JP4234645B2 - Antenna device - Google Patents

Description

  The present invention relates to a small antenna for a moving body, for example, an antenna device suitable as a vehicle-mounted antenna.

As an example of an antenna device that can be reduced in size and thickness, a square spiral antenna described in Patent Document 1 is known. This square spiral antenna has a radiating element composed of a square spiral microstrip line. The path length of the outer peripheral portion of the square spiral microstrip line is configured to be not less than 1 wavelength and not more than 2 wavelengths of the received radio wave.
JP 2001-251132 A

  In the case of the rectangular spiral antenna (antenna device) described in Patent Document 1, since the path length of the outer periphery of the rectangular spiral microstrip line requires one or more wavelengths of the received radio wave, the rectangular spiral is used. The size of one side of the main body of the antenna is also required to be about ¼ wavelength. For this reason, there has been a problem that the antenna size increases when the frequency of the radio wave decreases (when the wavelength increases).

  SUMMARY OF THE INVENTION An object of the present invention is to provide an antenna device that can reduce the antenna size while having a radiating element formed by winding a linear conductor in a spiral shape.

The antenna device of the present invention includes a substrate and a radiating element that is provided on the substrate by being spaced apart by a set distance and is configured by winding a linear conductor in a spiral shape . A plurality of conductive lines that are substantially point-symmetric with respect to the center of the spiral and are arranged along the spiral linear conductor, and a plurality of intermediate portions of the linear conductor of the radiation element, In order to increase the path length, the plurality of conductive lines are connected as a detour path. In the case of this configuration, since the path length of the linear conductor of the radiating element becomes long, the size of the substrate of the antenna device can be reduced, and therefore the antenna size can be reduced.

In the case of the above configuration, the shape of the radiating element may be a substantially square shape, and the conductive line may be configured to be connected to the linear conductor at four sides of the outer peripheral portion of the radiating element. preferable. Moreover, you may comprise the said electroconductive line so that it may connect to the said linear conductor in two edge parts of the outer peripheral part of the said radiation element.
Meanwhile, it is preferable that the conductive line is a strip line. The conductive line may be a microstrip line.

  Furthermore, it is even more preferable that a ground element is formed by winding a linear conductor in a spiral shape, and the linear conductor of the ground element is arranged between the linear conductors of the radiating element. . Furthermore, it is preferable that a ground plate is disposed on the surface of the substrate where the radiation element is not provided. Further, it is preferable that the radiating element has a substantially circular shape.

  The first embodiment of the present invention will be described below with reference to FIGS. First, FIG. 1 is a perspective view schematically showing the overall configuration of the antenna device 1 of the present embodiment. The antenna device 1 is an antenna device for GPS, for example, and is configured to be matched in a GPS radio wave frequency band (for example, 1.57542 GHz). As shown in FIG. 1, the antenna device 1 includes a substrate 2 and a radiating element 3 provided on the substrate 2.

  The substrate 2 is configured by bonding two substrates 4 and 5 together. These substrates 4 and 5 are formed of a dielectric plate, for example. Conductive foil, for example, copper foil (not shown) is provided on almost the entire upper surface of the upper substrate 4. Conductive foil, for example, copper foil (not shown) is provided on almost the entire lower surface of the lower substrate 5. Between the two substrates 4 and 5, four U-shaped strip lines (conductive lines) 6a to 6d are arranged at positions shown in the figure. These strip lines 6a to 6d are formed by, for example, printing a conductor pattern on one surface of the substrates 4 and 5.

  On the other hand, the radiating element 3 is configured by winding a linear conductor as a whole into a square (substantially square) spiral. Specifically, the radiating element 3 includes a first linear conductor 7 bent in a square shape from the center, a second linear conductor 8 bent in an L shape, and a first linear conductor 8 bent in an L shape. 3 linear conductors 9, a fourth linear conductor 10 bent in an L-shape, a straight fifth linear conductor 11, and the four strip lines 6 a to 6 d.

  In the case of this configuration, extended portions 7 a and 7 b that are bent downward are provided at both ends of the first linear conductor 7. The central extending portion 7a is connected to the feeding point 12 of the substrate 2 by soldering, for example, and the outer peripheral extending portion 7b is connected to one end of the strip line 6a by soldering, for example. Further, extended portions 8 a and 8 b that are bent downward are also provided at both ends of the second linear conductor 8. The extended portion 8a at one end is connected to the other end of the strip line 6a by soldering, for example, and the extending portion 8b at the other right end is connected to one end of the strip line 6b by soldering, for example. .

