Near field communication device intended for integration into a motor vehicle.

Abstract

A near-field communication device (200), intended for integration into a motor vehicle, comprising: - a printed circuit board having at least four functional layers (2101, 2102, 2103, 2104) of electrically conductive material, separated in pairs by insulating layers (2201, 2202, 2203) of dielectric material; - a near-field communication antenna (230) formed by four concentric turns integrated on the printed circuit board; and - at least one electronic circuit (250) for power supply and signal processing, connected to the antenna (230) and integrated on the printed circuit board. The four turns are distributed over only two adjacent functional layers (2101, 2102), which reduces antenna inductance drift from one device to another. Figure 2A

Description

Title of the invention: Near-field communication device intended to be integrated into a motor vehicle. Technical field

[0001] The invention relates to the automotive field and more particularly to a near-field communication device intended to be integrated into a motor vehicle.

[0002] In practice, such a device belongs to a vehicle access system, having functions for authenticating and locating a user using in particular communication between the vehicle and a badge worn by the user. The badge may be a dedicated device. Alternatively, it may be a smart phone, or smartphone, integrating a dedicated functionality. State of the art

[0003] Near-field communication devices intended to be integrated into a motor vehicle are known in the prior art, and comprising: - a printed circuit board; - a near-field communication antenna, integrated on the printed circuit board; and - at least one electronic power supply and signal processing circuit, connected to the antenna and integrated on the printed circuit board.

[0004] The near-field communication antenna is formed of several concentric turns, together forming a coil.

[0005] In use, the winding is crossed by an electric current, which generates an electromagnetic field oriented in a direction orthogonal to the plane of the turns. The electromagnetic coupling between two neighboring near-field communication antennas makes it possible to carry out a data exchange, or communication, between these two antennas. In particular, the current flowing in one coil, or antenna, will generate a magnetic field which will pass through the other coil, or antenna, and generate a current there.

[0006] The generated electromagnetic field decreases very rapidly as it moves away from the antenna, hence the concept of near field. A maximum communication distance between two near-field communication antennas is preferably less than 10 cm, or even less than 5 cm.

[0007] A near-field communication antenna therefore designates an antenna configured to transmit and receive an electromagnetic signal, by electromagnetic coupling with another near-field communication antenna. By abuse of language, we can speak of an NFC antenna (for the English "Near Field Communication") to designate a near field communication antenna, the term "NFC" can also designate a particular communication protocol implemented in a near field communication antenna.

[0008] Optimization studies have shown that, in the case of a near-field communication device intended to be integrated into a motor vehicle as part of a vehicle access system, a near-field communication antenna composed of exactly four turns leads to optimal performance. For example, an antenna with only two turns does not allow a sufficient inductance value to be achieved to operate the near-field communication device as part of a vehicle access system.

[0009] Advantageously, the near-field communication antenna is integrated on a multi-layer printed circuit board. A multi-layer printed circuit board is formed of an alternation of so-called functional layers, made of electrically conductive material, and so-called insulating layers, made of dielectric material.

[0010] In a manner known per se, the efficiency of the near-field communication antenna is proportional to the square of the surface area it surrounds. The person skilled in the art therefore seeks to size and arrange the four turns so as to maximize the surface area delimited by an internal contour of the antenna.

[0011] In order to reconcile this objective with the search for great compactness, the four turns are formed in a printed circuit board comprising four or more functional layers, and superimposed on top of each other each in a respective functional layer.

[0012] An objective of the invention is to optimize the performance of a near-field communication device, intended to be integrated into a motor vehicle, and incorporating a near-field communication antenna. Statement of the invention

[0013] This objective is achieved with a near-field communication device, intended to be integrated into a motor vehicle, and comprising: - a printed circuit board, comprising at least four superimposed so-called functional layers, made of electrically conductive material, separated two by two by respective so-called insulating layers, made of dielectric material; - a near-field communication antenna, formed by four concentric turns integrated on the printed circuit board; and - at least one electronic power supply and signal processing circuit, connected to the antenna and integrated on the printed circuit board.

[0014] The electronic power supply and signal processing circuit designates a circuit electronics configured for: - generate an electrical transmission signal, intended to be transformed by the antenna into a magnetic transmission signal (antenna power supply function); and - carry out signal (pre)processing on a received electrical signal, supplied by the antenna and corresponding to a magnetic signal received by the antenna and transformed by the latter into an electrical signal (signal processing function, comprising at least demodulation and amplification).

