JP5929274B2 - ANTENNA DEVICE AND ELECTRONIC DEVICE - Google Patents

Description

  The present invention relates to an antenna device and an electronic apparatus.

As a GPS (Global Positioning System) antenna used in a vehicle-mounted or portable navigation system, a patch antenna is usually used. This patch antenna has a structure in which a radiation electrode is formed on a dielectric, and is installed on a GND substrate.
While this patch antenna has good gain characteristics and is suitable for receiving circularly polarized radio waves such as GPS, the wavelength of one side of the antenna is shortened by the effective dielectric constant εe at the reception frequency. Of λ / 2 × 1 / √εe. For this reason, when a patch antenna that receives circularly polarized radio waves such as GPS is incorporated in a wristwatch or the like, the patch antenna occupies a large volume in the wristwatch, and the size of the wristwatch increases accordingly. .
On the other hand, there is a dielectric chip antenna as an antenna that is smaller in shape than the patch antenna. However, since the dielectric chip antenna is a linearly polarized antenna, there is a problem that when receiving a circularly polarized radio wave such as GPS, the receiving capability is half that of the circularly polarized antenna even under the same conditions. .
On the other hand, there is an antenna device composed of two dielectric chip antennas (for example, Patent Document 1). In this antenna device, two dielectric chip antennas are arranged so that their longitudinal directions are orthogonal to each other, and a signal phase entering the antenna feeding section of the two dielectric chip antennas is changed by a phase shifter formed of a microstrip line. It has a structure corresponding to circular polarization by shifting by 90 °.

Japanese Patent Laid-Open No. 11-239020

By the way, in the antenna device disclosed in Patent Document 1, two dielectric chip antennas must be arranged so that their longitudinal directions are orthogonal to each other, and a large mounting area is required.
Also, since the current of the two dielectric chip antennas vibrates in an L-shaped current path, it does not become a circular current, and it is difficult to make an antenna device having a circular polarization characteristic with good axial ratio characteristics. there were. This is because the dielectric chip antenna uses a dielectric having a high dielectric constant, so that the electrical length is short, and even if power is supplied to the two dielectric chip antennas by shifting the phase by 90 °, the entire area of the circuit board In contrast, the current distribution cannot be circularly polarized.
In addition, in order to obtain circular polarization characteristics with two dielectric chip antennas, the two dielectric chip antennas must be arranged in a position close to a certain extent. There were many.

  The present invention has been made in view of such problems, and an object of the present invention is to provide an antenna device and an electronic apparatus that can improve transmission / reception characteristics with respect to circularly polarized radio waves even under mounting conditions with a small substrate area. To do.

The antenna device according to the present invention is
A dielectric chip antenna;
A film antenna,
A circuit board on which the dielectric chip antenna and the film antenna are mounted;
With
The dielectric chip antenna and the film antenna are arranged such that normal polarization planes orthogonal to the main surface of the circuit board are substantially orthogonal to each other, and have a circular polarization characteristic. The power is fed with a predetermined phase difference .
An electronic apparatus according to the present invention includes the antenna device in an electronic apparatus main body.

According to the present invention, it is sufficient to provide only one dielectric chip antenna on the circuit board, and the antenna main part of the antenna element in the film antenna is located outside the circuit board. Compared with the case where two antennas are provided, the board area is small.
In addition, the dielectric chip antenna and the film antenna are arranged so that the polarization planes in the normal direction orthogonal to the main surface of the circuit board are almost orthogonal to each other, and have a predetermined phase difference so as to have circular polarization characteristics. Since power is supplied, even a small board area has excellent transmission / reception characteristics for circularly polarized radio waves such as GPS.

It is the perspective view which showed the principal part of embodiment of the antenna device which concerns on this invention. It is a top view of the antenna apparatus of FIG. It is a figure which shows the mounting method of the film antenna in the antenna apparatus of FIG. 1, (A) is the perspective view which showed the state before bending a film antenna, (B) is the perspective which showed the state which bent the film antenna 1 time. FIG. It is a perspective view which shows the modification of the antenna device of embodiment. It is the perspective view which showed the wristwatch to which the antenna apparatus which concerns on this invention was applied. It is the perspective view which showed the principal part of the antenna apparatus applied to the wristwatch of FIG. FIG. 6 is a cross-sectional view taken along line VII-VII of the wristwatch of FIG. It is a figure for demonstrating the installation conditions of the dielectric chip antenna and film antenna in the case of the wristwatch of FIG.

