JP2022182168A - antenna device - Google Patents

Abstract

To provide an antenna device that is composed of a plurality of antennas not sharing a ground plate, and that can suppress mutual interference between antennas and take even size reduction into consideration.SOLUTION: A first and a second antenna which constitute an antenna device and correspond to a common frequency band are so arranged as to form a slit having both ends made open between a first ground plate and a second ground plate that the first antenna and second antenna has respectively. The slit is so formed as to resonate in the frequency band that the first antenna and second antenna correspond to.SELECTED DRAWING: Figure 4

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna device configured with a plurality of antennas and used in equipment having communication functions.

In recent years, wireless data communication systems such as wireless LAN, WiMAX (registered trademark), WiFi (registered trademark), and BlueTooth (registered trademark) have been adopted for a wide variety of devices represented by information terminal devices. The demand for antennas used for communications is increasing.

Also, in order to improve the communication speed, there is a situation in which a single communication device is equipped with a large number of antennas.

A problem that arises when multiple antennas are mounted on a single communication device is the deterioration of communication characteristics due to mutual interference between antennas. Various methods have been proposed to suppress mutual interference between antennas. .

As methods for reducing mutual interference between antennas, a method of providing a slit in the ground between the antennas (Patent Document 1), a method of providing a projecting portion on the ground plate between the antennas (Patent Document 2), and the like have been proposed. However, since these methods share a ground plate with multiple antennas, the phenomenon in which the high-frequency current supplied to one antenna flows into the other antenna via the ground plate cannot be completely suppressed, resulting in mutual interference. In some cases, the reduction effect is insufficient.

Mutual interference can be reduced by eliminating sharing of ground planes by a plurality of antennas, but mutual interference caused by spatial propagation of radio waves still remains. As a method of reducing mutual interference when a plurality of antennas do not share a ground plate, a method of providing shielding plates between antennas has been proposed (Patent Document 3).

However, the method of installing a shielding plate between antennas requires securing a place for installing the shielding plate between the antennas, and the shielding plate itself has a certain area and volume, so it is difficult to reduce the size of the antenna. However, it is difficult to adopt this method when the space for mounting an antenna in a communication device is limited.

JP 2007-13643 A JP 2013-51644 A JP 2015-70408 A

SUMMARY OF THE INVENTION An object of the present invention is to provide an antenna device that is configured by a plurality of antennas that do not share a ground plate and that is capable of suppressing mutual interference between the antennas and is also designed to reduce the size of the antenna device.

As a result of intensive studies on the structure of the antenna and the method of arranging it in the apparatus, the present inventor found that by bringing the ground plates of the respective antennas close to each other at a predetermined length and distance, the spatial propagation of radio waves can be achieved even without shielding plates. The resulting mutual interference can be suppressed, and as a result, an antenna device that achieves miniaturization has been realized.

The following effects can be expected from the antenna device of the present invention.

(1) Since each antenna does not share a ground plate, mutual interference between antennas through the ground plate does not occur in principle.

(2) Mutual interference caused by spatial propagation of radio waves can be suppressed without additional members such as shielding plates, which contributes to miniaturization of the antenna device.

It is a basic configuration of the antenna device of the present invention. FIG. 4 is a conceptual diagram of the interference suppression effect of the antenna device of the present invention; It is a modification of the antenna device of the present invention. It is a particularly preferred variant of the antenna device of the invention. It is an antenna device of a comparative example. V. of the antenna used in Example 1 S. W. is R. It is the isolation between the antennas of Example 1. FIG. V. of the antenna used in Example 2. S. W. is R. It is the isolation between the antennas of Example 2. FIG. V. of the antenna used in Example 3 S. W. is R. It is the isolation between the antennas of Example 3. FIG. V. of the antenna used in the comparative example. S. W. is R. It is the isolation between the antennas of the comparative example.

The present invention will be described below with reference to FIG.

The antenna device 1 of the present invention, as shown in FIG. 1, has a first antenna A1 and a second antenna A2.

The first antenna A1 is connected to the first ground plate 11, the first radiation element portion 21 extending from the contour side of the first ground plate 11, and the first feeding point P1 provided on the first radiation element portion 21. It is composed of the first feeder line 31 and is configured to be able to transmit or receive a signal in an arbitrary frequency band f. In FIG. 1, the first radiation element portion 21 extends vertically from the contour side of the first ground plate 11, but the extension direction of the first radiation element portion 21 is not limited to this.