[0015] According to the invention, the four turns are distributed over only two neighboring functional layers of the printed circuit board.

[0016] This arrangement is therefore completely contrary to the prejudices of those skilled in the art, who until now thought that the optimal arrangement consisted of stacking the four turns one on top of the other, to combine great compactness and a large surface area inside the antenna.

[0017] The inventors noticed that, in a device with the four turns stacked, the inductance of the near-field communication antenna varies significantly from one device to another.

[0018] These inductance variations induce significant variations in the impedance seen by the electronic power supply and signal processing circuit, from one device to another. This results in variations in the impedance matching between the antenna and said circuit, from one device to another. Ultimately, this therefore results in variations in the performance of the near-field communication device, from one device to another.

[0019] The inventors then realized that these variations in inductance were linked to variations in the thickness of the different layers of the printed circuit board, from one device to another. In particular, there is a certain manufacturing tolerance on the thickness of each layer of the printed circuit board. This results in slight variations in the distance between two neighboring turns, from one device to another, and therefore variations in the inductance of the near-field communication antenna, from one device to another.

[0020] The inventors then had the idea of ​​proposing a device in which the four turns are no longer distributed over four superimposed layers of a printed circuit board, but over only two neighboring functional layers of the printed circuit board, with the printed circuit board still comprising four or more functional layers.

[0021] Thus, the cumulative variation in distance between two neighboring turns is reduced, by construction, which limits the variations in inductance from one device to another. In particular, the variation in inductance of the antenna, from one device to another, depends on the variation in thickness of a single layer of the printed circuit (the layer insulating layer located between the two neighboring functional layers receiving the turns), and not the sum of the variations in thickness of three superimposed insulating layers inserted between the four functional layers receiving the turns.

[0022] The invention thus proposes an arrangement of the turns that is completely counter-intuitive and contrary to the prejudices of those skilled in the art. This arrangement makes it possible, surprisingly, to limit the variation in inductance of the near-field communication antenna from one device to another. This limits variations in the impedance matching with the electronic power supply and signal processing circuit from one device to another. Ultimately, this limits variations in the performance of the near-field communication device from one device to another. This ensures, for example, that all the devices in the same production line have the same performance, particularly in terms of communication distance.

[0023] The invention thus proposes a robust design, with very little drift in the antenna parameters from one device to another.

[0024] The size is kept almost identical for the same efficiency of the near-field communication antenna, since the turns remain distributed in two layers, and are not all coplanar.

[0025] Preferably, the antenna is formed by four turns, with two first turns located on a first functional layer and two second turns located on a second functional layer, the first functional layer and the second functional layer being separated two by two by a single insulating layer.

[0026] Advantageously, the first two turns are superimposed two by two with the second two turns.

[0027] Said two neighboring functional layers preferably include an end layer of the printed circuit board.

[0028] The at least one electronic power supply and signal processing circuit is advantageously formed in at least one functional layer of the printed circuit board, distinct from the functional layers receiving the turns.

[0029] The at least one electronic power supply and signal processing circuit can be inscribed inside a surface delimited by an internal contour of the turns.

[0030] The device according to the invention may further comprise a capacitive electrode, inscribed inside a surface delimited by an internal contour of the turns, and connected to a detection circuit to form a capacitive presence sensor, with the detection circuit integrated on the printed circuit board.

[0031] Each turn is advantageously square in shape.

[0032] The invention also covers a door handle for a motor vehicle, comprising a device according to the invention. Description of figures

[0033] Other characteristics and advantages of the invention will become apparent from reading the description which follows. This is purely illustrative and must be read in conjunction with the appended drawings in which:

[0034] [Fig.lA] [Fig.lA] schematically illustrates, in a sectional view, a near-field communication device intended to be integrated into a motor vehicle, according to the prior art;

[0035] [Fig.lB] [Fig.lB] schematically illustrates, in a top view, one of the functional layers of the device of [Fig.lA];

[0036] [Fig.2A] [Fig.2A] schematically illustrates, in a sectional view, a near-field communication device according to the invention;

[0037] [Fig.2B] [Fig.2B] schematically illustrates, in a top view, the first of the functional layers receiving the near-field communication antenna, in the device of [Fig.2A];

[0038] [Fig.2C] [Fig.2C] schematically illustrates, in a top view, the second one of the functional layers receiving the near-field communication antenna, in the device of [Fig.2A];

[0039] [Fig.2D] [Fig.2D] schematically illustrates, in a transparent top view, the device of [Fig.2A]; and

[0040] [Fig.3] [Fig.3] schematically illustrates a comparison of the variation in inductance from one device to another, in devices similar to that of Figures 1A and 1B, and in devices similar to that of Figures 2A to 2D.

