Near field communication device intended to be integrated in motor vehicle

Abstract

A near field communication device (200) intended to be integrated in a motor vehicle and comprising:-a printed circuit board comprising at least four functional layers (2101, 2102, 2103, 2104) made of an electrically conductive material, said at least four functional layers (2101, 2102, 2103, 2104) being separated pairwise by insulating layers (2201, 2202, 2203) made of a dielectric material; -a near field communication antenna (230) formed by four concentric turns integrated on a printed circuit board; and-at least one power supply and signal processing electronic circuit (250) connected to the antenna (230) and integrated on a printed circuit board. The four turns are distributed only over two adjacent functional layers (2101, 2102), which reduces the drift of the inductance of the antenna between respective devices.

Description

Technical Field

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

[0002] In fact, such a device belongs to a vehicle access system having the function of authenticating and locating a user, in particular by means of communication between the vehicle and a badge carried by the user. The badge can be a dedicated device. As a variant, it can relate to a smart phone (or smartphone) integrating dedicated functionality. Background Art

[0003] Near-field communication devices are known in the prior art that are intended to be integrated into a motor vehicle and include the following:

[0004] - A printed circuit board;

[0005] - A near-field communication antenna integrated on the printed circuit board; and

[0006] - At least one power supply and signal processing electronic circuit connected to the antenna and integrated on the printed circuit board.

[0007] The near-field communication antenna is formed by a plurality of concentric turns that together form a coil.

[0008] In use, the coil is traversed by an electric current that generates an electromagnetic field oriented in a direction orthogonal to the plane of the turns. The electromagnetic coupling between two adjacent near-field communication antennas allows for data exchange or communication between the two antennas. In particular, the electric current flowing in one coil or antenna will generate a magnetic field that will pass through the other coil or antenna and generate an electric current therein.

[0009] The generated electromagnetic field decreases very rapidly as the distance from the antenna increases, hence the concept of near field. The maximum communication distance between two near-field communication antennas is preferably less than 10 cm, even less than 5 cm.

[0010] The near-field communication antenna thus denotes an antenna configured to transmit and receive electromagnetic signals by electromagnetic coupling with another near-field communication antenna. Without quibbling about terminology, the near-field communication antenna can be referred to as an NFC (for "Near Field Communication" in English) antenna, and the term "NFC" can also denote a specific communication protocol implemented in the near-field communication antenna.

[0011] Optimization studies have shown that, in the case of a near-field communication device intended to be integrated into a motor vehicle to form part of a vehicle access system, a near-field communication antenna consisting of exactly four turns offers optimized performance. By way of example, an antenna with only two turns does not allow a sufficient inductance value to be achieved to operate the near-field communication device within the framework of a vehicle access system.

[0012] Advantageously, the near-field communication antenna is integrated on a multilayer printed circuit board. The multilayer printed circuit board is formed by an alternation of so-called functional layers made of an electrically conductive material and so-called insulating layers made of a dielectric material.

[0013] In a manner known per se, the efficiency of the near-field communication antenna is proportional to the square of the surface it encloses. A person skilled in the art thus seeks to dimension and arrange the four turns so as to maximize the surface defined by the internal contour of the antenna.

[0014] In order to reconcile this objective with the quest for great compactness, the four turns are formed in a printed circuit board comprising four or more functional layers and are all stacked one on top of the other in the respective functional layers.

[0015] The object of the present 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. Summary of the Invention

[0016] This object is achieved by means of a near-field communication device intended to be integrated into a motor vehicle and comprising:

[0017] - a printed circuit board comprising at least four so-called functional layers that are stacked, said at least four so-called functional layers being made of an electrically conductive material and being separated pairwise by respective so-called insulating layers made of a dielectric material;

[0018] - a near-field communication antenna formed by four concentric turns integrated on the printed circuit board; and

[0019] - at least one power supply and signal processing electronic circuit connected to the antenna and integrated on the printed circuit board.

[0020] The power supply and signal processing electronic circuit denotes an electronic circuit configured as follows:

[0021] - to generate an electrical transmission signal intended to be converted by the antenna into a magnetic transmission signal (antenna power supply function); and

[0022] - to perform signal (pre)-processing on the received electrical signal, the received electrical signal being provided by the antenna and corresponding to the magnetic signal received by the antenna and converted by the antenna into an electrical signal (signal processing function, at least including demodulation and amplification).

[0023] According to the present invention, the four turns are only distributed on two adjacent functional layers of the printed circuit board.