The second antenna A2 is connected to the second ground plate 12, the second radiation element portion 22 extending from the contour side of the second ground plate 12, and the second feeding point P2 provided on the second radiation element portion 22. It is configured with the second feeder line 32 . Also, in principle, the second antenna A2 is configured to be able to transmit or receive signals in the frequency band f, like the first antenna A1. In FIG. 1, the second radiation element portion 22 extends vertically from the contour side of the second ground plate 12, but the extending direction of the second radiation element portion 22 is not limited to this.

A characteristic feature of the present invention is that the first ground plate 11 and the second ground plate 12 are opposed to each other so that a slit S with both ends opened is formed between the first ground plate 11 and the second ground plate 12 . It is to place

At this time, the slit S is formed so that the first antenna A1 and the second antenna A2 resonate in the corresponding frequency band f.

In order to form the slit S so as to resonate in the frequency band f, in principle, the length of the slit S should be approximately the wavelength λ of the radio waves in the frequency band f transmitted and received by the first antenna A1 and the second antenna A2. Set to 1/2.

The length of approximately half of the wavelength λ does not have to be exactly half of λ, and if half of λ is used as a reference, it may vary depending on the actual usage of the antenna device 1. is allowed.

It should be noted that the length of the slit S does not necessarily have to be set to approximately half the wavelength λ, and the length is determined by prioritizing that the slit S resonates in the frequency band f. For example, when the antenna device 1 of the present invention is housed in a housing of a communication device or the like, there is a dielectric material around the antenna device 1, and the wavelength shortening effect of the dielectric is affected. Alternatively, the length of the slit S may be set to a value in consideration of the wavelength shortening effect.

In the present invention, since the first antenna A1 and the second antenna A2 are electrically independent,
In principle, the high-frequency current supplied to the first antenna A1 does not flow into the second antenna A2, and vice versa.

Furthermore, in the present invention, mutual interference due to spatial propagation is suppressed by the presence of the slit S with both ends opened between the first ground plate 11 and the second ground plate 12 .

When the antenna device 1 performs communication, a high-frequency current corresponding to the frequency band f flows through the first ground plate 11 and the second ground plate 12 as well. Due to the presence of the slit S that resonates at f, slit resonance is generated in the slit S due to this high-frequency current.

When resonance occurs in the slit S, the slit S functions as a slit antenna that radiates radio waves corresponding to the frequency band f, as shown in FIG. That is, it can be said that the slit S is formed to imitate a slit antenna capable of radiating signals in the frequency band f.

Since there is a slit S between the first antenna A1 and the second antenna A2 that emits a radio wave corresponding to the frequency band f corresponding to both antennas A, the radio wave directed from the first antenna A1 to the second antenna A2 is present. is weakened by the interference of radio waves generated by the resonance of the slit S, and the interference of the first antenna A1 to the second antenna A2 due to spatial propagation is suppressed, as shown in FIG.

Similarly, the radio waves traveling from the second antenna A2 to the first antenna A1 are also weakened by the interference of the radio waves generated by the resonance of the slit S, resulting in the propagation of the radio waves from the second antenna A2 to the first antenna A1 due to spatial propagation. Interference is also suppressed.

In this way, the spatial propagation from the first antenna A1 to the second antenna A2 and the spatial propagation from the second antenna A2 to the first antenna A1 are each reduced. Mutual interference occurring between the antenna A1 and the second antenna A2 is suppressed.

As described above, in the present invention, mutual interference can be suppressed without requiring an additional member such as a shielding plate, and in order to form the slit S, the first antenna A1 and the second antenna A2 can be arranged close to each other. This contributes to miniaturization of the antenna device 1.

In the present invention, the first antenna A1 and the second antenna A2 are arranged close to each other. is ensured, and this point also contributes to suppression of mutual interference occurring between the first antenna A1 and the second antenna A2.

The width of the slit S is set so that the slit S functions as a slit antenna, and is usually set to about 1 to 5 mm.

Moreover, it is preferable that the slit S in the present invention has a shape having a bent portion as shown in FIGS.

When the slit S has a shape with a bent portion, radiation due to resonance of the slit S is generated in multiple directions, so that spatial propagation, which could not be sufficiently reduced by the linear slit S, can be reduced. Contributes to stabilization of the interference suppression effect.

Moreover, when the slit S having a bent portion is formed as shown in FIG. This contributes to miniaturization of the antenna device 1 .