[0041] Detailed description of at least one embodiment

[0042] In figures 1A to 2D, the axes of an orthonormal reference frame (Oxyz) are shown to facilitate understanding.

[0043] First of all, and with reference to FIGS. 1A and 1B, a near-field communication device 100 according to the prior art, intended to be integrated into a motor vehicle and to form part of a vehicle access system, is briefly described.

[0044] In [Fig. 1A], the near-field communication device 100 is shown, schematically, in a sectional view in a plane parallel to the plane (xOz).

[0045] The device 100 comprises a printed circuit board, composed here of four so-called functional layers 110i, 1102, 1103, 1104, between which insulating layers 120i, 1202, 1203 are interposed.

[0046] The functional layers 110i, 1102, 1103, 1104 are formed by electrically conductive metal tracks. They each extend parallel to the plane (Oxy), and are stacked one above the other along the axis (Oz).

[0047] The functional layers 110i, 1102, 1103, 1104 are separated two by two by the insulating layers 120i, 1202, 1203, made of dielectric material. The insulating layers 120i, 1202, 1203 each extend parallel to the plane (Oxy), and are stacked one above the other along the axis (Oz). A respective insulating layer is interposed between two neighboring functional layers, in direct physical contact with each of said functional layers.

[0048] The device 100 comprises a near-field communication antenna 130, comprising four superimposed turns 130i, 1302, 1303, 1304 each located in a respective one of the functional layers 110i, 1102, 1103, 1104. The turns are connected to each other by vertical vias 131, oriented along the axis (Oz) and each passing through at least one insulating layer 120i, 1202, 1203.

[0049] Each turn is formed by a respective metal track in the corresponding functional layer. [Fig. 1B] schematically illustrates one of the functional layers of the device 100, here the functional layer 1102 receiving the turn 1302.

[0050] Each of the turns 130i, 1302, 1303, 1304 has a substantially rectangular or square shape.

[0051] Next, with reference to FIGS. 2A to 2D, a near-field communication device 200 according to the invention is illustrated, intended to be integrated into a motor vehicle and to form part of a vehicle access system.

[0052] The device 200 will only be described for its differences relative to the device of figures 1A and 1B.

[0053] As in the prior art, the device comprises a printed circuit board, comprising an alternation of functional layers 210i, 2102, 2103, 2104 and insulating layers 220i, 2202, 2203 as described above, with at least four functional layers.

[0054] The device 200 comprises a near-field communication antenna 230, comprising four turns distributed in only two of the functional layers.

[0055] In particular, the four turns are distributed in two neighboring functional layers, separated by a single insulating layer.

[0056] Advantageously, and as illustrated in [Fig.2A], the four turns are distributed in two functional layers including an end functional layer of the printed circuit board. An end functional layer of the printed circuit board designates a functional layer located at one end of the stack of functional and insulating layers together forming the printed circuit board. An end functional layer is in contact with an insulating layer only at one of its two large faces.

[0057] Here, the four turns are distributed in the functional layers 210i and 2102

[0058] The four turns are divided into two pairs of turns 232i 2322, located respec tively in layers 210i and 2102, and arranged superimposed. The pairs of turns are connected together by a vertical via 231, oriented along the axis (Oz) and passing through at least the insulating layer 220i (in the direction of the thickness).

[0059] Each pair of turns 232b respectively 2322, is formed of two concentric and coplanar turns.

[0060] [Fig.2B] schematically illustrates the functional layer 210i receiving the pair of turns 232b

[0061] As illustrated in [Fig.2B], the pair of turns 232i is composed of two turns 230i and 2302 wound around each other. In other words, the two turns 230i and 2302 are formed by a single linear metal ribbon, formed in the functional layer 2101.

[0062] Each turn 230i and 2302 is substantially square or rectangular in shape. In particular, each turn 230i and 2302 is rectangular or square in shape, open due to the arrangement of the turns wound around each other.

[0063] In [Fig.2B], one terminal of the near-field communication antenna 230 is also represented by a black circle 233b.

[0064] [Fig.2C] schematically illustrates the functional layer 2102 receiving the pair of turns 2322.

