EP0805507B1 - Receive and/or transmit device for radio messages with an inductive and capacitive antenna - Google Patents

Abstract

The receiver is contained in a package (11) which is worn on the body (14) and comprises a single antenna (12) and a microreceiver (13). The antenna consists of two conductive plates (15,16) which are aligned, preferably parallelly, to the skin and separated by air or another dielectric and loaded by circuits (Z1,Z2). The plates detect the radial electric component (Er) of the EM wave carrying broadcast messages and constitute parts of a single-turn coil (17) which detects the azimuthal magnetic component (H ) of the EM field surrounding the body. The loads may be short or open circuits, low-resistance conductors, resistors, capacitors and/or inductors.

Description

The present invention relates to a device for reception and / or transmission of radio broadcast messages portable which includes an antenna capable of picking up a field electromagnetic carrying radio messages.

We already know portable devices of this type, devices which sometimes come in the form of a timepiece such as a wristwatch. A realization of such an arrangement is described in the patent European No 0 312 792. This document describes a wristwatch comprising an antenna and a microreceptor arranged in a box. The antenna includes a first loop-shaped conductive element located in the upper case, a second conductive element connected to the ground of the microreceptor and arranged in the lower part of the case. An adaptation circuit and okay connects these two conductive elements to the inputs of the microreceptor.

The first element of the antenna forms, on the one hand, with the second conductive element a capacitive doublet sensitive to an electrical component of the field electromagnetic carrying broadcast radio messages. On the other hand, the first element makes it possible to form a loop sensitive to a magnetic component of the field electromagnetic. So we can say that the antenna has a mixed electrical and magnetic aspect because it is sensitive to both electrical components and magnetic field of the electromagnetic field.

The two conductive elements are arranged in planes parallel to the dial of the case. Therefore, the loop formed by the first element captures the component radial magnetic of the electromagnetic field with respect on the user's wrist and the capacitive doublet formed by the two conductive elements picks up the component electric radial of the electromagnetic field with respect on the user's wrist.

However, such an arrangement poses problems of reception sensitivity because the two components captured are not the ones that are optimal near the surface of a user's body. In addition, this portable reception has a significant variation depending the frequency of the electromagnetic field that is picked up.

The object of the present invention is a device for reception of portable radio messages which remedies at least in part to these disadvantages.

Another object of the invention is a device for reception of portable radio broadcast messages including antenna gain / bandwidth product is optimized.

Another object of the invention is a device for reception of portable radio messages which allows regular behavior as a function of the frequency of electromagnetic field received.

In addition, the object of the invention is a device for reception of portable radio messages which includes a single antenna and whose construction is simple and space-saving.

The subject of the invention is therefore a device for reception and / or transmission of radio broadcast messages portable intended to be worn on a part of the body having the shape of a cylinder such as the arm or the trunk of this body. The device comprises a housing, a antenna capable of picking up both a magnetic component and an electrical component of an electromagnetic field carrier of broadcast radio messages, and a micro-receiver receiving messages received by the antenna. The antenna has two conductive plates arranged so as to capture the radial electric component of the field electromagnetic with respect to the body. The antenna is formed by a coil comprising a coil arranged in the case to pick up the azimuthal magnetic component of the electromagnetic field around said part of the body. The plates are part of the coil.

Advantageously, the present invention makes it possible to make a device for receiving radio broadcast messages portable whose antenna picks up the components electric radial and azimuthal magnetic of a field electromagnetic, which, on the one hand, increases the antenna performance and, on the other hand, makes the antenna less sensitive to variations in field frequency electromagnetic sensed.

• la figure 1 est une vue schématique d'un poignet d'un utilisateur portant un mode de réalisation d'un dispositif de réception portatif selon la présente invention;
• la figure 2 montre une figure humaine portant un autre mode de réalisation d'un dispositif de réception portatif selon la présente invention;
• la figure 3 est une vue schématique du dispositif de réception portatif de la figure 1;
• la figure 4 est une vue en perspective d'un détail du dispositif de réception portatif de la figure 3;
• la figure 5 est une vue en coupe d'un mode de réalisation du dispositif de réception portatif selon l'invention qui se présente sous forme d'une montre-bracelet, et
• la figure 6 est une vue en coupe d'un autre mode de réalisation du dispositif de réception portatif selon l'invention qui se présente sous forme d'une montre-bracelet.

