GB2579587A

GB2579587A - Apparatus and method for improving wired data communication in near field RF communications enabled device with auxiliary functionality

Info

Publication number: GB2579587A
Application number: GB1819799.6A
Authority: GB
Inventors: Diaz Victor; Freitas Vitor; Litwinow Sebastian; Lloyd Alison
Original assignee: Drayson Technologies Europe Ltd
Current assignee: Freevolt Technologies Ltd
Priority date: 2018-12-04
Filing date: 2018-12-04
Publication date: 2020-07-01
Anticipated expiration: 2038-12-04
Also published as: GB201819799D0; GB2579587B

Abstract

The invention relates to smartcard circuitry for providing a radio frequency (RF), interface between an inductive coupler 1016 of the smartcard 1000 and its near field RF communicator 1014. The circuitry comprises: an input signal connection for connecting to the inductive coupler to obtain an RF electrical input signal; an RF electrical output signal connection for providing a part of the input signal to the near field RF communicator; an auxiliary rectifier 1004, separate from the near field RF communicator, and coupled to the input signal connection, and configured to provide a DC output for powering an auxiliary circuit 1006, wherein the DC output is based on the input signal; a data communications connection for connecting to a wired data communications interface of said near field RF communicator, and a bandpass filter 1008 connected between the data communications connection and a reference voltage provided by the DC output of the auxiliary rectifier. The circuitry could also contain a splitter 1002. The aim of the invention is to reduce signal noise in wired connections in near field RF communications systems.

Description

Apparatus and Method for Improving Wired Data Communication in Near Field RF Communications Enabled Device with Auxiliary Functionality

Field of Invention

The present invention relates to methods and apparatus having particular utility in smartcard systems, and to methods and apparatus for reducing signal noise in wired data communications in near field radio frequency (RF) communications enabled systems, such as wired data communications between an auxiliary circuit and a near field RF communicator such as may be provided in a smartcard.

Background

Smartcards, also known as chip cards, or integrated circuit cards (ICC), are increasingly prevalent. A wide variety of such pocket-sized cards with embedded integrated circuits are in use in a wide variety of applications. The most frequent uses of such cards relate to financial transactions, mass transit systems, and access control. Smartcards are made of plastic, generally polyvinyl chloride, but sometimes polyethylene-terephthalatebased polyesters, acrylonitrile butadiene styrene or polycarbonate. Reusable smartcards may also be made from paper. Such cards often incorporate an integrated circuit, IC, and some source of power such as a near field RF communications interface for powering the IC and providing data communications to and from iL.

An IC device, often called a chip, traditionally consists of a single semiconductor die which has a particular function and which is adapted to interact with other chips and components. For example, a traditional chip might be a microprocessor, a memory controller, or a memory array. IC systems may include two or more chips, as well as other electronic and electrical components, each attached to and interconnected through a mounting system such as a printed circuit board.

Near field RF (radio frequency) communication requires an antenna of one near field RF communicator to be present within the 5 alternating magnetic field (H field) generated by the antenna of another near field RF communicator by transmission of an RF signal (for example a 13.56 MegaHertz signal) to enable the magnetic field (H field) of the RF signal to be inductively coupled between the communicators. The RF signal may be modulated 10 to enable communication of control and/or other data. Ranges of up to several centimetres (generally a maximum of 1 metre) are common for near field RF communicators.

Near field communication in the context of this application may be referred to as near-field RF communication, near field RFID (Radio Frequency Identification) or near field communication. The range of such devices depends on the antenna used but may be, for example, up to 1 metre.

Communication of data between NFC communicators may be via an active communication mode in which the NFC communicator transmits or generates an alternating magnetic field modulated with the data to be communicated and the receiving NFC communicator responds by transmitting or generating its own modulated magnetic field, or via a passive communication mode in which one NFC communicator transmits or generates an alternating magnetic field and maintains that field and the responding NFC communicator modulates the magnetic field to which it is inductively coupled with the data to be communicated, for example by modulating the load on the inductive coupling ("load modulation"). Near field RF communicators may be actively powered, that is have an internal or associated power source, or passively powered, that is derive a power supply from a received magnetic field. Generally an RF transceiver will be actively powered while an RF transponder may be passively or actively powered.

Examples of near field RF communicators are defined in various standards for example ISO/IEC 18092 and ISO/IEC 21481 for NFC communicators, and ISWIEC 14443 and iso/IEc 15693 for near field RF communicators.

The ability of near field RF communications devices to be passively powered is a significant benefit. Some near field communicator chips also provide auxiliary power outputs. This can enable power harvested by the near field RF communicator to be used by other circuits.