[0024] This arrangement is thus completely contrary to the expectations of those skilled in the art, who have so far considered the optimized arrangement to be: stacking the four turns one on top of the other to combine great compactness and a large surface area inscribed within the antenna.

[0025] The inventors have noticed that in devices with four stacked turns, the inductance of the near - field communication antenna varies in a non - negligible way from one device to another.

[0026] These variations in inductance cause significant variations in the impedance seen by the power - supply and signal - processing electronic circuits from one device to another. This results in variations in the impedance matching between the antenna and said circuits from one device to another. Ultimately, this thus leads to variations in the performance of the near - field communication devices from one device to another.

[0027] The inventors then realized that these variations in inductance are related to variations in the thickness of the respective layers of the printed circuit board from one device to another. In particular, there are specific manufacturing tolerances in the thickness of each layer of the printed circuit board. This results in slight variations in the distance between two adjacent turns from one device to another, and thus in variations in the inductance of the near - field communication antenna from one device to another.

[0028] The inventors then had the idea of proposing a device in which the four turns are no longer distributed on four stacked layers of the printed circuit board, but only on two adjacent functional layers of the printed circuit board, where the printed circuit board still includes four or more functional layers.

[0029] Thus, by the construction, the accumulation of variations in the distance between two adjacent turns is reduced, which also limits the variations in inductance from one device to another. In particular, the variations in the inductance of the antenna from one device to another depend on the variations in the thickness of a single layer of the printed circuit (the insulating layer between the two adjacent functional layers that receive the turns), rather than on the sum of the variations in the thicknesses of the three insulating layers inserted between and stacked among the four functional layers that receive the turns.

[0030] The present invention thus proposes an arrangement of turns that is completely counter - intuitive and contrary to the expectations of those skilled in the art. Surprisingly, this arrangement allows limiting the variations in the inductance of the near - field communication antenna from one device to another. Thus, it limits the variations in the impedance matching with the power - supply and signal - processing electronic circuits from one device to another. Ultimately, it thus limits the variations in the performance of the near - field communication devices from one device to another. This thus ensures that, for example, all devices on the same production line have the same performance, particularly with respect to the communication distance.

[0031] The present invention thus proposes a robust design with a very low drift of the antenna parameters between the various devices.

[0032] For the same efficiency of the near - field communication antenna, the volume is maintained to be almost the same because the turns remain distributed in two layers and are not completely coplanar.

[0033] Preferably, the antenna is formed by four turns, where two first turns are located on a first functional layer and two second turns are located on a second functional layer, and the first functional layer and the second functional layer are separated pairwise by a single insulating layer.

[0034] Advantageously, the two first turns are pairwise superposed with the two second turns.

[0035] The two adjacent functional layers preferably include the end layers of the printed circuit board.

[0036] The at least one power - supply and signal - processing electronic circuit is advantageously formed in at least one functional layer of the printed circuit board different from the functional layer receiving the turns.

[0037] The at least one power - supply and signal - processing electronic circuit can be incorporated inside the surface defined by the inner contour of the turns.

[0038] The device according to the invention may further include capacitive electrodes incorporated inside the surface defined by the inner contour of the turns and connected to a detection circuit to form a capacitive presence sensor, where the detection circuit is integrated on the printed circuit board.

[0039] Each turn is advantageously square - shaped.

[0040] The invention also covers a door handle for a motor vehicle, which includes the device according to the invention. Description of the Drawings

[0041] Other features and advantages of the present invention will become more apparent upon reading the following description. The description is purely illustrative and should be read in conjunction with the accompanying drawings, in which:

[0042] Figure 1A Figure 1A Is schematically illustrated in cross - section a near - field communication device intended to be integrated in a motor vehicle according to the prior art;

[0043] Figure 1B Figure 1B Is schematically illustrated in top view Figure 1A One of the functional layers of the device;

[0044] Figure 2A ​​​​​​Figure 2A The near - field communication device according to the invention is schematically illustrated in a sectional view;

[0045] Figure 2B Figure 2B The first functional layer in the functional layer accommodating the near - field communication antenna in the device of Figure 2A is schematically illustrated in a top view;

[0046] Figure 2C Figure 2C The second functional layer in the functional layer accommodating the near - field communication antenna in the device of Figure 2A is schematically illustrated in a top view;

[0047] Figure 2D Figure 2D The device of Figure 2A is schematically illustrated in a perspective top view; and

[0048] Figure 3 Figure 3 The comparison of the change in mutual inductance between devices in a device similar to the devices of Figure 1A and Figure 1B and in a device similar to the device of Figures 2A to 2D is schematically illustrated. DETAILED DESCRIPTION

[0049] In Figures 1A to 2D the axes of the normalized orthogonal reference system (0xyz) are shown to facilitate understanding.

