WO2013121122A2

WO2013121122A2 - Loudspeaker for a mobile telephone comprising an nfc device

Info

Publication number: WO2013121122A2
Application number: PCT/FR2013/050147
Authority: WO
Inventors: Bruno Charrat
Original assignee: Inside Secure
Priority date: 2012-02-09
Filing date: 2013-01-24
Publication date: 2013-08-22
Also published as: WO2013121122A3; FR2986928A1; FR2986928B1

Abstract

The invention relates to a loudspeaker module for a portable device, comprising a near field communication device (NFC) and its antenna. The loudspeaker (14) comprises a main coil (L) connected so as to receive an external audio signal through an excitation contact (A1), and the NFC device comprises a reception circuit (Tx) configured to extract data from a signal applied to the excitation contact (A1) of the main coil of the loudspeaker; and an emission circuit (Rx) configured to emit data in the sound emitted by the loudspeaker.

Description

SPEAKER FOR MOBILE TELEPHONE

COMPRISING AN NFC DEVICE

Technical field of the invention

The invention relates to near field communication devices, or NFC (Near Field Communication), and more particularly to the integration of such devices in mobile phones.

State of the art

NFC devices are commonly in the form of a card, in credit card format, containing information that can be transmitted to a reading terminal by bringing the card sufficiently close to the terminal. They essentially integrate an antenna coil in the plane of the card, a memory containing the information, and a management circuit. The reading terminal emits a normalized frequency magnetic field (13.56 MHz) that the antenna coil picks up to remote power the NFC circuits and that the management circuit modulates, by antenna impedance modulation, for transmit the information to the reading terminal.

The information contained in these maps often gives access to paid services (eg a subscription to public transport). This information is therefore securely accessed to prevent fraud.

As more and more users of such NFC cards also have a mobile phone, we now propose the integration of NFC devices in phones. Such an NFC device then has access to the secure information of the SIM card of the telephone, which can be used to identify the user and to check the services to which this user is entitled. Thus, instead of carrying a phone and one or more NFC cards, the user can use his only mobile phone to access several services, these services may be completely decorrelated from the user's telephone subscription .

Figure 1 schematically illustrates such a mobile phone. The elements of the telephone are housed in a housing 10 of generally flattened shape and, most often, elongated. Only the elements that will be useful for understanding this presentation are described here.

A BBP processor, called "baseband", handles most of the phone's functions, including access to secure SIM card information. "Subscriber Identification Module"), to identify the user on the telephone network. An ACTRL audio management circuit, generally including a DSP (of the "Digital Signal Processor"), assists the processor in processing the various audio signals used in the telephone. It processes in particular the signal coming from a microphone 12 and sends amplified audio signals to a loudspeaker 14.

An NFC device built into the phone has the phone's power source. As a result, the NFC device can be more sophisticated than when it is only remotely powered. It may be provided for exchanging data by wire with the elements of the telephone and even behaving as an NFC reader for receiving data from a contactless terminal. The NFC device has access to the contents of the SIM card and can also exchange data with the BBP processor. The processor can thus provide information that the NFC device transmits to a contactless terminal, and receive from the NFC device data transmitted by the terminal.

Given the placement constraints of the elements in the phone case, the location of the NFC device differs from one phone to another. As the antenna of the NFC device is flat, it is most often placed behind the battery.

Thus, to use the NFC function of the phone with a reading terminal in good conditions, the user is forced to present the back of the phone to the active face of the terminal. This forces the user to reposition the phone whose natural position is with the back on the palm of the hand. Moreover, since the slightest angle between the plane of the telephone and the active face of the reading terminal significantly removes the antenna coil from the active face, the user must make an extra effort to present the phone with the correct orientation.

Summary of the invention

It is thus desired to have a mobile phone incorporating an NFC functionality that is practical to manipulate to operate an NFC transaction while offering ease of integration for the telephone manufacturer.

This need is met by providing a portable device speaker module including a near field communication (NFC) device and its antenna.

According to one embodiment, the loudspeaker comprises a main coil connected to receive an external audio signal by an excitation contact, and the NFC device comprises a reception circuit configured to extract data from a signal applied to the excitation contact of the main coil of the loudspeaker; and a transmission circuit configured to transmit data in the sound transmitted by the speaker.

