FR2763186A1 - PORTABLE SIGNAL RECEIVER - Google Patents

Abstract

This receiver comprises a receiver unit 3 which receives by means of an antenna a signal transmitted inductively. It comprises three antennas in the form of coils Sx, Sy and Sz, the respective coil surfaces of which are arranged in pairs. substantially perpendicular to each other. Thus, within the range of a transmitting antenna, voltage can be induced in at least one of the three coils regardless of the angular position of the receiver.

Description

The invention relates to a portable signal receiver,

  in particular for an anti-theft system for a motor vehicle.

  A known signal receiver (DE 37 21 822 C1) is arranged on a chip card. As a receiving antenna, it includes a coil whose turns are located in the plane of the smart card. When such a signal receiver is used in an anti-theft system for a motor vehicle, a signal transmitter is also arranged on the chip card. Thus, signals can either be sent to an identification unit or be

received from it.

  When a user wishes to get into his vehicle, an interrogation-response dialogue is first triggered by actuation of a trigger means. An interrogation signal is transmitted inductively, by means of a magnetic field, from a transmitting antenna in the form of a coil located in the vehicle to a signal receiver carried by the user. If this receiver receives the interrogation signal, then a response signal is produced which is sent back to the vehicle. In this, the response signal is compared to a setpoint signal and, if there is a coincidence, a response signal.

release is produced.

  If the transmitting antenna in the vehicle and the signal receiver antenna are in the form of coils, electromagnetic fields are produced when the coils are controlled by sinusoidal signals. These fields induce a voltage in the coil of the signal receiver. In order for the induced voltage to be as large as possible, field lines must cross

  in sufficient quantity the coil of the signal receiver.

  In Figure 5, there is shown a magnetic field B which is produced by a coil (transmitting antenna 12) which is located in the motor vehicle. A signal receiver, with its coil 13, is brought into this magnetic field. Depending on the position (orientation of the plane of the turns) of the coil 13, it is traversed in a more or less intense manner by the magnetic field (field lines). A turn of the coil 13 surrounds a surface which is hereinafter called the surface of turn A. The intensity of the voltage induced in the coil 13 of the signal receiver (the compound flux D is proportional to it) depends, inter alia, on 'an angle a (see FIGS. 6a to 6c) which is the angle formed by the surface of coil A of the coil 13 of the signal receiver (in FIG. 6, there are shown surface vectors A', which are directed perpendicular to the surface of coil A, and vectors composed of flux () and the lines of the magnetic field B produced by the transmitting antenna 12 in the vehicle. The voltage induced in the coil 13 of the signal receiver has the most value large when the coil 13 is crossed perpendicularly by the magnetic field lines (Figure 6a) and is very small when the latter is arranged practically parallel to the field lines (Figure 6c). The amplitude of the voltage also depends on the surface of coil A effica this bounded by the turns of the

coil 13 of the signal receiver.

  The dependence of the compound flux D on the angle is provided by the generally known formula

= B * A * cosa.

  Consequently, it can happen that no voltage or only a very low voltage is induced in the coil 13 of the signal receiver when the coil 13 is arranged parallel to the field lines (a practically equal to 90 -> cosa = 0, this which corresponds to the coil 13 'in Figure 5). When the position of the coil 13 deviates from this parallel position (see coil 13 "in Figure 5), the induced voltage becomes greater. When, on the other hand, the coil 13 of the signal receiver is crossed perpendicularly by the lines magnetic field (a practically equal to 90 -> cosa k 1), it is then the maximum voltage which is induced in the coil 13 (see coil 13 "'

in Figure 5).

  A greater or lesser voltage is induced in the coil 13 of the signal receiver as a function of the position of the coil. To remedy this problem, it has been proposed, in a previous application (DE 195 42441), to provide in the vehicle two frame antennas arranged closely one next to the other. The two loop antennas are controlled in a phase shifted manner, so that there is a magnetic field moving in one direction and the other (see Figure 5, double arrow in broken lines). The same effect would be obtained if the coil of the signal receiver were moved back and forth (see coils 13 'and

13 "in figure 5).

