JP5006259B2 - Compound antenna - Google Patents

Description

  The present invention relates to a vehicle-mounted composite antenna including two or more antennas having different directivities.

  Conventionally, as a vehicle-mounted antenna, a GPS antenna is used by being installed on an instrument panel (hereinafter referred to as an instrument panel) in a vehicle interior. On the other hand, in recent years, the need for wireless communication in the passenger compartment has also increased. For example, there is a need to use a wireless hands-free device for using a mobile phone while driving. There is also a growing need for wireless data communication in a vehicle interior using a personal computer (hereinafter referred to as a personal computer) or various mobile devices. For example, a Bluetooth system is used for such wireless communication, and an in-vehicle wireless communication antenna corresponding to Bluetooth is installed in the vehicle interior.

  Development of a composite antenna in which a plurality of in-vehicle antennas are integrated has been promoted from the viewpoint of antenna installation space, scenery in a vehicle interior, and the like (for example, Patent Document 1). There is also a strong need for in-vehicle wireless communication antennas to be integrated with GPS antennas and incorporated into composite antennas.

In the in-vehicle wireless communication antenna, it is desirable that a high gain is obtained over almost the entire interior of the vehicle, and in particular, antenna characteristics having a wide angle directivity in the horizontal direction are preferable. Therefore, a monopole antenna or an inverted F antenna having a wide directivity in the horizontal direction is used as an in-vehicle wireless communication antenna. On the other hand, the GPS antenna needs directivity in the zenith direction, and is used in combination with a circularly polarized antenna element and a ground plane.
Japanese Patent Laid-Open No. 2005-260566

  In order to reduce the installation space as much as possible by combining the GPS antenna and the in-vehicle wireless communication antenna, it is necessary to dispose the in-vehicle wireless communication antenna on the ground plane of the GPS antenna. However, if the in-vehicle wireless communication antenna is arranged on the ground plane in this way, the in-vehicle wireless communication antenna that requires a wide angle directivity in the horizontal direction is strongly affected by the ground plane and the directivity is impaired. There is a problem.

  Accordingly, the present invention has been made to solve the above-described problem, and an object thereof is to provide an integrated composite antenna by reducing the influence of the ground plane of one antenna on the directivity of the other antenna. .

The first aspect of the composite antenna of the present invention includes a first antenna for circular polarization having a first directivity and a linear polarization having a second directivity different from the first directivity. a second antenna, but is disposed on the same substrate, the substrate is in place on the base plate, the center of the base plate holes were excised ground plane conductor to substantially match the position provided in the center of the base plate The first antenna is disposed substantially at the center of the ground plane, the second antenna is disposed at an upper portion of the ground plane hole, the wavelength of the first antenna is λ _1, and the second antenna when the wavelength is lambda _2, the wavelength lambda ₂ of the second antenna is shorter than the wavelength lambda ₁ of the first antenna, said base plate holes (lambda _2/5) ² or (lambda _1/5) ² or less It has the area of the magnitude | size of this.

  Another aspect of the composite antenna of the present invention is characterized in that the first antenna is a GPS antenna.

  Another aspect of the composite antenna of the present invention is characterized in that the second antenna is a Bluetooth communication antenna.

  According to the present invention, it is possible to provide an integrated composite antenna by reducing the influence on the directivity of the other antenna by providing the ground plane hole partially cut out on the ground plane of one antenna.

  A composite antenna according to a preferred embodiment of the present invention will be described in detail with reference to the drawings. In addition, about each structural part which has the same function, the same code | symbol is attached | subjected and shown for simplification of illustration and description. The composite antenna of the present invention is a composite antenna that can be integrated while maintaining the directivity of each antenna by reducing the influence of the ground plane of one antenna on the directivity of the other antenna that does not require a ground plane. It is mainly used as a vehicle-mounted antenna.

  A composite antenna according to an embodiment of the present invention is shown in FIGS. FIG. 1 shows a perspective view of a composite antenna 100 according to the present embodiment, and FIG. 2 shows a plan view of the composite antenna 100. The composite antenna 100 has a structure including a circularly polarized first antenna 120 that requires a ground plane 110 and a linearly polarized second antenna 130 that does not use a ground plane.