According to one embodiment, the loudspeaker comprises an auxiliary coil and the transmitting circuit is configured to modulate the impedance of the auxiliary coil.

According to one embodiment, the module comprises a power supply circuit of the NFC device, configured to rectify and filter an alternating signal applied to the excitation contact of the main coil.

There is also provided a portable device of generally flattened shape comprising a speaker module of the aforementioned type assembled in the vicinity of an edge of the portable device; a microphone ; and a programmable audio management system, connected to the speaker and the microphone.

According to one embodiment, the audio management system is programmed to output modulated data in an electrical signal applied to an excitation contact of the loudspeaker, and extract modulated data in a sound signal picked up by the microphone. The NFC device of the loudspeaker module is configured to extract modulated data in the signal applied to the speaker's excitation contact, and transmit data by modulating the sound emitted by the loudspeaker.

According to one embodiment, the NFC device is configured to draw its power supply from the signal applied to the excitation contact of the loudspeaker.

According to one embodiment, the loudspeaker comprises a main coil connected to the excitation contact of the loudspeaker, and an auxiliary coil. The NFC device is configured to modulate the sound emitted by the speaker by modulating the impedance of the auxiliary coil, and the audio management system is programmed to apply a carrier signal to the speaker's excitation contact when the NFC device modulates the impedance of the auxiliary coil.

According to one embodiment, the modulations are performed in an inaudible frequency band.

According to one embodiment, the antenna comprises a coil wound around the loudspeaker core.History Brief description of the drawings

Embodiments will be set forth in the following description, given as a non-limiting example in relation to the appended figures among which:

• Figure 1, previously described, schematically shows a mobile phone incorporating an NFC device;

FIGS. 2 to 5 schematically illustrate various embodiments of a loudspeaker module incorporating an NFC device connected to elements of the telephone; and

• Figure 6 schematically illustrates a variant for making the antenna coil of the NFC device.

Description of a preferred embodiment of the invention

We have observed that a user who wants to bring his phone closer to any object, without any constraints, naturally holds the phone in his hand in the position used to talk on the phone, and brings the top edge of the phone closer of the object, the plane of the phone making an angle around 45 ° to the vertical.

Thus, to facilitate the use of the NFC function of a mobile phone, it is envisaged to integrate an NFC device near the top edge of the phone. Given the placement constraints, this may not be possible in all situations, especially if the NFC device is an item to assemble individually.

The top edge of the phone is the part where the speaker is housed. The speaker is usually integrated into a ready-to-assemble module on the phone's motherboard. It is proposed here to mount the NFC device, including its antenna, in the housing of the speaker module.

The dimensions of the antenna coil of the NFC device are thus constrained by the dimensions of the housing, generally smaller than those of a conventional antenna coil. There is a tendency to reduce the range of communication. However, since the user can easily put the upper edge of the telephone in contact with the active face of the reading terminal, and the antenna coil will then be a few millimeters from the active face, a range of 1 to 2 cm would be enough. If the need exists, the range of the antenna coil can be increased by using the "active charge modulation" technique described in US7098770, which is suitable for situations where the NFC device has a power source. permanent, as is the case in a mobile phone. Figure 2 schematically illustrates a first embodiment of loudspeaker module 20 incorporating an NFC device. The loudspeaker 14 is secured to a housing 20a which protects the motor of the speaker, here a coil L, and carries two access contacts to the motor A1 and A2. The contacts A1 and A2 are intended to be connected to an analog audio signal source, for example to the analog output of the audio management circuit ACTRL and to the ground of the telephone. In some applications, the audio signal is differential, in which case the contact A2 is not grounded, but receives a signal in phase opposition with that received by the contact A1.

The housing 20a generally has a configuration conferring on the module a form easily manipulated by automated placement machines. Thus, the housing is parallelepiped and its dimensions exceed those of the horn of the speaker. The flag often having an elongated shape, dimensions of the order of 10x5x5 mm are common. A 10x5 mm antenna coil, with the active modulation technique, has a range equivalent to that of a traditional antenna coil, which exceeds the needs of the applications envisaged here. The NFC device, in the form of a printed circuit also carrying the antenna, may be secured, from the inside or the outside, to one of the walls of 10x5 mm. The printed circuit may even replace the wall. This wall is preferably the one that will be closest to the edge of the phone.

