HK1010293B - Portable radio device for receiving and/or transmitting comprising an inductive capacitive antenna - Google Patents

Description

Portable radio receiving and/or transmitting device comprising an inductive-capacitive antenna

The invention relates to a portable device for receiving and/or transmitting radio transmission information comprising an antenna capable of picking up an electromagnetic field carrying the radio transmission information.

Portable devices of this type, sometimes in the form of a timepiece such as a wristwatch, are known. One embodiment of such a device is disclosed in european patent No.0,312,792. This document discloses a watch comprising an antenna and a miniature receiver arranged in a housing. The antenna includes a first conductive element in an upper portion of the housing and a second conductive element in a lower portion of the housing connected to a ground voltage of the micro receiver. A matching and tuning circuit connects the two conductive elements to the input of the miniature receiver.

The first and second conductive elements of the antenna together form a capacitive dipole sensitive to an electrical component of an electromagnetic field carrying radio transmission information. The first element can constitute a loop that is sensitive to a magnetic component of the electromagnetic field. Thus, it can be said that the antenna has mixed electrical and magnetic properties, since it is sensitive to both the electrical and magnetic components of the electromagnetic field.

The two conductive elements are arranged in a plane parallel to the dial of the watch case. Thus, the loop formed by the first element picks up a magnetic component of the electromagnetic field that is radial to the user's wrist, while the capacitive dipole formed by the two conductive elements picks up an electrical component of the electromagnetic field that is radial to the user's wrist.

This type of device reception sensitivity is problematic because the two components that are picked up are not optimal values near the user's body surface. In addition, such portable receivers vary significantly with the frequency of the electromagnetic field picked up.

It is an object of the present invention to provide a portable device for receiving radio transmission information which at least partly overcomes the above-mentioned disadvantages.

It is another object of the invention to provide a portable device for receiving radio transmission information, the antenna gain bandwidth product of which is optimized.

It is another object of the present invention to provide a portable device for receiving radio transmission information that operates properly regardless of the frequency of the electromagnetic field being picked up.

Further, it is an object of the present invention to provide a portable device for receiving radio transmission information including a single antenna having a simple structure requiring a small space.

The present invention therefore relates to a portable device intended to be carried on a cylindrical part of the human body, such as the arm or torso, for receiving and/or transmitting radio-transmitted information. The device comprises: a housing; an antenna capable of picking up both a magnetic component and an electric component of an electromagnetic field carrying radio transmission information; and a micro receiver for receiving the information picked up by the antenna. The antenna comprises two conductive plates arranged so as to be able to pick up the electric components of the electromagnetic field radial to the body. The antenna is formed by a coil comprising a loop of coil arranged within a housing for picking up the angular magnetic component of the electromagnetic field around said part of the human body. The plate forms part of a coil.

The invention allows a portable device to receive radio transmission information in an advantageous manner, in which an antenna picks up radial and azimuthal magnetic components of an electromagnetic field, on the one hand increasing the output of the antenna, and on the other hand making the antenna less sensitive to frequency variations of the picked up electromagnetic field.

Other features and advantages of the present invention will become apparent from the following description, given by way of example only, which refers to the accompanying drawings. In the drawings:

FIG. 1 is a schematic illustration of a user's wrist carrying an embodied sample of a portable receiving device according to the present invention;

FIG. 2 shows a body diagram with another embodiment of a portable receiving device according to the invention;

FIG. 3 is a schematic view of the portable receiving device of FIG. 1;

FIG. 4 is a perspective view of a detail of the portable receiving device of FIG. 3;

FIG. 5 is a cross-sectional view of one embodiment of a portable receiving device according to the present invention in the form of a wristwatch; and

fig. 6 is a cross-sectional view of another embodiment of a portable receiving device according to the present invention in the shape of a wristwatch.