UK patent application GB2531378 describes an RFID system in which when an RFID reader sends a command to an RFID device, the device does not respond, but rather waits and harvests the power to drive some auxiliary functionality e.g. functionality not required for responding to the command, for example the command may be a "request to provide identification code" command. In this prior art system, a response to the command from the RFID device is intentionally delayed so as to allow the auxiliary function to be performed first. In this system, the auxiliary function is biometric authentication, and the RFID device does not respond to the command until the biometric authentication has been completed. This may extend the interaction time of the RFID device (e.g. the period of time for which an RFID device must be held in proximity to a reader). The perceived delay in operation associated with this may be unacceptable to users.

Summary

Aspects and examples of the present invention are set out in the appended claims. These and other aspects of the present disclosure aim to ameliorate the above described problems, amongst others. These apparatus and methods may provide power to auxiliary circuits by inductive coupling with an RF alternating H-field in near field range, whilst enabling concurrent digital data communication between a near field RF communicator and the auxiliary circuit. Such concurrent communication may present a particular difficulty because it may lead to the creation of unwanted "ground loop" connections between the RF (differential inputs) of the near field RF communicator and a ground voltage for the auxiliary rectifier.

One aspect of the disclosure is smartcard circuitry for providing a radio frequency, RF, interface between an inductive coupler of the smartcard and a near field RF communicator of the smartcard. This circuitry comprises: an input signal connection for connecting to the inductive coupler to obtain an RF electrical input signal; an RF electrical output signal connection for providing a part of the RF electrical input signal to the near field RF communicator; an auxiliary rectifier, separate from the near field RF communicator, and coupled to the input signal connection and configured to provide a DC output for powering an auxiliary circuit, wherein the DC output is based on the RF electrical input signal; a data communications connection for connecting to a wired data communications interface of said near field RF communicator, and a bandpass filter connected between the data communications connection and a reference voltage provided by the DC output of the auxiliary rectifier.

The smartcard circuitry may be carried by a dielectric substrate for incorporation into a smartcard, and may comprise a chip connector for connecting a near field RF communicator integrated circuit, IC, or chip to the smartcard circuitry. The substrate may carry a ground plane, such as a low impedance conductive connection, disposed on a surface of the substrate. This may be provided by a copper connecting track which is wider than other connections on the substrate (e.g. wider than those which mediate data communication between the near field RF communicator and the auxiliary circuit). The ground plane may also comprise one or more conductive lands disposed on the substrate. For example one of these may be provided on the substrate opposite the chip connector and/or opposite a rectification element of the auxiliary rectifier.

The data communications connection is arranged for communicating data between said near field RF communicator and said auxiliary circuit. It may comprise a serial computer bus, which may be single ended, and may be synchronous. One example of such a bus is I2C. Other examples of such communications connections to which the present disclosure may be applied comprise the so called single wire protocol (SWP) such as that used to provide a single-wire connection between a near field RF communicator (such as an NFC chip) and a UICC (commonly known as a SIM card) in cell phones and other user equipment. The communications connection may comprise a connection for any other digital communications protocol, such as SPI, 1-wire, RS232, CAN etc. Typically, the pass band of the band pass filter comprises a carrier frequency of the RF electrical input signal. In the case of an NFC or near field RFID, this carrier frequency may comprise 13.56 MHz.

The input signal connection may be provided by a splitter, such as a Wilkinson divider network, configured to divide the RF electrical input signal between the auxiliary rectifier and the RF electrical output signal connection.

The auxiliary rectifier may comprise: a first rectifier input and a second rectifier input for receiving the RF electrical input signal from one output of the splitter. The output of the splitter may be differential, or single ended.

The auxiliary rectifier may also comprise a first rectifier output connection and a second rectifier output connection for providing the DC electrical energy to the auxiliary circuit; and a rectifying element connected between the first rectifier input and the second rectifier input, wherein the first rectifier output connection is coupled to an output of the rectifying element and to the first rectifier input by a first inductor. For example, the auxiliary rectifier may comprise a so called 'buck rectifier' such as that described and/or claimed in the applicant's co-pending international patent application PCT/GB2018/053125, the entirety of which is hereby incorporated by reference as if fully set forth herein. The use of such a rectifier may reduce the need for a DC-to-DC converter to be used. This may reduce switching noise conducted or related to the rest of the system or nearby systems.

The second rectifier output connection provides the reference voltage at the DC output of the rectifier for connection data communications connection by the band pass filter. The second rectifier output connection may be connected to an input of the rectifying element and to the second rectifier input by a second inductor. One or more of the inductors of the rectifier may be provided by printed coil inductors.

The auxiliary rectifier and a separate, internal, rectifier of the near field RF communicator can both be connected to the 20 inductive coupler by the splitter to enable both to operate concurrently.

