WO2009130781A1

WO2009130781A1 - Planar antenna

Info

Publication number: WO2009130781A1
Application number: PCT/JP2008/057965
Authority: WO
Inventors: 智之藤枝; 雅美鈴木
Original assignee: パイオニア株式会社
Priority date: 2008-04-24
Filing date: 2008-04-24
Publication date: 2009-10-29
Also published as: CN102007643A; JPWO2009130781A1

Abstract

An antenna is constituted by providing a pair of elements (conductive wires) made of metal or the like on a surface of a planar base made of a dielectric. This antenna constitutes a so-called dipole antenna with the elements. Each element has a trunk part extending in the length direction of the base and a plurality of branch parts branched from the trunk part. With such structure, an effective path length can be gained as the element in a small space and the antenna itself can be downsized.

Description

Planar antenna

The present invention relates to a planar dipole antenna.

A film-like antenna used for pasting on a windshield of a vehicle is known. Examples of such a film antenna are described in Patent Documents 1 and 2.

The film antenna as described above generally has a structure in which a sheet on which an element is formed is attached to a windshield, and therefore cannot be reused after being attached once. For this reason, once a film-like antenna is pasted, the pasting position cannot be changed. Further, since the film antenna has an elongated sheet shape, the pasting operation is not always easy.

In addition, the body ground type antenna as described in Patent Document 1 needs to connect the ground wire to the metal body, so that the mounting position is restricted.

Japanese Patent Laid-Open No. 5-283921 JP 2007-194844 A

Examples of problems to be solved by the present invention include the above. An object of the present invention is to provide a planar antenna that is easy to attach because its shape is small and simple, and that can be reused.

The invention according to claim 1 is a planar antenna, comprising a planar substrate made of a dielectric, and a pair of elements provided on the substrate, each of the elements comprising: It has the trunk part extended in the length direction of the base material, and a plurality of branch parts branched from the trunk part.

It is a figure which shows the structure of the antenna which concerns on 1st Example. It is a figure which shows the structure of the antenna which concerns on 2nd Example. It is a figure explaining the taper shape of the antenna which concerns on 2nd Example. It is a figure which shows the structure of the antenna which concerns on 3rd Example. It is a figure which shows the structure of the other antenna which concerns on 3rd Example. It is a figure which shows the structure of the other antenna which concerns on 3rd Example. It is a figure which shows the structure of the antenna which concerns on various modifications. It is a figure explaining the use condition of an antenna.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Base material 5 Protective layer 7 Double-sided tape 10-10g Element 11-11g Trunk part 12-12g Branch part 13 Feeding point 20 Non-excitation element 100-100g Antenna

In a preferred embodiment of the present invention, the planar antenna includes a planar base material made of a dielectric and a pair of elements provided on the base material, each of the elements being the base. A trunk extending in a length direction of the material; and a plurality of branches branched from the trunk.

The antenna described above is configured by providing a pair of elements (conductive wires) such as metal on one surface of a planar substrate made of a dielectric. This antenna constitutes a so-called dipole antenna by a pair of elements. Each element has a trunk portion extending in the length direction of the base material and a plurality of branch portions branched from the trunk portion. With such a structure, an effective path length as an element can be obtained in a small space, and the antenna itself can be reduced in size.

In one aspect of the planar antenna, the plurality of branch portions are provided substantially symmetrically with the trunk portion as a center line. In this aspect, compared with the case where the branch portion is formed only on one side with the trunk portion as the center, the electrical characteristics as the antenna can be stabilized. Note that “substantially symmetrical” includes not only a symmetric shape but also a form in which a meander shape is partially formed as described later.

In another aspect of the planar antenna, a part of the plurality of branch portions has a meander shape.

In another aspect of the above planar antenna, each of the elements has a feeding point at one end of the trunk, and the plurality of branches have a longer length as the distance from the feeding point increases. In this aspect, the frequency characteristics can be expanded by making each element have a tapered shape.

