Antenna device integrable in a casing of an electronic instrument

Abstract

One aspect of the invention relates to an antenna device intended to be integrated into a housing (2) at least part of which is electrically conductive, in particular into a housing (2) of an electronic instrument (1) capable of being worn by a wearer, the device (3) comprising: - a first antenna part (4A) intended to be connected in a first connector (8A) to a functional module (7) positioned on a printed circuit board (10) located inside said housing (2), and - a second antenna part (4B) consisting of a ground plane comprising said at least electrically conductive part of the housing (2) to which is connected a second connector (8B) of the first antenna part (4A) by means of an electronic module (4C) for adjusting a resonant frequency and increasing the efficiency of the antenna device (3) as a function of an angular position of this device (3).

Description

Technical field of the invention

[0001] The invention relates to the field of antennas embedded in electronic instruments such as watches, whose cases are small in size or include enclosures with small volumes for the arrangement of an antenna device. Technological background

[0002] In the prior art, it is known to integrate an antenna device into a metal casing of an electronic instrument for the reception of GNSS signals as part of the implementation of a navigation or guidance system implemented within that instrument.

[0003] However, one of the major problems encountered in this configuration lies in the fact that mechanical characteristics, such as the shape and arrangement of the metal casing, or the presence of other metal components or parts within it, have a significant impact on the performance of this antenna device. Indeed, its performance is seriously degraded compared to what it would be in a context where the antenna device was not integrated into such a metal casing and thus confined. In effect, the mechanical environment of such an antenna device has a strong impact on its performance, notably reducing its performance in terms of matching, gain, radiation pattern, etc.

[0004] In general, the state of the art discloses different methodologies for designing antenna devices, including miniature ones, and in particular those exhibiting transmission / reception characteristics in the frequency bands relevant to GNSS signals.

[0005] However, no satisfactory solution is known for optimizing the performance of such antenna devices intended to be enclosed in metal casings.

[0006] Under these conditions, it is understandable that there is a need to find alternative solutions to those of the state of the art. Summary of the invention

[0007] One of the aims of the invention is to improve the performance of an antenna device arranged in a small housing comprising at least one metallic part and / or incorporating at least one metallic element within its enclosure.

[0008] Another objective of the invention is to ensure or even guarantee optimal reception of electromagnetic signals by this antenna device regardless of the orientation or position of this device relative to the source emitting these electromagnetic signals.

[0009] The invention relates to an antenna device intended to be integrated into a housing, at least part of which is electrically conductive, in particular into the housing of an electronic instrument capable of being worn by a wearer, the device comprising: a first antenna part intended to be connected in a first connector to a functional module positioned on a printed circuit board located inside said housing, and a second antenna part consisting of a ground plane including said part at least electrically conductive of the housing to which is connected a second connector of the first antenna part by means of an electronic module for adjusting a resonant frequency and increasing the efficiency of the antenna device as a function of an angular position of this device.

[0010] Another aspect of the invention concerns: The electronic module comprises an electrical circuit that can be dynamically configured according to the angular position of the antenna device and a module for detecting a change in the angular position of this antenna device; the electrical circuit comprises two components: a coil and a capacitor; the electrical circuit comprises three switches which are provided to configure this electrical circuit in first and second configuration modes in which a coil and a capacitor are arranged respectively in series and in parallel; the inductance values ​​of the coil and the capacitance of the capacitor in the first and second configuration modes are chosen so as to satisfy the following equation: L série × C série = L parallèle × C parallèle . The detection module includes at least one angular position sensor and a processing unit; the antenna device is configured to receive one or more GNSS signals transmitted by GNSS sources in a given frequency band; the antenna device is configured to radiate in a frequency band corresponding to a wavelength λ, the shape of the first antenna part and its length being configured such that this first antenna part has an electrical measurement length λ / 4; the frequency band is between 1559 MHz and 1610 MHz.

[0011] In another aspect, the invention relates to an electronic instrument worn by a wearer comprising a housing having at least one electrically conductive part configured to come into contact with a part of the wearer's body and in which housing are located an antenna device according to any one of the preceding claims and a printed circuit board comprising: the functional module which is electrically connected to the first connector of the first part of the antenna, and the electronic module for adjusting a resonant frequency and increasing the efficiency of the antenna device as a function of an angular position of this device, this electronic module being electrically connected to the second connector and to the ground plane of the antenna device.

[0012] Advantageously, the ground plane includes a first part included on the printed circuit board and a second part including the least electrically conductive part of the housing.