  In addition, extended portions 9 a and 9 b that are bent downward are also provided at both ends of the third linear conductor 9. The extending portion 9a at one end is connected to the other end of the strip line 6b by, for example, soldering, and the extending portion 9b at the other end is connected to one end of the strip line 6c by, for example, soldering. . Furthermore, extended portions 10 a and 10 b that are bent downward are also provided at both ends of the fourth linear conductor 10. The extended portion 10a at one end is connected to the other end of the strip line 6c by soldering, for example, and the extended portion 10b at the other end is connected to one end of the strip line 6d by soldering, for example. .

  An extension portion 11 a that is bent downward is provided at one end portion of the fifth linear conductor 11. The extending portion 10a at one end is connected to the other end of the strip line 6d by, for example, soldering. By configuring in this way, a configuration is realized in which the strip lines 6a to 6d provided on the substrate 2 are connected as detour paths in the middle of the linear conductor of the radiating element 3 in order to increase the path length. Has been.

  Furthermore, in the present embodiment, the path length of the outer peripheral portion of the radiating element 3 is configured to be λ (λ is the wavelength of the radio wave) (note that the total length of the path length of the radiating element 3 (spiral from the center). The total length of the shape is 2λ). Here, since the four strip lines 6a to 6d provided on the substrate 2 are connected to the middle portions of the four linear conductors of the radiating element 3, the path length is increased accordingly. For this reason, compared with the structure which does not connect stripline 6a-6d, the length of the linear conductor of the radiation element 3 can be shortened. In the case of the radiating element 3 of the present embodiment, the length of one side of the linear conductor on the outer peripheral portion (dimension L1 shown in FIG. 1) is set to 25 mm (0.125λ).

  Incidentally, when the radiating element 3 is composed of only the linear conductor 13, the configuration shown in FIG. 3 (comparative example) is obtained. In the case of this configuration, the length of one side of the linear conductor on the outer periphery of the radiating element 3 (dimension L2 shown in FIG. 3) is 60 mm (0.3λ). Therefore, it can be seen that the size of the antenna device 1 of this embodiment (see FIG. 1) is ½ or less than that of the comparative example (see FIG. 3).

On the other hand, in this embodiment, the five linear conductors 7 to 11 of the radiating element 3 are supported by a plurality of support portions (not shown) provided on the substrate 2, so that only a set distance is provided on the substrate 2. It is configured to be spaced apart.
And the result of having measured the return loss of the antenna apparatus 1 of the above-mentioned structure is shown in FIG. According to FIG. 2, it can be seen that the return loss is reduced in the frequency band of the GPS radio wave (for example, 1.57542 GHz) and matching is achieved, and the antenna device 1 operates well as a GPS antenna. I understand. In addition, the result of having measured the return loss of the antenna apparatus 1 of the said comparative example (refer FIG. 3) is shown in FIG. From FIG. 4, it can be seen that the antenna device 1 of the comparative example also works well as a GPS antenna.

  Next, the directivity of the antenna device 1 of this example was measured. The measurement surface in this case is shown in FIG. And the directivity measurement result in this measurement surface is shown in FIG. Further, with respect to the antenna device 1 of the comparative example (see FIG. 3), the directivity measurement result on the measurement surface is shown in FIG. From these FIG. 6 and FIG. 7, it can be seen that circularly polarized waves are radiated in the same direction in front of the antenna, and it can be seen that both the present example and the comparative example have good directivity.

  FIG. 8 shows a second embodiment of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals. In the second embodiment, the two strip lines 14a and 14b provided on the substrate 2 are connected to the two sides of the linear conductor on the outer periphery of the radiating element 3 as a detour path. . The other configuration of the second embodiment is the same as that of the first embodiment. Therefore, in the second embodiment, substantially the same operational effects as in the first embodiment can be obtained.

  FIG. 9 shows a third embodiment of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals. In the third embodiment, the microstrip lines 15a to 15d are used in place of the strip lines 6a to 6d. Specifically, four U-shaped microstrip lines (conductive lines) 15a to 15d are arranged at positions shown in the figure on the upper surface of the substrate 16 provided with copper foil (not shown) on almost the entire lower surface. It is installed. These microstrip lines 15a to 15d are formed by printing a conductor pattern on the upper surface of the substrate 16, for example.

  The configuration of the third embodiment other than that described above is the same as that of the first embodiment. Accordingly, in the third embodiment, substantially the same operational effects as in the first embodiment can be obtained.

  FIG. 10 shows a fourth embodiment of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals. The fourth embodiment includes a ground element 18 formed by winding a linear conductor 17 into a square (substantially quadrangular) spiral, and the linear conductor 17 of the ground element 18 is connected to a radiating element. It comprised so that it might arrange | position between 3 linear conductors.