In the embodiment of FIG. 2, the module comprises two additional contacts B1 and B2. The contact Bl serves to bring the supply voltage Vdd of the telephone to the NFC device. The ground voltage of the NFC device is taken on the contact A2 of the loudspeaker. The contact B2 makes it possible to establish a bidirectional serial communication link Tx / Rx between the BBP processor of the telephone and the NFC device. According to the communication protocol used, the contact B2 may actually represent a group of several contacts for carrying several signals (for example the DATA, CLOCK and RESET signals of the I2C protocol).

Thus, a loudspeaker module according to Figure 2 requires several connections in addition to those of the speaker. This requires an adaptation of the phone's motherboard. Tracks carrying the supply voltage Vdd are generally available everywhere on the motherboard, and adding a connection of such a track to the contact Bl of the module represents a minimal modification that most phone manufacturers would be ready to adopt to make compatible with their existing phone models with NFC functionality.

On the other hand, the addition of a Tx / Rx serial communication track is not trivial. It will be necessary not only to route a dedicated conductive track on the motherboard, but also, in most cases, provide an interface circuit with the BBP processor. Thus, the module according to Figure 2 is rather reserved for newly designed phones.

Figure 3 schematically shows a speaker module embodiment better suited to an existing mobile phone model. Here the contact B2 of FIG. 2, used for the exchange of Tx / Rx data between the NFC device and the BBP processor of the telephone, has been deleted. There remains the contact B l used to bring the supply voltage Vdd which, as previously indicated, requires minor modifications of the motherboard of an existing phone model.

A data exchange link is needed. This link is made using means that do not require a structural modification of the phone.

More specifically, the NFC device is configured to receive the data (Tx) of the BBP processor by the loudspeaker excitation contact A1, and to transmit the data (Rx) to the processor in the sound produced by the loudspeaker. 14, and collected by the microphone 12.

The contact A1 is normally provided to receive an audio signal produced by the ACTRL audio management circuit. Here it is planned to configure the circuit ACTRL to also transmit the Tx data. The operation of this circuit is generally programmable and managed by the processor BBP according to a firmware stored in a non-volatile memory MEM. Simply modify this firmware to give the audio system the required functionality, without any hardware changes.

The audio system may be programmed, for example, to produce on the contact A1 a signal formed of a carrier modulated in amplitude by the data Tx. The NFC device then comprises a demodulation circuit designed to extract the data from the signal present on the contact A1. The choice of the type of modulation is preferably such that the demodulation method is compatible with the computing resources traditionally available in the NFC device.

Since the modulation signal applied to the contact A1 is also reproduced by the loudspeaker 14, the parameters of the modulation (carrier frequency and data transmission rate) are preferably chosen so that the spectrum of the modulation comprises the least possible of audible components.

Now, to transmit the Rx data into the sound produced by the speaker, the NFC device can hardly act on the contacts Al and A2, which are low impedance. An auxiliary coil La is then provided to excite the loudspeaker. This coil can be part of the coil L. One of the terminals of the coil La is connected to the ground contact A2, and the other to a transmission circuit of the NFC device. This transmission circuit can be configured, for example, to modulate the amplitude Rx data on a carrier.

As this time the modulation signal is reproduced by the speaker 14 to be picked up by the microphone 12, the modulation parameters are preferably compatible with the bandwidths of the speaker and the microphone. Such components commonly used in small phones generally have an ultrasound bandwidth of up to 40 kHz. In this case, for example, a carrier of 40 kHz and a transmission speed of 10 kBaud are chosen. Such a modulation has a spectrum having low amplitude components in the audible band.

If we want to avoid any component in the audible band, we can use more sophisticated modulation techniques, including single sideband (SSB, or SSB), which removes the side of the spectrum to the left of the carrier frequency , so all the components that could have spilled over into the audible band. Thus, the sound as it is understood here can have a frequency ranging from audible to ultrasound, up to the maximum frequency transmissible by the loudspeaker and capable of being picked up by the microphone in good conditions. .