The inductive coupler and the near field RF communicator may both be made and sold separately, for example they may be assembled into the circuitry described and claimed herein as part of a separate manufacturing step. Examples of the present disclosure may therefore provide a kit of component parts for the manufacture of a smartcard, the kit comprising the smartcard circuitry described herein and at least one of the inductive coupler and the splitter. The auxiliary circuit may also be made and sold separately.

A variety of smartcards can thus be manufactured comprising any of the smartcard circuitry described and/or claimed herein.

In an aspect there is provided a method of reducing radio frequency, RF, signal noise in wired communication between a near field RF communicator and an auxiliary circuit of a near field RF communications enabled device, the method comprising: obtaining an RF electrical input signal from an inductive coupler of the near field RF communications enabled device; splitting the RF electrical input signal into a first part and a second part; providing the first part of the RF electrical input signal to the 10 near field RF communicator for providing near field RF communications via the inductive coupler; providing the second part of the RF electrical input signal to an auxiliary rectifier, separate from the near field RF communicator, wherein the auxiliary rectifier provides a DC output for powering an auxiliary circuit, wherein the DC output is based on the RF electrical input signal; and, communicating data via a wired data communications connection of said near field RF communicator, wherein the data communications connection is connected via a band pass filter to a reference voltage provided by the DC output of the auxiliary rectifier.

The data communication may relate to an authentication performed by at least one of the auxiliary circuit and the near field RF communicator to authenticate the device to a second near field RF communications enabled device in near field range. The data communication may be performed concurrently with (e.g. during) near field RF communication between the near field RF communicator and the second near field RF communications enabled

device in near field range.

The second near field RF communications enabled device provides data encoded on an alternating H-field, the alternating H-field having a carrier frequency in a pass band of the band pass 35 filter. This data encoded on the alternating H-field may comprise a request for security authentication, such as that associated with a financial transaction.

Embodiments of the present disclosure may enable the near field RF communicator to communicate via an alternating RF H-field with a second near field RF communications enabled device in near field range, whilst the auxiliary circuit concur/envly derives power from that same RF H-field. This concurrent power derivation can enable the auxiliary circuit to perform digital logic operations to provide digital data to the near field RF communicator. The near field RF communicator can then provide this digital data to the second near field RF communications enabled device. The auxiliary circuit may comprise a user interface for obtaining data from a user, examples of such an interface include a biometric sensor, e.g. a camera or fingerprint sensor and/or a data input interface such as a keypad. The auxiliary circuit may comprise a processor configured to perform data processing such as biometric authentication, and/or other authentication functions such as the generation of authentication one time keys.

A process of manufacturing smartcards may comprise manufacturing card blanks which comprise the body of the smartcard, and the inductive coupler (e.g. a near field RF communications antenna), and a chip assembly seat for seating a near field RF communications chip assembly in the card blank. The inductive coupler, and a substrate carrying the components of the smartcard circuitry described above may be integrated into a smartcard blank. It will thus be appreciated that smartcard circuitry of the present disclosure may be provided in a modular unit, such as a card blank with chip seat, to enable a near field RF communicator to be inserted into the smartcard blank during manufacture.

Accordingly in an aspect there is provided a smartcard blank comprising: an inductive coupler for coupling inductively with a radio frequency, RF, to provide an alternating RF voltage to the input signal connection of the smartcard circuitry to provide an RF electrical input signal to the smartcard circuitry. 5 The smartcard blank may have dimensions of a credit card such as that defined in ISO/IEC 7810 standard, for example it may be about 85mm by about 55mm (for example 85.60 by 53.98 millimetres). As an alternative, it may have an ID-000 form factor, e.g. about 25mm by 15mm (0.98 in x 0.59 in) commonly used 10 in SIM cards. The smartcard may comprise a body of a dielectric substance such as plastic, e.g. polyvinyl chloride, or a polyethylene-terephthalate-based polyester. It will be appreciated in the context of the present disclosure that the inductive coupler may be provided into the blank as part of the same manufacturing process as the other smartcard circuitry. In some possibilities the inductive coupler is absent to enable it to be incorporated into the blank separately after the circuitry has been manufactured.

Brief Description of Drawings

Embodiments of the disclosure will now be described in detail with reference to the accompanying drawings, in which: Figure 1 shows a smartcard; and Figure 2 shows apparatus for incorporation into a smartcard such as that illustrated in Figure 1.

In the drawings like reference numerals are used to indicate like elements.

Specific Description

Figure 1 illustrates a smartcard 1000 comprising a near field RF communicator 1014 and circuitry 1002, 1004, 1006, 1008, 1010, 1012, according to the present disclosure.