  Note that the end or middle portion of the ground element 18 is connected to a copper foil (ground) provided on the upper surface of the substrate 4 or the lower surface of the substrate 5. In addition, the ground element 18 is supported by a plurality of support portions (not shown) provided on the substrate 2, so that the ground element 18 is provided on the substrate 2 at a set distance, similarly to the radiation element 3. It has become.

  The configuration of the fourth embodiment other than that described above is the same as that of the first embodiment. Accordingly, in the fourth embodiment, substantially the same operational effects as in the first embodiment can be obtained. In particular, in the fourth embodiment, since the ground element 18 is arranged between the radiating elements 3, the gain can be improved.

  FIG. 11 shows a fifth embodiment of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals. In the fifth embodiment, a ground plate 19 made of a conductor plate is disposed on the surface of the substrate 2 where the radiating element 3 is not provided, that is, the lower surface of the substrate 5. The configuration of the fourth embodiment other than that described above is the same as that of the first embodiment.

  Accordingly, in the fifth embodiment, substantially the same operational effects as in the first embodiment can be obtained. In particular, in the fifth embodiment, since the ground plate 19 is arranged on the back surface of the antenna device 1 (the bottom surface of the substrate 5), the gain in the antenna front direction can be improved.

  In each of the above embodiments, the overall shape of the radiating element 3 is a substantially square shape, but is not limited thereto, and may be configured to be, for example, a circular shape or an elliptical shape. When configured in this way, the shape of the substrate 2 is preferably configured to be, for example, a circular shape or an elliptical shape.

Here, FIG. 12 shows a sixth embodiment of the present invention. The same components as those in the first embodiment are denoted by the same reference numerals. In the sixth embodiment, the entire shape of the radiating element 3 is configured to be substantially circular. The remaining configuration of the sixth embodiment is the same as that of the first embodiment.
Accordingly, in the sixth embodiment, substantially the same operational effects as in the first embodiment can be obtained.

  Further, in each of the above-described embodiments and modified examples, two or four strip lines or microstrip lines are provided. However, one, three, or five or more strip lines are provided. Also good.

The perspective view of the antenna apparatus which shows 1st Example of this invention Characteristic diagram showing return loss of antenna device FIG. 1 equivalent diagram showing a comparative example FIG. 2 equivalent diagram showing a comparative example A perspective view of an antenna device for explaining a measurement surface Characteristic diagram showing directivity of antenna device FIG. 6 equivalent diagram showing a comparative example FIG. 1 equivalent view showing a second embodiment of the present invention. FIG. 1 equivalent view showing a third embodiment of the present invention. FIG. 1 equivalent view showing a fourth embodiment of the present invention. FIG. 1 equivalent view showing a fifth embodiment of the present invention. FIG. 1 equivalent view showing a sixth embodiment of the present invention.

Explanation of symbols

In the drawings, 1 is an antenna device, 2 is a substrate, 3 is a radiating element, 6a to 6d are strip lines (conductive lines), 7 is a first linear conductor, 8 is a second linear conductor, and 9 is a first line conductor. 3 linear conductors, 10 is a fourth linear conductor, 11 is a fifth linear conductor, 13 is a linear conductor, 14a and 14b are strip lines, 15a to 15d are microstrip lines, 16 is a substrate, 17 Is a linear conductor, 18 is a ground element, and 19 is a ground plate.

Claims (8)

In an antenna device comprising a substrate and a radiating element that is provided on the substrate by being spaced apart by a set distance and configured by winding a linear conductor in a spiral shape,
A plurality of conductive lines provided on the substrate, being substantially point-symmetric with respect to the center of the spiral and arranged along the spiral linear conductor;
An antenna device, wherein the plurality of conductive lines are connected to a plurality of intermediate portions of the linear conductors of the radiating element as detour paths in order to increase a path length. The shape of the radiating element is substantially rectangular,
The antenna device according to claim 1, wherein the conductive line is configured to be connected to the linear conductor at four sides of an outer peripheral portion of the radiating element. The shape of the radiating element is substantially rectangular,
2. The antenna device according to claim 1, wherein the conductive line is configured to be connected to the linear conductor at two sides of the outer peripheral portion of the radiating element.   The antenna device according to claim 1, wherein the conductive line is formed of a strip line.   4. The antenna device according to claim 1, wherein the conductive line is configured by a microstrip line. A ground element is formed by winding a linear conductor in a spiral shape,
6. The antenna device according to claim 1, wherein the linear conductor of the ground element is arranged between the linear conductors of the radiating element.   The antenna device according to claim 1, wherein a ground plate is disposed on a surface of the substrate on which the radiating element is not provided. The antenna device according to claim 1, wherein the radiation element has a substantially circular shape.

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