EP1513220A1 - Patch antenna integrated in a wrist-watch - Google Patents

Abstract

The wristwatch has a radiofrequency module (27) arranged inside a metallic center (22) and connected to an earth plane and a radiating unit. The earth plane has a conductive surface portion (37) connected to metallic horn (35) and barrette (36) of the wristwatch. The radiating unit has a metallic back cover (25) arranged in a plane parallel to a median plane (Y) defined by the center.

Description

TECHNICAL AREA

The present invention relates, in general, to the integration of a antenna in a wristwatch, and more particularly, the arrangement in the wristwatch of the ground plane and the radiating element, these two elements forming an antenna.

The antenna can be used, in particular, to receive and / or transmit radio signals that are transmitted to a radiofrequency module integrated into the shows.

TECHNOLOGICAL BACKGROUND

It is known from the prior art, in particular from document EP 0 308 935, a Wristband antenna for radio receiver built into a watch. Like this is shown diagrammatically in FIGS. 1A and 1B, the watch 1 is formed of a housing 2 containing the radio receiver 3 and a bracelet 4. The bottom of the housing comprises a first metal part 5 which forms the mass of the receiver 3. The radiating element of the antenna is made by a first metallic conductor 6 disposed inside the bracelet 4 and connected to the input of the radio receiver 3. This first conductor 6 is in the form of a sinuous wire between the two side walls of the bracelet 4 whose unfolded length is close to λ / 4, λ being the wavelength corresponding to the center frequency of the signal to be received. The bracelet antenna can also comprise a second conductor 7 arranged in the bracelet and connected to the mass of the receiver. This conductor 7 may be in the form of a film. Each of them 6 and 7 are respectively disposed in one of the two strands 8 and 9 of the bracelet 4.

This bracelet antenna behaves like a dipole antenna of length electrical equal to λ / 2. When the watch 1 is attached to the wrist of the user, the bottom 5 of the housing, or the second strand 9 of the bracelet, ensures the grounding of the receiver 3. The other strand 8 of the bracelet makes a capacitor sensing the radial field around the arms. The dipole is made, at least in part, by the sinuous structure of the first conductor 6 allowing integration of the chord of the antenna in the strand himself. It is also possible to use a metallic bezel 10, shown only in Figure 1 B, isolated from the bottom 5 of the housing to increase the height effective average of the bracelet antenna.

The electrical connection between the conductive elements 6 and 7 arranged in the strands 8 and 9 of the bracelet and the receiver 3 disposed in the housing 2 can be realized by means of electrical contacts by means of bars, links flexible film or crimped, these elements are not shown in Figures 1A and 1 B. The insulation between the receiver mass and the radiating element forming the antenna dipole is ensured by the body of the housing 2 made necessarily necessarily with a insulating material.

In the context of the present invention, it has been demonstrated that such integrated dipole antenna in the wristband 4 of a watch presents some disadvantages. First, the electrical connections between the elements conductors 6 and 7 arranged in the strands 8 and 9 of the bracelet and the receiver 3 have complications if one wants to seal the inside of the housing 2. A solution that would consist in making these connections respectively via the bottom 5 the housing and via the bezel 10, both metal, nevertheless requires either through the housing 2 insulation, which makes the manufacturing much more complex and costly, ie to leave apparent electrical conductors, which is not desirable, especially at the aesthetic level. It will be noted that such integrated dipole antenna in the bracelet recommends the use at least for the element radiating a conductor 6 sinuous shape of unfolded length determined depending on the desired wavelength corresponding to the center frequency of the signal to receive, which can present, according to the desired reception frequency, problems of robustness of the antenna structure and therefore reliability of operation over time.

SUMMARY OF THE INVENTION

A general object of the present invention is therefore to propose a solution to provide a tight connection between the external antenna elements and the middle part of the watch in a simple, inexpensive and reliable way without the aesthetics of the whole, while ensuring that this set shows bracelet, as well as the antenna that is integrated, is robust.

The present invention thus relates to a wristwatch of the type mentioned above, the features of which are set forth in claim 1.

