JP2001257526A - Loop antenna device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a loop antenna device capable of improving antenna characteristics by keeping magnetic field components to be transmitted received in the directions of three axes by comparatively simple constitution and without increasing its size so much. SOLUTION: The loop antenna device 1 is provided with the first coil 3 arranged in the outer periphery of a ferrite core 2, the second coil 6 and the third coil 7 wound around the core 2. These coils 3, 6 and 7 are wound in mutually orthogonal directions. The first coil 3 and the second coil 6 are electromagnetically coupled through a link coil 4 wound around core 2. The third coil 7 arrangement is deviated upward compared with the center axis of the core 2 so that it can be coupled with the other coils 3 and 6 electromagnetically.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a loop antenna device capable of transmitting and receiving magnetic field components in different three axial directions.

[0002]

2. Description of the Related Art Conventionally, as an antenna device of this kind, 2
A loop antenna device having directivity in two different directions using one antenna is employed. For example, this loop antenna device is described in German Patent Publication DE 4105.
826, as shown in FIG.

[0003] As shown in FIG.
Reference numeral 1 denotes a first antenna 54 in which a parallel resonance circuit is formed by a coil 53 wound around a ferrite rod 52 and a resonance capacitor C2 connected in parallel to the coil 53, and a circle provided outside the ferrite rod 52. The second antenna 56 includes a coil 55 and a resonance capacitor C1 connected in parallel with the circular coil 55 to form a parallel resonance circuit. A power source (source) S is connected to the coil 53 of the first antenna 54. The first antenna 54 is arranged at a predetermined angle θ in the radial direction with respect to the second antenna 56, and both antennas 54 and 56 are magnetically coupled. When the power supply S oscillates, the coil 53 becomes y
The magnetic field component Hy in the axial direction is generated, and the circular coil 55 generates a magnetic field component Hz in the z-axis direction.
Are axis components orthogonal to each other.

[0004]

For example, when this loop antenna device 51 is used as one component of a keyless entry device, the loop antenna device 51 has two axes of magnetic field components to be transmitted and received, but still has strong directivity. There is a problem that the transmitted radio wave is difficult to detect depending on the angle (direction).

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to make the magnetic field components to be transmitted and received in three axial directions with a relatively simple configuration and without increasing the size. To provide a loop antenna device capable of improving antenna characteristics.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, there is provided a first antenna coil disposed at an outer periphery of a core with an interval therebetween, and A second antenna and a third antenna coil that are electromagnetically coupled to the first antenna coil while being wound around the core disposed in an internal space, and transmit to one of the three antenna coils A gist is that a source or a reception source is connected, and the three antenna coils are arranged so that their winding directions are substantially orthogonal or different from each other.

According to the present invention, for example, when a loop antenna apparatus is used for transmission, three different magnetic field components in three axial directions are radiated using three antenna coils.
As a result, radio waves having magnetic field components in three axial directions are transmitted,
The angle (direction) at which the intensity of the radio wave received at the receiving side is significantly reduced is eliminated or reduced, and the antenna characteristics of the loop antenna device are improved.

According to a second aspect of the present invention, in the first aspect of the present invention, the second antenna coil is electromagnetically coupled to the first antenna coil via a link coil wound around the core. The gist is that the third antenna coil is electromagnetically coupled to the second antenna coil by being wound around the core at a position off the axis of the second antenna coil. .

According to the present invention, in addition to the function of the first aspect, by winding the third antenna coil at a position off the axis of the core, the third antenna coil connects the link coil to the link coil. Even if not used, it is electromagnetically coupled to the first and second antenna coils.

[0010] In the third aspect of the present invention, the first antenna coil disposed at an interval around the outer periphery of the core, and the first antenna coil with respect to the core disposed in the internal space of the first antenna coil. A second antenna coil that is wound in a direction different from that of the first antenna coil and that is electromagnetically coupled to the first antenna coil via a link coil wound around the core; An oscillation source or a reception source is connected to one of the first and second antenna coils, and the first antenna coil is wound so as to draw a loop along a curved path passing through two planes having different directions from the loop surface of the second antenna coil. The gist is that it is being turned.