[0013] In particular, the functional module is a GNSS signal receiver module comprising a radio frequency circuit.

[0014] Advantageously, the electronic instrument is a watch, specifically a wristwatch. Brief description of the figures

[0015] Other features and advantages of the invention will become more apparent upon reading the following description of a particular embodiment of the invention, given by way of simple illustrative and non-limiting example, and the accompanying figures, among which: there figure 1 is a schematic representation of the casing of the electronic instrument, here a watch including the antenna device, according to embodiments of the invention; the figure 2A is a schematic diagram of an electrical circuit whose components, such as a coil and a capacitor, can be configured in this circuit to be arranged in series or in parallel, according to embodiments of the invention; the figure 2B is a schematic diagram of the electrical circuit in which the coil and capacitor are configured in series in this circuit, according to embodiments of the invention; the figure 2C is a schematic diagram of the electrical circuit in which the coil and capacitor are configured in parallel in this circuit, according to embodiments of the invention; the figure 3 is a radiation pattern of the antenna device integrated into the housing of the electronic instrument, here a watch case, when this housing is arranged in a horizontal position, according to embodiments of the invention, and the figure 4is a radiation pattern of the antenna device integrated into the housing of the electronic instrument, here a watch case, when this housing is arranged in a vertical position, according to embodiments of the invention. Detailed description of the invention

[0016] THE figures 1 to 4 relate to an antenna device 3, in particular a beam or directional antenna device capable of radiating or receiving greater power in specific directions. This antenna device 3 is intended to be integrated into a housing 2 of an electronic instrument 1.

[0017] Such an electronic instrument 1 is a communicating object whose casing 2 is small compared to the wavelengths used for communication. Typically, the casing 2 of this object covered by the invention has dimensions on the order of a few centimeters.

[0018] In a envisaged application, this antenna device 3 is integrated into a navigation or guidance system implemented in this electronic instrument 1, and is enclosed in a housing 2, at least part of which is electrically conductive. Such an electronic instrument 1 is preferably a watch, but alternatively, this instrument 1 may be, without limitation, a portable object such as a smartphone, a ring, a smartwatch, etc. However, it is understood that other applications can be envisaged for such an invention, provided that a small antenna device 3 is enclosed in a similarly small housing.

[0019] This watch 1, for example, is a classic wristwatch comprising, in addition to the antenna device 3, the case 2, a strap attached to said case 2, a crystal beneath which is located a display device enclosed within the case 2, and control components. The display device, in this particular case, comprises an analog display with two or three hands moving relative to a dial, notably to allow for a conventional indication of the time, and may be supplemented by a digital display using LCD or OLED display technologies.

[0020] In this watch 1, the case 2 includes a printed circuit board 10 including numerous locations intended to receive a plurality of electronic and electrical components of the watch 1 including elements of the antenna device 3. These electronic and electrical components include in particular a motor with its shafts for driving the hands, a first electrically conductive part 9A of a ground plane of the antenna device 3 as well as a source of electrical power supplying in particular the display device, a functional module 7 and an electronic module 4C included in this antenna device 3. This source of electrical power supply may consist of a conventional battery, a rechargeable battery or any other suitable source of electrical power.

[0021] In the context of a watch 1 implementing a navigation or guidance system, this antenna device 3 is configured to receive one or more GNSS signals transmitted by GNSS sources, in a frequency band used by a constellation of global positioning satellites. In other words, it is configured to receive satellite positioning and navigation signals, such as GPS signals from the American NAVSTAR satellite positioning system or other positioning signals from similar systems such as the Chinese BEIDOU system, the Russian GLONASS system, or the European GALILEO satellite positioning and navigation system.

[0022] Under these conditions, this antenna device 3 is then configured to receive signals belonging to at least one frequency band between 1559 MHz and 1610 MHz. More precisely, it is configured to receive signals within at least one of the following frequency bands: 1559 to 1610 MHz which includes the frequencies L1, E1, B1; 1215 to 1300 MHz which includes the frequencies L2, E6, B3, L6; 1164 to 1215 MHz which includes the frequencies L5, E5, B2, L3.

[0023] In the context of the embodiment described, the antenna device 3 will be considered to be configured to receive a signal of frequency L1 of approximately 1575.42 MHz.

[0024] As is known in the prior art, metallic components included in the housing 2, or even metallic parts of this housing 2 conventionally enclosing an antenna device, are likely to form masks that attenuate the performance of such a device. In this context, the invention proposes to form an antenna device 3 comprising two parts 4A, 4B, namely a first part 4A having an IFA antenna structure (“ inverted F antenna " Or " inverted F antenna » (in English) suitable for connection to a functional module 7 included on the printed circuit board 10 and a second part 4B consisting of the ground plane 9A, 9B including at least an electrically conductive part of the housing 2.