Other characteristics and advantages of the invention will become apparent during the description which follows, given solely by way of example and made with reference to the appended drawings in which:

• Figure 1 is a schematic view of a wrist of a user wearing an embodiment of a portable receiving device according to the present invention;
• FIG. 2 shows a human figure carrying another embodiment of a portable reception device according to the present invention;
• Figure 3 is a schematic view of the portable receiving device of Figure 1;
• Figure 4 is a perspective view of a detail of the portable receiving device of Figure 3;
• FIG. 5 is a sectional view of an embodiment of the portable reception device according to the invention which is in the form of a wristwatch, and
• Figure 6 is a sectional view of another embodiment of the portable receiving device according to the invention which is in the form of a wristwatch.

We know that the electrical components and magnetic fields of an electromagnetic field are orthogonal to each other. As a result, a component electric field can be picked up by an antenna capacitive while a magnetic component can be it by an inductive antenna. A capacitive antenna is in the form of two electrodes separated by a dielectric and an inductive antenna in the form of a coil. By dielectric, it should be understood here a insulating material separating the two electrodes, this matter can also be air. The polarization of the electrical component captured from the incident field is perpendicular to the electrodes of the capacitive antenna while the polarization of the magnetic component received from the incident field is parallel to the axis of the inductive antenna coil.

The present invention relates to a device of reception intended to be worn on a part of the body of a user, it is important to know the influence of this body on the configuration of the field electromagnetic. However, it was found that the amplitude and the direction of the electromagnetic field are strongly modified in the vicinity of the body, this being due mainly to the fact that the dielectric properties of human body are very different from air.

Various studies have established whether irradiates the human body with an electromagnetic field, on the one hand, that the electric component of the field is essentially perpendicular to the skin of the body at a distance less than 15 cm from the surface of the body or the part of the body in question and, on the other hand, that the magnetic component of the field essentially rotates around the body or part of the body in question (for example example. wrist) at a distance of less than 15 cm from the surface of the body. We will then use the word "radial" to qualify this electrical component of the field and the word "azimuth" to qualify this component magnetic field.

Figure 1 shows a forearm 1 of a user wearing a receiving device according to the invention which is in the form of a wristwatch 4 comprising a case 2 and a strap 3. On this case 2 act the two predominant components E _r (radial electrical components) and H _Φ (azimuthal magnetic component).

Figure 2 shows a human figure carrying a portable receiving device 5 comprising a housing 6 attached to a belt 7. On this portable receiving device 5 also act the radial electrical component E _r and the azimuthal magnetic component H _Φ of a field electromagnetic carrying radio broadcast messages.

Referring now to Figure 3, there is a schematic view of a portable receiving device 10 according to the invention which comprises a housing 11, a single antenna 12 adapted to receive both the azimuthal magnetic components H _Φ and electrical radial E _r of an electromagnetic field carrying broadcast radio messages and a microreceptor 13 receiving the messages picked up by the antenna to transform these messages into data perceptible by the user of the portable reception device. The latter is carried by the user so that the housing is close to its body 14.

The antenna 12 comprises two conductive plates 15 and 16 placed substantially parallel to one another and separated by air or any other dielectric. The plates 15 and 16 are arranged in the housing 11 to capture the radial electrical component E _r of the electromagnetic field with respect to the body 14. To maximize the efficiency of the antenna, the plates 15 and 16 are preferably mounted in the housing 11 so that they are substantially parallel to the surface of the user's skin in front of the portable receiving device when the latter is worn by the user.

We see in Figures 3 and 4 that the antenna 12 is constituted by a coil 17 comprising, in this example, a single turn disposed in the housing 11 for picking up the azimuthal magnetic component H _Φ of the electromagnetic field around the body 14. De preferably, the antenna is mounted in the housing 11 so that the longitudinal axis of the coil is substantially perpendicular to the surface of the user's skin in front of the portable receiving device, and arranged perpendicular to the longitudinal axis of the cylindrical part of the body in question, when this device is worn by the user.

According to the invention, the plates 15 and 16 form part of the coil 17. Thus, the portable reception device 10 comprises a single antenna 12 which takes advantage of two predominant components of the electromagnetic field carrying radio broadcast messages, namely the radial electrical component E _r and the azimuthal magnetic component H _Φ . By allowing the use of these two components at the same time, the efficiency of the antenna is increased.