[0050] First, a near - field communication device 100 according to the prior art is described quickly and with reference to Figure 1A and Figure 1B which is intended to be integrated into a motor vehicle and form part of a vehicle access system.

[0051] In Figure 1A the near - field communication device 100 is schematically represented in a sectional view in a plane parallel to the plane (x0z).

[0052] The device 100 includes a printed circuit board, which is here composed of four so - called functional layers 1101, 1102, 1103, 1104, and insulating layers 1201, 1202, 1203 are inserted between the four so - called functional layers 1101, 1102, 1103, 1104.

[0053] The functional layers 1101, 1102, 1103, 1104 are formed of conductive metal wiring. They all extend parallel to the plane (0xy) and are stacked one above the other along the axis (0z). ​​​​​​​​

[0054] The functional layers 1101, 1102, 1103, 1104 are separated pairwise by insulating layers 1201, 1202, 1203 made of a dielectric material. The insulating layers 1201, 1202, 1203 all extend parallel to the plane (0xy) and are stacked one above the other along the axis (0z). The respective insulating layers are inserted between two adjacent functional layers and are in direct physical contact with each of the functional layers.

[0055] The device 100 includes a near - field communication antenna 130. The near - field communication antenna 130 includes four stacked turns 1301, 1302, 1303, 1304. The four stacked turns 1301, 1302, 1303, 1304 are all located in a respective one of the functional layers 1101, 1102, 1103, 1104. The turns are connected to each other by vertical vias 131. The vertical vias 131 are oriented along the axis (0z) and all pass through at least one of the insulating layers 1201, 1202, 1203.

[0056] Each turn is formed by a respective metal wiring in the corresponding functional layer. Figure 1B One of the functional layers of the device 100 is schematically illustrated, here the functional layer 1102 that receives the turn 1302.

[0057] Each of the turns 1301, 1302, 1303, 1304 has a substantially rectangular or square shape.

[0058] Next, with reference to Figures 2A to 2D The near - field communication device 200 according to the present invention will be described. The near - field communication device 200 according to the present invention is intended to be integrated in a motor vehicle and form part of a vehicle access system.

[0059] Device 200 will only be described with respect to the differences of device 200 relative to Figure 1A and Figure 1B device.

[0060] As in the prior art, the device includes a printed circuit board that includes an alternation of functional layers 2101, 2102, 2103, 2104 and insulating layers 2201, 2202, 2203 as described above, having at least four functional layers.

[0061] The device 200 includes a near - field communication antenna 230. The near - field communication antenna 230 includes four turns that are only distributed in two of the functional layers.

[0062] In particular, the four turns are distributed in two adjacent functional layers separated by a single insulating layer.

[0063] In an advantageous manner, and as inFigure 2A As shown in the figure, four turns are distributed in two functional layers including the end functional layer of the printed circuit board. The end functional layer of the printed circuit board refers to the functional layer located at one end of the stack of the functional layer and the insulating layer that together form the printed circuit board. The end functional layer contacts the insulating layer only at a single one of its two major surfaces.

[0064] Here, four turns are distributed in functional layers 2101 and 2102.

[0065] Four turns are distributed as two pairs of turns 2321, 2322 respectively located in layers 2101 and 2102, and are arranged to be stacked. The pairs of turns are connected together by vertical vias 231, and the vertical vias 231 are oriented along the axis (0z) and pass through at least the insulating layer 2201 (in the thickness direction).

[0066] Each pair of turns 2321 (correspondingly pair of turns 2322) is formed by two concentric and coplanar turns.

[0067] Figure 2B The functional layer 2101 that receives the pair of turns 2321 is schematically illustrated.

[0068] As shown by Figure 2B the figure, the pair of turns 2321 is composed of two turns 2301 and 2302 wound around each other. In other words, the two turns 2301 and 2302 are formed by a single linear metal strip formed in the functional layer 2101.

[0069] Each of the turns 2301 and 2302 is substantially square or rectangular in shape. In particular, each of the turns 2301 and 2302 is in the shape of a rectangle or a square, which is open due to the arrangement of the turns wound around each other.

