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 pair of capacitive patch antennas; 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 capacitively coupled wireless communication interface between the microcontroller module and the fingerprint sensor module; and an inductively coupled wireless communication interface enabling communication between the microcontroller module and an external terminal, wherein the capacitively coupled wireless communication interface is configured to operate at a first frequency and the inductively coupled wireless communication interface is configured to operate at a second frequency different from the first frequency.

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 a capacitively coupled communication interface.

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.

In the present context, each pair of capacitive patch antennas refer to two separate capacitive plates configured to communicate with two corresponding opposing capacitive plates located in a different c conductive layer of the smartcard or in a component integrated in the smartcard. The reason for using a pair of capacitive antennas is that communication is typically performed differentially. In differential signaling, information is transmitted as the relative difference in voltage between the two capacitive plates for a pair of capacitive patch antennas.

A capacitively coupled wireless communication interface comprises at least two overlapping capacitive plates which are arranged so that a change in voltage on a first plate is detected by the second plate and which results in a detectable change in voltage on the second plate, thereby enabling wireless communication between the two plates. Capacitive plates can also be referred to as capacitive patch antennas. Moreover, the capacitively coupled wireless communication interface is at least partially implemented in one or more conductive layers of the smartcard.

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 a capacitively 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 an electrostatic 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 capacitively coupled wireless interface and the inductively coupled wireless interface at different frequencies. The capacitively coupled wireless communication interface is here an internal interface on the smartcard between the microcontroller module and the fingerprint sensor module and the 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 two 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 smartcard, thereby simplifying manufacturing of the smartcard. The conductive inlays in a smartcard used to form the wireless interfaces are easily patterned during manufacturing of the smartcard. In comparison, forming a galvanic contact between components on the smartcard requires both proper alignment of components 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 microcontroller module comprises a second pair of capacitive patch antennas and a first inductive coil; wherein the capacitively coupled wireless communication interface comprises a conductive circuit in one end comprising a third pair of capacitive patch antennas arranged to communicate with the first pair of capacitive patch antennas of the fingerprint sensor module and in the other end comprising a fourth pair of capacitive patch antennas arranged to communicate with the second pair of capacitive patch antennas of the microcontroller module; and the inductively coupled wireless communication interface comprises an antenna loop having a second inductive coil coupled to the first inductive coil of the microcontroller module and a third inductive coil arranged to communicate with an external terminal, and wherein the conductive circuit is configured to communicate at the first frequency and the antenna loop is configured to communicate at the second frequency.

The described embodiment thereby comprises two steps of galvanic isolation between the fingerprint sensor module and the microcontroller module. An additional layer of ESD protection is thus achieved by forming two galvanically isolated capacitive couplings between the fingerprint sensor module and the microcontroller module, thereby further reducing the risk of transferring a discharge current from the fingerprint sensor module to the microcontroller module. 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. Moreover, the conductive layer of the smartcard used to form the conductive circuit does not need to be galvanically connected to any other component, thereby simplifying the manufacturing process.

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 smartcard or externally with an external device. The antenna loop can be formed from a conductive wire arranged in a desired pattern in a layer the smartcard or by pattering a conductive foil and/or layer of the smartcard. Moreover, different antenna loops may be formed in several different conductive layers of a smartcard. In the present embodiment, the antenna loop provides an inductively coupled wireless interface between the microcontroller module and the antenna loop which comprises the third inductive coil for external communication. There is thus no galvanic connection of the antenna loop.

According to one embodiment of the invention, the conductive circuit further comprises a pair of inductive coils, each coil being arranged between a respective patch of the third and fourth pair of capacitive patch antennas and configured to determine a resonance frequency of a resonant circuit formed by the respective inductive coil, the third pair of capacitive patch antennas and the fourth pair of capacitive patch antennas. By means of the inductive coil, the resonance properties of the resulting resonant circuit can be altered by the fingerprint sensor module to backscatter the carrier wave power to the microcontroller module, i.e. , the fingerprint sensor module can load modulate the signal for backscattering communication purposes.

According to one embodiment of the invention, the microcontroller module comprises a first inductive coil; wherein the capacitively coupled wireless communication interface comprises a conductive circuit in one end comprising a third pair of capacitive patch antennas arranged to communicate with the first pair of capacitive patch antennas of the fingerprint sensor module and in the other end connected to the microcontroller module, the conductive circuit further comprising a pair of inductive coils, each coil arranged between a respective capacitive patch antenna of the third pair of capacitive patch antennas and the microcontroller module; and the inductively coupled wireless communication interface comprises an antenna loop having a second inductive coil coupled to the first inductive coil of the microcontroller module and a third inductive coil arranged to communicate with an external terminal, wherein the conductive circuit is configured to communicate at the first frequency and the antenna loop is configured to communicate at the second frequency.