It is well known that the electrical and magnetic components of an electromagnetic field are perpendicular to each other. Thus, the electrical component of the electromagnetic field may be picked up with a capacitive antenna, while the magnetic component may be picked up with an inductive antenna. A capacitive antenna takes the form of two electrodes separated by a dielectric, while an inductive antenna takes the form of a coil. A dielectric is here understood to be an insulating material separating the two electrodes, such a material also being air. The polarity of the electrical component picked up from the incident field is perpendicular to the electrodes of the capacitive antenna, while the polarity of the magnetic component picked up from the incident field is parallel to the coil axis of the inductive antenna.

Since the invention relates to the preparation of a receiving device to be worn on a part of the body of a user, it is important to know the influence of such a body on the structure of the electromagnetic field. It has been determined that the amplitude and direction of the electromagnetic field vary greatly near the body, primarily due to the large difference in the dielectric constant of the human body and that of air.

Various studies have shown that if the human body is irradiated by an electromagnetic field, on the one hand, at a distance of less than 15cm from the surface of the human body or from the part of the human body under consideration, the electrical component of the field is substantially perpendicular to the skin of the human body; on the other hand, at less than 15cm from the surface of the body, the magnetic component of the field rotates substantially around the body part (e.g., wrist) or body under consideration. In the following, the term "radial" is used to describe the electrical component of the field, while the term "angular" is used to describe the magnetic component of the field.

Fig. 1 shows a forearm 1 carrying a receiving device according to the invention in the shape of a wristwatch 4, said receiving device comprising a case 2 and a wristband 1. Two main components Er (radial electrical component) and H phi (azimuthal magnetic component) act on the housing 2.

Fig. 2 shows a body diagram with a portable receiving device 5, the receiving device 5 comprising a housing 6 attached to a belt 7. The radial electric component Er and the azimuthal magnetic component H phi of the electromagnetic field carrying the radio transmission information also act on this portable receiving device 5.

Referring now to fig. 3, there is seen a schematic diagram of a portable receiving device 10 according to the present invention, said receiving device 10 comprising: a housing 11; the single antenna 12 can pick up the radial electric component Er of the electromagnetic field carrying the radio transmission information and the angular magnetic component H phi of the electromagnetic field; and a miniature receiver for receiving information picked up by the antenna to convert such information into data that can be understood by a user of the portable receiving device. The user thus carries the device with the housing close to his body 14.

The antenna 12 comprises two conductive plates 15 and 16 configured such that: substantially parallel to each other and separated by air or other dielectric. The plates 15 and 16 are arranged inside the housing 11 for picking up the electrical component Er of the electromagnetic field radial to the human body 14. In order to maximise the output of the antenna, the plates 15 and 16 are preferably mounted within the housing 11 such that they are substantially parallel to the surface of the user's skin towards which the portable receiving device is facing when the user is wearing the receiving device.

Fig. 3 and 4 show a coil 17 forming an antenna 12, for example, single-turn, placed inside the housing 11 for picking up the angular magnetic component H phi of the electromagnetic field surrounding the human body 14. The antenna is preferably mounted in the housing 11 such that the longitudinal axis of the coil is substantially perpendicular to the surface facing the skin of the user of the portable receiving device and is arranged such that it is perpendicular to the longitudinal axis of the cylindrical part of the body in question when the device is worn by the user.

The plates 15 and 16 form part of a coil 17 according to the invention. Thus, the portable receiving device 10 comprises a single antenna 12 which benefits from the two main components of the electromagnetic field carrying the radio transmitted information, namely the radial electric component Er and the azimuthal magnetic component H. Since these two components can be used simultaneously, the output of the antenna can be increased.

The plates 15 and 16 preferably include connection areas 21 to 24 that connect the remainder of the coil 17. Connection regions 21 and 22 are provided at diametrically opposite ends of plate 15, and similarly connection regions 23 and 24 are provided at diametrically opposite ends of plate 16. In the example shown in fig. 3 and 4, the connection regions 21 to 24 are provided at peripheral positions of the plates 15 and 16. The resulting arrangement is relatively simple and efficient and allows the formation of an antenna having optimal electromagnetic dimensions with respect to the physical dimensions of the housing 11.