  In the following, for simplicity of explanation, the structure of the composite antenna 100 will be described using the coordinate system (X axis, Y axis, Z axis) shown in FIG. Here, as an example, the composite antenna 100 is an in-vehicle antenna, the X-axis direction is the vehicle front-rear direction, the Y-axis is the vehicle width direction, and the Z-axis is the vehicle height direction.

  As a vehicle-mounted antenna, a circularly polarized GPS antenna is used, which can be used as the first antenna 120. The GPS antenna uses radio waves having a center frequency of 1.575 GHz and has high directivity in the zenith direction. In order to give the GPS antenna high directivity in the zenith direction, it is preferable to install the ground plane 110 substantially horizontally and to arrange the GPS antenna at the approximate center thereof.

  In addition, as an example of the linearly polarized second antenna 130, an in-vehicle wireless communication antenna is used, for example. In the in-vehicle wireless communication antenna, for example, Bluetooth communication using a radio wave having a center frequency of 2.45 GHz can be used. The Bluetooth antenna used for in-vehicle wireless communication desirably has directivity to the entire vehicle interior, and preferably has wide-angle directivity in the horizontal direction. In the following, as an example, the circularly polarized first antenna 120 will be described as a GPS antenna, and the linearly polarized second antenna 130 will be described as a Bluetooth antenna.

  In the composite antenna 100 of the present embodiment, the GPS antenna 120 is disposed in the upper part near the center of the ground plane 110, and the GPS circuit board 140 is disposed below the GPS antenna 120. The Bluetooth antenna 130 is arranged further below the GPS circuit board 140. In order for the GPS antenna 120 to obtain a high gain in the zenith direction, the GPS antenna 120 is arranged at the top.

  As described above, the composite antenna 100 according to the present embodiment has a three-dimensional arrangement of the GPS antenna 120, the GPS circuit board 140, and the Bluetooth antenna 130, thereby reducing the antenna arrangement space and reducing the size. Yes. In the composite antenna 100 of the present embodiment, even if the GPS antenna 120 and the Bluetooth antenna 130 are three-dimensionally arranged, the gain characteristics are not adversely affected. This will be described below.

  The GPS antenna 120 needs to be disposed substantially at the center of the main plate 110 in order to provide directivity in the zenith direction. In addition, the Bluetooth antenna 130 is preferably arranged at a position away from the ground plate 110 so as not to be affected by the ground plane 110. However, in order to configure the composite antenna 100 of the present embodiment as described above, the Bluetooth antenna 130 is also arranged on the top of the ground plane 110. In order to reduce the influence from the ground plane 110, the ground plane hole 111 is provided by cutting the ground plane conductor from a location directly below the Bluetooth antenna 130.

  As described above, by providing the ground plane hole 111 directly below the Bluetooth antenna 130, the ground plane conductor that affects the directivity of the Bluetooth antenna 130 is eliminated. As described above, when a ground plane hole 111 is provided by cutting off a part of the conductor of the ground plane 110, this may affect the directivity of the GPS antenna 120. Therefore, in order to reduce the influence on the directivity of the GPS antenna 120 as much as possible, the ground plane hole 111 is arranged at substantially the center of the ground plane 110 directly below the GPS antenna 120. Thereby, the ground plane 110 can maintain the horizontal symmetry with respect to the center of the GPS antenna 120, and the directivity of the GPS antenna 120 in the zenith direction can be maintained.

  As described above, the ground plane hole 111 for reducing the influence on the directivity of the Bluetooth antenna 130 is provided substantially at the center of the ground plane 110 so as not to affect the directivity of the GPS antenna 120. Yes. As a result, the arrangement of the GPS antenna 120 on the ground plane 110 and the arrangement of the Bluetooth antenna 130 on the ground plane 110 coincide with each other, and in the present embodiment, both are arranged in an overlapping manner.

  The influence on the gain characteristics by providing the ground plane hole 111 at the center of the ground plane 110 will be described below. First, the influence of the size of the ground plane hole 111 on the gain characteristics of the GPS antenna 120 and the Bluetooth antenna 130 will be described with reference to FIG. 3A is a graph showing a change in gain in the zenith direction of the GPS antenna 120 depending on the size of the ground plane hole 111. FIGS. 3B and 3C are Bluetooth diagrams depending on the size of the ground plane hole 111. FIG. 6 is a graph showing a change in gain of the antenna 130 for use. In FIG. 3B, gains on the XY plane, the ZY plane, and the YZ plane are indicated by reference numerals 11, 12, and 13, respectively.