According to one embodiment of the invention an antenna loop may comprise a wire capacitance formed from adjacent wires of an antenna inlay, and wherein the wire capacitance is selected to provide a predetermined resonance frequency of the antenna loop. According to one embodiment of the invention, the microcontroller module comprises a second pair of capacitive patch antennas and a first inductive coil; wherein the capacitively coupled wireless communication interface comprises a conductive circuit in one end comprising a third pair of capacitive patch antennas arranged to communicate with the first pair of capacitive patch antennas of the fingerprint sensor module and in the other end comprising a fourth pair of capacitive patch antennas arranged to communicate with the second pair of capacitive patch antennas of the microcontroller module, the conductive circuit further comprising a pair of inductive coils each arranged between a respective patch of the third pair of capacitive patch antennas and the microcontroller module; and the inductively coupled wireless communication interface comprises an antenna loop coupled to the microcontroller module and comprising a third inductive coil arranged to communicate with an external terminal, wherein the conductive circuit is configured to communicate at the first frequency and the antenna loop is configured to communicate at the second frequency.

According to one embodiment of the invention, the capacitively coupled wireless communication interface comprises a conductive circuit in one end comprising a third pair of capacitive patch antennas arranged to communicate with the first pair of capacitive patch antennas of the fingerprint sensor module and in the other end connected to the microcontroller module, the conductive circuit further comprising a pair of inductive coils, each coil arranged between a respective patch of the third pair of capacitive patch antennas and the microcontroller module; and the inductively coupled wireless communication interface comprises an antenna loop coupled to the microcontroller module and comprising a third inductive coil arranged to communicate with an external terminal, wherein the conductive circuit is configured to communicate at the first frequency and the antenna loop is configured to communicate at the second frequency.

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 is 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 have its own energy harvesting functionality which further simplifies the overall layout of the smartcard.

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 with the fingerprint sensor module. The microcontroller module may thus be either a single-purpose 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 pair of capacitive patch antennas; 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 capacitively coupled wireless communication interface between the microcontroller module and the fingerprint sensor module; and an inductively coupled wireless communication interface enabling communication between the microcontroller module and an external terminal, wherein the capacitively coupled wireless communication interface is configured to operate at a first frequency and the inductively coupled wireless communication interface is configured to operate at a second frequency different from the first frequency, wherein 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 changes 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 module 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 self-clocked signal scheme such as Manchester 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;

Figs. 7A-B schematically illustrates features of a smartcard according to an embodiment of the invention; and

Figs. 8A-B schematically illustrates features of 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 is provided with means for wireless communication with a smartcard reader 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 will also comprise one or more electrically conductive layers embedded in the smartcard 100 to route signals between different parts of the card and to form antennas for power harvesting and communication. An electrically conductive layer can also be referred to as an inlay.

With reference to Figs. 2A-B, the smartcard 100 comprises a fingerprint sensor module 102 comprising a first pair of capacitive patch antennas 201 a-b, a microcontroller module 214 and a contact plate 216 comprising externally accessible contacts configured to communicate with a terminal, the contact plate 216 being galvanically connected to the microcontroller module.

The first pair of capacitive patch antennas 201 a-b of the fingerprint sensor module 102 may be arranged on an outer surface of the fingerprint sensor module 102 or they may be embedded within the fingerprint sensor module 102, allowing the fingerprint sensor module 102 to communicate wirelessly with other components through a capacitive coupling with the antennas 201 a-b.

The contact plate 216 may be of the type commonly used in credit cards having contact pads configured according to ISO/IEC 7816-2. 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 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 capacitively coupled wireless communication interface between the microcontroller module 214 and the fingerprint sensor module 102 which in Figs.2A-B is embodied by a conductive circuit 211 in one end comprising a third pair of capacitive patch antennas 203a-b arranged to communicate with the first pair of capacitive patch antennas 201 a-b of the fingerprint sensor module 102 and in the other end comprising a fourth pair of capacitive patch antennas 204a-b arranged to communicate with a second pair of capacitive patch antennas 202a-b of the microcontroller module 214. 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 216 has galvanic contact with the reader terminal, thereby reducing or eliminating the risk of an electrostatic discharge going from the fingerprint sensor module 102 to the reader terminal.