To improve the efficiency of the antenna, the coil 17 is preferably placed in the housing so that its longitudinal axis is substantially parallel to the azimuthal magnetic component H phi when the user is wearing the device, and similarly the two conductive plates are preferably substantially perpendicular to the radial electrical component Er when the user is wearing the device.

Advantageously, the portable receiving device is well suited for various purposes over all frequency bands, since the antenna has very little practical minimum or maximum frequency limit. Even under the assumption that the influence of the human body on the angular magnetic component H phi is reduced at a low frequency, even if the frequency is 0Hz, the radial electric component Er is not correspondingly limited in frequency.

The micro receiver 13 receives information picked up by the antenna and converts such information into data that can be understood by the user. For this purpose, the miniature receiver 13 comprises a matching and tuning circuit 18 which allows tuning to be accomplished in a known manner to the resonant circuit formed by the antenna 12, adjusting the resonant frequency of the antenna if necessary.

Since the output of the antenna 12 is high and the radial electrical component Er picked up by the antenna 12 is not very sensitive to frequency variations of the electromagnetic field carrying the radio transmission information, it is easy to adapt the antenna 12 to function as a broadband antenna in the required frequency range. For this purpose, the matching and tuning circuit 18 must be adjusted such that a narrow frequency band around the resonance frequency of the antenna lies outside this desired frequency range. Thus, the antenna operates normally regardless of whether the frequency is within this frequency range.

However, the antenna may also be used as a resonant antenna by adjusting the matching and tuning circuit 18 so that the resonant frequency of the antenna is within a desired frequency range.

It can be considered that the two boards 15 and 16 are connected to each other with load circuits Z1 and Z2. Each load circuit Z1 and Z2 may be simply formed by a conductive element having the least resistance that forms the remainder of the coil 17 and/or by resistive, capacitive and/or inductive elements, such as the matching and tuning circuit 18 that forms the load circuit Z1 in the antenna 12 shown in fig. 3. Each of the load circuits Z1 and Z2 may also be formed with a short circuit or an open circuit.

As shown in fig. 3, the azimuthal magnetic component H phi of the electromagnetic field picked up by the coil 17 (out of the paper in fig. 3) induces a current i in the coil 17. The current i rotates counterclockwise. As a result, a positive voltage V is induced across the load circuit Z1_H1And a negative voltage V is induced across the load circuit Z2_H2。

In contrast, the voltage induced by the electrical component Er across the two load circuits Z1 and Z2 is an equal positive voltage. It can then be noted that the voltage V induced by the two components on the load circuit Z1_E1And V_E2Are added to each other and subtracted from each other at the load circuit Z2. Therefore, the input terminal of the micro receiver 13 can be connected via the load circuit Z1 to further increase the output of the antenna 12.

Fig. 4 shows an embodiment of the conductive plates 15 and 16 and the micro receiver 13 of fig. 3. Each of the two plates may have one or more openings, such as a central opening 20. The plate 15 is disposed in an upper portion of the housing 11 of the portable receiving device 10, and the plate 16 is disposed in a lower portion of the housing 11.

This configuration is useful in the case where the antenna 12 is incorporated into a watch. Fig. 5 is a cross-sectional view of the wristwatch-shaped portable receiving device 30 of fig. 4. This watch comprises a dial 40 and a movement 41 housed in a case 42. The antenna provided in the watch 30 includes a first conductive plate 31 and a second conductive plate 32. In this example, the upper plate 31 has the same profile as that shown in fig. 4, so that it is blocked from view by the annular portion 43 of the housing 42. The plate 31 shown in fig. 5 is formed by a circumferential metallization of crystals 33.

The plate 32 may be a metal back cover, which may be entirely metal, or, as shown in FIG. 5, a metal sheet secured to a plastic back cover 34.

However, the plates 31 and 32 may be mounted in the receiving means 30 in several ways. For example, at least one of the two plates may be provided on a scale or on any other element of the portable receiving device 30, or it may constitute such an element itself. At least one of the two plates may be embedded in the back cover of the housing 42 or any other portion of the portable receiving device 30.

