JP5189004B2 - Monopole antenna - Google Patents

Description

  The present invention relates to a monopole antenna, and more particularly to a monopole antenna for UWB (Ultra Wide Band).

  Wireless communication using UWB is attracting attention as a large-capacity communication means in an ultra-wide band. As a result, in 2002, the use of 3.1 GHz to 10.6 GHz was approved by the American FCC (Federal Communications Commission) standard.

  An antenna used for UWB communication is required to have an ultra-wideband and small structure. In order to satisfy this demand, an antenna in which a radiating element and a ground plate are arranged on the same plane has been proposed (see, for example, Patent Document 1).

  In the conventional antenna, the radiating element and the ground plate are arranged on the same plane, a loop is formed in the radiating element, and the area of the ground plate is made larger than that of the radiating element. With this configuration, the VSWR (Voltage Standing Wave Ratio) is set to 2 or less in a frequency band of about 3 GHz or more.

JP 2007-235404 A

  However, the conventional monopole antenna has a strong antenna directivity.

  Accordingly, an object of the present invention is to improve the omnidirectionality of a monopole antenna in which a radiating element and a ground plate are arranged on the same plane.

  The inventors of the present invention, by experiment, in the monopole antenna in which the radiating element and the ground plate are arranged on the same plane, by arranging the strip-shaped conductor connected to the feeding point to the ground plate along the radiating element, We found that the omnidirectionality of the monopole antenna is improved.

  Specifically, in the monopole antenna according to the present invention, the radiating element and the ground plate are arranged on the same plane, and a feeding point to the radiating element and the ground plate is arranged on a first straight line that crosses both. A monopole antenna having one end connected to the feeding point to the ground plate and the other end being open, the band conductor being disposed along the outer periphery of the radiating element The interval between the strip conductor and the radiating element is characterized by continuously spreading from the one end to the other end of the strip conductor.

  According to the present invention, in the monopole antenna in which the radiating element and the ground plate are arranged on the same plane, the omnidirectionality of the antenna can be improved.

  In the monopole antenna according to the present invention, the outer peripheral shape of the radiating element and the ground plate is axisymmetric with respect to the first straight line, and the other end of the strip conductor is the outer periphery of the radiating element. It is preferable that the radiating element and the ground plate extend to a position that does not cross the first straight line beyond a proximity portion where the radiating element and the ground plate face each other.

In the monopole antenna according to the present invention, a straight line connecting the feeding point to the ground plate and the other end of the strip conductor, and a straight line connecting the feeding point to the ground plate and the feeding point of the radiating element. The formed angle is preferably 5 ° or more.
When the angle is less than 5 °, the directivity of the antenna may become strong. For this reason, according to the present invention, the omnidirectionality of the antenna can be improved by setting the angle to 5 ° or more.

In the monopole antenna according to the present invention, the width of the strip-shaped conductor is preferably 0.1 mm or more and 2 mm or less.
If the width of the strip conductor exceeds 2 mm, the directivity of the antenna may become strong. For this reason, according to the present invention, the omnidirectionality of the antenna can be improved.
On the other hand, when the width of the strip-shaped conductor is 0.1 mm or more, the monopole antenna according to the present invention can be easily manufactured. For this reason, the manufacturing cost of the monopole antenna can be suppressed by the present invention.

In the monopole antenna according to the present invention, the radiating element and the ground plate have a loop shape, and the shape of the outer periphery of the radiating element and the outer periphery of the ground plate in a proximity portion where the radiating element and the ground plate face each other The shape is preferably line symmetric with respect to a second straight line orthogonal to the first straight line.
It has been confirmed by experiments that the omnidirectionality of the antenna is improved by adopting the configuration according to the present invention. In addition, it has been confirmed by experiments that the ground plate and the radiating element can have the same area by adopting the configuration according to the present invention. Therefore, according to the present invention, it is possible to improve the omnidirectionality and size of the monopole antenna.

  According to the present invention, in the monopole antenna in which the radiating element and the ground plate are arranged on the same plane, the omnidirectionality of the antenna can be improved.

It is a composition schematic diagram of the monopole antenna concerning this embodiment. It is a pick-up figure which shows the 1st form of a radiation element and a ground board. It is the structure schematic which shows the other form of a radiation element and a ground board, (a) is a 2nd form, (b) is a 3rd form, (c) is a 4th form, (d) is a 5th form, (e ) Shows the sixth embodiment, and (f) shows the seventh embodiment. 3 is a measurement result of VSWR characteristics of the monopole antenna according to Example 1. FIG. 3 is a measurement result of directivity of the monopole antenna according to Example 1. FIG.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiment described below is an example of the configuration of the present invention, and the present invention is not limited to the following embodiment.