According to the present invention, the first antenna coil and the second antenna coil are linked by the link coil of the first antenna coil.
Are electromagnetically coupled with the antenna coil of the second antenna. And in a loop antenna device having two antenna coils,
Since the first antenna coil is bent so as to draw a loop passing through two planes having different directions from the second antenna coil, for example, when a loop antenna device is used for transmission, magnetic field components in three different axial directions are radiated. You. As a result, the antenna characteristics of the loop antenna device are improved with a simple structure having two antenna coils.

According to a fourth aspect of the present invention, there is provided a loop antenna device disposed at a position near a conductor surface, wherein the first antenna coil is disposed at an interval around the outer periphery of a core; The first antenna coil is wound around a core disposed in an internal space of the antenna coil in a direction substantially orthogonal to the first antenna coil, and is electromagnetically connected to the first antenna coil via a link coil wound around the core. A coupled second antenna coil, a transmission source or a reception source is connected to one of the two antenna coils, and the first antenna coil is arranged to be inclined at a predetermined angle with respect to the conductor surface. Is the gist.

According to the present invention, the first antenna coil and the second antenna coil are linked by the first antenna coil.
Antenna coils are electromagnetically coupled. By arranging the loop antenna device in a state where the first antenna coil is inclined at a predetermined angle with respect to the conductor surface, for example, when the loop antenna device is used for transmission, the horizontal direction and the vertical direction of the conductor surface are reduced by three. Assuming that the axis is a reference axis, apparently different magnetic field components in three axial directions are emitted. In addition, due to the magnetic field radiated from the two antenna coils, the magnetic field generated from the conductor surface in a direction to cancel the radiated magnetic field of the antenna coil is weakened. Therefore, the strength of the magnetic field component generated from the loop antenna device is also ensured.

According to the fifth aspect of the present invention, the first to fourth aspects are provided.
In the invention described in any one of the above, the first antenna coil has a shape similar to the outer shape of the core, and the gist is that the transmission source or the reception source is connected to the first antenna coil. I do.

According to this invention, in addition to the operation of the invention described in any one of the first to fourth aspects, for example, when the loop antenna device is mounted on an upright mounting surface such as a door, Since it is desired to relatively increase the magnetic field component in the direction orthogonal to the mounting surface, the loop antenna device is configured such that the loop surface of the first antenna coil connected to the transmitting source or the receiving source and the mounting surface They are arranged in a substantially parallel direction. Therefore,
Since the first antenna coil has a shape similar to the outer shape of the core, a compact loop antenna device can be obtained.
Since the loop antenna device is assembled in this direction, the thickness of the assembly portion can be reduced.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) Hereinafter, a first embodiment in which the present invention is embodied in a loop antenna device mounted on a vehicle will be described.
An embodiment will be described with reference to FIGS. The loop antenna device of the present example is a transmission antenna for a keyless entry device, and is particularly employed in a smart entry device in which a door lock is unlocked only when a key holder approaches a vehicle,
For example, it is disposed inside a door handle of a vehicle (such as an automobile).

As shown in FIGS. 1 and 2, the loop antenna device 1 includes a first antenna ANT1 and a second antenna AN.
T2 and a third antenna ANT3 are provided. The first antenna ANT1 has a rectangular parallelepiped ferrite core (ferrite bar) 2 as a core, and a first antenna coil (hereinafter simply referred to as a first coil) disposed on the outer periphery thereof.
3 and a link coil 4 having one end of the first coil 3 wound around the ferrite core 2 by a predetermined number of turns (for example, 3 to 5 turns). Therefore, the ferrite core 2
Is placed in the center of the internal space created by the first coil 3 of the first antenna ANT1. Also, the first antenna AN
T1 has a rectangular ring shape similar to the outer shape (rectangular parallelepiped) of the ferrite core 2, and the size is reduced by narrowing the gap between the two. The winding directions of the first coil 3 and the link coil 4 are orthogonal to each other.