(First embodiment)
FIG. 1 is a perspective view showing an embodiment of an antenna device according to the present invention, and FIG. 2 is a plan view of the antenna device.
The antenna device 100 of this embodiment has two antennas, one of which is a dielectric chip antenna 20 installed on the circuit board 10, and the other one antenna is a circuit. The film antenna 30 is installed outside the substrate 10. The latter film antenna 30 is configured as an inverted F antenna.

  The longitudinal direction of the dielectric chip antenna 20 and the longitudinal direction of the film antenna 30 are set so as to be orthogonal to each other, and the planes of polarization in the normal direction orthogonal to the main surface of the circuit board 10 are substantially orthogonal to each other.

A T-branch transmission line 12 is connected to a feeding point 11 installed on the circuit board 10, and the transmission line 12 a constituting one of the T-branches is fed to the dielectric chip antenna 20. The transmission line 12b connected to the part 21a and constituting the other branch part is connected to the power feeding part 32c of the film antenna 30 via the terminal T1.
In FIG. 2, reference numeral 40 denotes a matching circuit.

In this case, the transmission line length from the feeding point 11 to the feeding part 21a and the transmission line length from the feeding point 11 to the feeding part 32c are set to be different from each other. In order to cause the antenna device 100 to function as a circularly polarized antenna, a phase difference is generated between the feeding from the feeding unit 11 to the feeding unit 21a and the feeding from the feeding unit 11 to the feeding unit 32c. Yes.
Usually, in order for the antenna device 100 to function as a circularly polarized antenna, the transmission line length is set so that the signal phase of the power feeding unit 31c is 90 ° behind the signal phase of the power feeding unit 21a. (In the case of right polarization characteristics).
However, in practice, the current distribution on the circuit board 10 varies depending on the shape of the circuit board 10 and the arrangement of the antennas. Therefore, a 90 ° phase difference is not always appropriate for obtaining circular polarization characteristics. Therefore, in such a case, it is necessary to adjust the length of the transmission line so as to obtain the most appropriate phase difference for obtaining circular polarization characteristics.
The phase difference can be adjusted using a phase shifter instead of adjusting the transmission line length.

Next, the dielectric chip antenna 20 and the film antenna 30 will be described.
The dielectric chip antenna 20 is obtained by forming a conductor pattern to be an inverted F antenna in a helical shape on the surface of a dielectric. In addition, the type which forms a conductor pattern in a helical antenna form may be sufficient.

  On the other hand, the film antenna 30 is configured as an inverted F antenna as described above. The film antenna 30 includes a film 31 and an antenna element 32 made of a planar conductor such as a copper foil attached on the film 31.

Of these films, the film 31 is an FPC (Flexible Print Circuit) film and is made of an insulator such as polyimide. The film 31 is bent as shown in FIG. 1 when the film antenna 30 is mounted.
When the film 31 is viewed in a state before being folded (deployed state), as shown in FIG. 2, the film 31 is composed of a long film main body 31a and one end of the film main body 31a with respect to the film main body 31a. When it is viewed from a direction perpendicular to the main surface of the film 31, it has an L shape as a whole.
Further, when the film 31 is unfolded and viewed from a direction orthogonal to the main surface of the film 31, the film main body 31a extends in parallel with one side of the circuit board 10, and the film extending portion 31b is the film main body 31a. It is the shape extended toward the circuit board 10 from the one end part.

On the other hand, the antenna element 32 on the film 31 includes a long antenna main body 32a, a short short-circuit portion 32b extending in one direction orthogonal to the antenna main body 32a at one end of the antenna main body 32a, and a power feed. It has a portion 32c. A predetermined interval is provided between the short-circuit portion 32b and the power feeding portion 32c.
Among these, the antenna main body 32a is formed on the film main body 31a of the film 31 so that the longitudinal directions thereof coincide with each other. As a result, the antenna main body 31 a extends in parallel with one side of the circuit board 10. Moreover, the short circuit part 32b and the electric power feeding part 32c are formed over the film main body 31a of the film 31, and the film extension part 31b.
And the short circuit part 32b is connected to the GND layer of the circuit board 10 via the terminal T2, and the electric power feeding part 32c is connected to the transmission line 12b of the circuit board 10 via the terminal T1.