  FIG. 1 is a schematic configuration diagram of a monopole antenna according to the present embodiment. The monopole antenna according to the present embodiment includes a ground plate 11, a radiating element 12, a feeding point 13 to the ground plate 11, a feeding point 14 to the radiating element 12, and a strip conductor 15. The radiating element 12 and the ground plate 11 have proximity portions that face each other. In the present embodiment, a part 22 on the outer periphery of the radiating element 12 and a part 21 on the outer periphery of the ground plate 11 are opposed to each other to form a proximity portion.

  The radiating element 12 and the ground plate 11 are disposed on the same plane. For example, the radiating element 12 and the ground plate 11 are formed on a common substrate. The substrate material may be an insulator such as polyimide or polyethylene terephthalate (PET), but may be a dielectric such as an epoxy resin or an acrylic resin. The monopole antenna according to this embodiment can be reduced in size while obtaining good VSWR characteristics even if the substrate material is an insulator. Since the substrate material is a dielectric, the monopole antenna can be further reduced in size.

  The shapes of the outer circumferences of the radiating element 12 and the ground plate 11 are line symmetric with respect to the first straight line A that crosses both. For example, if the outer peripheral shape of the radiating element 12 and the ground plate 11 is an ellipse, the minor axis of the ellipse is arranged on the first straight line A. The shape of the outer periphery of the radiation element 12 and the ground plate 11 is not limited to an ellipse, and may be a circle, an ellipse, a polygon, or a combination thereof. In this case, the center points of the outer peripheral shapes of the radiating element 12 and the ground plate 11 are arranged on the first straight line A. The radiating element 12 and the ground plate 11 are preferably closest to each other on the first straight line A.

  The feeding points 13 and 14 are arranged on the first straight line A. Thereby, it is possible to supply power to the position where the radiating element 12 and the ground plate 11 are closest. The feeding points 13 and 14 are preferably arranged at a position equidistant from the second straight line B. Here, the second straight line B is a straight line orthogonal to the first straight line A and passing through the centers of the radiating element 12 and the ground plate 11. The distance between the feeding point 13 and the feeding point 14 is preferably 0.2 mm or more, and more preferably approximately 0.35 mm.

  The strip conductor 15 is disposed between the radiating element 12 and the ground plate 11 along the outer periphery of the radiating element 12. One end of the strip conductor 15 is connected to a feeding point 13 to the ground plate 11 and the other end of the strip conductor 15 is open. From such a structure, it is considered that the strip conductor 15 functions as a capacitance. Here, since the feeding point 13 is arranged on the first straight line A, the strip conductor 15 is arranged on one side divided by the first straight line A. Thereby, it is considered that reactance is generated in one of the radiating elements 12 divided by the first straight line A.

  The width of the strip conductor 15 is preferably 0.1 mm or more and 2 mm or less. The width of the strip conductor 15 may be uniform or non-uniform. In the case of non-uniformity, it is preferable that the width of the strip-shaped conductor 15 is 0.1 mm or more at the narrowest portion and the width of the strip-shaped conductor 15 is 2 mm or less at the thickest portion. If the width of the strip-shaped conductor 15 is 0.1 mm or more, the strip-shaped conductor 15 can be easily formed by printing or punching.

  The radiating element 12 has a loop shape. For example, the structure is such that the conductor at the center of the radiating element 12 is removed. The shape of the inner peripheral portion from which the conductor has been removed can be any shape such as a circle, an ellipse, a polygon more than a triangle, or a combination thereof. Similarly to the radiating element 12, the ground plate 11 is preferably in a loop shape.

FIG. 2 is a pickup diagram showing a first form of the radiating element and the ground plate.
Lx1 is the major axis of the outer circumference of the radiating element 12, Ly1 is the minor axis of the outer circumference of the radiating element 12, Lx2 is the major axis of the inner circumference of the radiating element 12, Ly2 is the minor axis of the inner circumference of the radiating element 12, and Lx3 is the minor axis of the inner circumference of the radiating element 12 The major axis of the outer periphery, Ly3 is the minor axis of the outer periphery of the ground plate 11, Lx4 is the major axis of the inner periphery of the ground plate 11, and Ly4 is the minor axis of the inner periphery of the ground plate 11.
Wy1 is the width from the inner circumference to the outer circumference of the radiating element 12 on the side far from the second straight line B, Wy2 is the width from the inner circumference to the outer circumference of the radiating element 12 on the side closer to the second straight line B, and Wy3 is the second The width from the inner periphery to the outer periphery of the ground plate 11 on the side close to the straight line B, Wy4 is the width from the inner periphery to the outer periphery of the ground plate 11 on the side far from the second straight line B.
D1 is the distance between the second straight line B and the outer peripheral portion 22 of the radiating element 12, and D2 is the distance between the second straight line B and the outer peripheral portion 21 of the ground plate 11.