The smartcard 1000 also comprises an inductive coupler 1016, such as a near field RF communications antenna. The circuitry includes an auxiliary rectifier 1004, which is separate from the near field RF communicator 1014, and which provides DC power to the auxiliary circuit 1006. The auxiliary rectifier 1004 may also be connected to provide power to a digital side of the near field RF communicator (e.g. digital logic and/or a memory which may form part of the same integrated circuit, IC, as the near field RF communicator.

A splitter 1002 connects both the auxiliary rectifier 1004 and the near field RF communicator 1014 to the inductive coupler 1016. A data communication connection 1012 between the near field RF communicator 1014 and the auxiliary circuit 1006 is connected to a DC output of the auxiliary rectifier 1004 by a band pass filter to reduce RF signal noise present on that data communication connection 1012.

The components 1002 to 1014 of the smartcard may be carried by a dielectric substrate, which may be flat and sheet-like for incorporation into the smartcard 1000. For example, this substrate may be laminated with (e.g. sandwiched between) other dielectric layers to provide the body of the smartcard 1000. The smartcard 1000 may thus encapsulate the circuitry 1002, 1004, 1006, 1008, 1010, 1012. The smartcard 1000 may also encapsulate the inductive coupler 1016.

As noted above, the circuitry comprises a splitter 1002, and an auxiliary rectifier 1004. The splitter 1002 provides an input signal connection which can be connected to the inductive coupler 1016 for receiving an RF electrical input signal. The splitter is also connected to the near field RF communicator 1014 and to the auxiliary rectifier 1004. The connection between the inductive coupler 1016 and the splitter 1002 may be a differential (e.g. two-terminal) connection for the provision of a differential signal. Likewise, the connection between the splitter 1002 and the auxiliary rectifier 1004, and between the splitter 1002 and the near field RF communications apparatus 1014 may also be a differential connection. Single ended embodiments are also envisaged.

The splitter is configured to provide a first part of the input RF electrical signal to the near field RF communicator 1014, and to provide a second part to the auxiliary rectifier 1004. This functionality may be provided by a network of electrical impedances, such as inductors and capacitors, connected together to divide the incoming signal into two parts. One example of such a network is a Wilkinson divider.

The auxiliary rectifier 1004 has a differential output comprising two output connections 1010, 1011. These are connected to the auxiliary circuit 1006 for providing rectified DC electrical energy, derived from the second part of the RF electrical input signal. One output 1010 of the auxiliary rectifier 1004 provides a reference voltage, e.g. a ground. This may be connected to a ground conductor' on the substrate of the circuitry to enable other components carried on the substrate to be referenced to that same voltage. For example, the auxiliary circuit 1006 may also be connected to that ground or reference voltage, and that ground or reference voltage may fix a reference for the voltage levels used in digital logic and/or digital ccmmunication operations performed by the auxiliary circuit.

A data communications connection 1012 connects a data communications terminal of the near field RF communicator 1014 to a corresponding data communications terminal of the auxiliary circuit 1006.

The filter 1008 connects the data communications connection 1012 to the output 1010 of the auxiliary rectifier which provides a reference voltage. The filter 1008 comprises a band pass filter, having a pass band which includes the principal operating frequency of the near field RF communicator 1014, for example the carrier frequency of a near field RF communications signal. This provides a low impedance path to ground for RF signal components which may be present on the communications connection 1012 between the near field RF communicator 1014 and the auxiliary circuit 1004. Such a band pass filter may be provided by any appropriate circuitry, for example by a series connection of an inductor and a capacitor. The inductor may be provided by a printed coil inductor, and may have an inductance selected based on the carrier frequency of the near field RF communicator and/or based on the capacitance of the capacitor. The capacitor may be provided by a lumped capacitor component and may have a capacitance selected based on the carrier frequency and/or based on the inductance of the inductor. For the purposes of the data communications connection 1012, this arrangement provides a notch filter the stop band of this notch may be between 1 MHz and 100MHz, for example between 3 MHz and 50 MHz, for example between 5MHz and 20 MHz for example between 10 MHz and 15MHz, and is typically centred on the carrier frequency of the near field RF communications signal, e.g. 13.56 MHz. The width (FWHM) of this stop band may be about at least 50KHz, for example less than 6 MHz, for example more than 2MHz, for example less than 5MHz, for example about 4MHz..

The inductive coupler 1016 of the apparatus described herein generally comprises an electrical conductor such as a conductive track or wire arranged for coupling inductively with an alternating H-field to provide an alternating electrical signal. Such arrangements may be referred to as an NFC antenna. Typically, such an antenna comprises a loop having one or more turns. It will be appreciated in the context of the present disclosures that an NFC antenna may have a large inductance, perhaps of 1!_tH or more. Such antennas may be adapted for coupling with signals in a near field RF frequency band, which generally comprises 13.56MHz. It will be appreciated in the context of the present disclosure that such signal may have a wavelength of approximately 22m.