Next, the size of the antenna element 32 will be described.
If the wavelength of the received radio wave is λ and the dielectric constant of the film 31 is εe, the wavelength λg of the antenna is shortened as λg = λ / √ (εe).
The length of the antenna element (radiating element) 32 of the film antenna 30 (the length including the short-circuited portion 31b) is in a relationship of λg / 4 with respect to the wavelength λg that has been shortened.
Therefore, in the antenna device 100 of the embodiment, the dielectric constant of the film 31 and the length of the radiation element of the film antenna 30 are determined so as to satisfy the above relationship.
On the other hand, the positions and lengths of the short-circuit portion 32b and the power feeding portion 32c of the antenna element 32 are adjusted so that the input impedance of the antenna is about 50Ω.

Next, a method for mounting the film antenna 30 of the antenna device 100 of this embodiment will be described.
The film antenna 30 is attached to the circuit board 10 in a state before being bent, for example.
Specifically, the film antenna 30 before bending is prepared (antenna preparation process).
Then, as shown in FIG. 3A, the short-circuit portion 32b of the film antenna 30 is connected to the GND layer of the circuit board 10 via the terminal T2, and the power feeding portion 32c is transmitted to the circuit board 10 via the terminal T1. It connects to the track | line 12b and the film antenna 30 is attached to the circuit board 10 (antenna attachment process).
Next, as shown in FIG. 3B, the film antenna 30 is placed in the middle of the short-circuit portion 32 b and the power feeding portion 32 c so that the main surface of the film main body 31 a is substantially perpendicular to the main surface of the circuit board 10. Bend (antenna bending process).
Here, the film antenna 30 is bent after the antenna connecting step, but may be bent before the antenna connecting step.
When the film antenna 30 is bent, it is preferable to provide a certain amount of clearance between the circuit board 10 and a conductor such as a GND layer to prevent an adverse effect on the antenna characteristics.

Next, the simulation result of the current distribution of the antenna device 100 will be described.
Here, the simulation was performed by delaying the signal phase of the power feeding unit 32c in stages such as 0 °, 45 °, and 90 ° with respect to the signal phase of the power feeding unit 21a.
As a result, the following simulation results were obtained.
When the phase difference of the input alternating current (1.57542 GHz) was 0 °, the current density of the dielectric chip antenna 20 was high and the current density of the film antenna 30 was low. In addition, when the phase difference of the input alternating current was set to 45 °, the portion where the current density was high shifted from the dielectric chip antenna 20 toward the film antenna 30. Furthermore, when the phase difference was 90 °, the current density of the film antenna 30 was high, and the current density of the dielectric chip antenna 20 was low.
From this, it was confirmed that the portion where the current density is high rotates counterclockwise and has the right polarization characteristic as the antenna characteristic.

As apparent from the above description, according to the antenna device 100, the following effects can be obtained.
According to this antenna device 100, one dielectric chip antenna 20 is provided on the circuit board 10, and the film antenna 30 is provided at a position outside the circuit board 10. Thus, since it is sufficient to provide only one dielectric chip antenna 20 on the circuit board 10, the board area can be reduced as compared with the case where two antennas are provided on the circuit board 10.
In addition, the dielectric chip antenna 20 and the film antenna 30 are arranged so that the polarization planes in the normal direction orthogonal to the main surface of the circuit board 10 are substantially orthogonal to each other, and have a predetermined circular polarization characteristic. Since power is supplied with a phase difference, even a small substrate area has excellent transmission / reception characteristics for circularly polarized radio waves such as GPS.
Further, since the main surface of the antenna main portion 32a is disposed so as to be substantially perpendicular to the main surface of the circuit board 10, the mounting area in the direction along the main surface of the circuit board 10 can be reduced. .

  FIG. 4 shows a modification of the antenna device 100. In this modification, when the film antenna 30 is longer than the opposite sides of the circuit board 10, the film antenna 30 is curved along the side surface of the circuit board 10. In this way, even when there is a wall of the device main body of the electronic device in the vicinity of the periphery of the circuit board 10, it can be dealt with.