The shape of the slit S can be set to any shape within the scope of the technical idea of the present invention. A curved shape is preferable. When forming the substantially L-shaped slit S, as shown in FIG. Since it can be formed by changing, the slit S having the bent portion can be formed with little effort.

Note that the substantially L-shaped slit S refers to a slit S in which the bending angle of the bent portion is 90°, but the bending angle does not have to be strictly 90°, and some variation is allowed.

When the slit S is formed in a substantially L shape, L1:L2 is set within the range of 2:1 to 1:2, where L1 is the length of the horizontal portion and L2 is the length of the vertical portion. is preferred.

This setting is based on the L1:L2 ratio of 1:1, and is intended not to change significantly from the standard.

By setting L1:L2 within the above range, the resonance generated in the slit S is stabilized, and a stable mutual interference suppression effect can be obtained.

In addition, in the present invention, by considering the positional relationship of the radiating element sections 20 of the antennas A, it is possible to obtain a better effect of suppressing mutual interference between the antennas A. FIG.

Specifically, as shown in FIGS. 3 and 4, the contour sides of the first ground plate 11 from which the first radiation element portion 21 extends and the second ground plate 12 from which the second radiation element portion 22 extends It is preferable that the positional relationship of the contour sides of is substantially perpendicular.

By providing the radiating element section 20 in such a positional relationship, the direction of the directivity main axis of the first antenna A1 and the direction of the directivity main axis of the second antenna A2 will be different, and the radio waves transmitted and received by each antenna A will differ. , and the effect of suppressing mutual interference between antennas A is stabilized.

The shape of the radiating element portion 20 of the antenna A used in the present invention is not limited to a specific shape, and various shapes can be used according to desired communication characteristics. In addition to linear elements that function as inverted F-shaped antennas, those that have folded structures such as U-shaped or meander-shaped antennas, branched elements that correspond to multiple frequencies, etc. can be used. A parasitic element may be provided for capacitively coupling with 20 to develop antenna characteristics. 1 and 2 show the radiating element portion 20 having a folded structure as an example.

The antenna A used in the present invention is an antenna element or an antenna element integrally formed by punching out a single metal plate having a thickness of about 0.1 to 1 mm made of nickel silver (cupronickel), copper, iron, brass, steel, or the like. , an antenna element in which a conductive pattern is provided on a dielectric substrate, or an antenna element in which both are combined.

As the feeder line 30 used in the present invention, a well-known high-frequency coaxial cable such as a fluororesin-coated cable may be used. In order to connect the inner conductor or the outer conductor of this high-frequency coaxial cable to a predetermined location of the antenna A, fixing by soldering or fixing by caulking may be used.

The antenna device 1 of the present invention is used by being incorporated in a communication device.

As an embodiment of the present invention, an antenna device 1 shown in FIGS. 1 to 3 was produced and evaluated. Hereinafter, a method of making and evaluating an antenna device, which is common to each embodiment, will be described.

1. Preparation of Antenna A galvanized steel plate having a thickness of 0.4 mm is punched out to prepare an antenna element having a ground plate 10 of a predetermined shape and a radiating element portion 20 .
In each embodiment, the same basic shape of the radiating element section 20 having a folded structure is used, and the detailed dimensions are an antenna capable of transmitting or receiving radio waves in the wireless LAN band (2.45 GHz band, wavelength λ≈122 mm). configured to function as

As the feeder line 30, a coaxial cable including an inner conductor, a fluororesin (PFA) insulator, an outer conductor, and a PFA jacket was prepared.
The tip of the coaxial cable was step-stripped, and an internal conductor was soldered to a predetermined location of the radiating element section 20 to form a feeding point P. As shown in FIG.
An external conductor was soldered to a predetermined location on the ground plate 10 to form a ground point G, and the antenna A was completed.
A well-known coaxial cable connector is provided on the opposite side of the coaxial cable so that it can be connected to a high frequency circuit.

2. Fabrication of Antenna Apparatus The first antenna A1 and the second antenna A2 fabricated according to the fabrication method of the antenna A described above are arranged so that the first ground plate 11 and the second ground plate 12 face each other to form a slit S. The antenna device 1 was completed by fixing it on the resin base material. The length of the slit S is set to a dimension that causes resonance in the slit S, taking into account the effect of shortening the wavelength due to the presence of the resin base material.

3. Evaluation of Antenna Apparatus A high-frequency signal of 2.45 GHz band was fed to each of the first antenna A1 and the second antenna A2. S. W. Mutual interference (isolation) generated between R and the first antenna A1 and the second antenna A2 was measured.