Moreover, the smartcard 100 comprises an inductively coupled wireless communication interface in the form of an antenna loop 212 having a second inductive coil 206 inductively coupled to the first inductive coil 205 of the microcontroller module and a third inductive coil 207 arranged to communicate with an external terminal. The conductive circuit 211 is configured to communicate at the first frequency and the antenna loop 212 is configured to communicate at the second frequency.

The antenna loop 212 further comprises a capacitance 220 for providing the desired resonance frequency of the antenna loop 212. The capacitance 220 is preferably provided as a wire capacitance formed between adjacent wires of the antenna loop 212 as illustrated in Fig. 2B. The magnitude of the capacitance can be controlled by controlling the geometry of the wires and the distance between the wires.

Fig. 2B illustrates an example of how the conductive inlay layer of the smartcard 100 can be configured to form the conductive circuit 211 and the antenna loop 212. The third pair of capacitive patch antennas 203a-b is arranged to overlap the corresponding first pair of capacitive patch antennas 201 a-b of the fingerprint sensor module 102, and the fourth pair of capacitive patch antennas 204a-b is arranged to overlap the corresponding second pair of capacitive patch antennas 202a-b of the microcontroller module 214 in order to enable communication between the fingerprint sensor module 102 and the microcontroller module 214.

The conductive circuit 211 is configured to communicate at a first frequency and the 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 different wireless interfaces, and thereby for communication using the respective first and second interface, interference between the two communication interfaces can be reduced or avoided.

The antenna loop 212 which comprises the inductive antenna 207 for commination with an external reader is preferably also configured to harvest energy from an external electromagnetic field, for example provided by the reader. Moreover, in such implementations, the microcontroller module 214 is advantageously configured to transfer energy from the antenna loop 212 to the conductive circuit 211 , thereby powering the fingerprint sensor module 102 without the need for a galvanic connection between the fingerprint sensor module 102 and a power source.

The smartcard of Figs. 3A-B is similar to the smartcard illustrated in Figs. 2A-B but with the addition of a pair of inductive coils 301 a-b, where each inductive coil is arranged between a respective patch of the third and fourth pair of capacitive patch antennas 203a-b, 204a-b. The inductive coils 301 a-b are configured to determine a resonance frequency of the resonant circuits formed by the respective inductive coil 301 a-b, the third pair of capacitive patch antennas 203a-b and the fourth pair of capacitive patch antennas 204a- b. As illustrated in Fig. 3B, the pair of inductive coils 301 a-b can be formed in a conductive layer of the smartcard 100.

Figs. 4A-B schematically illustrate an embodiment of the smartcard 100 where the microcontroller module 214 comprises a first inductive coil 205. The capacitively coupled wireless communication interface comprises a conductive circuit 211 in one end comprising a third pair of capacitive patch antennas 203a-b arranged to communicate with the first pair of capacitive patch antennas 201 a-b of the fingerprint sensor module 102 and in the other end connected to the microcontroller module 214. The conductive circuit 211 further comprises a pair of inductive coils 301 a-b, each coil being arranged between a respective patch of the third pair of capacitive patch antennas 203a-b and the microcontroller module 214. The conductive circuit 211 is thereby galvanically coupled to the microcontroller module 214. The conductive circuit may be 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 inductively coupled wireless communication interface comprises an antenna loop 212 having a second inductive coil 206 coupled to the first inductive coil 205 of the microcontroller module 214 and a third inductive coil 207 arranged to communicate with an external terminal, wherein the conductive circuit 211 is configured to communicate at the first frequency and the antenna loop 212 is configured to communicate at the second frequency. The antenna loop 212 further comprises a capacitance 220 for providing the desired resonance frequency of the antenna loop 212.

Fig. 4B illustrates an example configuration of a conductive inlay showing the conductive circuit 211 comprising the third pair of capacitive patch antennas 203a-b and the pair of inductive coils 301 a-b, and the antenna loop 212 comprising the inductive coils 206 and 207 for internal and external communication, respectively.

