JP5133186B2 - antenna - Google Patents

Description

  The present invention relates to a multiband antenna used for a mobile phone, a wireless LAN, and the like, and more particularly to a miniaturized planar antenna mounted on a digital home appliance.

Conventionally, antennas in which wires are arranged in parallel on a ground plate and antennas in which a radiating element is mounted on a mounting board have been proposed as multiband antennas (see, for example, Patent Documents 1 and 2).
JP 2007-49249 A JP 2006-2107026 A

  However, when the wires are installed in parallel on the ground plate, a three-dimensional structure is formed, resulting in a volume. In addition, when a radiating element is mounted on a mounting board, a large ground plate is often required. For this reason, it has been difficult to mount conventional multiband antennas on digital home appliances.

  Therefore, an object of the present invention is to achieve a wide bandwidth with a low VSWR (Voltage Standing Wave Ratio) in a planar antenna that can be easily mounted on a digital home appliance.

  A radiating element folded back in a U-shape, and when the open end of the radiating element and the feeding position are arranged near the center of the antenna, even a small planar antenna has a low VSWR and a wide bandwidth. The inventors have discovered through experiments.

Specifically, an antenna according to the present invention includes a ground plate having a substantially linear flat portion at least at a part of an outer edge, a feeding point connected to the flat portion and fed with high-frequency power, and a U-shape. A radiating element that is folded once into the mold and receives power from the feeding point from the lower bottom of the U-shape, and the lower bottom of the U-shape is disposed substantially parallel to the flat portion. The feeding point is arranged at a position less than 10% of the width of the ground plate in the specific direction from the center of the ground plate in a specific direction parallel to the flat portion, and is open at the upper bottom of the U-shaped. been the distance in a particular direction less than 30% der width of said ground plate from end to said feed point is, the ground plate is rectangular to one side of the flat portion, shaped the co The width of the bottom base in the specific direction is The width of the ground plate is equal to the width in the specific direction, and the open end of the U-shaped lower bottom portion is connected to one end of the flat portion, and the U-shaped folded portion is the flat portion. The ground plate, the feeding point, and the radiating element are integrally formed on the same plane .

In the antenna according to the present invention, it is preferable that the feeding point is disposed at a center of the ground plate in the specific direction.
The antenna input characteristics are best when the feeding position is at the center. Therefore, according to the present invention, the input characteristics of the antenna can be optimized.

In the antenna according to the present invention, the width of the ground plate in the specific direction is 13 mm, and the distance in the specific direction from the open end of the U-shaped upper bottom to the feeding point is 3. It is preferable that the distance from the open end of the U-shaped upper base portion to the folded portion is 10 mm.
In the experiment, the input characteristics of the antenna were the best when the distance from the open end of the U-shaped upper base to the folded portion was 10 mm. Therefore, according to the present invention, the input characteristics of the antenna can be optimized.

  According to the present invention, it is possible to achieve a wide bandwidth with a low VSWR in a planar antenna that can be easily mounted on a digital home appliance.

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 an antenna according to this embodiment. The antenna according to this embodiment includes a ground plate 11, a radiating element 12, and a feeding point 13.

  It is preferable that the ground plate 11, the feeding point 13, and the radiating element 12 are integrally formed on the same plane. For example, a polyimide base material is used as the base base material, and the ground plate 11 and the radiating element 12 are formed thereon using copper foil.

  The radiating element 12 is folded once in a U-shape, and includes a lower bottom portion 12a, a folded portion 12b, and an upper bottom portion 12c in order from the side closer to the ground plate 11. The ground plate 11 has a substantially linear flat portion 11a on at least a part of the outer edge. The U-shaped lower bottom portion 12a is disposed substantially parallel to the flat portion 11a. The radiating element 12 receives power from the feeding point 13 from the U-shaped lower bottom 12a. The direction parallel to the flat portion 11a is the specific direction, and the y-axis direction is the specific direction in FIG.

  The feeding point 13 is connected to the flat portion 11a and fed with high-frequency power. Power feeding is performed directly or via a coaxial cable. The feeding point 13 is disposed at a position less than 10% of the width W of the ground plate 11 from the center 51. The center 51 is the center of the ground plate 11 in a specific direction. The width W of the ground plate 11 is the width of the ground plate 11 in a specific direction. In particular, the feeding point 13 is preferably disposed at the center 51 in the specific direction of the ground plate 11. By setting the feeding position to the center 51 of the ground plate 11, the bandwidth can be widened at a high resonance frequency.

  The distance d1 is less than 30% of the width W. Changing the value of the distance d1 changes the resonance frequency of the antenna. Here, the distance d1 is a distance in a specific direction from the open end 12d of the U-shaped upper base 12c to the feeding point 13. The width W is a width in a specific direction of the ground plate 11. For example, if the width W is 13 mm, the distance d1 is 3.9 mm. At this time, the distance d2 from the open end 12d of the upper bottom portion 12c to the folded portion 12b is more than 2.6 mm and less than 10.4 mm. In particular, it is preferable that the distance d1 is 3.5 mm and the distance d2 is 10 mm.

  The antenna according to the present embodiment is preferably a square having a width W in the y-axis direction and a width H in the z-axis direction in order to facilitate mounting on a digital home appliance. In this case, the ground plate 11 has a square shape with the flat portion 11a as one side. The width of the lower bottom portion 12a in the specific direction is equal to the width W of the ground plate 11, and the open end portion of the lower bottom portion 12a is connected to one end of the flat portion 11a. The folded portion 12b is folded at the other end of the flat portion 11a.