In another aspect of the planar antenna, the feeding point is provided at a position shifted in the end direction from the center position in the length direction of the base material. Thereby, impedance matching is ensured and efficient power feeding is realized.

Another embodiment of the above planar antenna includes a non-excitation element provided on the base material and on a surface opposite to the surface on which the element is provided. Another aspect includes a non-excitation element provided on the base material, on the same surface as the surface on which the element is provided, or on another surface. Yet another embodiment includes a non-excitation element disposed on the base material and at a position not overlapping the element. Thereby, the frequency band of an antenna can be expanded using the resonance by the side of a non-excitation element. In a preferred example, the non-excitation element is provided at a position shifted from the center position in the length direction of the base material toward the feeding point.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[First embodiment]
FIG. 1 shows a configuration of a planar antenna 100 (hereinafter simply referred to as “antenna”) according to a first embodiment of the present invention. 1A is a plan view of the surface of the antenna 100, FIG. 1B is a side view of the antenna 100, and FIG. 1C is a plan view of the back surface of the antenna 100. FIG.

The antenna 100 includes a planar (thin flat plate) substrate 1 and a pair of elements (conductors) 10 provided on one surface of the substrate 1. The substrate 1 is made of a dielectric material such as a plastic film or rubber, but a rigid material (ceramics or the like) may be used. The pair of elements 10 constitute a dipole antenna.

Each element 10 is formed of a metal such as silver or copper, and has a trunk portion 11 that extends in the length direction of the substrate 1, and a plurality of branch portions 12 that branch out in a direction substantially perpendicular to the trunk portion 11, and A feeding point 13 provided at one end of the trunk 11. As described above, each element 10 has a corrugated shape or a fishbone-like shape (hereinafter referred to as “corrugated structure”) provided so that the plurality of branch portions 12 are substantially orthogonal to the trunk portion 11. By adopting the corrugated structure, the effective path length of the element 10 can be gained in a small space, and the overall dimensions of the antenna 100 can be reduced. That is, by adopting a corrugated structure, the element 10 can be electrically equivalent to one long linear element. By miniaturizing the antenna 100, the area occupied by the antenna 100 in the mounted portion can be reduced. This is particularly effective when the antenna 100 is attached to a windshield or the like of a vehicle, because it becomes easy to arrange the attachment position of the antenna 100 outside the driver's field of view.

In addition, in 1st Example, nothing is provided in the back surface (surface on the opposite side to the surface in which the element 10 was provided) of the base material 1. FIG.

In a preferred example of the present invention, the dimensions of the antenna 100 are a length L = 150 mm, a width W = 20 mm, and a thickness H = 5 mm. When an antenna having linear elements as in the above-mentioned Patent Document 2 is configured with the same electrical characteristics, the dimensions are, for example, length L = 235 mm, width W = 20 mm, and thickness H = 1 mm. It will be about. That is, according to the present invention, the length of the entire antenna can be considerably shortened by adopting the corrugated structure.

In the antenna 100, the pair of feeding points 13 are provided at positions shifted from the end of the base material 1 with respect to the center position in the length direction of the base material 1. Thereby, impedance matching can be taken and electric energy can be efficiently supplied from the feeding point to the antenna 100.

The plurality of branch portions 12 may be provided only on one side of the trunk portion 11, but in the first embodiment, they are provided symmetrically about the trunk portion 11 as a central axis as shown in the figure. In this way, by providing the plurality of branch portions 12 symmetrically with the trunk portion 11 as the central axis, the electrical characteristics as an antenna are stable compared to the case where the plurality of branch portions 12 are provided only on one side of the trunk portion 11. Can be

[Second Embodiment]
FIG. 2 shows a configuration of an antenna 100a according to the second embodiment of the present invention. 2A is a plan view of the surface of the antenna 100a, FIG. 2B is a side view of the antenna 100a, and FIG. 1C is a plan view of the back surface of the antenna 100a.