The first coil 3 is made of a bobbin 5 (FIG. 2) made of a resin such as ABS resin or polycarbonate.
(See FIG. 1A) (however, the bobbin 5 is omitted in FIG. 1). The ferrite core 2 uses a material such as manganese zinc or nickel zinc in order to improve antenna efficiency. Further, the shape of the ferrite core 2 may be a cylindrical shape.

The second antenna ANT2 is connected to the first antenna A
It has a second antenna coil (hereinafter simply referred to as a second coil) 6 wound around the ferrite core 2 in the same direction as the winding direction of the link coil 4 of the NT1.

The third antenna ANT3 is a third antenna coil (hereinafter, referred to as a coil) wound directly on the surface of the ferrite core 2 in a direction orthogonal to both the winding directions of the first coil 3 and the second coil 6. 7). Therefore, the winding directions of the first coil 3, the second coil 6, and the third coil 7 are orthogonal to each other. This third
A copper foil ribbon 8 is used for the coil 7. The copper foil ribbon 8 is directly adhered to the surface of the ferrite core 2, and is displaced vertically with respect to the axis of the ferrite core 2 (in this example, the (A position deviated from). That is, although the third coil 7 is orthogonal to the second coil 6, it is electromagnetically coupled to the second coil 6 to form a loop at a position off the center line (axial center) of the second coil 6. Note that a linear coil may be used for the third coil 7 instead of the copper foil ribbon 8.

FIG. 2A is a diagram for explaining how each coil is wound, and FIG. 2B is an equivalent circuit of the loop antenna device.
In FIG. 2B, L11, L12, L2, and L3 are:
The inductance of the coils 3, 4, 6, 7 is shown.

As shown in FIG. 2A, a resonance capacitor (capacitor) C1 and a power supply (oscillator) OS are connected in series between a terminal p of the first coil 3 and a terminal q of the link coil 4. I have. A resonance capacitor (capacitor) C2 is connected between the terminals r of the second coil 6. Therefore,
The first antenna ANT1 has a first coil 3, a link coil 4
And the resonance capacitor C1 are connected in series to form a series resonance circuit. In the second antenna ANT2, the second coil 6 and the resonance capacitor C2 are connected in parallel to form a parallel resonance circuit.

The resonance capacitance C1 is set to a value that causes series resonance at the operating frequency f, and the resonance capacitance C2 is set to a value that causes parallel resonance at the operating frequency f. Also, the first coil 3 and the second coil 3
The degree of coupling of the coil 6 can be freely set by the number of turns of the link coil 4. Further, the degree of coupling between the third coil 7 and the first coil 3 and the second coil 6 is set by the winding position of the third coil 7 (copper foil ribbon 8) around the ferrite core 2 and its inductance L3. The strength (output) of the magnetic field component emitted by the third antenna ANT3 is determined by the degree of coupling.

Next, the operation of the loop antenna device 1 configured as described above will be described. First antenna AN
When the power supply OS of T1 is oscillated, a magnetic field is formed in the y-axis direction by the first coil 3, and the link coil 4 is excited to cause a current to flow through the second coil 6. Also,
A current also flows through the third coil 7 electromagnetically coupled to the second coil 6. Therefore, as shown in FIG. 1, at the time of oscillation, a magnetic field Hx in the x-axis direction is radiated by the second coil 6 and the link coil 4 of the second antenna ANT2, and the first antenna ANT2 is radiated.
One first coil 3 radiates a magnetic field Hy in the y-axis direction, and a third coil 7 of the third antenna ANT3 radiates a magnetic field Hz in the z-axis direction. Therefore, the magnetic field components generated from the loop antenna device 1 are different three-axis components in the Hx, Hy, and Hz directions.

FIG. 3 is a graph showing the radiation directivity of the electric field component on the xy plane in FIG. In the figure, the horizontal axis represents the angle θ indicating the detection direction of the radio wave transmitted from the loop antenna apparatus 1 when the y-axis direction in FIG.
(Deg.), The vertical axis indicates the electric field strength (dBμV /
m). The larger the value of the electric field strength, the higher the antenna characteristics can be used, and it is particularly desirable that the average value of the electric field strength is high. In this figure, a solid line connecting white circles is a conventional loop antenna device having only two axes of magnetic field components, and a solid line connecting black circles is a loop antenna device corresponding to three axes. As shown in the figure, the use of the three-axis loop antenna device 1 of the present example significantly improves the electric field strength around -45 to 15 degrees, and further increases the average value of the entire electric field strength. are doing. Therefore, when this loop antenna device 1 is used for a keyless entry device,
A device having high antenna characteristics can be obtained.