FIGS. 3A and 3B show characteristics when the size of the ground plane 110 is a square of 70 mm × 70 mm (area 4900 mm ² ), and FIG. 3C shows the size of the ground plane 110 of 90 mm × The characteristic is shown when the square is 90 mm (area 8000 mm ² ). The horizontal axis of each graph represents the area of the base plate hole 111 using the wavelengths λ ₁ and λ ₂ of the respective radio waves used in GPS and Bluetooth, and the unit is mm ² . Than the change in the zenith direction in the gain characteristic of the GPS antenna 120 shown in FIG. 3 (a), the gain of the zenith direction by providing Chiban'ana 111 slightly decreases, the area of Chiban'ana 111 (λ _1/9. 5) It can be seen that a substantially constant gain can be obtained from ² mm ² to (λ ₁ /5.5) ² mm ² corresponding to approximately ¼ of the area of the ground plane 110.

  On the other hand, when the area of the ground plane hole 111 exceeds approximately ¼ of the area of the ground plane 110, it can be seen that the gain in the zenith direction rapidly decreases and the ground plane 110 does not function as a reflector. From the above, in order to give the GPS antenna 120 a high gain characteristic in the zenith direction, it is preferable that the area of the ground plane hole 111 is set to about 1/4 or less of the area of the ground plane 110.

In addition, it can be seen from the gain characteristics of the Bluetooth antenna 130 shown in FIGS. 3B and 3C that the gain is significantly improved by providing the ground plane hole 111. Then, corresponding to substantially 1/5 area of the area of the main plate 110 of Chiban'ana 111 (λ ^_2/4) highest when a 2 mm ² mm, good gain (λ _{^2/5) 2} or Has been obtained. When the area of the base plate hole 111 is further increased, the gain characteristic gradually decreases.

Holding the above, the area of Chiban'ana 111, (λ ^_2/5) and ^two or more (λ ^_1/5) good to ² or less, thereby the zenith direction in the gain characteristic of the GPS antenna 120 suitably In addition, the gain characteristic of the Bluetooth antenna 130 can be improved.

Next, the influence of the size of the ground plane 110 on the gain characteristics of the GPS antenna 120 and the Bluetooth antenna 130 will be described with reference to FIG. In the figure, the horizontal axis represents the area (unit mm ² ) of the ground plane 110, the gain characteristic (right-handed circularly polarized wave) of the GPS antenna 120 is denoted by reference numeral 20, and the XY plane, ZY plane, and YZ of the Bluetooth antenna 130 are represented. The gains in the plane are denoted by reference numerals 21, 22, and 23, respectively.

In Figure 4, the area a (λ _{^2/4) 2} of Chiban'ana ^{_{111 ((λ 1 /6.3) 2}} ) fixed to mm ^2, respectively in the case of changing the area by changing the external dimensions of the main plate 110 The characteristic change is shown. The characteristics of the GPS antenna 120 indicated by reference numeral 20 tend to gradually deteriorate as the area of the ground plane 110 reaches a peak when the area is about (λ ₁ /3.2) ² mm ² and becomes larger. It can be seen. However, it can be seen that by setting the area of the base plate 110 to 3500 mm ² or more, almost good characteristics can be obtained.

  Further, the influence of the shape of the ground plane hole 110 on the gain characteristics of the GPS antenna 120 and the Bluetooth antenna 130 will be described with reference to FIGS. In the above, the shape of the main plate hole 111 is a square, and each side is formed so as to be substantially parallel to each side of the main plate 110. However, the effect when the shape or orientation of the main plate hole 111 is changed will be described below. To do.

  As the shape of the main plate hole 111, a case where four types shown in FIG. FIG. 5A shows a square shape used in the above embodiment, and each side of the main plate hole 111 is formed in parallel with each side of the main plate 110. In FIG. 5B, the shape of the base plate hole 111 is a square, but each side is rotated by about 45 ° with respect to each side of the base plate 110. FIG. 5C shows a case where the shape of the main plate hole 111 is a hexagon, and FIG. 5D shows a case where the shape of the main plate hole 111 is a dodecagon. In any case, the center position of the main plate 110 and the center position of the main plate hole 111 are formed to coincide with each other.