[0025] Thus, with reference to the figure 1The first part of the antenna 4A consists of a segment, or strand, having a curved shape. This segment is an electrically conductive element which serves as a radiating element of the antenna device 3 and which is oriented parallel to a plane comprising an opening 13 made in the face of the case 2, this opening 13 being intended to be closed by the crystal of this watch 1.

[0026] This segment has a length equal to a fraction of the incident electromagnetic wavelength to be received, which is converted into an electrical signal received by the functional module 7. More specifically, this segment is configured to radiate in a frequency band corresponding to wavelength λ, its shape and length being configured such that it has an electrical length of λ / 4. In this embodiment, the antenna device 3 radiates in response to a received electromagnetic wave having a frequency L1 of 1575.42 MHz. In this configuration, the length of the segment is then between 44 and 46 mm, and preferably 45.7 mm.

[0027] It should be noted that in this case 2 of the watch 1, the first part of the antenna 4A, and in particular the segment, is arranged above the dial, for example in the bezel or in the rehaut of this watch 1, being oriented parallel to the plane including the opening referenced 13 of the case 2. In this context, this bezel and this rehaut are made of a non-conductive (dielectric) material such as a plastic material, allowing the antenna device 3 to be electrically isolated from the case 2.

[0028] This first antenna section 4A includes a first connector 8A located approximately in the middle of the segment, that is, in a portion 11C situated between the two ends 11A and 11B of this segment. This first connector 8A, which is also called "Antenna device base", "antenna device power supply point" or in English " antenna feed " is configured to be connected to the functional module 7 intended to be positioned on the printed circuit board 10 arranged in the housing 2.

[0029] This functional module 7 is a GNSS signal receiver module comprising a radio frequency circuit. In this embodiment, it is configured to receive a specific L1 type satellite radio signal associated with a carrier frequency and bandwidth. This functional module 7 is electrically powered by the power supply.

[0030] This first antenna section 4A also includes a second connector 8B located at one of the two ends 11A, 11B of the segment. This second connector 8B is also called " antenna device charging point "or in English" antenna load " is configured to be connected to the ground plane 9A, 9B via the electronic module 4C for adjusting a resonant frequency and increasing the efficiency of the antenna device 3.

[0031] As we have already mentioned, this electronic module 4C of the antenna device 3 is arranged on the printed circuit board 10. Such a module 4C consists of an electrical circuit 5A which is dynamically configurable according to the angular position of the antenna device 3, and a detection module 5B for changing the angular position of this device 3.

[0032] In this module 4C, the detection module 5B includes at least one angular position sensor 6A comprising, but not limited to, an inertial measurement unit and / or a gyroscope. This detection module 5B also includes a processing unit 6B, such as a microcontroller. This processing unit 6B is capable of controlling / driving the configuration of the electrical circuit 5A based on angular position measurements of the housing 2, and therefore of the antenna device 3, which it receives from said sensor 6A.

[0033] With reference to Figures 1 and 2A, this electrical circuit 5A includes a first connection point P electrically connected to the second connector 8B and a second connection point M connected to the first part of the ground plane 9A of the antenna device 3, defined on the printed circuit board 10.

[0034] In this configuration, such an electrical circuit 5A is configured to act on the load of the first antenna segment 4A and not on its power supply. Under these conditions, this electrical circuit 5A comprises two components: a coil L and a capacitor C. It also includes three switches S1, S2, S3, whose opening and closing are controlled by the processing unit 6B in order to parameterize / configure the electrical circuit 5A in: a first configuration mode visible on the figure 2B, in which the coil L and the capacitor C are arranged in series, by closing switch S2 and opening switches S1 and S3, and a second configuration mode visible on the figure 2C in which the coil L and the capacitor C are arranged in parallel, by closing switches S1 and S3 and opening switch S2.

[0035] These two modes of configuration of the electrical circuit 5A act differently on the load of the first part of the antenna 4A, by generating a displacement of the minima and maxima of the radiation of this first part of the antenna 4A, that is to say by varying the gain of the antenna device 3 in a direction of space according to different angular positions of the housing 2 and therefore of the antenna device 3.