The near field RF communicator 1014 may comprise an integrated circuit, which may be implemented as a single semiconductor die (a chip). The near field RF communicator 1014 may comprise a front end, for connection to the antenna 1016. The front end may Include things such as a voltage regulator, a dedicated rectifier for the near field RF communicator, or other circuitry for connecting the near field RF communicator to the antenna 1016.

The near field RF communicator 1014 may also comprise an RF controller for performing simple data operations such as modulating and demodulating data from signals received via the antenna 1016. The near field RF communicator 1014 may comprise DC digital logic circuits configured to obtain data from and/or provide data to the RF controller. The digital logic may also communicate such data to/from the auxiliary circuit 1006 via the communications connection 1012. This can provide data communications between the RF interface of the near field RF communicator 1014 and the auxiliary circuit. Such communication may enable the auxiliary circuit 1006 to perform functions such as authentication (e.g. by biometric means) and user input/output for a device communicating with the near field RF communicator 1014 via the RF interface.

The auxiliary rectifier 1004 comprises a rectifying element, such 25 as a diode, arranged to convert the alternating electrical signal received from the splitter into a direct current, DC, electrical signal. This DC electrical signal may be used to power the auxiliary circuit. The auxiliary rectifier may also comprise components for matching the input and/or output impedance of the 30 rectifier to the circuits to which it is connected.

The power splitter 1002 may comprise a network of electrical impedances, such as capacitors and inductors, connected together to provide: (a) an input impedance which matches the output impedance of the antenna 1016, and (b) a bifurcated electrical conduction path which divides an RF electrical signal received from the antenna 1016 into two parts; (c) a first output impedance which matches the input impedance of the near field RF communicator 1014; (d) a second output impedance which matches the input impedance of the auxiliary rectifier 1004.

For example this functionality of the splitter 1002 may be provided by: an antenna matching network for matching the output impedance of the antenna 1016; a chip matching network for matching the input impedance of the near field RF communicator 1014, and a rectifier matching network for matching the input impedance of the auxiliary rectifier 1004. Connections may be provided between the antenna matching network on the one hand, and, on the other hand, the chip matching network and to the rectifier matching network so that the conduction path from the antenna is bifurcated.

In operation, the power splitter 1014 thus divides the RF electrical input signal from the antenna into two parts each of which comprises part of the energy of the original signal. The first part is provided to the near field RF communicator 1014, and the second part is provided to the auxiliary rectifier 1004.

The division may be even or uneven, but typically it is performed such that the information encoded on the RF electrical input signal (e.g. by modulation of data onto that signal) is also encoded on at least a first part of the signal. This first part of the signal provides power to the near field RF communicator 1014. The second part of the signal is provided to the auxiliary rectifier, which converts the RF electrical input signal into DC electrical energy and provides this DC electrical energy to the auxiliary circuit 1006.

The data carried by the first part of the signal may be demodulated by the near field RF communicator, and may cause the near field RF communicator 1014 to perform further data communication with the auxiliary circuit 1006 via the data communication connection 1012. However, because the auxiliary circuit 1006 is powered by the auxiliary rectifier 1004, there may be significant RF signal noise present on the data communication connection 1012. The filter 1008 provides a low impedance path to ground 1010 for this RF noise thereby to reduce the noise. Generally, in smartcard systems where an auxiliary rectifier is present, the filtering in the rectifier is often imperfect because of a wish to avoid using inductors. Where filtering of RF signal components by the rectifier is imperfect, often the DC output of the rectifier carries a high level of RF signal noise. However, counterintuitively, providing an additional connection between the communication line and the output of the rectifier ( a key noise source) serves to reduce the noise on the communication line. Improving the signal to noise ratio on this communication line may increase the reliability and/or data rate of communication on that line.

Figure 2 illustrates one example of apparatus which can provide the smartcard circuitry of Figure 1.

The apparatus may comprise an inductive coupler 1016 arranged to provide a differential RF electrical signal to a splitter 1002. The splitter has a differential input, which is connectable to the inductive coupler 1016 to obtain an RF electrical input signal. The input signal connection provided by the splitter has two output signal connections. Each of these two output signal connections 2000A, 2000B, comprises a differential output connection for providing a differential RF electrical output signal.