As shown in the drawing, the antenna 100a according to the second embodiment is configured by providing a pair of elements 10a on a base material 1 made of a dielectric, like the antenna 100 according to the first embodiment. However, in the antenna 100a according to the second embodiment, the shape of each element 10a is different from that of the antenna 100 according to the first embodiment. The antenna 100a of the second embodiment is the same as the antenna 100 of the first embodiment except for the shape of the element 10a.

As shown in the figure, the element 10 a includes a trunk portion 11, a plurality of branch portions 12 a extending in a direction substantially orthogonal to the trunk portion 11, and a feeding point 13. Here, the element 10a according to the second embodiment has a tapered shape in which the length of the branch portion 12a increases as the distance from the feeding point 13 increases. That is, the branch portion 12a located near the feeding point 13 has a shorter length in the direction perpendicular to the trunk portion 11, and the branch portion 12a located farther from the feeding point 13 has a length in the direction perpendicular to the trunk portion 11. It is getting longer.

Thus, the band of the antenna 100a can be widened by making the element 10a into a tapered shape. This is shown in FIG. FIG. 3A shows a frequency characteristic 51 of an antenna whose element is non-tapered as in the first embodiment, and a frequency characteristic 52 of an antenna whose element is tapered as in the second embodiment. By making the element have a tapered shape, the antenna characteristics can be widened.

As shown in FIG. 3B, the taper angle θ (θ1 and θ2) indicating the degree of the taper shape of the element 100a is determined according to the target characteristic of the antenna 100a.

Other than the above, the antenna 100a according to the second embodiment is the same as the antenna 100 according to the first embodiment. That is, by adopting the corrugated structure, the entire antenna can be reduced in size. The plurality of branch portions 12 are preferably provided symmetrically about the trunk portion 11 as a central axis, but may be provided only on one side of the trunk portion 11.

[Third embodiment]
FIG. 4 shows the planar shapes of the

antennas

100c and 100d according to the third embodiment of the present invention. In the third embodiment, one or more non-excitation elements (non-feed elements) 20 are provided on the back surface of the substrate 1, that is, the surface opposite to the surface on which the element 10 is formed. In the example of FIG. 4C, two non-excitation elements 20 are provided.

Specifically, the surface of the antenna 100c is the same as that of the antenna 100 according to the first embodiment as shown in FIG. 4A, but the non-exciting element 20 is formed on the back surface as shown in FIG. Is provided. A frequency characteristic of the antenna 100c is shown as a characteristic 61 in FIG.

Similarly, the surface of the antenna 100d is the same as that of the antenna 100a of the second embodiment as shown in FIG. 4 (b), but the excitation element 20 is provided on the back surface as shown in FIG. 4 (c). ing. The frequency characteristic of the antenna 100d is shown as a characteristic 62 in FIG.

Thus, by providing the non-excitation element 20 on the back surface of the substrate 1, the frequency characteristics of the antenna can be expanded. Specifically, the antenna can be broadened by double resonance caused by resonance by the elements on the front surface side of the

antennas

100c and 100d and resonance by the non-excitation element on the back surface side.

In addition, it is preferable that the position of the non-excitation element 20 on the back surface of the base material 1 is a position shifted to the feeding point 13 side from the center position in the length direction of the base material 1. Further, in the positional relationship between the non-excitation element 20 and the feeding point 13 in the longitudinal direction of the base material 1, an arrangement relationship is preferable in which the arrangement position of the feeding point 13 is placed at least at a part of the arrangement position of the non-excitation element 20. . In the example of FIG. 4C, the non-excitation element 20 is provided at a position shifted from the center position in the length direction of the base material 1 from the end on the side where the feeding point 13 is provided.

Further, the non-excitation element 20 is not limited to this arrangement. For example, as shown in FIG. 5A, the non-excitation element 20 may be disposed on the same surface as the surface on which the element is disposed. In that case, as shown in FIG. 5B, the non-excitation element 20 may be arranged along the tapered shape of the element 10.