Preferably, the plates 15 and 16 include connection zones 21 to 24 through which they are connected to the remaining part of the coil 17. The zones connection points 21 and 22 are arranged in places diametrically opposed on the plate 15. Similarly, the connection zones 23 and 24 are arranged at the locations diametrically opposed on the plate 16. In the example shown in Figures 3 and 4, the connection areas 21 to 24 are arranged in a periphery region of the plates 15 and 16. The resulting arrangement is simple, efficient and allows to form an antenna which has dimensions electromagnetic in relation to dimensions body 11.

To increase the efficiency of the antenna, the coil 17 is preferably arranged in the housing so that its longitudinal axis is substantially parallel to the azimuthal magnetic component H _Φ when said device is worn by a user. Likewise, it is preferable that the two conductive plates are arranged so that they are substantially perpendicular to the radial electrical component E _r when said device is worn by the user.

Advantageously, the portable reception device is well suited to various applications in all frequency bands because the antenna has very little practical limitation of minimum or maximum frequency. Indeed, even under the hypothesis of a reduction in the effect of the human body for the azimuthal magnetic component H _Φ at low frequency, there is no corresponding frequency limitation for the radial electrical component E _r , even at a frequency of 0 Hz.

The microreceptor 13 receives the messages picked up by the antenna to transform these messages into data noticeable by the user. To this end, the microreceptor 13 has an adaptation circuit and agree 18 which, in known manner, makes it possible to complete the tuning of the resonant circuit which constitutes the antenna 12 and adjust if necessary the resonant frequency of it.

Thanks to the high efficiency of the antenna 12 and to the fact that the radial electrical component E _r picked up by the antenna 12 is not very sensitive to changes in frequency of the electromagnetic field carrying radio-broadcast messages, the antenna 12 can easily be adapted so that it works as a broadband antenna in a desired frequency range. To do this, it suffices that the matching and tuning circuit 18 is set so that the narrow band around the resonant frequency of the antenna is set outside of this desired frequency range. Thus, the antenna may have regular behavior as a function of the frequency in this frequency range.

However, the antenna can also be used like a resonant antenna by adjusting the circuit adaptation and agree 18 so that the frequency of antenna resonance be brought in the range of desired frequency.

We can consider that the two plates 15 and 16 are connected to each other by load circuits Z1 and Z2. Each of the charging circuits Z1 and Z2 can be consisting simply of a conductive element to minimum resistance forming the remaining part of the coil 18, and / or by resistive, capacitive elements and / or inductive, such as, for example, the circuit adaptation and agreement 18 which constitutes the circuit of load Z1 in the antenna 12 shown in FIG. 3. Each load circuits Z1 and Z2 can even be constituted by a short circuit or an open circuit.

As seen in Figure 3, a current i is induced in the coil 17 by the azimuthal magnetic component H _Φ (leaving the page in Figure 3) of the electromagnetic field picked up by the coil 12. The current i rotates in the direction counterclockwise. This results in a positive induced voltage V _H1 through the charge circuit Z1 and a negative induced voltage V _H2 through the charge circuit Z2.

On the other hand, the voltages induced by the radial electrical component E _r are equal and positive across the two load circuits Z1 and Z2. It can therefore be seen that the voltages V _E1 and V _E2 induced by the two components add up through the load circuit Z1 and subtract through the load circuit Z2. Consequently, it will be a question of connecting the input of the microreceptor 13 through the load circuit Z1 to further increase the efficiency of the antenna 12.

Figure 4 shows an embodiment of the plates conductors 15 and 16 as well as the microreceptor 13 of the figure 3. Each of the two plates can have one or several openings, such as the central opening 20. The plate 15 is arranged in the upper part of the housing 11 of the portable receiving device 10 while that the plate 16, for its part, is arranged in the lower part of the housing 11.

Such an arrangement could be useful in the case where the antenna 12 is incorporated in a wristwatch. The Figure 5 shows a sectional view of a portable reception in the form of a wristwatch 30. The latter comprises a dial 40 and a movement 41 housed in a housing 42. The antenna arranged in this watch 30 has a first conductive plate 31 and a second conductive plate 32. In this example, the upper plate 31 has the same shape as that shown in Figure 4 so that it is hidden from view by a annular part 43 of the housing 42. The plate 31 shown at Figure 5 consists of a metallization ice peripheral 33.