[0070] In Figure 2B it, one terminal of the near - field communication antenna 230 is also represented by a black circle 2331.

[0071] Figure 2C The functional layer 2102 that receives the pair of turns 2322 is schematically illustrated.

[0072] As shown by Figure 2C the figure, 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 strip formed in the functional layer 2102.

[0073] Each turn 2303 and 2304 is substantially square or rectangular in shape. In particular, each turn 2303 and 2304 has a rectangular or square shape that is open due to the arrangement of turns wound one around the other.

[0074] In Figure 2C the other terminal of the near - field communication antenna 230 is also represented by the black circle 2332.

[0075] Figure 2D The device 200 is illustrated schematically and in a perspective top view.

[0076] In Figure 2D the insulating layer is represented perspectively so as to observe the superposition of two pairs of turns 2321 and 2322. As illustrated by Figure 2D each turn in the first pair of turns 2321 is superposed with a corresponding one of the turns in the second pair of turns 2322.

[0077] In Figure 3 the variation in the inductance of the near - field communication antenna between the respective devices is represented. The values of the variation in inductance were obtained by simulation.

[0078] The bar on the left represents the variation in inductance in a prior - art device formed on a printed circuit board with a thickness of 0.8 mm as described in the introduction section. The variation in inductance is on the order of 2.5%.

[0079] The bar on the right represents the variation in inductance in a device according to the invention formed on a printed circuit board with the same thickness of 0.8 mm. The variation in inductance is on the order of 0.25%.

[0080] Here it is seen that the variation in the inductance of the near - field communication antenna between the respective devices is reduced to one - tenth. This indeed confirms the inventor's insight that the variation in inductance can be reduced by limiting the number of layers of turns on which the antenna extends. Various simulations have been carried out. In all cases, the variation in inductance has been reduced to between one - tenth and one - third.

[0081] According to the invention, the device 200 further comprises at least one power - supply and signal - processing electronic circuit 250.

[0082] As detailed in the introduction section, the power supply and signal processing electronic circuit 250 is configured to: generate an electrical transmission signal, which is intended to be transformed by the antenna 230 into a magnetic transmission signal; and perform signal preprocessing on the electrical signal, which is provided by the antenna 230 and corresponds to the magnetic signal received by the antenna 230 and transformed by the antenna 230 into an electrical signal. The signal preprocessing particularly includes demodulating and amplifying the electrical signal provided by the antenna 230 so as to be able to extract useful information therefrom. The electronic circuit 230 may be referred to as a "transmitting and receiving circuit", or simply as a "transceiver". The power supply and signal processing electronic circuit includes a transmitting stage, a receiving stage (demodulation, amplification) and possibly a signal processing stage (for extracting useful information).

[0083] The circuit 250 is connected to the antenna 230 by at least one vertical through-hole 251 oriented along the axis (0z). It has at least the following functions: powering the antenna 230 and receiving and processing the electrical signal provided by the antenna 230.

[0084] The circuit 250 extends in at least one functional layer of the printed circuit board different from the layer accommodating one or more turns of the antenna. Here, the circuit 250 extends in the functional layer 2104 furthest from the antenna 230. In an unrepresented variant, the circuit 250 extends in a plurality of stacked functional layers all different from the layer accommodating one or more turns of the antenna. Advantageously, the circuit 250 extends at least in the functional layer furthest from the antenna 230.

[0085] In Figures 2B to 2D the outline 255 of the circuit 250 is schematically represented in a perspective view.

[0086] Advantageously, and as represented in Figures 2B to 2D the circuit 250 is placed inside the turns. In other words, the circuit 250 is inscribed inside the surface 238 delimited by the inner contour of the turns. Or rather, according to the representation presented in a top view, the circuit 250 is inscribed inside the surface 238 delimited by the inner contour of the turns. Or rather, in the orthogonal projection of the turns and the circuit 250 in the same plane parallel to the plane (0xy), the projection of the circuit 250 is located inside the surface delimited by the inner contour of the projection of the turns. In Figure 2D the surface 238 is represented in shaded form.

[0087] This arrangement provides optimized compactness.

[0088] In an unrepresented variant, the device according to the invention further includes capacitive electrodes, which are also inscribed inside the surface delimited by the inner contour of the turns.

[0089] If required, the capacitive electrode and the power supply electronic circuit are both arranged in at least one different layer of the printed circuit board in a stacked manner.

