide a data transfer rate required for communication between the fingerprint sensor module and the microcontroller module.
According to a second aspect of the invention, there is provided a method of controlling communication in a smartcard comprising: a fingerprint sensor module comprising a first inductive coil; a microcontroller module; a contact plate comprising externally accessible contacts configured to communicate with a terminal, the contact plate being galvanically connected to the microcontroller module; a first inductively coupled wireless communication interface between the microcontroller module and the fingerprint sensor module; and a second inductively coupled wireless communication interface enabling communication between the microcontroller module and an external terminal, wherein the first wireless communication interface is configured to operate at a first frequency and the second wireless communication interface is configured to operate at a second frequency different from the first frequency. The method comprises controlling wireless communication between the microcontroller module and the fingerprint sensor module by load modulation.
Load modulation can be described as data transmission back to the carrier source component by back scattering of carrier power through the mutual transmission line by the load component. The back scattering can be achieved by mismatching the end of the transmission line by load modulation. In practice, a transmission line can be designed as a resonance circuit and by changing the load of the resonance circuit, the resonance frequency of the circuit is changed and the power is reflected by to the source, where it can be detected as a digital data signal. The inlay of the smartcard will then need to include the resonance circuit. Moreover, the microcontroller includes the carrier frequency source with a detector of the backscattering power and the fingerprint sensor module includes the energy harvest and load modulation. To a large extent, the same interface building blocks can be used as in the near field communication (NFC) standard.
According to one embodiment of the invention, the wireless communication between the microcontroller module and the fingerprint sensor module is performed using a self-clocked signal scheme such as Manchester coding or similar coding.
Additional effects and features of the second aspect of the invention are largely analogous to those described above in connection with the first aspect of the invention.
Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following description. The skilled person realize that different features of the present invention may be combined to create embodiments other than those described in the following, without departing from the scope of the present invention.
Brief Description of the Drawings
These and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing an example embodiment of the invention, wherein:
Fig. 1 schematically illustrates a smartcard comprising a fingerprint sensor module according to an embodiment of the invention;
Figs. 2A-B schematically illustrates a smartcard according to an embodiment of the invention;
Figs. 3A-B schematically illustrates a smartcard according to an embodiment of the invention; Figs. 4A-B schematically illustrates a smartcard according to an embodiment of the invention;
Figs. 5A-B schematically illustrates a smartcard according to an embodiment of the invention;
Figs. 6A-B schematically illustrates a smartcard according to an embodiment of the invention; and
Figs. 7A-B schematically illustrates a smartcard according to an embodiment of the invention.
Detailed Description of Example Embodiments
In the present detailed description, various embodiments of the smartcard and method for controlling communication in a smartcard according to the present invention are mainly described with reference to a smartcard comprising a capacitive fingerprint sensor embedded therein.
Fig. 1 schematically illustrates a smartcard 100 comprising a fingerprint sensor module 102 according to an embodiment of the invention. The smartcard 100 is provided with means for wireless communication with a reader terminal such as a point-of-sale (POS) terminal 104.
Figs. 2A-B schematically illustrate a smartcard 100 according to an embodiment of the invention where Fig. 2A is a circuit schematic describing components of the smartcard 100 and Fig. 2B is an exemplary illustration of how an electrically conductive inlay of the smartcard 100 can be configured to achieve the described functionality.
The smartcard 100 can be considered to be formed as a laminate structure comprising a plurality of layers, such as one or more core layers and outer layers on respective sides of the core layer(s). Typically, the smartcard 100 will also comprise one or more electrically conductive layers embedded within the smartcard 100 to route signals between different parts of the card and to form antennas for energy harvesting and communication. An electrically conductive layer of the smartcard can also be referred to as an inlay or a conductive inlay. With reference to Figs. 2A-B, the smartcard 100 comprises a fingerprint sensor module 102 comprising a first inductive coil 201 , a microcontroller module 214, and a contact plate 216 comprising externally accessible contacts configured to communicate with a terminal, the contact plate being galvanically connected to the microcontroller module 214. The first inductive coil 201 of the fingerprint sensor module 102 may be arranged on an outer surface of the fingerprint sensor module 102 on either side of the fingerprint sensor module 102 or it may be embedded within the fingerprint sensor module 102, allowing the fingerprint sensor module 102 to communicate wirelessly with other components using the first inductive coil 201.