[0065] As illustrated in [Fig.2C], the pair of turns 2322 is composed of two turns 2303 and 2304 wound around each other. In other words, the two turns 2303 and 2304 are formed by a single linear metal ribbon, formed in the functional layer 2102.

[0066] Each turn 2303 and 2304 is substantially square or rectangular in shape. In particular, each turn 2303 and 2304 is rectangular or square in shape, open due to the arrangement of the turns wound around each other.

[0067] In [Fig.2C], the other terminal of the near-field communication antenna 230 is also represented by a black circle 2332.

[0068] [Fig.2D] illustrates schematically, and in a transparent top view, the device 200.

[0069] In [Fig.2D], the insulating layers are shown transparent, so that the superposition of the two pairs of turns 232i and 2322 is observed. As illustrated by [Fig.2D], each turn of the first pair of turns 232i is superimposed with a respective one of the turns of the second pair of turns 2322.

[0070] In [Fig. 3], variations in inductance of the near-field communication antenna are shown from one device to another. The inductance variation values ​​were obtained by simulation.

[0071] The left bar represents the inductance variation in a prior art device as described in the introduction, formed on a 0.8 mm thick printed circuit board. The inductance variation is of the order of 2.5%.

[0072] The right bar represents the inductance variation in a device according to the invention, formed on a printed circuit board also 0.8 mm thick. The inductance variation is of the order of 0.25%.

[0073] Here we observe a reduction of a factor of 10 in the inductance variations of the near-field communication antenna, from one device to another. This confirms the inventors' intuition that the inductance variations can be reduced by limiting the number of layers over which the turns of the antenna extend. Different simulations were implemented. In all cases, the inductance variations are reduced by a factor of between 3 and 10.

[0074] According to the invention, the device 200 further comprises at least one electronic power supply and signal processing circuit 250.

[0075] As detailed in the introduction, the electronic power supply and signal processing circuit 250 is configured to generate an electrical transmission signal intended to be transformed by the antenna 230 into a magnetic transmission signal, and to carry out signal preprocessing on an electrical signal provided by the antenna 230 and corresponding to a magnetic signal received by said antenna 230 and transformed by the latter into an electrical signal. The signal preprocessing notably comprises demodulation and amplification of the electrical signal provided by the antenna 230, in order to then be able to extract the useful information therefrom. The electronic circuit 230 may be called a “transmission and reception circuit”, or simply “transceiver”. The electronic power supply and signal processing circuit comprises a transmission stage, a reception stage (demodulation, amplification), and possibly a signal processing stage (to extract the useful information).

[0076] The circuit 250 is connected to the antenna 230 by at least one vertical via 251, oriented along the axis (Oz). It has at least one function of powering the antenna 230 and of receiving and processing an electrical signal supplied by the antenna 230.

[0077] The circuit 250 extends in at least one functional layer of the printed circuit board, distinct from a layer receiving one or more turns of the antenna. Here, the circuit 250 extends in the functional layer 2104 furthest from the antenna 230. In variants not shown, the circuit 250 extends in several superimposed functional layers, all distinct from a layer receiving one or more turns of the antenna. Advantageously, the circuit 250 extends, at least, in the functional layer furthest from the antenna 230.

[0078] In Figures 2B to 2D, the contour 255 of the circuit 250, shown in transparency, is schematically represented.

[0079] Advantageously, and as shown in FIGS. 2B to 2D, the circuit 250 is placed inside the turns. In other words, the circuit 250 is inscribed inside a surface 238 delimited by an internal contour of the turns. In other words, according to a top view representation, the circuit 250 is inscribed inside the surface 238 delimited by an internal contour of the turns. In other words, in an orthogonal projection of the turns and the circuit 250 in the same plane parallel to the plane (Oxy), the projection of the circuit 250 is located inside a surface delimited by the internal contour of the projection of the turns. In [Fig.2D], the surface 238 is shown hatched.

[0080] This arrangement provides optimal compactness.

[0081] In variants not shown, the device according to the invention further comprises a capacitive electrode, also inscribed inside a surface delimited by the internal contour of the turns.

[0082] Where appropriate, the capacitive electrode and the electronic power supply circuit are arranged superimposed, each in at least one separate layer of the printed circuit board.

[0083] Such a capacitive electrode is used, in a manner known per se, to form a measuring capacitor with the ground so as to carry out presence detection.