Therefore, in this embodiment, the following effects can be obtained. (1) The loop antenna device 1 can radiate magnetic field components in three axial directions using the three antenna coils 3, 6, and 7. As a result, when the loop antenna device 1 is used, for example, for a keyless entry device or the like, it can be a device having good antenna characteristics.

(2) The third coil 7 is electromagnetically coupled to the second coil 6 by disposing the third coil 7 on the ferrite core 2 at a position shifted from the axis of the second coil 6. It is not necessary to use a link coil structure for electromagnetic coupling with the third coil 7.

(3) Three antennas ANT1 to ANT3
The three-axis compatible loop antenna device having
Since the coil 3 has a shape similar to the outer shape of the ferrite core 2, the loop antenna device 1 can be made small (compact). Further, when the loop antenna device in which the power supply OS is connected to the first coil 3 is assembled to, for example, a door of an automobile or the like for use in a keyless entry device or the like, the loop surface of the first coil 3 is formed on the inner wall of the door. Since the mounting is performed so as to be substantially parallel to the mounting surface (substantially vertical plane), the mounting portion can be made thin while emitting a relatively strong magnetic field component.

(Second Embodiment) Next, a second embodiment will be described with reference to FIGS. The present embodiment is different from the first embodiment in that only two antenna coils are used instead of using three antenna coils to radiate magnetic fields in three different axes directions.
The same components as those of the first embodiment are denoted by the same reference numerals, and the detailed description is omitted.

As shown in FIG. 4, the loop antenna device 1
Has a first antenna ANT1 and a second antenna ANT2. The first antenna ANT1 has a first coil 3 disposed outside a rectangular parallelepiped ferrite core 2 and a link coil 4 having one end of the first coil 3 wound around the ferrite core 2 by a predetermined number of turns. ing. Also, the second
The antenna ANT2 has a second coil 6 wound around the ferrite core 2 in the same winding direction as the link coil 4.

The first coil 3 has a winding x shown in FIG.
A loop is formed by a path that is bent so as to pass through two planes, a −y plane and an xz plane. That is, the first coil 3 is three-dimensionally wound so as to draw a closed loop in both the y-axis direction and the z-axis direction.

FIG. 5A is an explanatory diagram of how each coil is wound, and FIG. 5B is an equivalent circuit of the loop antenna device.
In FIG. 5B, L11, L12, and L2 indicate the inductances of the coils 3, 4, and 6.

As shown in FIG. 5A, the first antenna A
The NT1 forms a series resonance circuit with the first coil 3, the resonance capacitor C1, and the power supply OS. The second antenna ANT2 forms a parallel resonance circuit by the second coil 6 and the resonance capacitor C2. The resonance capacitance C1 is equal to the operating frequency f
The resonance capacitance C2 is also set to a value that causes parallel resonance at the operating frequency f. Further, the degree of coupling between the first coil 3 and the second coil 6 can be freely set by the number of turns of the link coil 4.

In order to wind the first coil 3 three-dimensionally, FIG.
The bobbin 12 shown in FIG. Bobbin 12
Has a size that allows the ferrite core 2 to be arranged in the center of the internal space, and has a ring shape similar to the outer shape of the ferrite core 2. The bobbin 12 has a guide groove 13 for winding a coil around its outer periphery, and y in FIG.
It has a pair of guide grooves 14 for guiding the winding in the direction bent in the axial direction, and a guide portion 15 for guiding the winding wound between the two guide grooves 14. The first coil 3 is
It is wound around the guide groove 13 of the bobbin 12 over a half circumference, and is bent along the pair of guide grooves 14 in the y-direction shown in FIG. 4 and then extends between the pair of guide grooves 14. It has a loop shape wound around.