The contact plate 216 may be of the type commonly used in credit cards having contact pads configured according to ISO/IEC 7816-2 where the contact plate is capable of communicating with a reader terminal when in physical contact with the reader terminal. The contact plate, contact pads and /or the contact area may also be referred to as an “ISO-plate”.
In addition to controlling communication via the contact plate 216, the microcontroller module 214 may further comprise a secure element, SE, used in fingerprint authentication and the microcontroller module 214 may also be configured to control communication with and/or operation of the fingerprint sensor module 102. Thereby, there is no need for a separate secure element or for a specific controller for the fingerprint sensor module 102. However, some or all of the described functionality may equally well be integrated in the fingerprint sensor module 102 or be provided as separate modules.
Moreover, the microcontroller module 214 may include a microprocessor, microcontroller, programmable digital signal processor or another programmable device. The control unit may also, or instead, include an application specific integrated circuit, a programmable gate array or programmable array logic, a programmable logic device, or a digital signal processor. Where the microcontroller module 214 includes a programmable device such as the microprocessor, microcontroller or programmable digital signal processor mentioned above, the processor may further include computer executable code that controls operation of the programmable device.
The smartcard 100 further comprises a first inductively coupled wireless communication interface between the microcontroller module 214 and the fingerprint sensor module 102 which in Figs.2A-B is embodied by the first inductive coil 201 of the fingerprint sensor module 102 and a first antenna loop 211 connected to the microcontroller module 214, the first antenna loop 211 comprising a second inductive coil 202 arranged to communicate with the first inductive coil 201 of the fingerprint sensor module 102. The fingerprint sensor module 102 is thereby galvanically isolated from the microcontroller module 214, and also from the contact plate 216 which means that there is no galvanic connection between the fingerprint sensor module 102 and a reader terminal when the smartcard 100 is arranged so that the contact plate has galvanic contact with the reader terminal, thereby reducing or eliminating the risk of an electrostatic discharge going from the finger sensor module to the reader terminal. In the present context, that a component is connected to another component should be interpreted as a galvanic connection unless stated otherwise. Correspondingly, components and antennas which are described as inductively coupled are galvanically separated from each other, i.e. there galvanic isolation between inductively coupled antennas.
The smartcard 100 further comprises a second inductively coupled wireless communication interface which in Figs. 2A-B is embodied by a second antenna loop 212 connected to the microcontroller module 214, the second antenna loop 212 comprising a third inductive coil 203 arranged to communicate with an external terminal. That the second antenna loop 212 is connected to the microcontroller module 214 here refers to a galvanic connection unless specified otherwise.
Fig. 2B illustrates an example of how a conductive inlay layer of the smartcard 100 can be configured to form the first and second antenna loops 211 , 212. The second inductive coil 202 is arranged to overlap with the fingerprint sensor module 102 in order to communicate with the first inducive coil (not shown) 201 of the fingerprint sensor module 102. It is also possible to form the different antenna loops and inductive coils in different layers of the smartcard.
As further illustrated in Fig. 2B, each of the first and second antenna loop, 211 , 212, is physically connected to the microcontroller module 214 by means of soldering, bonding, a conductive adhesive or the like. However, in certain applications the described physical connection could be replaced by a capacitive coupling.
The first antenna loop 211 is configured to communicate at a first frequency and the second antenna loop 212 is configured to communicate at a second frequency, where the first frequency is higher than second frequency. The first frequency may for example be in the range of 30 MHz to 900 MHz while the second frequency is 13.56 MHz which is a standardized frequency for NFC communication. It is course possible to use other frequencies as long as there is a sufficient separation between the first and second frequency. By using different frequencies for the two antenna loops, and thereby for communication using the respective first and second interface, interference between the two communication interfaces can be avoided.
