JP2017063345A - Planar antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a planar antenna capable of setting the antenna gain and half-value angle appropriately according to the request, with simple configuration.SOLUTION: A planar antenna 2 includes, as a radiator, a patch 4 formed on a dielectric substrate 6 and, as a baseplate, and a metal plate 8 placed on the surface of the dielectric substrate 6, oppositely to the patch 4, with a predetermined interval by a spacer 12. In this planar antenna 2, when the thickness of an air layer 9 is increased, the antenna gain increases and the half-value angle becomes narrower. Conversely, when the thickness of the dielectric substrate 6 is increased, the antenna gain decreases and the half-value angle becomes wider. Consequently, a planar antenna ensuring desired antenna gain and half-value angle can be achieved easily.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a planar antenna in which a radiator and a ground plane are arranged with a dielectric layer in between.

  In general, in a planar antenna, a conductor layer constituting a patch or a microstrip line as a radiator is formed on one surface of a dielectric substrate serving as a dielectric layer, and a ground plane ( It is configured by forming a conductor layer serving as a ground pattern.

  Also, in this type of planar antenna, antenna gain is obtained by laminating a plurality of dielectric layers including an air layer on the surface of the dielectric substrate on which the radiator is formed (that is, the radiation direction of the planar antenna). Has been proposed (see, for example, Patent Document 1).

Japanese Patent No. 4128686

  However, in the proposed planar antenna, the multilayer dielectric layer arranged in the radiation direction of the radio wave functions as a director, and although the antenna gain can be increased as compared with the antenna without the multilayer dielectric layer, There is a problem that the half-value angle becomes narrow and the communicable range is limited.

The half-value angle is a radiation angle at which the antenna gain is halved (-3 dB) when the central axis that maximizes the antenna gain in the radio wave radiation direction is 0 degree.
For this reason, the proposed technique cannot meet the demand for expanding the half-value angle (and thus the communicable range) even at the sacrifice of the antenna gain.

  In addition, the proposed planar antenna requires a multilayer dielectric layer to be laminated on the conductor layer side of the dielectric substrate on which the conductor layers constituting the radiator and the ground plane are formed, and thus the manufacturing process becomes complicated. There is also a problem.

  The present invention has been made in view of these problems, and an object of the present invention is to provide a planar antenna that can appropriately set an antenna gain and a half-value angle as required and that has a simple configuration.

  The planar antenna of the present invention includes a first conductor layer that constitutes a radiator, and a second conductor layer that is disposed at a distance from the first conductor layer and that constitutes a ground plane for the radiator. And a plurality of dielectric layers including an air layer as an intermediate layer between the first conductor layer and the second conductor layer.

  Therefore, unlike the conventional planar antenna described above, it is not necessary to arrange the dielectric layer and the multilayer dielectric layer so as to sandwich the radiator, so that the device configuration is simplified and manufactured compared to the conventional planar antenna. Can be made easier.

  The intermediate layer is composed of a plurality of dielectric layers including an air layer. If the thickness of the air layer in the intermediate layer is increased, the antenna gain is increased and the half-value angle is reduced. Conversely, if the thickness of the dielectric layer is increased, the antenna gain is decreased and the half-value angle is increased.

  Therefore, according to the planar antenna of the present invention, a planar antenna capable of obtaining a desired antenna gain and half-value angle can be easily realized by appropriately adjusting the thicknesses of the air layer and the dielectric layer constituting the intermediate layer. .

  Here, as the intermediate layer, for example, a pair of dielectric layers may be arranged so as to sandwich the air layer, or more air layers and dielectric layers may be stacked. On the other hand, in order to make the configuration of the planar antenna simpler, the intermediate layer may be composed of one air layer and one dielectric layer.

  In this case, the first conductor layer is laminated on the dielectric layer, and the second conductor layer is disposed on the opposite side of the dielectric layer from the first conductor layer with the air layer interposed therebetween. If it does so, the intensity | strength of a planar antenna can be ensured by thickening the thickness of the ground plane which comprises a 2nd conductor layer.

  Further, in this case, when the patch antenna patch is formed with the first conductor layer constituting the radiator, the size in the surface direction of the patch laminated on the dielectric layer is the same as the dielectric layer, Alternatively, it may be smaller than the dielectric layer. In addition, the size of the dielectric layer facing the second conductor layer across the air layer is the same as the second conductor layer or smaller than the second conductor layer. Good.

It is a perspective view showing the appearance of the planar antenna of an embodiment. It is a top view showing the state which looked at the planar antenna from the patch side which is a radiator. It is explanatory drawing showing the cross-section of a planar antenna. It is a perspective view showing the external appearance of the planar antenna of a modification. It is explanatory drawing showing the cross-section of the planar antenna of a reference example.