Next, the loop antenna device 1 of the present embodiment
The operation of will be described. Oscillation of the power supply OS of the first antenna ANT1 causes a current to flow through the first coil 3, and excites the second coil 6 via the link coil 4 to cause a current to flow through the second coil 6. Therefore, as shown in FIG. 4, at the time of oscillation, a magnetic field Hx in the x-axis direction is radiated by the second coil 6 of the second antenna ANT2, and the first antenna A
The first coil 3 of the NT1 radiates a magnetic field Hy in the y-axis direction by a closed loop as viewed in the y-axis direction,
The magnetic field Hz in the z-axis direction due to the closed loop viewed in the z-axis direction
Is emitted. Therefore, the magnetic field components generated from the loop antenna device 1 are different three-axis components in the Hx, Hy, and Hz directions. Also, the degree of generation of the magnetic fields Hx and Hz is adjusted by the bending position of the first coil 3 which determines the ratio of the area of the first coil 3 projected on the xy plane to the area projected on the xz plane. Is done.

FIG. 6 is a graph showing the radiation directivity of the electric field component on the xy plane in FIG. 4, and shows the same characteristics as those in the graph of FIG. 1 of the first embodiment. Also in this case, the larger the value of the electric field strength, the higher the antenna characteristic can be used, and it is particularly desirable that the average value of the electric field strength is high. In this figure, a solid line connecting white circles is a conventional loop antenna device having only two axes of magnetic field components, and a solid line connecting black circles is a loop antenna device 1 in which the first coil is bent. In this case, the electric field intensity around -45 to 0 degrees is greatly improved. When the loop antenna device 1 is used for a keyless entry device, the operator often performs key operations mainly at an angle of about 0 degrees, but the electric field strength near 0 degrees is improved. Therefore, if this loop antenna device 1 is used, a device having good antenna characteristics can be obtained.

Also in this configuration, the following effects described in the first embodiment can be obtained. (1) High antenna characteristics can be obtained by radiating magnetic field components in three axial directions. (3)
In addition to the downsizing of the loop antenna device 1 and the thinning of the assembly portion, the following effects can be obtained.

(4) The two antennas A are bent by bending the first coil 3 so as to draw a loop passing through two planes.
Only NT1 and NT2 can emit mutually different magnetic field components in three axial directions. Therefore, it is possible to provide the loop antenna device 1 which can radiate a three-axis component magnetic field with a simple structure without increasing the number of components, and without increasing the size.

Third Embodiment Next, a third embodiment will be described with reference to FIGS. In this embodiment, when the loop antenna device is arranged in the vicinity of the conductor plate forming the door or the door component, the magnetic field loss is reduced and the three-axis component of the magnetic field is apparently radiated. is there. The same components as those in the first and second embodiments are denoted by the same reference numerals, and detailed description is omitted.

As shown in FIGS. 7 and 8, the loop antenna device 1 includes a first antenna ANT1 and a second antenna AN.
T2 is provided. The first antenna ANT1 includes a first coil 3 disposed on the outer periphery of the ferrite core 2 and a first coil
One end of the coil 3 has a link coil 4 wound around the ferrite core 2 by a predetermined number of turns. The winding directions of the first coil 3 and the link coil 4 are orthogonal to each other. The second antenna ANT2 has a second coil 6 wound around the ferrite core 2 in the same winding direction as the link coil 4.

In the loop antenna device 1, one side surface (a surface orthogonal to the thickness direction) of the loop antenna device 1 forms a door or a door part in order to reduce the thickness of an assembly portion when the vehicle is assembled. 30 (see FIG. 7). The loop antenna device 1 is arranged in a posture inclined at a predetermined angle (a value in the range of 25 to 30 degrees in this example) with respect to the conductor surface 30a of the conductor plate 30 with its lower side as an axis. Further, the loop antenna device 1 is arranged with a slight gap (for example, about 3 mm) between the lower side and the conductor plate 30. In addition, the inclination angle of the loop antenna device 1 is not limited to a value within the range of 25 to 30 degrees, and can be appropriately set according to desired antenna characteristics.