The second antenna loop 212 which comprises the antenna 203 for commination with an external reader is preferably also configured to harvest energy from an external electromagnetic field, for example provided by an NFC reader terminal. Moreover, in such implementations, the microcontroller module 214 is advantageously configured to wirelessly transfer energy from the second antenna loop 212 to the first antenna loop 211 at the first frequency, thereby powering the fingerprint sensor module 102 without the need for a galvanic connection between the fingerprint sensor module 102 and a power source.
Figs 3A-B schematically illustrate an embodiment of the smartcard 100 where the first inductively coupled wireless communication interface comprises a first antenna loop 311 comprising a second inductive coil 302 arranged to communicate with the first inductive coil 201 of the fingerprint sensor module and a third inductive coil 303 configured to communicate with a fourth inductive coil 304 of the microcontroller module 214. There are thus in practice two separate inductively coupled wireless interfaces between the fingerprint sensor module 102 and the microcontroller module 214. The first antenna loop 311 further comprises a capacitor 320 for tuning the frequency of the first antenna loop 320. The capacitor can be referred to as a tuning capacitor which is formed by the parasitic capacitance between adjacent wires of the conductive inlay.
The second inductively coupled wireless communication interface comprises a second antenna loop 312 connected to the microcontroller module 214, the second antenna loop comprising a fifth inductive coil 305 arranged to communicate with an external terminal. The first antenna loop 311 is configured to communicate at the first frequency and the second antenna loop 312 is configured to communicate at the second frequency.
Fig. 3B illustrates an example configuration of a conductive inlay showing the first and second antenna loops 311 , 312 and inductive coils 302, 303 and 305 of the smartcard 100.
Figs. 4A-B schematically illustrate an embodiment of the smartcard where the microcontroller module 214 comprises a second inductive coil 402 and a third inductive coil 403. The second and third inductive coils 402, 403 may be integrated within the microcontroller module 214 or they may be arranged on a surface of the microcontroller module 214.
The first inductively coupled wireless communication interface comprises a first antenna loop 411 comprising a fourth inductive coil 404 arranged to communicate with the first inductive coil 201 of the fingerprint sensor module 102 and a fifth inductive coil 405 arranged to communicate with the second inductive coil 402 of the microcontroller module 214.
The second inductively coupled wireless communication interface comprises a second antenna loop 412 comprising a sixth inductive coil 406 arranged to communicate with the third inductive coil 403 of the microcontroller module 214 and a seventh inductive coil 407 arranged to communicate with an external terminal. Each of the first and second antenna loops 411 , 412 comprise a respective capacitor 420, 422 for providing the desired resonance frequency of the respective antenna loop 411 , 412. The first antenna loop 411 is configured to communicate at the first frequency and the second antenna loop 412 is configured to communicate at the second frequency.
Fig. 4B illustrates an example configuration of a conductive inlay showing the first and second antenna loops 411 , 412 and inductive coils 404, 405, 406 and 407 of the smartcard 100.
Figs. 5A-B schematically illustrate an embodiment of the smartcard 100 where the microcontroller module 214 comprises a second inductive coil 502, and where the smartcard further comprises an antenna loop 511 comprising a third inductive coil 503 arranged to communicate with the first inductive coil 201 of the fingerprint sensor module, a fourth inductive coil 504 arranged to communicate with the second inductive coil 502 of the microcontroller module 214 and a fifth inductive coil 505 configured to communicate with an external terminal. The first inductively coupled wireless communication interface between the microcontroller module 214 and the fingerprint sensor module 102 is formed by the first, second, third and fourth inductive coils 201 , 502, 503 ,504 and the second inductively coupled wireless communication interface is formed by the fifth inductive coil 505 which is configured to communicate with an external reader.