The plates 31 and 32 can be similarly constructed in several ways, for example, at least one of which can be constructed by metal deposition, by separately made conductive elements or grids.

The plates 31 and 32 are contiguous with an intermediate portion 44 made of insulating material. The plates 31 and 32 are connected to the input of a miniature receiver 18 which is mounted within the housing 42 between the dial 33 and the back cover 34.

Fig. 6 shows a cross-sectional view of a second embodiment of a watch-shaped portable receiving device 50. The watch comprises a dial 40, a movement 41 and a miniature receiver 13, shown in figure 5, housed in a case 51. In this embodiment, the antenna includes two conductive plates, which are not necessarily flat, that is, a first conductive plate 52 and a second conductive plate 53, which form the upper and lower portions of the housing 51, respectively. The plates 52 and 53 are separated by an annular disc 54 of insulating material.

This structure allows the output of the antenna to be improved because the plates 52 and 53 have the largest area for the portable receiving device 50 itself.

In this example, both plates 52 and 53 form part of the housing 51. However, in an alternative embodiment, only one of the two plates can be formed by a portion of the housing.

Finally, it should be pointed out that several variations and/or adaptations can be made to the device according to the invention without departing from the framework of the invention.

Indeed, although several of the embodiments described above relate primarily to a watch-shaped portable receiving device, the principles of such an antenna may be equally applicable to other timepiece applications or to conventional portable receiving devices.

Claims (7)

1. A portable device intended to be worn on a cylindrical part of a human body, such as an arm or a human torso, for receiving and/or transmitting radio transmitted information, said device comprising:

-a housing (11; 42; 51);

-an antenna (12; 31, 32; 52, 53) capable of picking up both the magnetic and the electrical components of the electromagnetic field carrying the radio transmission information; and

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

said antenna comprising two conductive plates (15, 16; 31, 32; 52, 53) arranged substantially parallel to each other inside a housing and separated by air or any other dielectric material and positioned perpendicular to a radial direction with respect to said human body when said device is worn, so that they are able to pick up an electrical component (Er) of said electromagnetic field that is radial to said human body,

characterized in that said antenna (12; 31, 32; 52, 53) is constituted by a coil (17) comprising at least one turn formed by said two conductive plates and two connection zones (21, 22) placed at diametrically opposite positions of said two conductive plates, so that said antenna picks up the azimuthal magnetic component (Hphi) of the electromagnetic field that surrounds said part of the human body when said device is worn.

2. Device according to claim 1, characterized in that each of said conductive plates (15, 16; 31, 32; 52, 53) comprises connection areas (21 to 24) which are located at both ends of the diameter and by which each of said conductive plates is connected to the other part of said coil (17).

3. Device according to claim 1 or 2, characterized in that said connection areas (21 to 24) are arranged in the circumferential area of said conductive plates (15, 16; 31, 32; 52, 53).

4. A device according to claim 1 or 2, characterized in that said coil (17) is arranged in said housing (11; 42; 51) in such a way that the longitudinal axis of the coil is substantially parallel to said azimuthal magnetic component (Hφ) when the device is worn.

5. An arrangement according to claim 1 or 2, characterized in that said antenna further comprises at least one load circuit (Z1, Z2) connected to said conductive plate, and said miniature receiver (13) is connected to said coil (17) via said load circuit (Z1), said angular magnetic component (H Φ) and said magnetic component (H Φ) being connected across the load circuit (Z1)Voltage (V) induced by radial electric component (Er)_H1，V_H2，V_E1，V_E2) Are added to each other.

6. A device according to claim 1 or 2, said device being intended to pick up an electromagnetic field in a predetermined frequency range, characterized in that said micro receiver comprises a matching and tuning circuit (18) which is adapted such that a narrow band around the resonance frequency of the antenna (12) falls outside said predetermined frequency range.

7. A device according to claim 1 or 2, characterized in that it takes the form of a watch.