FIG. 8A is an explanatory diagram of how each coil is wound, and FIG. 8B is an equivalent circuit of the loop antenna device.
In FIG. 8B, L11, L12, and L2 indicate inductances of the coils 3, 4, and 6.

As shown in FIG. 8A, the first antenna A
The resonance capacitor C1 and the power supply OS are connected in series between the first coil 3 and the link coil 4 of the NT1, and the first antenna ANT
1 forms a series resonance circuit. Further, a resonance capacitor C2 is connected to the second antenna ANT2, and the second antenna A
NT2 forms a parallel resonance circuit. The resonance capacitance C1 is set to a value that causes series resonance at the operating frequency f.
2 is also set to a value that causes parallel resonance at the operating frequency f. Further, the degree of coupling between the first coil 3 and the second coil 6 can be freely set by the number of turns of the link coil 4.

Next, the loop antenna device 1 of the present embodiment
The operation of will be described. FIG. 9 illustrates magnetic field components radiated on the y-axis and the z-axis when the power supply OS oscillates. Since the first coil 3 is inclined with respect to the conductor surface 30a, the magnetic field -Hy radiated from the conductor plate 30 in the opposite direction due to the magnetic field Hy radiated by the first coil 3 decreases. For this reason, a relatively strong magnetic field Hy with little loss in the y-axis direction can be obtained. In addition, the first coil 3 has a conductor surface 30.
Since the magnetic field Ha (the two-dot chain line in FIG. 9) emitted by the first coil 3 has components in the y-axis direction and the z-axis direction due to the inclination with respect to a, the magnetic field in the y-axis direction is apparent. Hy
And a magnetic field Hz in the z-axis direction is emitted.

Accordingly, at the time of oscillation, a magnetic field Hx (see FIG. 7) is radiated by the second coil 6 and the link coil 4,
A magnetic field Hy in a direction perpendicular to the conductor surface 30a by the inclined first coil 3 and a magnetic field Hz in a direction perpendicular to the magnetic field Hy
Are emitted. Therefore, by arranging the loop antenna device 1 so as to be inclined with respect to the conductor surface 30a, the magnetic field components generated from the loop antenna device 1 are Hx, Hy, H
There are three different axial components in the z direction. Therefore, the antenna characteristics of the loop antenna device 1 are improved.

FIG. 10 is a graph showing the radiation directivity of the electric field component on the xy plane of FIG. 7, and shows the same characteristics as the graph of FIG. 1 of the first embodiment. Also in this case, the larger the value of the electric field strength, the higher the antenna characteristic can be used, and it is particularly desirable that the average value of the electric field strength is high. In this figure, a solid line connecting white circles is a loop antenna device when the loop plane of the first coil 3 and the conductor surface 30a are arranged in parallel, and a solid line connecting black circles connects the first coil 3 to the conductor surface 30a. This is a loop antenna device 1 of the present example that is inclined at a predetermined angle with respect to the loop antenna device 1 of the present example. Again, -4
The electric field intensity around 5 to 15 degrees is greatly improved, and the average value of the entire electric field intensity is also increased. Therefore, when the loop antenna device 1 is used for a keyless entry device, the device can have high antenna characteristics.

Also in this configuration, the following effects described in the first embodiment, (1) a high and high antenna characteristic can be obtained by radiating a magnetic field component in three axial directions.
(3) In addition to the downsizing of the loop antenna device 1 and the thinning of the assembly portion, the following effects can be obtained.

(5) By inclining the loop antenna device 1 having the first antenna ANT1 and the second antenna ANT2 and emitting a magnetic field in two axial directions by a predetermined angle with respect to the conductor surface 30a, an apparent three-axis A magnetic field component can be emitted. Therefore, for example, when this loop antenna device 1 is employed in a keyless entry device, a reception error is unlikely to occur regardless of the direction in which the receiver in the communication area is located. In addition, the loop antenna device can be adapted to three axes easily and at low cost.

(6) Since the magnetic field −Hy radiated from the conductor plate 30 is reduced by inclining the loop antenna device 1, a relatively strong magnetic field H with little loss from the first coil 3.
y can be emitted. As a result, the loop antenna device 1 having higher antenna characteristics can be obtained.