In the embodiment illustrated in Figs. 5A-B there is only one antenna loop which comprises three separate antenna coils 503, 504, and 505. The first inductively coupled wireless communication interface is thus used for communication between the fingerprint sensor module 102 and the microcontroller module 214 at the first frequency. In the illustrated embodiment, the fingerprint sensor module 102 may communicate directly with an external reader by means of the inductive coupling between the first inductive coil 201 of the fingerprint sensor module and the third inductive coil 503 of the antenna loop 511. It is also possible to configure communication so that all communication with an external reader is handled by the microcontroller module 214 in which case the fingerprint sensor module 102 communicates with the microcontroller module 214 via the first, second, third and fourth inductive coils 201 , 502, 503, and 504.
Figs. 6A-B schematically illustrate an embodiment of the smartcard 100 where the first inductively coupled wireless communication interface comprises a first antenna loop 611 connected to the fingerprint sensor module 102, the first antenna loop 611 comprising the first inductive coil 201 of the fingerprint sensor module 102 arranged to communicate with the second inductive coil 602 of the microcontroller module 214. Here, the first inductive coil 201 is formed in the first antenna loop 611 which is part of the smartcard inlay, and the first antenna loop 611 is in turn connected to the fingerprint sensor module 102. Moreover, the first inductive coil 201 overlaps the second inductive coil 602 of the microcontroller module 214 to enable communication with the microcontroller module 214.
The second inductively coupled wireless communication interface comprises a second antenna loop 612 which is connected to the microcontroller module 214. The second antenna loop 612 comprises a third inductive coil 603 arranged to communicate with an external terminal. The first antenna loop 611 is configured to communicate at the first frequency and the second antenna loop 612 is configured to communicate at the second frequency.
Fig. 6B illustrates an example configuration of a conductive inlay showing the first and second antenna loops 611 , 612 and the first and third inductive coils 201 , 603 of the smartcard 100.
Figs. 7A-B schematically illustrate an embodiment of the smartcard 100 where the microcontroller module 214 comprises a second inductive coil 702 and a third inductive coil 703.
The first inductively coupled wireless communication interface comprises a first antenna loop 711 connected to the fingerprint sensor module 102, the first antenna loop comprising the first inductive coil 201 of the fingerprint sensor module 102 arranged to communicate with the second inductive coil 702 of the microcontroller module 214. The second inductively coupled wireless communication interface comprises a second antenna loop 712 comprising a fourth inductive coil 704 arranged to communicate with the third inductive coil 703 of the microcontroller module 214 and a fifth inductive coil 705 arranged to communicate with an external terminal. The first antenna loop 711 is configured to communicate at the first frequency and the second antenna loop 712 is configured to communicate at the second frequency.
The second antenna loop 712 further comprises a capacitance 720 for providing the desired resonance frequency of the antenna loop 712. The capacitance is preferably provided as a wire capacitance between adjacent wires of the antenna loop 712 as illustrated in Fig. 7B. The magnitude of the capacitance can be controlled by controlling the geometry of the wires and the distance between the wires.
Fig. 7B illustrates an example configuration of a conductive inlay showing the first and second antenna loops 711 , 712 and the first, fourth and fifth inductive coils 201 , 704 and 705 of the smartcard 100.
As illustrated by the described embodiments, the general concept of using inductive communication between different modules of the smartcard can be implemented in various ways. The embodiments show solutions of the integration that will solve problems associated with integrating and physically connecting active modules on the card. From a production point of view, the integration of different modules and formation of galvanic connections risk causing a yield loss. The described embodiments simplify the manufacturing process by removing at least some of the galvanic contacts from the card.
The present invention also relates to a method of controlling communication between components of a smartcard comprising a first and a second inductively coupled wireless interface operating at different frequencies.
Following standardized technology, NFC typically communicates at 13.56 MHz. In the present context, the microcontroller module 214 and the fingerprint module 102 communicate with each other using a higher frequency, such as in the range of 30 MHz to 900 MHz, or within the UHF (Ultra High Frequency) range.