[0036] For example, when the housing 2 is in a so-called "horizontal" position, the upper face of the first antenna section 4A is positioned facing, or nearly facing, the GNSS source. Under these conditions, the electrical circuit 5A is then configured by the processing unit 6B in the first configuration mode. In this first mode, the radiation pattern of the antenna device 3 is visible on the figure 3 This classically defines the power distribution of this antenna device 3 in space. This radiation pattern describes the direction in which this antenna device 3 radiates with the most power, here the direction of the Oz axis.

[0037] In this radiation diagram of the figure 3 We observe that: The maximum gain is -10.77 dBi - the 3 dB cutoff is 157.6 degrees

[0038] In another example, when housing 2 moves from a horizontal position to a new position, in this case a vertical position, electronic module 4C detects this change in the angular position of housing 2. Under these conditions, electronic module 4C then configures electrical circuit 5A in the second configuration mode. In this context, the radiation pattern of the antenna device 3 visible on the figure 4 , describes a direction in which this antenna device 3 radiates with the most power, here a direction included between the directions of the Oy and Oz axes.

[0039] In this radiation diagram of the figure 4 We observe that: The maximum gain is -10.65 dBi - the 3 dB cutoff is 147.2 degrees

[0040] Note that in these radiation diagrams, the case 2 of the watch 1 is positioned on the wearer's wrist 12. Furthermore, note that spherical coordinate angles (θ, φ) are used, as shown in the diagrams. figures 3 and 4 . The angle “θ” is located with respect to the Oz axis and the angle “φ” is located in the xOy plane and is located with respect to the Ox axis.

[0041] In this 5A electrical circuit, when capacitor C and coil L are used in the first and second configuration modes of the 5A circuit, the values ​​of series capacitance C, parallel capacitance C of capacitor C and series capacitance L, parallel capacitance L of coil L are chosen so that the following equation is verified: L série × C série = L parallèle × C parallèle with : L series and C series are the inductance and capacitance values ​​of coil L and capacitor C in the first configuration of the 5A circuit; L parallel and C parallel are the inductance and capacitance values ​​of coil L and capacitor C in the second configuration of the 5A circuit.

[0042] Selecting or choosing these inductance and capacitance values ​​from this equation helps ensure that the load resonates at the correct frequency. Furthermore, it contributes to increasing the efficiency of the antenna device, as illustrated by the radiation patterns visible on the... figures 3 and 4 .

[0043] As we have mentioned, the antenna assembly 3 also includes the second antenna part 4B, consisting of the ground plane 9A, 9B. This ground plane 9A, 9B is an extended ground plane because it consists of the first and second parts 9A, 9B of this plane, the second part 9B including the said electrically conductive part of the housing 2. This ground plane is connected to the second connector 8B of the first antenna part 4A via the electronic module 4C.

[0044] In this ground plane, the first part 9A is connected to the second part 9B via a conductive trace. Indeed, the printed circuit board 10 may include such a conductive trace on its underside. This trace is then electrically connected to the first part 9A of the ground plane. This conductive trace may be located on the periphery of the printed circuit board 10 and is specifically situated in a mechanical contact area between the printed circuit board 10 and the least electrically conductive part of the housing 2, for example, via a shoulder formed on the body of this least electrically conductive part. This conductive trace may preferably extend around essentially the entire periphery of the printed circuit board 10, although it is possible to interrupt this conductive trace at one or more points on the periphery.Providing the trace around virtually the entire periphery of the printed circuit board 10 has the advantage of improving the quality of the electrical contact with the electrically conductive part of the housing 2. With this configuration, it is understood that the surface area of ​​the ground plane is maximized by extending it to the electrically conductive part of the housing 2. In addition, this widening of the ground plane of the antenna device improves the detection sensitivity of this antenna device.

[0045] It should be noted that the electrically conductive part is made of an electrically conductive material, advantageously a metal (for example, steel, titanium, or aluminum), or a base material covered with an external electrically conductive layer. This electrically conductive part preferably includes an area or portion of this casing 2 intended to be in contact with a part 12 of the wearer's / user's body, such as their wrist, as may be the case, for example, with the bottom of this casing 2.

[0046] Thanks to the device according to the invention, it is possible to integrate this antenna device 3 into this case 2 of the watch 1, while exploiting a part of said metallic case 2 to optimize the performance of this antenna device 3. Moreover, as we have seen, the electronic module 4C included in this antenna device 3 makes it possible to integrate "beamforming" and "beamsteering" techniques into the operation of this device 3 and also to improve the performance of this antenna device 3, particularly in terms of gain, matching, efficiency and radiation.