(7) Conventionally, in order to reduce the magnetic field -Hy radiated from the conductor plate when the coil is energized, it has been necessary to arrange the loop antenna device at a relatively large distance from the conductor plate. However, in this example, since the magnetic field -Hy is reduced by inclining the loop antenna device 1, the distance from the conductor plate 30 can be reduced, and the assembly portion (door handle, etc.) of the loop antenna device 1 can be made thin. Can be.

The embodiment is not limited to the above, and may be modified as follows, for example. In the first embodiment, the configuration is not limited to the configuration in which the third coil 7 (copper foil ribbon 8) is arranged on the surface of the ferrite core 2 at a position off the axis of the second coil 6 and electromagnetically coupled. For example, the third coil 7 includes the ferrite core 2
Alternatively, a structure may be employed in which electromagnetic coupling is performed with one of the first coil 6 and the second coil 6 via a link coil wound in the same direction as the link coil 4 of the first antenna ANT1.

In the first embodiment, a resonance capacitor (capacitor) may be connected to the third coil 7 to form a parallel resonance circuit. In the first embodiment, the winding direction of the first coil 3, the second coil 6, and the third coil 7 (copper foil ribbon 8) is not limited to the direction orthogonal to each other, and the winding directions are different from each other ( For example, the direction may be 45 degrees or more).

In the second embodiment, the angle formed by the two planes formed by the first coil 3 by the loop is not limited to approximately 90 degrees, but an angle at which a magnetic field can be emitted in three axial directions (for example, 45 degrees or more). Any number of times is acceptable.

In the above embodiments, the loop antenna device 1 is used for transmission in this example, but a detector (reception source) for detecting a current (voltage) flowing through the first coil 3 is connected instead of the power supply OS. And may be used for reception. Alternatively, a device having both functions of an oscillator (transmission source) and a detector (reception source) may be connected to use the loop antenna apparatus 1 for transmission and reception.

In the first embodiment, the oscillator O
S is the second antenna instead of connecting to the first antenna ANT1.
It may be connected to the antenna ANT2 or the third antenna ANT3. In the second and third embodiments,
The oscillator OS may be connected to the second antenna ANT2 instead of the first antenna ANT1.

In the above embodiments, the mounting position of the loop antenna device 1 is not limited to the inside of the door handle. For example, it may be inside a door plate forming a door. In each of the above embodiments, the loop antenna device 1 is not limited to being used for a keyless entry device. For example, the loop antenna device 1 of this example may be used for a device that requires remote control. Furthermore, the present invention is not limited to the use of the loop antenna device 1 in a vehicle such as an automobile, and can be applied to a device requiring remote control by radio waves.

The technical ideas other than the claims which can be grasped from the embodiment and other examples will be described below together with their effects. (1) In claim 1, the third antenna coil is a metal foil (copper foil ribbon 8) wound inside the second coil and wound directly on the surface of the core. In this case, a small loop antenna device can be provided.

(2) In claim 2, the two planes formed by the first antenna coil are substantially orthogonal. In this case, since a high magnetic field radiation property in three axial directions can be obtained, particularly high antenna characteristics can be obtained.

(3) In claim 3, the predetermined angle is 25 to 30 degrees. Also in this case, since a high magnetic field radiation property in three axial directions can be obtained, particularly high antenna characteristics can be obtained.

(4) In any one of claims 1 to 5, the first antenna coil forms a series resonance circuit or a parallel resonance circuit, and the second antenna coil and the third antenna coil ( At least one of the first, second, and fifth aspects forms a parallel resonance circuit.

[0061]

As described in detail above, claims 1, 2 and 5
According to the invention described in (1), the directions of the magnetic field components to be transmitted / received are different from each other, and are different in three axial directions due to the three antenna coils that are electromagnetically coupled. Therefore, the antenna characteristics of the loop antenna device can be relatively simplified. , And can be improved without increasing the size.

According to the third and fifth aspects of the present invention, the magnetic field component transmitted and received by bending the loop of the first coil so as to pass through two planes becomes a component in three axial directions. The characteristics can be improved with a relatively simple structure and without increasing the size.