  An interval F between the strip conductor 15 and the radiating element 12 continuously extends from one end connected to the feeding point 13 to the other open end. For this reason, the space | interval F becomes the minimum in the edge part connected to the feed point 13, and becomes the maximum in the open edge part. The interval F is preferably within 5 mm.

  The other open end of the belt-like conductor 15 extends to a position on the outer periphery of the radiating element 12 that exceeds the proximity portion where the radiating element 12 and the ground plate 11 face each other and does not exceed the first straight line A. For example, the other end of the strip-shaped conductor 15 faces a part 23 on the outer periphery of the radiating element 12. A part 23 of the outer circumference of the radiating element 12 is one of the outer circumferences of the radiating element 12 farther from the second straight line B than the part 22 of the outer circumference of the radiating element 12 and divided by the first straight line A. It is an area. In this way, the strip-shaped conductor 15 is disposed within a range of 90 ° from the feeding point 13 to the ground plate 11 to the radiating element 12, and does not wrap around the outer periphery of the radiating element 12.

  An angle θ formed by a straight line connecting the feeding point 13 to the ground plate 11 and the other end of the strip conductor and a straight line connecting the feeding point 13 to the ground plate 11 and the feeding point 14 of the radiating element 12 is 5 ° or more. Is preferred. Here, when the feeding point 13 and the feeding point 14 are arranged on the first straight line A, the straight line connecting the feeding point 13 and the feeding point 14 becomes the first straight line A. The VSWR characteristics of the monopole antenna are improved by adjusting the length of the strip conductor 15 so that the other end of the strip conductor 15 does not intersect the first straight line A and the angle θ is 5 ° or more. can do.

  The shape of the outer peripheral portion 22 of the radiating element 12 and the outer peripheral portion 21 of the ground plate 11 are symmetrical with respect to the second straight line B. For example, the distance D1 and the distance D2 on the straight line parallel to the first straight line A are equal.

  A part 22 of the outer periphery of the radiating element 12 and a part 21 of the outer periphery of the ground plate 11 have a curved shape such that the radiating element 12 and the ground plate 11 are closest to each other on the first straight line A. preferable. In particular, the shape of the outer peripheral portion 22 of the radiating element 12 and the outer peripheral portion 21 of the ground plate 11 is preferably an elliptical portion. In this case, the minor axis of the ellipse is arranged on the first straight line A.

  The distance (D1 + D2) between the radiating element 12 and the ground plate 11 on the first straight line A where the radiating element 12 and the ground plate 11 are closest is preferably 0.2 mm or more, and is further approximately 0.35 mm. Preferably there is.

  The outer peripheral shape and inner peripheral shape of the radiating element 12 are preferably an ellipse in which the minor axis of the ellipse is arranged on the first straight line A. In this case, the major axis of the outer periphery of the radiating element 12 is preferably 14 mm or greater and 40 mm or less. Further, the ratio of the major axis to the minor axis Lx1: Ly1 and Lx2: Ly2 is preferably 1: 0.3 or more and 1: 0.7 or less. In particular, the ratio of the major axis to the minor axis is preferably 2: 1. When Lx1 is 40 mm, Ly1 is preferably 20 mm, Lx2 is 20 mm, and Ly2 is preferably 10 mm.

  The shape of the outer periphery and the inner periphery of the radiating element 12 is preferably an ellipse having the same ratio of major axis to minor axis, that is, ellipticity. For example, there is a relationship of Lx1 / Ly1 = Lx2 / Ly2. The ground plate 11 is the same, and preferably has a relationship of Lx3 / Ly3 = Lx4 / Ly4.

  The major axis of the inner periphery of the radiating element 12 is preferably equal to the minor axis of the outer periphery of the radiating element 12. For example, it has a relationship of Ly1 = Lx2. The ground plate 11 is the same, and in this case, there is a relationship of Ly3 = Lx4.

  The radiating element 12 and the ground plate 11 preferably have the same shape and the same area. In particular, it is preferable that the shape of the outer periphery and inner periphery of the radiating element 12 and the shape of the outer periphery and inner periphery of the ground plate 11 are ellipses having the same ellipticity. In this case, Lx1 / Ly1 = Lx2 / Ly2 = Lx3 / Ly3 = Lx4 / Ly4, Wy2 = Wy3, and Wy1 = Wy4.

  The width from the inner periphery to the outer periphery of the radiating element 12 and the ground plate 11 is preferably thicker on the side farther from the side closer to the second straight line B. For example, there is a relationship of Wy1> Wy2, Wy3 <Wy4.

  FIG. 3 is a schematic configuration diagram illustrating another embodiment of the radiating element and the ground plate. (A) is a second embodiment, (b) is a third embodiment, (c) is a fourth embodiment, and (d) is a fifth embodiment. Form, (e) shows the sixth form, and (f) shows the seventh form.