  The relationship between the distance d1 and the antenna characteristics was evaluated. FIG. 2 is a schematic configuration diagram of an antenna according to the present embodiment. The y-axis direction is a specific direction. The feeding point 13 is arranged at the center 51 of the ground plate 11, the width W is 13 mm, and the width H in the z-axis direction is 19 mm. Under this condition, the distance d2 was changed, and the input characteristics of the antenna at that time were measured.

  FIG. 3 shows the input characteristics of the antenna in this embodiment. From the left, the distance d2 is 13 mm, 10 mm, 6.5 mm, 4 mm, and 0 mm. When the distance d2 was 4.5 mm or more and 13 mm or less, VSWR ≦ 2 was obtained at any frequency of 4.3 to 6 GHz. Further, the capacity of the antenna is suddenly insufficient when the distance d2 is between 0 mm and 4 mm, and the bandwidth of the antenna is rapidly narrowed when the distance d2 is between 10 mm and 13 mm. From this result, it was found that the input characteristics of the antenna are in a preferable range when the distance d1 is less than 30% of the width W = 13 mm.

  The relationship between the position of the feeding point 13 and the antenna characteristics was evaluated. FIG. 4 is a schematic configuration diagram of an antenna according to the present embodiment. The y-axis direction is a specific direction. The width W was 13 mm, the distance d2 was 6.5 mm, and the width H in the z-axis direction was 19 mm. Under this condition, the distance f from the end of the ground plate 11 was changed, and the input characteristics of the antenna at that time were measured.

  FIG. 5 shows the input characteristics of the antenna in this embodiment. From the left, the distance f is 8.5 mm, 7.5 mm, 6.5 mm, 5.5 mm, and 4.5 mm. When the distance f was 6.5 mm or more and 7.5 mm or less, VSWR ≦ 2 was obtained in the vicinity of the frequency of 5 GHz. Further, when the distance f is 5.5 mm, the capacity of the antenna is insufficient, and when the distance f is 8.5 mm, the bandwidth of the antenna is rapidly narrowed. From this result, it was found that when the position of the feeding point is less than 10% of the width W = 18 mm of the ground plate 11 in the specific direction from the center 51 of the ground plate 11, the input characteristics of the antenna are in a preferable range. .

  The antenna directivity was verified. FIG. 6 is a schematic configuration diagram of an antenna according to the present embodiment. The y-axis direction is a specific direction. The feeding point 13 is arranged at the center of the ground plate 11 in a specific direction, the width W is 13 mm, the distance d2 is 8 mm, and the width H in the z-axis direction is 19 mm. A 100 mm coaxial cable (φ1.13 mm) was used for feeding to the feeding point 13.

  FIG. 7 shows the characteristics of the antenna according to the present embodiment, where (a) shows the input characteristics and (b) shows the directivity at 5.2 GHz. As shown in FIG. 7A, VSWR ≦ 2 was obtained in the band of 4.9 GHz to 5.725 GHz, which is the use frequency band of the wireless LAN. Further, as shown in FIG. 7B, E_θ indicating the radiation directivity in the horizontal plane is omnidirectional, and a gain of about 1 dBi is obtained at the maximum.

  The present invention can be used for a wireless LAN compatible 5 GHz antenna. In particular, it can be used for antennas mounted on digital home appliances such as televisions and notebook computers.

1 is a schematic configuration diagram of an antenna according to an embodiment. 1 is a schematic configuration diagram of an antenna according to Example 1. FIG. The input characteristic of the antenna in Example 1 is shown. 6 is a schematic configuration diagram of an antenna according to Example 2. FIG. The input characteristic of the antenna in Example 2 is shown. FIG. 7 is a schematic configuration diagram of an antenna according to Example 3. It is the characteristic of the antenna which concerns on Example 3, (a) is an input characteristic, (b) shows the directivity in 5.2 GHz.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Ground plate 11a Flat part 12 Radiation element 12a U-shaped lower bottom part 12b U-shaped folding part 12c U-shaped upper bottom part 12d Open end part in U-shaped upper bottom part 13 Feeding point 51 Center of ground plate

Claims (3)

A ground plate having a substantially linear flat portion at least at a part of the outer edge;
A feeding point connected to the flat part and fed with high-frequency power;
A radiating element that is folded back into a U-shape and receives power from the feeding point from the bottom of the U-shape,
The U-shaped lower bottom portion is disposed substantially parallel to the flat portion,
The feeding point is arranged at a position less than 10% of the width of the ground plate in the specific direction from the center of the ground plate in a specific direction parallel to the flat part.
Ri less than 30% der of the width of the distance in a particular direction the ground plate from the open end of the upper base portion of the shape of the U to said feed point,
The ground plate is a square having the flat portion as one side,
The width in the specific direction of the bottom of the U-shaped is equal to the width in the specific direction of the ground plate,
An open end portion of the U-shaped lower bottom portion is connected to one end of the flat portion,
The U-shaped folded portion is folded at the other end of the flat portion,
The antenna, wherein the ground plate, the feeding point, and the radiating element are integrally formed on the same plane .   The antenna according to claim 1, wherein the feeding point is arranged at a center of the ground plate in the specific direction. The width of the ground plate in the specific direction is 13 mm,
The distance in the specific direction from the open end of the U-shaped upper base to the feeding point is 3.5 mm,
3. The antenna according to claim 1, wherein a distance from an open end of the U-shaped upper bottom portion to the folded portion is 10 mm.

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