  In any event, this first requires very complex means for the transmitting antenna.

  in the vehicle. This requires on the one hand two antennas-

  frames arranged closely next to each other and, on the other hand, the two frame antennas must also be out of phase with each other. Furthermore, before getting into his vehicle, the user should move the signal receiver back and forth to

  that the interrogation signal is received in a secure manner.

  The problem underlying the invention is to provide a portable signal receiver which, regardless of the angular position relative to a transmitting antenna, receives a signal from the transmitting antenna in a secure manner when it is arranged in the vicinity of this

transmitting antenna.

  To this end, the subject of the invention is a portable signal receiver comprising a receiving unit which receives by means of an antenna a signal transmitted in an inductive manner, characterized in that it comprises three antennas in the form of coils of which the respective turn surfaces are arranged two by two practically

  perpendicular to each other.

  If the signal receiver is within the range of a transmitting antenna, thanks to the three-dimensional arrangement of the coils, it is regardless of the angular position of the signal receiver that a voltage is induced in the minus one of the three coils, this voltage can be subjected to further processing in

the signal receiver.

  The portable signal receiver according to the invention can also have one or more of the following features: - the coils are produced in the form of coils without iron or in the form of ferrite coils, - a ferrite core is arranged inside coils, - the ferrite core has two branches practically in the shape of a cross around which two of the coils are wound perpendicularly to each other, - it comprises a support plate which is produced practically in the form of a credit card and on which the coils and the receiving unit are arranged, - the support plate is arranged on a key handle, - next to the receiving unit, it also has a transmitting unit and it is used for an anti-theft system

for motor vehicle.

  Thus, the coils can be produced in the form of ironless coils or in the form of ferrite coils comprising a ferrite core. The ferrite cores can be made in the form of a single piece on which one or more coils are respectively

  wound two by two perpendicular to each other.

  The reels can be placed on a card the size of a credit card or on the handle of a key.

classic door.

  Examples of implementation of the invention are set out below in detail with reference to the schematic figures. We see: in Figure 1, a top view of a signal receiver according to the invention, in Figure 2, another embodiment of a signal receiver, in Figures 3a to 3c, examples of realization for ferrite cores on which coils are wound, in figure 4, a block diagram of the signal receiver, in figure 5, a graph of the lines of a magnetic field produced by a transmitting antenna in a motor vehicle and, in FIGS. 6a to 6c, magnetic flux compositions of a coil located in the magnetic field of

Figure 5.

  A portable signal receiver 1 (FIG. 1) is preferably used for an anti-theft system of a motor vehicle. It comprises a support plate 2 and at least three receiving antennas in the form of coils Sx, Sy and Sz. The three coils Sx, Sy and Sz are electrically connected to a receiving unit 3 which can be placed on the support plate 2 as a

  integrated semiconductor component.

  In the case of use for an anti-theft system, an interrogation signal is first emitted by means of an electromagnetic field from a transmitting antenna, not shown, for example located in the covering of

  door or in the vehicle's exterior mirrors.

  When the signal receiver 1 is placed in the vicinity of the transmitting antenna, it receives the interrogation signal via one or more of the coils Sx, Sy and Sz, a voltage which depends on the angular position of the coils compared to the magnetic field being induced in the coils. The interrogation signal is then analyzed

in the receiving unit 3.

  So that a user can prove his authorization (authentication), provision may also be made, arranged on the support plate 2, a transmitting unit 4 which, after reception of the interrogation signal, produces a response signal which contains coded information specific to the user or the vehicle. Since the coils Sx, Sy and Sz can also be used as transmitting coils, the response signal is returned to the vehicle via one or more of the coils Sx, Sy and Sz. It can however also be provided, arranged on the support plate 2, another transmitter, for example in the form of another coil, at the

  means by which the response signal is issued.