Advantageous embodiments of the present invention are the subject of the dependent claims.

Still in the context stated above, it is also advantageous to make sure that the radiating element is integrated in the watch itself. So, a patch antenna type antenna solution is particularly suitable for these constraints, such an antenna comprising a ground plane, a dielectric substrate and one or more radiating elements of reduced size compared to that of the plane of mass. Here we mean by plane of mass, one or more surface elements or voluminal conductors connected together and serving as a mass for the module radio frequency.

It is thus proposed to make the radiating element by means of a bottom metal isolated from the caseband via a dielectric element. This element dielectric which can be formed by a plastic gasket having a constant permittivity depending on the temperature.

Advantageously, the radiating element comprises two surface elements conductors each arranged in a plane substantially parallel to the mean plane defined by the middle and connected together in order to define a cylinder of radiation. The two conductive surface elements that can be realized at average respectively of the metal background of the watch and a metal layer applied to part of the non-visible face of the dial so as to be isolated from the middle, the uncoated portion of the dial being formed by a dielectric material.

Advantageously, the bracelet comprises first and second strands, in each of which a flexible conductive plate is overmolded and connected to the middle by means of conductive fasteners.

BRIEF DESCRIPTION OF THE DRAWINGS

• les figures 1A et 1 B, déjà décrites, montrent une vue de dessus et une vue en coupe d'une antenne bracelet pour récepteur radioélectrique intégré dans une montre selon l'art antérieur ;
• la figure 2 montre une vue schématique en coupe d'une montre bracelet selon un premier mode de réalisation de l'invention ;
• la figure 3 montre une vue schématique en coupe d'une montre bracelet selon un deuxième mode de réalisation de l'invention ;
• la figure 4 montre une vue agrandie des connexions entre le module radiofréquence et les éléments formant antenne, ainsi que l'isolation de ces éléments entre eux, selon les premier et deuxième modes de réalisations de l'invention ;
• la figure 5 montre une vue de dessous du cadran de la montre selon le deuxième mode de réalisation de l'invention.

Other characteristics and advantages of the present invention will appear more clearly on reading the following detailed description of embodiments of the invention given solely by way of non-limiting example and illustrated by the appended drawings in which:

• Figures 1A and 1B, already described, show a top view and a sectional view of a radio receiver antenna antenna integrated in a watch according to the prior art;
• Figure 2 shows a schematic sectional view of a wristwatch according to a first embodiment of the invention;
• Figure 3 shows a schematic sectional view of a wristwatch according to a second embodiment of the invention;
• FIG. 4 shows an enlarged view of the connections between the radiofrequency module and the antenna elements, as well as the insulation of these elements with each other, according to the first and second embodiments of the invention;
• FIG. 5 shows a view from below of the dial of the watch according to the second embodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

In the rest of this description, most of the elements that do not have directly related to the scope of the present invention, such as, for example, the watch movement, motors, power sources, display means time, etc. have not been shown in the various figures for the sake of simplification. The identical elements common to the different figures bear the same numerical references.

One of the aims of the invention is to integrate an antenna into a wristwatch comprising a radio frequency module for receiving and / or transmitting signals radio. In this context, it is preferably provided to use an antenna comprising the largest possible ground plane.

At first, by way of non-limiting example, we will focus on the figure 2 showing a schematic sectional view of a wristwatch according to a first embodiment of the invention.

The watch 21, as shown, notably comprises a middle part metal 22, which can be made in one piece or separately with a window 23, the middle part 22 defining a mean plane Y of the watch. The watch 21 is closed by the top by means of a window 24 supported by the middle part 22 and fixed so sealing, for example, by driving in a material, for example, in Hytrel, making seal. In the context of this first embodiment, the watch is closed from below by means of a metal base 25, isolated from the middle part 22 by means of a joint 43, preferably malleable plastic, for example, Hytrel. An enlarged view the dashed area is given in Figure 4.