Figs. 5A-B schematically illustrate an embodiment of the smartcard 100 where the microcontroller module 214 comprises a second pair of capacitive patch antennas 202a-b. The capacitively coupled wireless communication interface comprises a conductive circuit 211 in one end comprising a third pair of capacitive patch antennas 203a-b arranged to communicate with the first pair of capacitive patch antennas 201 a-b of the fingerprint sensor module 102 and in the other end comprising a fourth pair of capacitive patch antennas 204a-b arranged to communicate with the second pair of capacitive patch antennas 202a-b of the microcontroller module 214. The conductive circuit 211 further comprises a pair of inductive coils 301 a-b each arranged between a respective patch of the third pair of capacitive patch antennas 203a-b and the microcontroller module 214 Moreover, the inductively coupled wireless communication interface comprises an antenna loop 212 connected to the microcontroller module and comprising a third inductive coil 207 arranged to communicate with an external terminal. Here, the antenna loop 212 is galvanically connected to the microcontroller module 214. Moreover, the conductive circuit 211 is configured to communicate at the first frequency and the antenna loop 212 is configured to communicate at the second frequency.

Fig. 5B illustrates an example configuration of a conductive inlay showing the conductive circuit 211 comprising the third pair of capacitive patch antennas 203a-b and the pair of inductive coils 301 a-b, and the antenna loop 212 comprising the inductive coil 207 for external communication.

Figs. 6A-B schematically illustrate an embodiment of the smartcard 100 where the capacitively coupled wireless communication interface comprises a conductive circuit 211 in one end comprising a third pair of capacitive patch antennas 203a-b arranged to communicate with the first pair of capacitive patch antennas 201 a-b of the fingerprint sensor module 102 and in the other end connected to the microcontroller module 214. The conductive circuit 211 further comprises a pair of inductive coils 301 a-b, each coil being arranged between a respective patch of the third pair of capacitive patch antennas 203a-b and the microcontroller module 214. Moreover, the inductively coupled wireless communication interface comprises an antenna loop 212 coupled to the microcontroller module 214 and comprising a third inductive coil 207 arranged to communicate with an external terminal. The conductive circuit 211 is configured to communicate at the first frequency and the antenna loop 212 is configured to communicate at the second frequency.

Fig. 6B illustrates an example configuration of a conductive inlay showing the conductive circuit 211 comprising the third pair of capacitive patch antennas 203a-b and the pair of inductive coils 301 a-b, and the antenna loop 212 comprising the inductive coil 207 for external communication.

As illustrated by the described embodiments, the general concept of using capacitive 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 smartcard. 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 smartcard.

Figs. 7A-B schematically illustrate a resonant circuit 700 formed in a first conductive layer capacitively coupled to a capacitive circuit 702 formed in a second conductive layer of the smartcard 100. The resonant circuit 700 comprises a first pair of capacitive patch antennas 708a-b, a pair of inductive coils 712a-b and a second pair of capacitive patch antennas 709a-b which together form a pair of resonant circuits enabling differential communication between two components of a smartcard. The conductive circuit 702 comprises a third pair of capacitive patch antennas 710a-b and a fourth pair of capacitive patch antennas 711a-b. Each of the resonant circuit 700 and the capacitive circuit 702 can be capacitively coupled to either a component or to another conductive layer by means of the respective pairs of capacitive patch antennas 708a-b and 710a-b. It should be noted that capacitive plates 711a-b in Fig. 7B are offset in relation to capacitive plates 709a-b for illustrative purposes, and that the best capacitive coupling can be achieved when the respective capacitive plates are fully overlapping.

Figs. 8A-B schematically illustrate an example of a first resonant circuit 800 formed in a first conductive layer capacitively coupled to second resonant circuit 802 formed in a second conductive layer of the smartcard 100. The first resonant circuit 800 comprises a first pair of capacitive patch antennas 808a- b, and a pair of inductive coils 820a-b also forming a capacitive coupling to the second resonant circuit 802 which comprises a second pair of inductive coils 822a-b and a second pair of capacitive patch antennas 810a-b. As illustrated in Fig. 8B, the pairs of overlapping inductive spiral coils 820a, 822a and 820b, 822b form both a resonance for the respective first and second resonant circuit 800, 802 as well as a capacitive coupling between the resonant circuits 800, 802. Each of the first and second resonant circuit 800, 802 can be capacitively coupled to either a component or to another conductive layer by means of the respective pairs of capacitive patch antennas 808a-b and 810a-b. In practice, the spiral coils of the respective conductive layer are overlapping to achieve the best capacitive coupling.

The present invention also relates to a method of controlling communication between components of a smartcard comprising a capacitively coupled wireless interface and an 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 differential two-wire 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.