  The response signal received here is analyzed in a control device. For this purpose, it is compared to an expected setpoint signal (authentication) and, when the two signals coincide at least to a large extent, a signal, a release signal is produced by means of which for example the doors of the vehicle are unlocked (access control) or a set necessary for starting the vehicle (electronic start lock)

is released into the vehicle.

  If the signal receiver 1 is located near a transmitting antenna, an interrogation signal must in each case be received, regardless of the angular position of the signal receiver 1 relative to the transmitting antenna or the field magnetic produced by it. This is why the coils Sx, Sy and Sz are oriented on the signal receiver "in a three-dimensional way", in such a way that their turns surfaces and therefore their respective magnetic flux vectors À are oriented two to

  two practically perpendicular to each other.

  Thus, each coil Sx, Sy and Sz has a preferential reception characteristic marked according to

another spatial direction.

  In the first embodiment, the coil Sz is wound with its turns situated in the plane of the support plate 2 (the direction of the turns is indicated in FIG. 1 by the arrow which goes around), so that its vector magnetic flux cz enters the plane of Figure 1 (this must correspond to the Z axis of a Cartesian coordinate system). The second coil Sy is wound on a ferrite core 5 so that its magnetic flux vector cy is directed upwards in FIG. 1 (this corresponds to the Y axis of the Cartesian coordinate system). The third coil Sx is also wound on a ferrite core 6 so that its magnetic flux vector cx is directed to the right in Figure 1 (this corresponds to the X axis of the Cartesian coordinate system). Thus, the magnetic flux vectors 1x ', (y and 4z of the three coils Sx, Sy and Sz are arranged practically along the three axes of the Cartesian coordinate system. The respective turn surfaces of the three coils Sx, Sy and Sz are located perpendicular to the respective three axes of the Cartesian coordinate system. As a result, components Bx, By and Bz of the spatial magnetic field produced by the transmitting antenna induce a voltage in the coil Sx, Sy or Sz each time oriented in a The amplitude of the voltage each time induced depends in any event on the angular position of the coil Sx, Sy and Sz considered with respect to the associated magnetic field component Bx, By or Bz and on the intensity of this one (see also figures

6a to 6c).

  The coils Sx, Sy and Sz can be arranged on the support plate 2 in a distributed manner and being spatially separated from each other. It is also possible that the coils Sx, Sy and Sz are wound side by side as closely as possible, but with the turn surfaces oriented practically perpendicular to each other. This is shown in the case of the exemplary embodiment of FIG. 2. In this case, the coils Sx and Sy are wound on a ferrite core 7 which is made in the shape of a cross with pole pieces 8 at the ends of its branches. The coils Sx and Sy are each wound diagonally with respect to the respective branches of the ferrite core 7 and therefore perpendicular to one another (each perpendicular to the plane of the drawing). The coil Sz is wound in a substantially annular manner on the pole pieces 8 of the ferrite core 7. Its coil surface A is parallel to the plane of the drawing. Thus, the turn surfaces of the three coils Sx, Sy and Sz are respectively arranged two by two perpendicular to one another. The dimensions of signal receiver 1 conform to

  the embodiment of Figure 2 are very small.

  The coils Sx, Sy and Sz are arranged with the smallest possible footprint. Thus, such a signal receiver 1 can be suitably mounted in a housing of small dimensions. The coil Sz is produced in FIG. 1 in the form of an iron-free coil and in FIG. 2 only partially in the form of a ferrite coil. In an ironless coil, the inside of the coil is not filled

  of a magnetically conductive material.

  The coil Sz is mounted directly on the support plate 2. It can for example consist of wires which are fixed in the form of a coil on the support plate 2, for example in grooves. The support plate 2 can also be produced in the form of a printed circuit board and the coil Sz can be produced with its turns being in the form of conductive tracks. The support plate can be provided with a ferrite type material in the area of the coil surface of the coil Sz, which increases its coupling factor / quality. In FIGS. 1 and 2, the coils Sx and Sy are represented in the form of ferrite coils in which

  the turns are wound on a ferrite core 5, 6, 7.