Inside the watch, are represented, the printed circuit 26 supporting the radiofrequency module 27, the clock circuit 28 to which is fixed the movement watchmaker (not shown) and the dial 29 may have openings 31 to through which are visible display means 30 such as, for example, a LCD screen. Other display means, not shown here, may also be provided, in particular, needles driven by the movement watchmakers can be placed between the window 24 and the dial 29.

Receipt and / or emission of electrical signals by the module radio frequency 27 is effected by means of an antenna, advantageously of the type patch, comprising on the one hand a ground plane, the widest possible, and on the other one or more radiating elements, the ground plane and the element (s) radiators being insulated by means of a dielectric element having a permittivity substantially constant as a function of temperature.

For this purpose, the watch includes a bracelet 32 formed by first and second strands 33 and 34, represented here in a truncated manner, each of the strands being attached to the middle part 22 by means of conductive fasteners. The means of fasteners are constituted, for each strand of the bracelet, by two horns 35 metal integral with the middle part 22 between which is arranged a bar 36, also metallic. Inside, at least one strand of the bracelet 32, it is planned to arranging a flexible conductive plate 37, whose end, on the middle side, carries out a electrical contact with the fastening means, for example, by folding this end of the plate 37 around the metal bar 36.

Thus, the ground plane of the antenna comprises the conductive plate 37, the means of conductive fasteners 35 and 36 and the metal middle part 22. Advantageously, it will be noted that the two strands 33 and 34 of the bracelet are provided each of a conductive plate 37 for the purpose of maximizing the area of the ground plane of the antenna. The electrical contact between the ground plane and the radiofrequency module 27 is produced via an annular conductive track printed on the periphery of the printed circuit board 26 making contact with a shoulder ring of the middle provided for this purpose and whose detail is given in Figure 4.

The radiating element of the antenna comprises at least one surface element conductor arranged in a plane substantially parallel to the mean plane (Y) defined by the middle part 22 and, according to this first embodiment of the invention, this element surface consists of the metal bottom 25, the latter being connected electrically to the radiofrequency module 27 by any suitable means, for example, by means of a screw or any other electrical contact element 42.

In a second step, also as an example, we will focus on FIG. 3 showing a schematic sectional view of a wristwatch according to a second embodiment of the invention.

This second embodiment differs from the first mode presented above, basically at the level of the structure used to achieve the radiating element of the antenna. Indeed, it has been demonstrated in the context of the present invention that the radiating element has better characteristics, in particular reception, with a cylindrical radiating structure. So, in order to get this radiating cylinder, the radiating element comprises two conductive surface elements, each being arranged in a plane substantially parallel to the mean plane defined by the middle part 22.

According to this second embodiment, the two surface elements are constituted, on the one hand, by the metal base 25 and, on the other hand, by a layer metal 38 applied to a portion of the non-visible face of the dial 29, so not to contact the middle part 22, the uncovered portion of the dial being formed by a dielectric material insulating the middle part of this metal layer 38. An example of depositing this metal layer 38 on the dial 29 is given in FIG.

The electrical contact between the two surface elements forming the cylinder radiating element can be achieved by any suitable electrical contact element 45, such as for example a screw, isolated from the ground plane.

FIG. 4 shows, by way of example, an enlarged view of the zones in dotted lines of Figures 2 and 3, showing the connections between the radio frequency module 27 and the antenna elements, as well as the insulation of these elements with each other, according to the first and second embodiments of the invention described above.

As already mentioned, the middle metal 22 is an element of the plane of mass and the metal bottom 25 corresponds to the radiating element or only to a part of it. The electrical connections of these antenna elements with the radiofrequency module 27 are as follows. The middle part 22 presents a shoulder 40 against which rests the printed circuit board 26 supporting the radio frequency module 27. To provide the electrical connection, a conductive track 41 is deposited at the level of the support zone, that is to say, on the periphery of the circuit printed 26. With regard to the bottom 25, it will be possible to make the electrical contact, by means of a suitable contact element 42.