[0090] Such a capacitive electrode is used in a manner known per se to form a measuring capacitor with the ground so as to enable presence detection.

[0091] The capacitive electrode is advantageously connected to a detection circuit (not shown), which includes a microcontroller, a switch and a discharge capacitor. The measuring capacitor defined between the capacitive electrode and the ground and the discharge capacitor are installed together in an arrangement of the capacitive voltage divider bridge type. The switch is driven 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 charge is balanced between the two capacitors, and the presence of the target can be detected based on the voltage representation signal of the discharge of the measuring capacitor.

[0092] The invention also covers a door handle (not shown) for a motor vehicle, the door handle incorporating a device according to the invention as described with reference to Figures 2A to 2D the device described.

[0093] The device according to the invention is configured to communicate with an accessory device carried by the user, which accessory device is itself also equipped with a near-field communication antenna and includes a memory storing the identifier of the user. The accessory device can be a smart phone integrating specific functions or a dedicated device such as a vehicle entry badge.

[0094] Advantageously, the power supply and signal processing electronic circuit 250 is configured to generate the transmission of an interrogation signal from the device according to the invention to the accessory device, the interrogation signal being adapted to request the transmission of data related to the identifier stored in the accessory device.

[0095] Advantageously, the power supply and signal processing electronic circuit 250 is configured to process the electrical identification signal provided by the antenna 230. The electrical identification signal corresponds to the conversion of a magnetic identification signal into an electrical identification signal by the antenna 230. The electrical identification signal encodes information related to the identifier stored in the accessory device.

[0096] The power supply and signal processing electronic circuit 250 can be configured to extract data related to the identifier stored in the accessory device from the electrical identification signal and transmit the data to a central controller, which compares the data with a list of at least one authorized identifier and generates an unlocking command for opening when the data corresponds to at least one authorized identifier.

[0097] The present invention is not limited to the examples illustrated in the figures. For example, in a variant not shown, the printed circuit board includes more than four functional layers, for example six functional layers. In this case, the near field communication antenna remains distributed in only two functional layers of the printed circuit board, preferably in two adjacent layers including the end layers of the printed circuit board.

[0098] In a less preferred variant of the present invention, four turns are distributed, with three turns in the first functional layer and a single turn in the second functional layer, the first functional layer and the second functional layer being separated from each other by a single insulating layer.

Claims

1. A near-field communication device (200) intended to be integrated in a motor vehicle and comprising: - A printed circuit board including at least four so-called functional layers (2101, 2102, 2103, 2104) superposed on one another, said at least four so-called functional layers (2101, 2102, 2103, 2104) superposed on one another being made of an electrically conductive material and separated two by two by so-called insulating layers (2201, 2202, 2203) each made of a dielectric material; - A near-field communication antenna (230) formed by four concentric turns (2301, 2302, 2303, 2304) integrated in the printed circuit board; and - At least one power supply and signal processing electronic circuit (250) connected to the antenna (230) and integrated in the printed circuit board; Characterized in that said four turns (2301, 2302, 2303, 2304) are distributed only on two adjacent functional layers (2101, 2102), and said at least one power supply and signal processing electronic circuit (250) is formed in at least one functional layer (2103; 2104) of the printed circuit board different from the functional layers (2101, 2102) receiving the turns, said at least one power supply and signal processing electronic circuit (250) being inscribed inside the surface (238) delimited by the internal contour of the turns.

2. The device (200) according to claim 1, characterized in that, The antenna (230) is formed by four turns, two first turns (2301, 2302) being located on a first functional layer (2101) and two second turns (2303, 2304) being located on a second functional layer (2102), the first functional layer (2101) and the second functional layer (2102) being separated two by two by a single insulating layer (2201).

3. The device (200) according to claim 2, characterized in that, Said two first turns (2301, 2302) are superposed two by two with said two second turns (2303, 2304).

4. The device (200) according to any one of claims 1 to 3, characterized in that, Said two adjacent functional layers (2101, 2102) include end layers of the printed circuit board.

5. The device (200) according to any one of claims 1 to 4, characterized in that, It further includes capacitive electrodes inscribed inside the surface delimited by the internal contour of the turns and connected to a detection circuit to form a capacitive presence sensor, the detection circuit being integrated in the printed circuit board.

6. The device (200) according to any one of claims 1 to 5, characterized in that, Each turn (2301, 2302, 2303, 2304) is of square shape.

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

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