  The interior of the coils Sx and Sy is then to a large extent filled with a material with very high relative permeability ir. As we know, a ferrite core amplifies the magnetic flux DI. It follows that with the same effect, the diameter of the turns (and therefore the turn surface) of the coils Sx, Sy and Sz can be reduced in the

  case where the coils are wound on a ferrite core.

  Other embodiments provided for the coils Sx and Sy and their ferrite cores 5, 6 or 7 are shown in Figures 3a to 3c. The ferrite cores 5, 6 or 7 can be produced in the form of a single piece practically in the form of a cross. However, each coil Sx and Sy can also have its own ferrite core 5, 6, each then being arranged practically perpendicular to the ferrite core of the other coil, overlapping

  partially each other as in Figure 3c.

  When the coil Sz is particularly large (which means a very high coupling factor or a large quality factor, for example in the form of an ironless coil with a large turn diameter or in the form of a large ferrite coil comprising a material of ferrite type with high permeability), this has the advantage that with the reception of the electromagnetic field, energy can also be received. In the case where no energy accumulator is placed on the support plate 2 or in the case where this energy accumulator is empty, the energy received can alone be sufficient to analyze the interrogation signal and

  possibly produce and send the response signal.

  Thus, such a particularly suitable coil then serves to fulfill an emergency function in the event of a failure of

the battery.

  Energy can also be received by means of a separate coil, not shown. When this coil is provided with a particularly high coupling factor and / or a particularly good quality factor, the transmission

  energy is particularly effective.

  The three coils Sx, Sy and Sz are all connected to the receiver unit 3 and to the transmitter unit 4 (Figure 4). The voltage produced in each coil Sx, Sy and Sz is amplified individually in a respective amplifier 9 which is specific to it and is sent to a common adder 10. In the adder 10, the induced voltages resulting from the spatial components of the magnetic field Bx,

By and Bz are added.

  Instead of the adder 10, it is also possible to provide a maximum detector, not shown, which transmits for operation only the greatest voltage induced in the coils Sx, Sy and Sz. Thus, very small magnetic fields undesirable are deleted for operation (an overshoot is avoided). Thus, in the case where too low a voltage is induced in one or two of the three coils, there always remains the third coil in which a larger voltage is induced due to the spatial magnetic field and the three-dimensional arrangement of the coils, if signal receiver 1 is located in the vicinity of the transmitting antenna and therefore

inside the magnetic field.

  The reels Sx, Sy and Sz are provided sufficiently small in size so that the support plate 2 comprising the reels fits on a small flat card in the form of a credit card (also called a smart card). The support plate 2 can also be provided so small that it can be fixed with the coils Sx, Sy and Sz on the handle of a mechanical door / ignition key. The user can wear

  comfortably the signal receiver 1 on him.

  The signal receiver 1 can also be arranged in other functionally equivalent housings. The shape of the housing is of little importance for the invention. It is however essential that the coils Sx, Sy and Sz are arranged two by two perpendicular to each other and that their

dimensions are very small.

  Since the three coils Sx, Sy and Sz are oriented substantially in the three directions of the space x, y and z, the angular position of the signal receiver 1 relative to the transmitting antenna does not intervene. Thus, the user can carry his signal receiver 1 both in one of his pockets and in a document pocket. The signal receiver 1 can also be placed in the vehicle in a compartment. As long as the signal receiver 1 is within the range of the transmitting antenna and the latter produces a sufficiently large magnetic field, the interrogation signal is received safely by the receiver

  of signals 1 according to the invention.

  When a transmitting unit 4 is also further provided, the latter may, after reception of the interrogation signal, return a response signal. Authentication is thus carried out. When authentication is successfully carried out, i.e. when the response signal turns out to be authorized, the door locks can be locked or unlocked or a starting block located in the

vehicle can be triggered.