FIG. 5 shows a wristwatch to which the antenna device 100 is applied, FIG. 6 shows a main part of the antenna device 100, and FIG. 7 shows a cross section taken along line VII-VII in FIG.
In this application example, the antenna device 100 is mounted on a wristwatch 200.
In the wristwatch 200, the circuit board 10 has a substantially circular shape in plan view, and the circuit board 10 is provided with a dielectric chip antenna 20, a film antenna 30, and other antenna elements. The circuit board 10 is incorporated in a watch module 203 disposed in a resin watch case 202.
Here, the dielectric chip antenna 20 is installed in the 12 o'clock direction of the pointer type timepiece. On the other hand, the film antenna 30 is bent in the direction of the watch glass 204 in the middle of the short-circuit portion 32b and the power feeding portion 32c of the film 31 so that the film main body 31a of the film 31 is orthogonal to the main surface of the circuit board 10. It is curved in an arc shape so as to be along the outer periphery that is opposite to the operation button 201 of the wristwatch 200 among the ten outer periphery. The film antenna 30 is disposed along the watch case 202 in the gap between the watch module 203 and the module holder 205.
In this case, in order to obtain a desired circular polarization characteristic, as shown in FIG. 8, the surface of the center of the circuit board 10 and the surface of the dielectric chip antenna 20 that faces the center side of the circuit board 10. The area A1 divided by two lines connecting the both ends of the circuit board 10 and the area A2 divided by two lines connecting the center of the circuit board 10 and both ends of the film antenna 30 in the longitudinal direction do not overlap, It is necessary to form a predetermined gap G between them.

The wristwatch 200 configured as described above provides the following effects.
That is, in addition to the effect of the antenna device 100, since the folding direction of the film antenna 30 is the direction of the watch glass 43, when the back cover of the wristwatch 200 is formed of metal, the antenna of the film antenna 30 is used. Since the element 32 can be moved away from the metal back cover and can also be moved away from the human arm, it is possible to prevent the deterioration of the antenna characteristics based on them.
Further, since the film antenna 30 is installed along the outer periphery opposite to the operation button 201 of the wristwatch 200, it does not interfere with the arrangement of the operation button 201, and the operation button 201 is made of metal. The antenna element 32 of the film antenna 30 can be moved away from the metal operation button 201.

The invention described in the scope of claims attached to the application of this application will be added below. The item numbers of the claims described in the appendix are as set forth in the claims attached to the application of this application.
[Appendix]
<Claim 1>
An antenna device comprising two antennas,
One of the two antennas is a dielectric chip antenna mounted on a circuit board,
The other antenna of the two antennas is a film antenna constituting an inverted-F antenna and is mounted on the circuit board, and the antenna main part of the antenna element is located outside the circuit board,
The two antennas are arranged so that the polarization planes in the normal direction orthogonal to the main surface of the circuit board are substantially orthogonal to each other,
The antenna device, wherein the two antennas are fed with a predetermined phase difference from a feeding point so as to have circular polarization characteristics.
<Claim 2>
The film antenna is bent at a position of a feeding portion and a short-circuit portion of the antenna element, and is arranged so that a main surface of the antenna main portion is substantially perpendicular to a main surface of the circuit board. The antenna device according to claim 1.
<Claim 3>
An electronic device comprising the antenna device according to claim 1 in an electronic device main body.
<Claim 4>
An operation button is provided on a part of the side surface of the electronic device body,
The electronic apparatus according to claim 3, wherein the film antenna is disposed along a side surface of the circuit board on which the operation button is not provided.

DESCRIPTION OF SYMBOLS 10 Circuit board 20 Dielectric chip antenna 30 Film antenna 31 Film 32 Antenna element 100 Antenna apparatus 200 Wristwatch

Claims (6)

A dielectric chip antenna;
A film antenna,
A circuit board on which the dielectric chip antenna and the film antenna are mounted;
With
The dielectric chip antenna and the film antenna are arranged such that normal polarization planes orthogonal to the main surface of the circuit board are substantially orthogonal to each other, and have a circular polarization characteristic. The antenna device is fed with a predetermined phase difference from the antenna device. The circuit board is connected to a region divided by two lines connecting the center of the circuit board and both ends of the dielectric chip antenna, and the center of the circuit board and both ends of the film antenna in the longitudinal direction. 2. The antenna according to claim 1, wherein the dielectric chip antenna and the film antenna are mounted in a state where a predetermined gap is formed between the region divided by two lines. apparatus.   The antenna apparatus according to claim 1, wherein the film antenna is an inverted-F antenna, and an antenna main part of an antenna element is located outside the circuit board.   The film antenna is bent at a position of a feeding portion and a short-circuit portion of the antenna element, and is arranged so that a main surface of the antenna main portion is substantially perpendicular to a main surface of the circuit board. The antenna device according to claim 3.   An electronic apparatus comprising the antenna apparatus according to claim 1 in an electronic apparatus main body. An operation button is provided on a part of the side surface of the electronic device body,
The electronic apparatus according to claim 5, wherein the film antenna is disposed along a side surface of the circuit board on which the operation button is not provided.

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