Insulation between the middle and the bottom is achieved by means of an element dielectric 43 waterproof deformable. So, this element 43 not only allows to isolate the ground plane of the radiating element, but also to ensure the tightness of the inside of the watch. Preferably, this dielectric element 43 is a malleable plastic seal having a substantially constant permittivity in temperature function.

FIG. 5 shows a bottom view of the dial 29 of the watch 21 according to the second embodiment of the invention. We find the openings 31 allowing to see through the dial 29 display elements (not shown here), as well as an opening 48 for passing a shaft supporting means analog display arranged between the dial and the ice. In order to maintain the dial in the watch, it is conventionally provided fixing means 46, by example screws, which advantageously adds the contact element 45. This element 45 is arranged on the metal layer 38 in order to realize the electrical contact between this layer and the radiofrequency module. Layer metal 38 can have any shape, but preferably it covers the most large area available. Finally, the insulation between the middle and the metal layer is made by a peripheral zone 47 not covered by the metal layer 38, this zone 47 being preferably made of a dielectric material with a substantially constant permittivity as a function of temperature.

It will be understood that various modifications and / or improvements evident for those skilled in the art can be made to the various embodiments of the invention described in the present description without departing from the scope of the invention defined by the appended claims.

In particular, concerning the means of conductive fasteners used for electrically contact the conductive parts of the bracelet with the metal case, according to an alternative embodiment, it is intended to use in each of the strands, a flexible conductive plate 37 whose end, middle side, forms the bar 36, the two elements 36 and 37 being one piece.

Note that it is also possible to provide only one strand of bracelet with a conductive plate.

Claims (9)

Wristwatch (21) comprising a middle part (22, 44) defining a middle plane (Y), fastening means (35, 36) conducting the wristband (32) to the middle part, a radiofrequency module (27) arranged in the middle interior of the caseband and connected, on the one hand, to a ground plane and, on the other hand, to a radiating element isolated from one another and forming an antenna, the ground plane comprising at least a portion conductive surface (37) of the bracelet connected to the fastening means of the bracelet, characterized in that the ground plane further comprises the middle which is conductive, the latter being connected from the inside to the radiofrequency module and in that the radiating element comprises a first conductive surface element (25, 38) arranged in a plane substantially parallel to the mean plane defined by the middle part. Wristwatch according to claim 1, characterized in that the first conductive surface element is formed by means of a metal base (25) isolated from the middle part by means of a dielectric element (43). Wristwatch according to claim 2, characterized in that the dielectric element is formed by a malleable plastic seal having a substantially constant permittivity as a function of temperature. Wristwatch according to claim 2 or 3, characterized in that the radiating element comprises a second conductive surface element (38) also arranged in a plane substantially parallel to the mean plane defined by the middle part and connected to the first surface element so as to define a radiation cylinder. Wristwatch according to claim 4, comprising a dial (29) having a first face visible through an ice (24) and a second face, not visible, opposite to the first face, characterized in that the second conductive surface element is made by means of a metal layer (38) applied to a part of the non-visible face of the dial so as not to contact the middle part, and in that the uncoated part (47) of the dial is formed by a material dielectric isolating the middle of the second surface element. Wristwatch according to one of claims 1 to 5, the bracelet (32) comprising first (33) and second (34) strands, characterized in that the conductive surface portion is formed by a flexible conductive plate (37) overmolded in one of the two strands of the bracelet and connected to the middle part by means of fasteners. Wristwatch according to claim 6, characterized in that the ground plane further comprises a second conductive plate (37) flexible overmolded in the other strand of the bracelet and also connected to the middle through the fastening means. Wristwatch according to claim 6 or 7, characterized in that the fastening means comprise, for each strand of the bracelet, two metal horns (35) integral with the middle part between which is arranged a metal bar (36) and in that the conductive plate or plates are folded around the corresponding strip or bars. Wristwatch according to claim 6 or 7, characterized in that the fastening means comprise, for each strand of the bracelet, two metal horns (35) integral with the middle part and in that the conductive plate or plates (37) have a rigid bar-shaped end (36) cooperating with the horns.

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