Embodiments of the present invention will be described below with reference to the drawings.
The planar antenna 2 of this embodiment is used, for example, for reading identification information from an RFID tag, and is configured as a patch antenna that can radiate circularly polarized radio waves.

  Therefore, as shown in FIGS. 1 to 3, the planar antenna 2 includes a dielectric substrate 6 on which a patch 4 constituting a radiator of a patch antenna is formed (laminated), and a patch 4 on the dielectric substrate 6. And a metal plate 8 disposed at a predetermined interval with respect to the opposite plate surface.

  The metal plate 8 is a second conductor layer that constitutes the ground plane of the planar antenna 2, and sandwiches the dielectric substrate 6 and the intermediate layer 10 including the air layer 9 between the dielectric substrate 6 and the first plate. They are arranged so as to be parallel to the patch 4 which is a conductor layer.

  Further, five spacers 12 made of an insulating material such as a synthetic resin are provided between the dielectric substrate 6 and the metal plate 8, and the distance between the dielectric substrate 6 and the metal plate 8 is determined by this spacer. 12 at regular intervals.

  The dielectric substrate 6 and the metal plate 8 have the same size and shape in the opposing surface direction, and the size in the surface direction of the patch 4 is the same as that of the dielectric substrate 6 on which the patch 4 is laminated. It is smaller than the substrate surface.

  As shown in FIG. 2, the patch 4 is substantially square, and the five spacers 12 are on the diagonal line connecting the substantially center position of the patch 4 and the four corners (corner portions) of the patch 4 through the center position. It is arrange | positioned at four places, respectively.

  In the patch 4, the positions where the impedance becomes a predetermined value (for example, 50Ω) on the two central axes 14 a and 14 b parallel to two sides orthogonal to each other are feed points 16 a and 16 b for circularly polarized wave transmission / reception. Is set.

A central axis of a coaxial cable (not shown) inserted from the metal plate 8 side is connected to the feeding points 16a and 16b, and an outer conductor of the coaxial cable is connected to the metal plate 8.
Thus, the planar antenna 2 of the present embodiment is an intermediate between the patch 4 that is the first conductor layer constituting the radiator and the metal plate 8 that is the second conductor layer constituting the ground plane. The layer 10 includes a dielectric substrate 6 that is a dielectric layer and an air layer 9.

  Table 1 shows that in the planar antenna 2 of the present embodiment configured as described above, the thickness of the air layer 9 where the thickness of the entire intermediate layer 10 is 8.2 mm and the dielectric constant ε is about 1.0 is 0 to 0. The measurement result which measured the change of an antenna gain and a half-value angle when changing to 8.2 mm is represented.

この測定結果から明らかなように、中間層１０全体の厚みを一定にした場合、空気層９の厚みを大きくして、誘電体基板６の厚みを小さくすれば、アンテナ利得が高く、半値角度が狭い（換言すれば指向性の鋭い）平面アンテナを実現できる。

As is clear from this measurement result, when the thickness of the entire intermediate layer 10 is constant, if the thickness of the air layer 9 is increased and the thickness of the dielectric substrate 6 is decreased, the antenna gain is increased and the half-value angle is reduced. A narrow planar antenna (in other words, sharp directivity) can be realized.

  Conversely, if the thickness of the dielectric substrate 6 is increased and the thickness of the air layer 9 is decreased, a planar antenna having a wide half-value angle (in other words, a wide transmission and reception range) can be realized although the antenna gain is reduced. .

  Therefore, according to the planar antenna 2 of the present embodiment, a planar antenna that can obtain a desired antenna gain and a half-value angle can be easily obtained by appropriately adjusting the thicknesses of the dielectric substrate 6 and the air layer 9 constituting the intermediate layer 10. Can be realized.

  Further, in order to increase the antenna gain, it is not necessary to dispose a multilayer dielectric layer on the radiation surface of the planar antenna (the substrate surface of the dielectric substrate 6 on which the patch 4 is disposed) as in the prior art. Further, the dielectric substrate 6 having the patch 4 can be formed of a printed wiring board.

  For this reason, the planar antenna 2 of the present embodiment is simply configured by simply arranging a printed wiring board on which a conductor layer to be the patch 4 is formed and a metal plate 8 to be the ground plane in parallel with a space therebetween. Manufacturing cost can be reduced.

As mentioned above, although one Embodiment of this invention was described, this invention is not limited to the said embodiment, A various aspect can be taken in the range which does not deviate from the summary of this invention.
For example, in the embodiment described above, the dielectric substrate 6 and the metal plate 8 have the same shape and size in the opposing surface direction, and the dielectric substrate 6 is described as being larger than the patch 4. On the other hand, the size in the surface direction of the dielectric substrate 6 on which the patch 4 is disposed may be the same as that of the patch 4 and smaller than the metal plate 8 as shown in FIG.