Furthermore, as shown in FIGS. 6 (a) and 6 (b), the non-excitation element 20 may be disposed on the side surface of the substrate 1. 6A is a plan view of the antenna 100j when the non-excitation element 20 is disposed on both side surfaces of the substrate 1, and FIG. 6B is the antenna 100j when viewed in the direction of the arrow 72 in FIG. 6A. FIG. In the case where the non-excitation element 20 is disposed on the side surface of the substrate 1, one non-excitation element 20 may be provided only on one side surface.

[Modification]
Next, various modifications of the antenna according to the present invention will be described.

FIG. 7A shows a planar shape of an antenna 100e according to one modification. As illustrated, the interval between the branch portions 12e constituting the element 10e of the antenna 100e may not be constant. That is, the plurality of branch portions 12e may not be provided at equal intervals. In the example of FIG. 7A, the branch portion 12e has a portion provided at the interval p1 and a portion provided at the interval p2 (<p1).

FIG. 7B shows a planar shape of an antenna 100f according to another modification. As shown in the drawing, the width of the branch portion 12f in the length direction of the substrate 1 may not be constant. In the example of FIG. 7B, the width W1 of the branch portion 12f in the area 61 is smaller than the width W2 of the branch portion 12f in the area 62.

FIG. 7C shows a planar shape of an antenna 100g according to still another modification. As illustrated, a part of the element 10g may have a meander shape. In the area 64, the trunk portion 11g is located at the approximate center in the width direction of the base material 1, but in the area 63, the position of the trunk portion 11g is alternately shifted in the width direction of the base material 1 to form a so-called meander shape. In FIG. 7C, the element 10 is not completely symmetric with respect to the center line passing through the trunk portion 11g, but “substantially symmetric” in the present embodiment is such a part of the meander. The form which is a shape is also included.

[Example of use]
Next, a usage example of the antenna according to the embodiment will be described. FIG. 8 is a cross-sectional view showing an example of use of the antenna. In the antennas 100 to 100j according to each of the above-described embodiments and modifications, the protective layer 5 made of a resin or the like is provided on both surfaces (front and back surfaces) of the substrate 1 when used, and the double-sided adhesive sheet 7 such as a double-sided tape. It is affixed on the to-be-attached part 70 using. A typical example of the mounted portion is a windshield of a vehicle.

The antennas 100 to 100j of the present invention are affixed to the attached portion 70 using an adhesive sheet such as a double-sided tape. When it is desired to correct the pasting position after pasting once, the operator only has to peel off the adhesive sheet and replace it with a new one. That is, the antenna itself can be used any number of times.

The present invention can be used for a planar antenna that is used by being attached to a mounted portion. In a preferred example, the planar antenna is used by being attached to a windshield of a vehicle.

Claims

A planar substrate made of a dielectric;
A pair of elements provided on the substrate,
Each of the elements has a trunk extending in the length direction of the base material and a plurality of branches branched from the trunk.
The planar antenna according to claim 1, wherein the plurality of branch portions are provided substantially symmetrically with the trunk portion as a center line.
The planar antenna according to claim 2, wherein a part of the plurality of branch portions has a meander shape.
Each of the elements has a feeding point at one end of the trunk,
The planar antenna according to any one of claims 1 to 3, wherein the plurality of branch portions are longer in length as the distance from the feeding point is longer.
The planar antenna according to any one of claims 1 to 4, wherein the feeding point is provided at a position shifted in an end direction from a center position in a length direction of the base material. .
The planar antenna according to any one of claims 1 to 5, further comprising a non-excitation element provided on the base material and on a surface opposite to a surface on which the element is provided. .
6. The flat surface according to claim 1, further comprising a non-excitation element provided on the base material on the same surface as the surface on which the element is provided or on another surface. Antenna.
The planar antenna according to any one of claims 1 to 5, further comprising a non-excitation element disposed on the base material so as not to overlap the element.
The planar shape according to any one of claims 6 to 8, wherein the non-excitation element is provided at a position shifted from the center position in the length direction of the base material to the feeding point side. antenna.