The influence on the gain of the Bluetooth antenna 130 when the shape of the main plate hole 111 is as shown in FIG. 5 will be described with reference to FIG. FIG. 6 shows the change in the gain of the Bluetooth antenna 130 when the horizontal axis is the area of the main plate hole 111 (unit: mm ² ), as in FIG. 3, and (a), (b), (c ) Respectively indicate gains in the XY plane, ZY plane, and YZ plane. In each figure, when the shape of the ground plane hole 111 is a square, when the square is rotated by 45 ° with respect to the ground plane 110, when it is a hexagon, when it is a dodecagon, it is denoted by reference numerals 31, 32, 33, 34, respectively. Show.

  In FIG. 6, the gain characteristic indicated by reference numeral 31 is the case where the shape of the ground plane hole 111 is the same square as that in the above embodiment (FIG. 5A), and is the same as the result shown in FIG. . When the gain changes indicated by reference numerals 32 to 34 other than this are compared with the gain change of reference numeral 31, a large difference is not observed in each. That is, it can be seen that even if the shape of the ground plane hole 111 is different, substantially the same gain can be obtained if the area of the ground plane hole 111 is the same.

Based on the above results, when the composite antenna 100 is formed by integrating the circularly polarized GPS antenna 120 and the linearly polarized Bluetooth antenna 130, the Bluetooth antenna 130 It is preferable to superimpose and arrange both at the approximate center of the main plate 110 and form the main plate hole 111 at the center of the main plate 110. At this time, by setting the area of Chiban'ana 111 (λ ^_2/5) and ^two or more (λ ^{_1/5) 2} or less, suitably holding miniaturized possible composite antenna 100 to each of the directional Can be provided. The ground plane 111 can also be used to fix a lid (not shown) that protects the composite antenna 100.

  In the above description, the composite antenna 100 including the GPS antenna 120 and the Bluetooth antenna 130 is described as the vehicle-mounted antenna. However, the present invention is not limited to this, and according to the present invention, the ground plane partially cut away from the ground plane of one antenna is described. By providing the hole, it is possible to provide an integrated composite antenna with reduced influence on the directivity of the other antenna.

  Note that the description in the present embodiment shows an example of the composite antenna according to the present invention, and the present invention is not limited to this. The detailed configuration and detailed operation of the composite antenna in the present embodiment can be appropriately changed without departing from the spirit of the present invention.

1 is a perspective view of a composite antenna according to an embodiment of the present invention. It is a top view of the compound antenna concerning this embodiment. It is a figure which shows the influence which the magnitude | size of a ground-plate hole has on the gain characteristic of the antenna for GPS and the antenna for Bluetooth. It is a figure which shows the influence which the magnitude | size of a ground plane has on the gain characteristic of the antenna for GPS and the antenna for Bluetooth. It is a top view of the composite antenna which shows the Example from which the shape of a ground-plate hole differs. It is a figure which shows the influence which the shape of a ground-plate hole has on the gain characteristic of the antenna for Bluetooth.

Explanation of symbols

100 composite antenna 110 ground plane 111 ground plane hole 120 first antenna (GPS antenna)
130 Second antenna (Bluetooth antenna)
140 GPS circuit board

Claims (3)

A first antenna for circular polarization having a first directivity;
A linearly polarized second antenna having a second directivity different from the first directivity is disposed on the same substrate;
The substrate is arranged at a predetermined position on the ground plane;
Center ground plane hole provided with resected ground plane conductor to substantially coincide located at the center of the base plate,
The first antenna is disposed at substantially the center of the ground plane;
The second antenna is disposed above the main plate hole;
When the wavelength of the first antenna is λ ₁ and the wavelength of the second antenna is λ ₂ , the wavelength λ ₂ of the second antenna is shorter than the wavelength λ ₁ of the first antenna , and the ground plane hole composite antenna which is characterized by having an area of (λ _{^2/5) 2} or (λ _1/5) ² or less in size. The composite antenna according to claim 1, wherein the first antenna is a GPS antenna. The composite antenna according to claim 1 , wherein the second antenna is a Bluetooth communication antenna.

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