[0047] Thus a watch 1 equipped with this antenna device 3 and which is worn on the wrist 12 of the wearer is able to optimally receive GNSS signals regardless of its position / orientation with respect to the reception area of ​​these GNSS signals induced by the movement of the wearer's wrist when he performs a physical or sporting activity (hiking, cycling, etc.).

[0048] The present invention is particularly intended for implementation in the watchmaking field, but can also be implemented in other fields.

[0049] It is further specified that the present invention is not limited to the examples described above and is susceptible to numerous variants accessible to those skilled in the art. Nomenclature

[0050] 1. Electronic instrument 2. Housing 3. Antenna device 4A. First antenna section 4B. Second antenna section 4C. Electronic module 5A. Dynamically configurable electrical circuit 5B. Angular position change detection module 6A. Angular position sensor 6B. Processing unit 7. Functional module 8A. First connector of the first antenna section 8B. Second connector of the first antenna section 9A. First part of the antenna device ground plane 9B. Second part of the ground plane including the electrically conductive part of the housing 10. Printed circuit board 11A. First end of the first antenna section 11B. Second end of the first antenna section 11C. Portion located approximately equidistant from the ends of the segment 12. Part of the wearer's body such as their wrist 13. Opening in the front of the housing

Claims

1. Antenna device (3) intended to be integrated into a housing (2) at least part of which is electrically conductive, in particular into a housing (2) of an electronic instrument (1) capable of being worn by a wearer, the device (3) comprising: - a first antenna part (4A) intended to be connected in a first connector (8A) to a functional module (7) positioned on a printed circuit board (10) located inside said housing (2), and - a second antenna part (4B) consisting of a ground plane comprising said at least electrically conductive part of the housing (2) to which is connected a second connector (8B) of the first antenna part (4A) by means of an electronic module (4C) for adjusting a resonant frequency and increasing the efficiency of the antenna device (3) as a function of an angular position of this device (3).

2. Antenna device (3) according to the preceding claim in which said electronic module (4C) comprises an electrical circuit (5A) that is dynamically configurable according to the angular position of the antenna device (3) and a detection module (5B) for a change in the angular position of this antenna device (3).

3. Antenna device (3) according to the preceding claim, in which the electrical circuit (5A) comprises two components: a coil (L) and a capacitor (C).

4. Antenna device (3) according to any one of claims 2 and 3, wherein the electrical circuit (5A) comprises three switches (S1, S2, S3) which are provided to parameterize this electrical circuit (5A) in first and second configuration modes in which a coil (L) and a capacitor (C) are arranged respectively in series and in parallel.

5. Antenna device (3) according to the preceding claim, wherein inductance values ​​(L série , L parallèle ) of the coil (L) and capacitance (C série , C parallèle ) of the capacitor (C) in the first and second configuration modes, are chosen so as to verify the following equation: L série × C série = L parallèle × C parallèle .

6. Antenna device (3) according to any one of the preceding claims, wherein the detection module (5B) comprises at least one angular position sensor (6A) and a processing unit (6B).

7. Antenna device (3) according to any one of the preceding claims wherein it is configured to receive one or more GNSS signals transmitted by GNSS sources in a given frequency band.

8. Antenna device (3) according to any one of the preceding claims wherein it is configured to radiate in a frequency band corresponding to a wavelength λ, the shape of the first antenna part (4A) and its length being configured such that this first antenna part (4A) has an electrical length of measure λ / 4.

9. Antenna device (3) according to the preceding claim in which the frequency band is between 1559 MHz and 1610 MHz.

10. Electronic instrument (1) worn by a wearer comprising a housing (2) having at least one electrically conductive part configured to make contact with a part (12) of the wearer's body and in which housing (2) are housed an antenna device (3) according to any one of the preceding claims and a printed circuit board (10) comprising: - the functional module (7) which is electrically connected to the first connector (8A) of the first antenna part (4A), and - the electronic module (4C) for adjusting a resonant frequency and increasing the efficiency of the antenna device (3) as a function of an angular position of this device (3), this electronic module (4C) being electrically connected to the second connector (8B) and to the ground plane of the antenna device (3).

11. Electronic instrument (1) according to the preceding claim, in which the ground plane comprises a first part (9A) included on the printed circuit board (10) and a second part (9B) comprising the at least electrically conductive part of the housing (2).

12. Electronic instrument (1) according to the preceding claim, wherein the functional module (7) is a GNSS signal receiver module comprising a radio frequency circuit.

13. Electronic instrument (1) according to any one of claims 10 to 12 wherein it is a watch in particular a wristwatch.

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