The apparatus may also comprise a chip seat 2002, for seating a near field communicator chip assembly in the card blank. Such a chip assembly may comprise an IC bonded to a substrate which carries the signal, power, and data connections for The IC. The chip seat comprises a connection to a first one 2000A of the two output signal connections of the splitter 1002, so that the splitter 1002 can provide a differential RF electrical output signal to a chip assembly in the chip seat 2002. The chip seat may comprise a recess in a body of a smartcard blank, and the chip assembly may have a complementary shape adapted to fit within the recess so that, when it is fitted into the recess, an RF signal input of the near field communicator chip is connected to the first output signal connection of the splitter.

The apparatus comprises an auxiliary rectifier, so-called because it is separate from the near field RF communicator, for providing a DC supply in addition to any such supply which might be provided by the near field RF communicator IC. The auxiliary Rectifier illustrated in Figure 2 comprises differential signal inputs, which are connected to the second 2000B of the two differential signal outputs from the splitter 1002. It may be particularly advantageous to employ a so called 'buck rectifier' of the type which is described and claimed in the applicant's co-pending international patent application PCT/GB2018/053125, the entirety of which is hereby incorporated by reference as if fully set forth herein. In one example, such a rectifier 1004 comprises: a first rectifier input A and a second rectifier input B for connection to two corresponding outputs of the splitter 1002 for receiving the RF electrical input signal. It also comprises a first rectifier output connection 1011 and a second rectifier output connection 1010 for providing the DC electrical energy to the auxiliary circuit. The second rectifier output connection of this example may provide the ground or reference voltage 1010. A rectifying element 17, such as a diode, for example a Schottky diode is connected between the first rectifier input A and the second rectifier input B. The first rectifier output connection of this "buck rectifier" is also connected to an output of the rectifying element and to the first rectifier input by an inductor 19.

A variety of configurations may be used for this rectifier 1004. In the example illustrated in Figure 2 the rectifier may comprise a first capacitor 34, a second capacitor 36, a first inductor 19, a second inductor 38, and a rectifying element 17. The rectifying element 17 is configured to provide a one way conduction path for electrical current to flow from the input of the rectifying element 17 to the output of the rectifying element 17. The rectifying element 17 may comprise a diode, such as a Schottky diode. A first plate of the first capacitor 34 may be connected to the second rectifier input B. A second plate of the first capacitor 34 is connected to the output of the rectifying element 17, and to the first inductor 19. The first inductor 19 connects the second plate of the first capacitor 34 and the output of the rectifying element 17 to the first rectifier output connection 1011.

A first plate of the second capacitor 36 may be connected to second rectifier input B. A second plate of the second capacitor 36 may be connected to the input of the rectifying element 17, and to the second inductor 38. The second inductor 38 connects the second plate of the capacitor and the input of the rectifying element 17 to the rectifier output 1010, which may act as a ground or reference voltage.

The rectifying element 17 can provide, based on the alternating input voltage, a DC voltage difference between the input of the rectifying element 17 and the output of the rectifying element 17. This DC voltage can charge the first capacitor 34 so that electrical energy is stored on the first capacitor 34. The first inductor 19 helps to keep the current high in both halves of each RF cycle. It will be appreciated in the context of the present disclosure that the second capacitor 36 and the second inductor 38 provide corresponding functions.

In addition, the inductor 38 is optional, and may be removed. This is particularly the case in single ended embodiments. An output storage capacitor 43 may be connected across the outputs 1010, 1011 for the rectifier. For example the output storage capacitor 43 may be connected to the input of the rectifying element 17 by the inductor 38, and to the output of the rectifying element 17 by the first inductor 19. In this position, such a capacitor may perform the function of storing DC output energy (hence its name).

The second capacitor 36 is also optional, and may be removed. Again, this is of particular relevance in single ended embodiments. In these embodiments, a filter capacitor 42 may be connected between the input of the rectifying element 17, and the output of the rectifying element 17. In particular, a first plate of this filter capacitor 42 may be connected to the input of the rectifier 1004, and to the input of the rectifying element 17 whilst a second plate of this filter capacitor 42 is connected to the output of the rectifying element 17 by the capacitor 34.

The apparatus illustrated in Figure 2 also comprises an auxiliary circuit such as any one of the described or claimed herein. It also comprises a data communication connection, for wired digital communication between the auxiliary circuit and a digital output of a near field RF communicator connected to the splitter. This data communications connection may comprise a single ended serial communications bus, such as an I2C interface.

A band pass filter is connected between this data cormunications 35 connection and a reference voltage provided by the DC output of the auxiliary rectifier. The band pass filter is configured to provide a frequency selective connection between the data communications connection and a voltage level against which digital logic in the auxiliary circuit can be referenced. This frequency selective connection may have a low impedance frequency band (a pass band) which comprises a carrier frequency of the signals which the near field RE' communicator is designed to operate with, for example it may comprise 13.56MHz. Counterintuitively, providing this additional coupling between this digital output of the near field RF communicator and another RF powered circuit (the auxiliary rectifier), serves to reduce RF noise at this digital output.