[Example 1]
As Example 1, an antenna device 1-1 having the configuration shown in FIG. 1 was produced. In Example 1, the same antenna was used as the first antenna A1-1 and the second antenna A2-1. The size of the ground plate 10 of each antenna A was 27 mm×24.5 mm, and the contour sides of 27 mm in length were arranged to face each other to form a slit S of 27 mm in length and 3 mm in width. The outer dimensions of the antenna device 1 are 27 mm×52 mm. The radiation element portion 20 extends perpendicularly to the ground plate 10 from the contour side opposite to the contour side of the ground plate 10 forming the slit S. As shown in FIG.

V. of the antenna device 1-1 of the first embodiment. S. W. FIG. 6 shows R and FIG. 7 shows isolation. In FIG. 6, the solid line indicates the V.V. of the first antenna A1-1, and the dashed line indicates the V.V. of the second antenna A2-1. S. W. is R.

[Example 2]
As Example 2, an antenna device 1-2 having the configuration shown in FIG. 3 was produced. In Example 2, the same first antenna A1-1 used in Example 1 was used as the first antenna A1-2. The second antenna A2-2 is based on the second antenna A2-1 used in Example 1, and from the second ground plate 12a with a size of 27 mm×24.5 mm, an L-shaped antenna with a length of 27 mm×width of 5 mm. The structure is such that the extension part 12b is extended. The length of the extending portion 12b is the dimension at the center of the extending portion 12b in the width direction.

In Example 2, the positional relationship between the contour side of the first ground plate 11 from which the first radiation element portion 21 extends and the contour side of the second ground plate 12 from which the second radiation element portion 22 extends is substantially perpendicular. A first antenna A1 and a second antenna A2 were arranged as above, and an L-shaped slit S with a width of 3 mm was formed between the ground plates. The length of the slit S is the dimension at the center in the width direction of the slit S. The length L1 of the horizontal portion is 9.5 mm, the length L2 of the vertical portion is 28.5 mm, and the total length is 38 mm. The external dimensions of the antenna device 1 are 40 mm×54 mm.

V. of the antenna device 1-2 of the second embodiment. S. W. FIG. 8 shows R and FIG. 9 shows isolation. In FIG. 8, the solid line indicates the V.V. of the first antenna A1-2, and the dashed line indicates the V.V. of the second antenna A2-2. S. W. is R.

[Example 3]
As Example 3, an antenna device 1-3 having the configuration shown in FIG. 4 was produced. In Example 3, the first antenna A1-3 is based on the first antenna A1-1 used in Example 1, and the first ground plate 11a having a size of 27 mm x 24.5 mm is extended to a length of 32 mm x width of 5 mm. The linear extension portion 11b of the is extended. As the second antenna A2-3, the same antenna as the second antenna A2-1 used in Example 1 was used.

In Example 3, the positional relationship between the contour side of the first ground plate 11 from which the first radiation element portion 21 extends and the contour side of the second ground plate 12 from which the second radiation element portion 22 extends is substantially perpendicular. A first antenna A1 and a second antenna A2 were arranged as above, and an L-shaped slit S with a width of 3 mm was formed between the ground plates. The length of the slit S is the dimension at the center in the width direction of the slit S. The length L1 of the horizontal portion is 28.5 mm, the length L2 of the vertical portion is 20.5 mm, and the total length is 49 mm. The external dimensions of the antenna device 1 are 32 mm×56 mm.

V. of the antenna device 1-3 of the third embodiment. S. W. FIG. 10 shows R and FIG. 11 shows isolation. In FIG. 10, the solid line indicates the V.V. of the first antenna A1-2, and the dashed line indicates the V.V. of the second antenna A2-2. S. W. is R.

[Comparative example]
As a comparative example, an antenna device 1' having the aspect shown in FIG. 5 was produced. The antenna device 1' of the comparative example is a mode in which the extending portion 11b is omitted from the antenna device 1-2 of the second embodiment, and sufficient resonance does not occur in the slit S' between the ground plates 10'. It's becoming

V. of the antenna device 1' of the comparative example. S. W. FIG. 12 shows R and FIG. 13 shows isolation. 12, the solid line indicates the V.V. of the first antenna A1' and the dashed line indicates the V.V. of the second antenna A2'. S. W. is R.