  In the 2nd form shown to Fig.3 (a), it has the shape which provided the strip | belt-shaped conductor on the long axis of the inner periphery of the ground board 11 shown in FIG. In the 3rd form shown in FIG.3 (b), it has the shape which provided the strip | belt-shaped conductor on the long axis of the inner periphery of the radiation element 12 and the ground board 11 shown in FIG. Thus, the radiation element 12 and the ground plate 11 may be formed with a plurality of loops.

In the 4th form shown in FIG.3 (c), it has the shape which cut | disconnected the radiation | emission element 12 shown in FIG. 2 in a short axis direction, and connected the open ends with a strip | belt-shaped conductor. Further, the loop of the ground plate 11 is removed.
In the fifth embodiment shown in FIG. 3D, the radiating element 12 shown in FIG. 2 is cut in the minor axis direction, and the open ends are connected to each other with a strip-shaped conductor. Further, the ground plate 11 shown in FIG. 2 is cut in the minor axis direction to remove the loop.
In the sixth embodiment shown in FIG. 3 (e), the radiating element 12 and the ground plate 11 shown in FIG. 2 are cut in the short axis direction, and the open ends are connected with a strip-shaped conductor.
Thus, the outer peripheral shape of the radiating element 12 and the ground plate 11 can be an arbitrary shape except for the proximity portion. In particular, the monopole antenna can be miniaturized by providing a shape in which the end portions of the proximity portion are passed by a band-shaped conductor.

  In the seventh embodiment shown in FIG. 3F, the loop of the ground plate 11 shown in FIG. 2 is removed. Thus, the ground plate 11 does not have to be formed with a loop.

  The directivity and VSWR characteristics of the monopole antenna shown in FIG. 1 were measured. The parameters shown in FIG. 2 at this time are Lx1 = Lx3 = 40 mm, Ly1 = Ly3 = Lx2 = Lx4 = 20 mm, and Ly2 = Ly4 = 10 mm. The width of the strip conductor 15 is 1 mm, the angle θ is 10 °, and the distance between the feeding points 13 and 14 is 0.347 mm. A PET film was used as the substrate.

  As Comparative Example 1, the directivity of a monopole antenna not provided with the strip conductor shown in FIG. The parameters shown in FIG. 2 are the same as those in the first embodiment.

  FIG. 4 shows the measurement results of the VSWR characteristics of the monopole antenna according to this example. In both cases, the lowest frequency is 1.57 GHz, which has a sufficient margin with respect to 3.1 GHz which is the input characteristic value of the UWB antenna, and sufficient VSWR characteristics were obtained without using a dielectric substrate.

  FIG. 5 is a measurement result of directivity of the monopole antenna according to this example. In the XY plane radiation characteristic of the monopole antenna according to Example 1, a radiation characteristic close to a perfect circle of approximately 0 dBi was obtained. As described above, the directivity of the monopole antenna according to Example 1 is improved compared to the directivity of the monopole antenna according to Comparative Example 1.

  The present invention can be used for an antenna incorporated in an information terminal device such as a notebook personal computer, a PDA (portable information device) terminal, a mobile phone, or a VICS (Vehicle Information and Communication System).

11: ground plate 12: radiating element 13, 14: feeding point 15: strip-shaped conductor 21: part of outer periphery 22 of ground plate 11, 23: part of outer periphery of radiating element 12

Claims (5)

A monopole antenna in which a radiating element and a ground plate are arranged on the same plane, and a feeding point to the radiating element and the ground plate is arranged on a first straight line crossing both,
One end is connected to the feeding point to the ground plate, the other end is provided with a strip-shaped conductor that is open,
The strip-shaped conductor is disposed along the outer periphery of the radiating element,
The monopole antenna, wherein a distance between the strip conductor and the radiating element continuously extends from the one end to the other end of the strip conductor. The outer peripheral shape of the radiating element and the ground plate is line symmetric with respect to the first straight line,
The other end of the strip-shaped conductor extends to a position in the outer periphery of the radiating element that exceeds a proximity portion where the radiating element and the ground plate face each other and does not cross the first straight line. The monopole antenna according to claim 1.   An angle formed by a straight line connecting the feeding point to the ground plate and the other end of the strip conductor and a straight line connecting the feeding point to the ground plate and the feeding point of the radiating element is 5 ° or more. The monopole antenna according to claim 1 or 2, wherein the monopole antenna is provided.   4. The monopole antenna according to claim 2, wherein a width of the strip conductor is 0.1 mm or more and 2 mm or less. The radiating element and the ground plate are loop-shaped,
The shape of the outer periphery of the radiating element and the shape of the outer periphery of the ground plate in a proximity portion where the radiating element and the ground plate face each other are symmetrical with respect to a second straight line orthogonal to the first straight line. The monopole antenna according to any one of claims 1 to 4, wherein the monopole antenna is provided.

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