Demodulation methods are generally more complex than modulation methods. This is compatible with the present configuration, since the modulation is performed by the transmission circuit of the NFC device, which has modest computing resources, while the demodulation is performed by the audio system on the signal picked up by the microphone. The BBP processor associated with the audio system has powerful digital signal processing resources, including demodulation, since it is designed to demodulate telephone signals received according to different standards.

The required functionality of the audio system, namely extracting the data of the signal received by the microphone, is thus achievable through a simple modification of the processor firmware, without modification of the hardware.

In sum, by integrating a speaker module of the type of Figure 3, a manufacturer can integrate NFC functionality into an existing phone model by a simple update of the firmware and a minor modification of the motherboard to bring the supply Vdd on the contact Bl. Figure 4 illustrates a speaker module embodiment requiring no modification of the motherboard to integrate an NFC functionality into an existing phone model. The contact Bl has been removed for this purpose. The supply voltage Vdd of the NFC device is produced by a circuit 40 which rectifies and filters the AC voltage supplied by the audio system on the contact A1. The supply voltage Vdd can thus be produced from any signal present on the contact A1, this signal possibly being an audio signal to be reproduced by the loudspeaker, or a modulation signal for transmitting data from the processor. to the NFC device.

Nevertheless, the current capacity of such a type of power supply remains limited. It is possible that the NFC device does not have enough current to excite the auxiliary coil La with a modulation signal of sufficient amplitude for the microphone. Moreover, since the contacts A1 and A2 are of low impedance, the coil L is short-circuited, which significantly reduces the driving efficiency of the signal applied to the coil La. To avoid these difficulties, the NFC device is preferably intended to modulate the impedance of the coil La, according to the same technique as the impedance modulation of the antenna in the field of a reader. The impedance modulation of the coil La does not make sense if there is no carrier to modulate. In fact, the carrier is provided by the audio management system on the coil L. This carrier is therefore modulated by the impedance modulation of the coil La in the sound emitted by the speaker. At the same time, the carrier, applied to the contact A1, serves to produce the supply voltage Vdd of the NFC device.

In a typical configuration, it is the NFC device that initiates the exchanges with the processor of the phone, when it is put in the field of a reader. However, for the NFC device initiates exchanges, it is desirable that it can transmit data at any time. However, it can not transmit if no carrier is present on the coil L.

To avoid this difficulty, it is expected that the audio system applies a permanent carrier on the contact Al. Then, in the presence of an audio signal, the carrier and the audio signal are added together.

Nevertheless, the application of a carrier permanently consumes a significant energy. It is preferable to apply a carrier intermittently, at regular intervals. The NFC device can then be designed to detect the presence of the carrier on the contact A1, and synchronize the beginning of the data exchange with the beginning of the appearance of the carrier. The audio system is then configured to hold the carrier until the end of the exchange.

The intermittent application of the carrier also has the effect of regularly recharging the capacitor of the power supply circuit 40. However, it is not necessary for the voltage Vdd to be permanently maintained at a level sufficient for the NFC device to be fully operational. . Indeed, the NFC device will "wake up" at the next appearance of the carrier, which recharges the capacitor, at the time when the exchanges can be initiated.

Thus, the carrier idle interval determines the reaction time of the NFC device. It will be chosen to offer a reasonable compromise depending on the type of use.

Figure 5 schematically illustrates a fourth speaker module embodiment. In this embodiment, the speaker is conventional and has a single coil L. The excitation terminal of the coil is here connected to the contact A1 by a switch S I and the transmission circuit of the NFC device by a switch S2. The switches S I and S2 are controlled in phase opposition by the NFC device. The other elements of the module are unchanged compared to Figure 4.

In normal operation, the switch SI is closed, connecting the loudspeaker to the audio system, and the switch S2 is open. When the NFC device is put in the field of a reader, it wakes up and switches the switches S1 and S2. The speaker coil is connected to the transmitting circuit of the NFC device and the driving efficiency of the signal applied to it is maximum, since there is no, as in FIGS. short circuit in his field. The residual charge in the capacitor of the supply circuit 40 may be sufficient to produce a short audio signature by the speaker which, after capture by the microphone 12, is interpreted by the audio system as an identification of an exchange start. The audio system then supplies the NFC device via contact Al.