[0084] The capacitive electrode is advantageously connected to a detection circuit, not shown, comprising a microcontroller, switches, and a discharge capacitor. The measuring capacitor defined between the capacitive electrode and ground, and the discharge capacitor, are mounted together in a capacitive voltage divider type arrangement. The switches are controlled so that the measuring capacitor is alternately charged and discharged into the discharge capacitor. When the measuring capacitor is discharged into the discharge capacitor, the charges are balanced between the two capacitors and it is possible to detect the presence of a target as a function of a voltage signal representative of the discharge of the measuring capacitor.

[0085] The invention also covers a door handle for a motor vehicle, not shown, incorporating a device according to the invention such as that described with reference to Figures 2A to 2D.

[0086] The device according to the invention is configured to communicate with an ancillary device carried by a user, the ancillary device also being equipped with a near-field communication antenna and comprising a memory storing a user identifier. The ancillary device may be a smartphone integrating a specific functionality, or a dedicated device such as a vehicle access badge.

[0087] Advantageously, the electronic power supply and signal processing circuit 250 is configured to generate the sending of an interrogation signal, from the device according to the invention to the ancillary device, the interrogation signal being adapted to require the sending of data relating to an identifier stored in the ancillary device.

[0088] Advantageously, the electronic power supply and processing circuit 250 signal is configured to process an electrical identification signal, provided by the antenna 230. The electrical identification signal corresponds to the transduction, by the antenna 230, of a magnetic identification signal into an electrical identification signal. The electrical identification signal encodes information relating to an identifier stored in the ancillary device.

[0089] The electronic power supply and signal processing circuit 250 can be configured to extract, from the electrical identification signal, data relating to an identifier stored in the auxiliary device, and to transmit this data to a central controller which compares this data to a list of at least one authorized identifier, and generates an opening unlocking command when said data corresponds to at least one authorized identifier.

[0090] The invention is not limited to the examples illustrated by the figures. For example, in variants not shown, the printed circuit board comprises more than four functional layers, for example six. In this case, the near-field communication antenna remains distributed in only two functional layers of the printed circuit board, preferably two neighboring layers including an end layer of the printed circuit board.

[0091] In less preferred variants of the invention, the four turns are distributed with three turns in a first functional layer and a single turn in a second functional layer, the first functional layer and the second functional layer being separated two by two by a single insulating layer.

Claims

Claims

1. Near-field communication device (200), intended to be integrated into a motor vehicle, and comprising: - a printed circuit board, comprising superimposed at least four so-called functional layers (210i, 2102, 2103, 2104), made of electrically conductive material, separated two by two by respective so-called insulating layers (220i, 2202, 2203), made of dielectric material; - a near-field communication antenna (230), formed by four concentric turns (230i, 2302, 2303, 2304) integrated on the printed circuit board; and - at least one electronic power supply and signal processing circuit (250), connected to the antenna (230) and integrated on the printed circuit board;characterized in that the four turns (230i, 2302, 2303, 2304) are distributed over only two neighboring functional layers (210i, 2102), and in that the at least one electronic circuit (250) for power supply and signal processing is formed in at least one functional layer (2103; 2104) of the printed circuit board, distinct from the functional layers (210i, 2102) receiving the turns, the at least one electronic circuit (250) for power supply and signal processing being inscribed inside a surface (238) delimited by an internal contour of the turns.;

2. Device (200) according to claim 1, characterized in that the antenna (230) is formed by four turns, with two first turns (230i, 2302) located on a first functional layer (210i) and two second turns (2303, 2304) located on a second functional layer (2102), the first functional layer (210i) and the second functional layer (2102) being separated two by two by a single insulating layer (220i).

3. Device (200) according to claim 2, characterized in that the two first turns (230i, 2302) are superimposed two by two with the two second turns (2303, 2304).

4. Device (200) according to any one of claims 1 to 3, characterized in that said two neighboring functional layers (210i, 2102) include an end layer of the printed circuit board.

5. Device (200) according to any one of claims 1 to 4, characterized in that it further comprises a capacitive electrode, inscribed within a surface delimited by an internal contour of the turns, and connected to a detection circuit to form a capacitive presence sensor, with the detection circuit integrated on the printed circuit board.

6. Device (200) according to any one of claims 1 to 5, characterized in that each turn (230i, 2302, 2303, 2304) is square in shape.

7. Door handle for a motor vehicle, comprising a device (200) according to any one of claims 1 to 6.

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