The communication is preferably self-clocked single wired communication that includes both SPI CLK (Serial Peripheral Interface Clock) and MOSI (Master Out Slave In) communication at half duplex. Assuming that the master in the communication channel is the microcontroller module 214 and the fingerprint sensor module 102 is the slave, using load modulation will require high speed load modulation by the slave in-order-to accomplish the required communication. This can be done using for example Manchester modulation. Moreover, the communication between the microcontroller module 214 and the fingerprint sensor module 102 takes place in the silent WTX (Waiting Time Extension) slot when the microcontroller module 214 is not load modulating the NFC communication with an external reader.
Even though the invention has been described with reference to specific exemplifying embodiments thereof, many different alterations, modifications and the like will become apparent for those skilled in the art. Also, it should be noted that parts of the method may be omitted, interchanged or arranged in various ways, the method yet being able to perform the functionality of the present invention.
Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

1 . A smartcard (100) comprising: a fingerprint sensor module (102) comprising a first inductive coil (201 ); a microcontroller module (214); a contact plate (216) comprising externally accessible contacts configured to communicate with a terminal, the contact plate being galvanically connected to the microcontroller module; a first inductively coupled wireless communication interface between the microcontroller module (214) and the fingerprint sensor module (102); and a second inductively coupled wireless communication interface enabling communication between the microcontroller module (214) and an external terminal, wherein the first inductively coupled wireless communication interface is configured to operate at a first frequency and the second inductively coupled wireless communication interface is configured to operate at a second frequency different from the first frequency.
2. The smartcard according to claim 1 , wherein the first inductively coupled wireless communication interface comprises a first antenna loop (211 ) connected to the microcontroller module (214), the first antenna loop (211 ) comprising a second inductive coil (202) arranged to communicate with the first inductive coil (201) of the fingerprint sensor module, the second inductively coupled wireless communication interface comprises a second antenna loop (212) connected to the microcontroller module, the second antenna loop comprising a third inductive coil (203) arranged to communicate with an external terminal, and wherein the first antenna loop (211 ) is configured to communicate at the first frequency and the second antenna loop (212) is configured to communicate at the second frequency.
3. The smartcard according to claim 1 , wherein the first inductively coupled wireless communication interface comprises a first antenna loop (311 ) comprising a second inductive coil (302) arranged to communicate with the first inductive coil (201 ) of the fingerprint sensor module and a third inductive coil (303) configured to communicate with a fourth inductive coil (304) of the microcontroller module; and the second inductively coupled wireless communication interface comprises a second antenna loop (312) connected to the microcontroller module, the second antenna loop comprising a fifth inductive coil (305) arranged to communicate with an external terminal, wherein the first antenna loop is configured to communicate at the first frequency and the second antenna loop is configured to communicate at the second frequency.
4. The smartcard according to claim 1 , wherein the microcontroller module comprises a second inductive coil (402) and a third inductive coil (403); the first inductively coupled wireless communication interface comprises a first antenna loop (411 ) comprising a fourth inductive coil (404) arranged to communicate with the first inductive coil (201 ) of the fingerprint sensor module and a fifth inductive coil (405) arranged to communicate with the second inductive coil (402) of the microcontroller module; and the second inductively coupled wireless communication interface comprises a second antenna loop (412) comprising a sixth inductive coil (406) arranged to communicate with the third inductive coil (403) of the microcontroller module and a seventh inductive coil (407) arranged to communicate with an external terminal, wherein the first antenna loop (411 ) is configured to communicate at the first frequency and the second antenna loop (412) is configured to communicate at the second frequency.
5. The smartcard according to claims 3 or 4, wherein the first and/or second antenna loop comprises a wire capacitance (320, 420, 422) formed from adjacent wires of a conductive inlay, and wherein the wire capacitance is selected to provide a predetermined resonance frequency of the respective first and/or second antenna loop.