The plate 32 can be a metallic bottom which is entirely metallic or, as shown in figure 5, a metal sheet affixed to a background 34 of material plastic.

However, plates 31 and 32 can be mounted in the receiving device 30 according to several variants. For example, at least one of the plates could also be deposited on the dial or any other element from the portable receiving device 30 or it could even constitute this element itself. At least one of plates could also be embedded in the bottom of the box 42 or in any other part of the device portable reception 30.

Likewise, plates 31 and 32 can be produced according to several variants. For example, at least one of plates could consist of a metallic deposit, by a conductive element produced separately or by a wire rack.

The plates 31 and 32 are supported on a middle part 44 made of insulating material. Plates 31 and 32 are connected to the input of the microreceptor 18 which is mounted in the housing 42 between the dial 33 and the bottom 34.

Figure 6 shows a sectional view of a second embodiment of a portable receiving device in the form of a wristwatch 50. The latter comprises the dial 40, the movement 41 and the microreceptor 13, shown in Figure 5, which are housed in a housing 51. In this embodiment, the antenna has two conductive plates which are not not necessarily planar, i.e. a first plate conductive 52 and a second conductive plate 53 which constitute respectively an upper part and a lower part of the housing 51. The plates 52 and 53 are separated by an annular disc 54 made of material insulating.

This arrangement makes it possible to increase the yield of the antenna because the plates 52 and 53 have a surface maximum in relation to the dimensions of the portable reception 50 itself.

In this example, the two plates 52 and 53 constitute parts of the housing 51. However, only one of the plates could be formed by a part of the housing in another embodiment.

Finally, it should be noted that several modifications and / or adaptations can be made to the system identification of objects according to the invention without departing from the part of it.

For this purpose, although the embodiments described above mainly concern a device portable reception in the form of a wristwatch, the principle of this antenna can also be used for other watchmaking applications or for devices conventional portable reception systems.

Claims (7)

1. Portable device for receiving and/or transmitting radio-transmitted messages intended to be worn on a part of the body having a cylindrical shape such as an arm or the trunk of the body, said device comprising:

   a case (11; 42; 51),

   an antenna (12; 31, 32; 52, 53) capable of picking up both a magnetic component and an electric component of an electromagnetic field carrying radio-transmitted messages, and

   a micro-receiver (13) receiving the messages picked up by the antenna,

   said antenna comprising two conductive plates (15, 16; 31, 32; 52, 53) disposed so that they pick up the radial electric component (E_r) of said electromagnetic field with respect to said body,
   characterized in that said antenna (12; 31, 32; 52, 53) is formed by a coil (17) comprising a turn arranged in said case (11; 42; 51) for picking up the azimuthal magnetic component (H_) of said electromagnetic field around said part of the body and in that said plates (15, 16; 31, 32; 52, 53) form part of said coil (17).
2. Device according to claim 1, characterized in that each of said plates (15, 16; 31, 32; 52, 53) comprises connecting zones (21 to 24) which are diametrically opposite and via which it is connected to the remaining part of said coil (17).
3. Device according to any one of claims 1 or 2, characterized in that said connecting zones (21 to 24) are disposed in a peripheral region of said plates (15, 16; 31, 32; 52, 53).
4. Device according to any one of the preceding claims, characterized in that said coil (17) is disposed in said case (11; 42; 51) in such a way that its longitudinal axis is substantially parallel to said azimuthal magnetic component (H_) when said device is worn.
5. Device according to any one of the preceding claims, characterized in that said antenna further comprises at least one load circuit (Z1, Z2) which connects said plates, and in that said micro-receiver (13) is connected to said coil (17) through said load circuit (Z1) through which voltages (V_H1, V_H2, V_E1, V_E2) induced by said azimuthal magnetic component (H) and said radial electric component (E_r) are added together.
6. Device according to any one of the preceding claims, said device being intended to pick up electromagnetic fields within a determined frequency range, characterized in that said micro-receiver comprises a matching and tuning circuit (18) adjusted so that a narrow band around the resonance frequency of the antenna (12) is placed outside said determined frequency range.
7. Device according to any one of the preceding claims, characterized in that it takes the form of a wristwatch.

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