The stability of the ground or reference voltage provided by the 15 auxiliary rectifier output 1010 may be enhanced by the provision of a DC regulator 1015 connected between the two DC outputs 1010 of the auxiliary rectifier 1006. The regulator 1015 may comprise a linear voltage regulator, such as a low drop out regulator (LD0). This may provide improved voltage stability at the DC 20 output 1010 of the auxiliary rectifier whilst also avoiding adding switching noise to the DC output 1010 of the auxiliary rectifier 1004. This improved voltage stability may further enable the filter 1008 to reduce noise on the data communication connection 1012.

As mentioned above, the inductor used to provide the band pass filter may comprise a printed coil inductor. Such an inductor may comprise a laminar conductive coil on one surface of a dielectric, which follows a spiral path in from an input connection at the outside of the spiral to a connection through the dielectric inside the spiral. On the other side of the dielectric, a second laminar conductive coil may follow a mirror image of the same path out from this connection to an output connection at the outward edge of the spiral. The output connection may also be connected back through the dielectric so that input and output to the inductor may be provided on the same surface of the dielectric. The dielectric may comprise a substrate upon which a circuit is printed in the manner of a PCB. Other types of printed coil inductors may be used. A printed coil inductor may comprise a conductive wire with an insulating coating placed on a surface of a dielectric, which follows a spiral path on just one side of the dielectric.

The circuitry described herein may be provided on sheet-like dielectric substrates. This can provide a low profile system adapted for being fully encapsulated within the smartcard 1000, which may have a thickness of less than 3mm, for example less than 2mm, for example about 0.76 millimetres (0.030 in) thick. Embodiments of the present disclosure may provide circuit assemblies for integration into smart cards which are less than 0.5mm thick (of which 0.1mm may be accounted for by the substrate + copper, and 0.35mm by other circuitry components). Such assemblies may then be integrated into a smart card by being sandwiched between other layers such as a plastic front and back of the card. In some embodiments the substrate may be around 2011m, and the total thickness of the substrate with the copper components may be about 50um.

The sheet-like dielectric substrate described herein may be provided by any laminar dielectric, and may be flexible. One example is a polyamide sheet, but other substrates may be used.

The embodiments shown in the Figures are merely exemplary, and include features which may be generalised, removed or replaced as described herein and as set out in the claims. With reference to the drawings in general, it will be appreciated that schematic functional block diagrams are used to indicate functionality of systems and apparatus described herein. It will be appreciated however that the functionality need not be divided in this way, and should not be taken to imply any particular structure of hardware other than that described and claimed below. The function of one or more of the elements shown in the drawings maV be further subdivided, and/or distributed throughout apparatus of the disclosure. In some embodiments the function of one or more elements shown in the drawings may be integrated into a single functional unit.

In some examples the auxiliary circuits described herein may comprise connections for connecting to an IC, or other removable component. This may be assembled to the substrate after the analogue components have been manufactured. This component may provide a controller, such as a microprocessor, configured to perform a method such as biometric authentication using power supplied from a near field RF communications antenna via a auxiliary rectifier as described herein. The auxiliary circuit may provide any selected auxiliary functionality and need not be concerned with authentication. For example it may comprise a location determiner such as a GPS receiver, or something similar, or a communication interface such as a Bluetooth or similar.

In some examples this controller may comprise digital logic, such as field programmable gate arrays, FPGA, application specific integrated circuits, ASIC, a digital signal processor, DSP, or bV any other appropriate hardware. In some examples, one or more memory elements can store data and/or program instructions used to implement the operations described herein. Embodiments of the disclosure provide tangible, non-transitory storage media comprising program instructions operable to program a processor to perform any one or more of the methods described and/or claimed herein and/or to provide data processing apparatus as described and/or claimed herein. The controller may comprise an analogue control circuit which provides at least a part of this control functionality. An embodiment provides an analogue control circuit configured to perform any one or more of the methods described herein.

The above embodiments are to be understood as illustrative examples. Further embodiments are envisaged. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which 10 is defined in the accompanying claims.