6. The smartcard according to claim 1 , wherein the microcontroller module comprises a second inductive coil (502), the smartcard further comprising an antenna loop (511 ) comprising a third inductive coil (503) arranged to communicate with the first inductive coil (201 ) of the fingerprint sensor module (102), a fourth inductive coil (504) arranged to communicate with the second inductive coil (502) of the microcontroller module and a fifth inductive coil (505) configured to communicate with an external terminal, wherein the first inductively coupled wireless communication interface between the microcontroller module (214) and the fingerprint sensor module (102) is formed by the first, second, third and fourth inductive coils (201 , 502, 503 ,504) and the second inductively coupled wireless communication interface is formed by the fifth inductive coil (505).
7. The smartcard according to claim 1 , wherein the microcontroller module (214) comprises a second inductive coil (602), wherein the first inductively coupled wireless communication interface comprises a first antenna loop (611 ) connected to the fingerprint sensor module (102), the first antenna loop comprising the first inductive coil (201) of the fingerprint sensor module (102) arranged to communicate with the second inductive coil (602) of the microcontroller module (214); the second inductively coupled wireless communication interface comprises a second antenna loop (612) connected to the microcontroller module, the second antenna loop comprising a third inductive coil (603) arranged to communicate with an external terminal, wherein the first antenna loop (611 ) is configured to communicate at the first frequency and the second antenna loop (612) is configured to communicate at the second frequency.
8. The smartcard according to claim 1 , 22 wherein the microcontroller module comprises a second inductive coil (702) and a third inductive coil (703); the first inductively coupled wireless communication interface comprises a first antenna loop (711 ) connected to the fingerprint sensor module (102), the first antenna loop comprising the first inductive coil (201 ) of the fingerprint sensor module (102) arranged to communicate with the second inductive coil (702) of the microcontroller module (214); the second inductively coupled wireless communication interface comprises a second antenna loop (712) comprising a fourth inductive coil (704) arranged to communicate with the third inductive coil (703) of the microcontroller module and a fifth inductive coil (705) arranged to communicate with an external terminal, wherein the first antenna loop (711 ) is configured to communicate at the first frequency and the second antenna loop (712) is configured to communicate at the second frequency.
9. The smartcard according to any one of the preceding claims, wherein the first frequency is higher than second frequency.
10. The smartcard according to any one of the preceding claims, wherein the first frequency is in the range of 30 MHz to 900 MHz and the second frequency is 13.56 MHz.
11 . The smartcard according to any one of claims 2 to 5, 7 and 8, wherein the second antenna loop is configured to harvest energy from an external electromagnetic field.
12. The smartcard according to claim 11 , wherein the microcontroller module is configured to transfer energy from the second antenna loop to the first antenna loop. 23
13. The smartcard according to claim 6, wherein the antenna loop is configured to harvest energy from an external electromagnetic field.
14. The smartcard according to any one of the preceding claims, wherein the microcontroller module comprises a secure element, SE.
15. The smartcard according to any one of the preceding claims, wherein the microcontroller module is configured to control communication to and from the fingerprint sensor module.
16. The smartcard according to any one of the preceding claims, wherein the first frequency is different from an overtone of the second frequency.
17. The smartcard according to any one of the preceding claims, wherein the first frequency is at least ten times higher than the second frequency.
18. Method of controlling communication in a smartcard comprising: a fingerprint sensor module (102) comprising a first inductive coil (201 ); a microcontroller module (214); a contact plate (216) comprising externally accessible contacts configured to communicate with a terminal, the contact plate being galvanically connected to the microcontroller module; a first inductively coupled wireless communication interface between the microcontroller module and the fingerprint sensor module; and a second inductively coupled wireless communication interface enabling communication between the microcontroller module and an external terminal, wherein the first wireless communication interface is configured to operate at a first frequency and the second wireless communication interface is configured to operate at a second frequency different from the first frequency, wherein the method comprises: 24 controlling wireless communication between the microcontroller module and the fingerprint sensor module by load modulation.
19. The method according to claim 18, wherein the wireless communication between the microcontroller module and the fingerprint sensor module is performed using a self-clocked signal scheme.
PCT/SE2022/051209 2021-12-21 2022-12-20 Communication arrangement and method of controlling communication in a smartcard comprising a fingerprint sensor module WO2023121548A1 (en)

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