In order for the NFC device to have enough current to issue the signature on the loudspeaker at any time, the capacitor of the power supply circuit 40 must be kept charged. This can be done by applying a frequency burst at regular intervals. inaudible on the contact Al. The interval between bursts does not affect the reaction time of the NFC device here. These bursts may therefore be spaced apart to have a negligible impact on consumption. Note that with this structure the data transmissions can be operated in both directions (Tx, Rx) at the same time. Moreover, the modulation signal applied to the contact A1 is not transmitted to the loudspeaker. This relaxes the constraints of the modulation parameters on the audible components, and this reduces the consumption. Once the NFC device leaves the reader's field, or the transaction is complete, the switches S1 and S2 are switched to their default position.

FIG. 6 schematically represents an alternative embodiment of the antenna coil 16 of the NFC device, in the context of the embodiment of FIG. 2. The antenna coil 16 is here wound around the core of the loudspeaker 14, on the same support as the excitation coil L. The use of the single core of the speaker for the manufacture of inductors allows a gain in productivity during the production of such products. The kernel properties remain acceptable at the carrier frequency used by the NFC devices (13.56 MHz). This gives an antenna 16 of small footprint (small diameter turns) having a range of communication compatible with the standards in force.

Although there are shown separate elements in the speaker module embodiments, all these elements are preferably mounted on the printed circuit of the NFC device, or even provided in the integrated management circuit of the NFC device.

Although the loudspeaker modules have been described here in connection with a mobile phone, it is clear that such a speaker module can be used in other portable devices requiring a speaker, and having a microphone for the modules of Figures 3 to 5, such as a music player, a dictaphone ...

Claims

claims

A loudspeaker module configured to be assembled into a portable device comprising an audio signal source, the module comprising a speaker excitation contact (Al) (14) configured to be connected to the audio signal source during assembly of the module, characterized in that the module integrates a near-field communication device (NFC) and its antenna.

Module according to claim 1, wherein the loudspeaker (14) comprises a main coil (L) connected to the excitation contact (Al), and the NFC device comprises:

A reception circuit (Tx) configured to extract data from a signal applied to the excitation contact (A1) of the main coil of the loudspeaker; and

• a transmission circuit (Rx) configured to transmit data in the sound emitted by the loudspeaker.

3. Module according to claim 2, wherein the loudspeaker comprises an auxiliary coil (La) and the transmission circuit (Rx) is configured to modulate the impedance of the auxiliary coil.

4. Module according to claim 2, comprising a supply circuit of the NFC device, configured to rectify and filter an alternating signal applied to the excitation contact (A1) of the main coil (L).

5. Portable generally flattened device comprising:

A loudspeaker module (20) according to claim 1 assembled in the vicinity of an edge of the portable device; A microphone (12); and

• a programmable audio management system (ACTRL), connected to the speaker (14) and the microphone.

Portable device according to claim 5, wherein The audio management system (ACTRL) is programmed to transmit modulated data (Tx) in an electrical signal applied to the excitation contact (Al) of the loudspeaker, and to extract modulated data (Rx) in a sound signal picked up by the microphone (12); and the NFC device of the loudspeaker module is configured to extract modulated data (Tx) in the signal applied to the excitation contact (Al) of the loudspeaker, and transmit data (Rx) by the modulation of the sound emitted by the speaker.

7. Portable device according to claim 6, wherein the NFC device is configured to draw its supply (Vdd) of the signal applied to the excitation contact (A1) of the loudspeaker.

The portable device according to claim 6, wherein the loudspeaker comprises a main coil (L) connected to the excitation contact of the loudspeaker, and an auxiliary coil (La), and the NFC device is configured to modulate the sound emitted by the loudspeaker by modulating the impedance of the auxiliary coil (La), and

• The audio management system (ACTRL) is programmed to apply a carrier signal to the speaker's excitation contact when the NFC device modulates the impedance of the auxiliary coil.

9. Portable device according to claim 6, wherein the modulations are performed in an inaudible frequency band.

10. Module according to claim 1, wherein the antenna (16) comprises a coil wound around a core of the loudspeaker (14).