  The signal receiver 1 may not be used only in anti-theft systems for motor vehicles. It can especially be used in cases where a signal is emitted by a transmitting antenna inductively by means of a magnetic field and must be received by the portable signal receiver 1. Binary information to be transmitted is then transmitted d '' a modulated way by means of the magnetic field. Upon receipt of

  signal, the binary information is demodulated and analyzed.

  The range of inductively transmitted signals is practically 1 to 2 m. This range depends on the transmission frequency which is preferably 125 kHz in the case

  of uses in the field of automotive technology.

  The range also depends on the transmission power and the radiation pattern of the transmitting antenna. The response signal is for example returned to the vehicle at a transmission frequency of 433 MHz. The scope can in this case

to be much larger.

  Ferrites can be made of pure magnetic materials (compounds (of oxides) of iron and oxides of manganese, nickel or zinc) or also of a plastic material in which the ferro magnetic particles are coated (plastoferrites). Ferrite cores are made up of ferrites and can be made with a very small thickness in the form of parts cut with the press. Thus, the thickness of a coil wound on a ferrite core can be between 1 and 2 mm. The length of the branches of the ferrites can be of the order of a centimeter. It is thus possible to produce small structural shapes which occupy only a small space on

the support plate 2.

  In the case where the signal receiver 1 is placed on a smart card, it can preferably be carried in the shirt or pants pocket of the user. It can also be easily transported in a pouch to

documents or whatever.

  Depending on a preferred direction in which the magnetic field produced by the transmitting antenna is directed and a preferred angular position of the signal receiver 1, it is then that of the coils Sx, Sy and Sz which is mainly crossed by the magnetic field for this preferred direction which can be carried out in a particularly characteristic manner. This is how we can give the turns of this coil Sx, Sy or Sz a larger turn diameter (larger turn surface). Likewise, the permeability can be increased by means of a ferrite core with high permeability. The number of turns of the coil Sx, Sy or Sz can also be increased. Due to this multiplication of means, it is then more likely that a signal is received by the signal receiver 1 with sufficient intensity when this receiver is within the limits of the range of the transmitting antenna.

  and that it also emits a signal.

  It is sufficient that the signal receiver 1 can receive signals. For use in an anti-theft system of a motor vehicle, it is advantageous that provision is also made for a transmitting unit 4 which, after reception of the interrogation signal, returns a response signal. Since the coils Sx, Sy and Sz can receive signals as well as transmit them, the signal receiver 1 can constitute with the transmitting unit 4 a transponder which triggers the production of the response signal under the effect of the reception of the interrogation signal.

Claims (7)

  1. Portable signal receiver comprising a receiving unit (3) which receives by means of an antenna a signal transmitted in an inductive manner, characterized in that it comprises three antennas in the form of coils (Sx, Sy and Sz) whose respective turn surfaces are arranged two by two practically perpendicular one to the other.   2. Signal receiver according to claim 1, characterized in that the coils (Sx, Sy and Sz) are produced in the form of coils without iron or in the form of ferrite coils.   3. Signal receiver according to claim 1, characterized in that a ferrite core (5, 6, 7) is   arranged inside the coils (Sx, Sy and Sz).   4. Signal receiver according to claim 3, characterized in that the ferrite core (7) has two branches practically in the shape of a cross around which two of the coils (Sx, Sy and Sz) are wound   perpendicular to each other.   5. Signal receiver according to one of the   previous claims, characterized in that it comprises   a support plate (2) which is practically in the form of a credit card and on which the coils (Sx,   Sy and Sz) and the receiving unit (3) are arranged.   6. Signal receiver according to one of the   Claims 1 to 3, characterized in that the plate   support (2) is arranged on a key handle.   7. Signal receiver according to one of the   previous claims, characterized in that next to   the receiving unit (3), it further comprises a transmitting unit (4) and in that it is used for a system anti-theft device for motor vehicle.