V.V. of each antenna constituting the antenna devices of Examples 1 to 3 and Comparative Example S. W. R decreases near 2450 MHz (2.45 GHz) and V. S. W. On R, it has necessary and sufficient performance as an antenna device used in the 2.45 GHz band.

On the other hand, when checking the isolation of each antenna device, the isolation between the antennas A' in the antenna device 1' of the comparative example was approximately -12 dB in the vicinity of 2.45 GHz.

Compared to the antenna device 1' of the comparative example, the isolation between the antennas A in the antenna device 1-1 of the first embodiment in which the linear slit S is provided between the antennas A is approximately -17 dB in the vicinity of 2.45 GHz. , which is an improved value compared to the comparative example.

From the above, it was confirmed that the mutual interference between the antennas A can be suppressed by providing the slit S whose length is set so that resonance occurs between the antennas A.

Further, in the antenna device 1-2 of Example 2 in which the L-shaped slit S is provided between the antennas A, the isolation between the antennas A is reduced to about -19 dB, which is slightly improved compared to Example 1. . From this result, it was confirmed that the effect of suppressing mutual interference between the antennas A was improved by providing the slits S having bent portions between the antennas A. FIG.

Furthermore, an L-shaped slit S is provided between the antennas A, and the ratio L1:L2 between the length L1 of the horizontal portion and the length L2 of the vertical portion of the slit S is set to 1.39:1, which is close to 1:1. In the set antenna device 1-3 of Example 3, the isolation between the antennas A was reduced to about -23 dB. It was confirmed that the interference between the antennas A can be suppressed more effectively by providing a slit S having a bent portion between the antennas A and considering the dimensional ratio between the horizontal portion and the vertical portion thereof.

An antenna device compatible with the wireless LAN band (2.45 GHz band) has been described above, but this is merely an example of the present invention. It goes without saying that it can also be applied to In particular, the specific configuration of the antenna used in the antenna device is not limited to the examples described above, and various conventionally proposed antenna configurations can be appropriately selected and used within the scope of the idea of the present invention. .

Also, the number of antennas constituting the antenna device of the present invention is not limited to two, and the antenna device may be constructed using three or more antennas. When three or more antennas are used, it is not always necessary to form slits between the ground plates of all antennas. Depending on the desired performance of the antenna device, slits are formed only between the ground plates of two selected antennas. It is good also as the aspect which formed.

INDUSTRIAL APPLICABILITY The antenna device of the present invention can be applied to various devices having communication functions, and can be suitably used for industrial devices used in IoT, information appliances having communication functions, automobile-related equipment, access points, and the like.

1 Antenna Device A Antenna A1 First Antenna A2 Second Antenna 10 Ground Plates 11, 11a First Ground Plate 11b First Ground Plate Extensions 12, 12a Second Ground Plate 12b Second Ground Plate Extension 20 Radiation Element portion 21 First radiation element portion 22 Second radiation element portion 30 Feeding line 31 First feeding line 32 Second feeding line S Slit P Feeding point P1 First feeding point P2 Second feeding point G Ground point G1 First ground point G2 2nd earth point

Claims (7)

An antenna device having a first antenna and a second antenna,
The first antenna includes a first ground plate, a first radiation element portion extending from the contour side of the first ground plate, and a first feed connected to a first feeding point provided on the first radiation element portion. It consists of a line and
The second antenna includes a second ground plate, a second radiation element portion extending from the contour side of the second ground plate, and a second antenna connected to a second feeding point provided on the second radiation element portion. It is composed of a power supply line and
The first antenna and the second antenna transmit or receive radio waves in a common frequency band,
An antenna device, wherein the first ground plate and the second ground plate are opposed to each other so that a slit with both ends opened is formed between the first ground plate and the second ground plate. 2. The antenna device according to claim 1, wherein said slit is formed so as to resonate in said frequency band. 3. The antenna device according to claim 1, wherein the length of said slit is approximately half the wavelength of radio waves in said frequency band. 4. The antenna device according to any one of claims 1 to 3, wherein the slit has a bent portion. 5. The antenna device according to claim 4, wherein the slit is bent in a substantially L shape. When the length of the horizontal part of the substantially L-shaped slit is L1 and the length of the vertical part is L2,
6. The antenna device according to claim 5, wherein L1:L2 is in the range of 2:1 to 1:2. A positional relationship between a contour side of the first ground plate from which the first radiation element extends and a contour side of the second ground plate from which the second radiation element extends is substantially perpendicular. The antenna device according to any one of claims 1 to 6, wherein:

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