Claims

Claims: 1. Smartcard circuitry for providing a radio frequency, RF, interface between an inductive coupler of the smartcard and a 5 near field RF communicator of the smartcard, the circuitry comprising: an input signal connection for connecting to the inductive coupler to obtain an RF electrical input signal; an RF electrical output signal connection for providing a 10 part of the RF electrical input signal to the near field RF communicator; an auxiliary rectifier, separate from the near field RF communicator, and coupled to the input signal connection and configured to provide a DC output for powering an auxiliary circuit, wherein the DC output is based on the RF electrical input signal; a data communications connection for connecting to a wired data communications interface of said near field RF communicator, and a bandpass filter connected between the data communications connection and a reference voltage provided by the DC output of the auxiliary rectifier.
2. An apparatus comprising the smartcard circuitry of claim 1 carried by a dielectric substrate for incorporation into a smartcard.
3. The apparatus of claim 2 wherein the substrate comprises a chip connector for connecting a near field RF communicator 30 integrated circuit, IC, chip to the smartcard circuitry.
4. The apparatus of claim 3 wherein the substrate carries a ground plane disposed on a surface of the substrate opposite the chip connector
5. The apparatus of claim 4 wherein the bandpass filter is connected between the data communications connection and the ground plane.
6. An apparatus for providing power to an auxiliary circuit of a near field radio frequency, RF, communications enabled device, the apparatus comprising: an input signal connection for connecting to an inductive coupler of the near field RF communications enabled device to 10 obtain an RF electrical input signal; an RF electrical output signal connection for providing a part of the RF electrical input signal to a near field RF communicator of the near field RF communications enabled device; an auxiliary rectifier, separate from the near field RF 15 communicator, coupled to the input signal connection and configured to provide a DC output for powering an auxiliary circuit, wherein the DC output is based on the RF electrical input signal; a data communications connection for connecting to a wired 20 data communications connection of said near field RF communicator, and a band pass filter connected between the data communications connection and a reference voltage provided by the DC output of the auxiliary rectifier.
A dielectric substrate for incorporation into a smartcard, wherein the substrate carries the apparatus of claim 6.
8. The apparatus of any preceding claim wherein the data 30 communications connection is arranged for communicating data between said near field RF communicator and said auxiliary circuit.
9. The apparatus of any preceding claim wherein a pass band of 35 the band pass filter comprises a carrier frequency of the RF electrical input signal.
10. The apparatus of claim 9 wherein the band pass filter comprises an inductance and a capacitance connected in series.
11. The apparatus of any preceding claim, wherein the input signal connection comprises a splitter, configured to divide the RF electrical input signal between the auxiliary rectifier and the RF electrical output signal connection.
12. The apparatus of any preceding claim, wherein the auxiliary rectifier comprises: a first rectifier input and a second rectifier input for receiving the RF electrical input signal, a first rectifier output connection and a second rectifier output connection for providing the DC electrical energy to the auxiliary circuit; and a rectifying element connected between the first rectifier input and the second rectifier input, wherein the first rectifier output connection is coupled to an output of the rectifying element and to the first rectifier input by a first inductor.
13. The apparatus of claim 12 wherein the second rectifier 25 output connection provides the reference voltage at the DC output of the rectifier for connection data communications connection by the band pass filter.
14. The apparatus of claim 12 wherein the second rectifier 30 output connection is coupled to an input of the rectifying element and to the second rectifier input by a second inductor.
15. The apparatus of any preceding claim wherein the auxiliary rectifier is connected to the inductive coupler in parallel with 35 a rectifier of the near field RF communicator.
16. The apparatus of any preceding claim further comprising at least one of the inductive coupler and the near field RF communicator.
17. A smartcard comprising the apparatus of any preceding claim.
18. A method of reducing radio frequency, RF, signal noise in wired communication between a near field RF communicator and an 10 auxiliary circuit of a near field RF communications enabled device, the method comprising: obtaining an RF electrical input signal from an inductive coupler of the near field RF communications enabled device; splitting the RF electrical input signal into a first part 15 and a second part; providing the first part of the RF electrical input signal to the near field RF communicator for providing near field RF communications via the inductive coupler; providing the second part of the RF electrical input signal to an auxiliary rectifier, separate from the near field RF communicator, wherein the auxiliary rectifier provides a DC output for powering an auxiliary circuit, wherein the DC output is based on the RF electrical input signal; and, communicating data via a wired data communications connection of said near field RF communicator, wherein the data communications connection is connected via a band pass filter to a reference voltage provided by the DC output of the auxiliary rectifier.
19. The method of claim 18 wherein the data communication relates to an auxiliary function performed by at least one of the auxiliary circuit and the near field RF communicator to provide data for communication to the second near field RF communications enabled device in near field range via near field RF communicator, for example wherein the auxiliary function comprises at least one of authentication, location determining, and communication via a different communication interface.
20. The method of claim 19 wherein the second near field RF 5 communications enabled device provides data encoded on an alternating H-field, the alternating H-field having a carrier frequency in a pass band of the band pass filter.