According to the fourth and fifth aspects of the present invention, 2
By inclining a loop antenna device having two antennas capable of emitting an axial component magnetic field at a predetermined angle with respect to a conductor surface, a magnetic field component to be transmitted and received becomes apparently a three-axis direction component. Can be improved with a relatively simple structure and without a large size.

[Brief description of the drawings]

FIG. 1 is a perspective view of a loop antenna device according to a first embodiment.

FIG. 2A is an explanatory diagram of how to wind a coil, and FIG. 2B is an equivalent circuit of a loop antenna device.

FIG. 3 is a graph showing electric field strength with respect to an angle.

FIG. 4 is a perspective view of a loop antenna device according to a second embodiment.

FIG. 5A is an explanatory diagram of how a coil is wound, and FIG. 5B is an equivalent circuit of a loop antenna device.

FIG. 6 is a graph showing electric field strength versus angle.

FIG. 7 is a perspective view of a loop antenna device according to a third embodiment.

8A is an explanatory diagram of how to wind a coil, and FIG. 8B is an equivalent circuit of a loop antenna device.

FIG. 9 is an explanatory diagram showing magnetic field components emitted in the y-axis and z-axis directions.

FIG. 10 is a graph showing electric field strength versus angle.

11A and 11B show a conventional loop antenna device that radiates magnetic field components in two axial directions, wherein FIG. 11A is an explanatory diagram of how a coil is wound, and FIG. 11B is an equivalent circuit of the loop antenna device.

[Description of Signs] 1 ... Loop antenna device, 2 ... Ferrite core as core, 3 ... First antenna coil (first coil), 4 ...
Link coil, 6: second antenna coil (second coil), 7: third antenna coil (third coil), 30
a: conductor surface, OS: power supply as a transmission source.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Satoshi Muramoto 2-1-1 Asahi-cho, Kariya-shi, Aichi Aisin Seiki Co., Ltd. (72) Eiji Mushiaki 2-1-1 Asahi-cho, Kariya-shi, Aichi Aisin Seiki Co., Ltd. F-term (reference) 5J021 AA03 AB04 CA05 HA10 JA07

Claims (5)

[Claims] 1. A first antenna coil disposed at an interval around an outer periphery of a core, and the first antenna wound around the core disposed in an internal space of the first antenna coil. A second antenna and a third antenna coil that are electromagnetically coupled to the coil, a transmission source or a reception source is connected to one of the three antenna coils, and a winding direction of the three antenna coils is A loop antenna device, wherein the loop antenna devices are arranged substantially orthogonally or in different directions. 2. The second antenna coil is electromagnetically coupled to the first antenna coil via a link coil wound around the core, and the third antenna coil is connected to the second antenna coil with respect to the core.
The loop antenna device according to claim 1, wherein the loop antenna device is electromagnetically coupled to the second antenna coil by being wound at a position off the axis of the antenna coil. 3. A first antenna coil arranged at an interval around an outer periphery of a core, and a direction different from that of the first antenna coil with respect to the core arranged in an internal space of the first antenna coil. And a second antenna coil electromagnetically coupled to the first antenna coil via a link coil wound around the core,
An oscillation source or a reception source is connected to one of the two antenna coils, and the first antenna coil loops along a path bent so as to pass through two planes having different directions from the loop surface of the second antenna coil. A loop antenna device characterized by being wound so as to draw a circle. 4. A loop antenna device disposed at a position near a conductor surface, comprising: a first antenna coil disposed at an interval around an outer periphery of a core; and a loop antenna device disposed in an internal space of the first antenna coil. A second antenna that is wound around the core in a direction substantially perpendicular to the first antenna coil, and that is electromagnetically coupled to the first antenna coil via a link coil wound around the core. A loop antenna, comprising: an antenna coil; a transmission source or a reception source connected to one of the two antenna coils; and the first antenna coil being arranged to be inclined at a predetermined angle with respect to the conductor surface. apparatus. 5. The antenna according to claim 1, wherein the first antenna coil has a shape similar to the outer shape of the core, and the transmission source or the reception source is connected to the first antenna coil. The loop antenna device according to any one of the above.