  When the planar antenna 2 is configured in this way, there is no dielectric substrate 6 outside the plate surface of the patch 4 and the periphery of the plate surface of the patch 4 becomes an air layer. Therefore, as shown in Table 2, the dielectric substrate 6 The antenna gain can be increased as compared with the case where the size of is equal to that of the metal plate 8. However, in this case, the half-value angle becomes narrow.

従って、本実施形態の平面アンテナ２によれば、パッチ４を配置する誘電体基板６の大きさを調整することによっても、アンテナ特性（アンテナ利得、半値角度）を任意に設定することができる。

Therefore, according to the planar antenna 2 of the present embodiment, the antenna characteristics (antenna gain, half-value angle) can be arbitrarily set by adjusting the size of the dielectric substrate 6 on which the patch 4 is arranged.

  Next, in the above-described embodiment, the patch 4 serving as the radiator of the patch antenna is formed on the dielectric substrate 6, and the metal plate 8 serving as the ground plate is disposed with a space from the dielectric substrate 6. However, a conductor layer serving as a ground plane may be formed on another dielectric substrate.

In this case, if the two dielectric substrates are arranged with the ground plate and the patch outside and spaced apart from each other, the planar antenna 2 that can obtain the same effect as the above embodiment can be realized.
Further, the same effect can be obtained by configuring the patch 4 with a metal plate, forming a conductor layer serving as a ground plate on the dielectric substrate, and arranging them at a predetermined interval.

The shape of the patch 4 does not have to be a square, and may be, for example, a circle, an ellipse, or a rectangle.
Moreover, although the said embodiment demonstrated as what uses the spacer 12 in order to form the air layer 9, for example, the dielectric board 6 in which the patch 4 was formed, or the metal plate 8 used as a ground plane is a synthetic resin case. The air layer 9 may be formed by being housed inside. That is, you may make it form the air layer 9 with the fixing member which fixes these each part in a case.

  In the above embodiment, the feeding point to the patch 4 has been described as two points (16a, 16b) arranged on the central axes orthogonal to each other. For example, the feeding point to the patch 4 is There may be one place, or three places or more.

  In the above embodiment, the planar antenna 2 is described as constituting a patch antenna. However, for example, by forming a microstrip line having a predetermined shape on the dielectric substrate 6, a radiator is configured. May be.

As a reference example of the present invention, FIG. 5 shows a planar antenna 2A having a configuration different from that of the above embodiment.
As shown in FIG. 5, the planar antenna 2 </ b> A of this reference example is the same as the planar antenna 2 of the above-described embodiment, where the formation (lamination) surface of the patch 4 on the dielectric substrate 6 faces the metal plate 8 with the air layer 9 in between In this manner, the dielectric substrate 6 and the metal plate 8 are connected via the spacer 12.

  In the planar antenna 2A of the reference example configured as described above, the dielectric substrate 6 functions as a director for the patch 4 (that is, the radiator). Can be increased. However, since the space between the patch 4 as the radiator and the metal plate 8 as the ground plane becomes the air layer 9, the half-value angle is adjusted by the thickness of the air layer 9 (in other words, the height of the spacer 12). it can.

  DESCRIPTION OF SYMBOLS 2 ... Planar antenna, 4 ... Patch (radiator, 1st conductor layer), 6 ... Dielectric substrate (dielectric layer), 8 ... Metal plate (2nd conductor layer), 9 ... Air layer, 10 ... intermediate layer, 12 ... spacer, 14a, 14b ... central axis, 16a, 16b ... feeding point.

Claims (4)

A first conductor layer constituting the radiator;
A second conductor layer disposed at a distance from the first conductor layer and constituting a ground plane for the radiator;
With
A planar antenna comprising a plurality of dielectric layers including an air layer as an intermediate layer between the first conductor layer and the second conductor layer. The intermediate layer includes one air layer and one dielectric layer,
The first conductor layer is laminated on the dielectric layer;
2. The planar antenna according to claim 1, wherein the second conductor layer is disposed on the opposite side of the dielectric layer from the first conductor layer with the air layer interposed therebetween. The first conductor layer constitutes a patch antenna patch as the radiator,
The planar antenna according to claim 2, wherein the size of the patch in the surface direction is the same as or smaller than that of the dielectric layer.   In the dielectric layer, the size of the facing surface facing the second conductor layer across the air layer is the same as the second conductor layer or the second conductor layer The planar antenna according to claim 3, which is smaller than the planar antenna.

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