JP3923329B2 - Compound antenna - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a composite antenna for receiving both broadcast signals transmitted by both satellite waves and terrestrial waves, such as XM satellite radio broadcasts and Sirius satellite broadcasts that start broadcasting in the continental United States.
[0002]
[Prior art]
Refer to FIG. 9 for an example of a conventional composite antenna that receives both a satellite wave transmitted from a satellite and a terrestrial wave received by the ground station and transmitted again from the ground station with a different modulation method. To explain.
[0003]
FIG. 9 is a perspective view of an example of a conventional composite antenna. In FIG. 9, a rectangular planar radiation element 12 is disposed on the surface of the dielectric plate 10, a ground plate 14 is disposed on the back surface of the dielectric plate 10, and the dielectric plate is disposed on the planar radiation element 12 from the back surface side. A circularly polarized wave receiving patch antenna 16 that receives a circularly polarized satellite wave transmitted from a satellite is configured by a planar radiation element 12 and a ground plate 14 that are electrically connected to a feeder line (not shown) penetrating 10. Has been. In addition, a vertical linearly polarized wave receiving antenna element 18 that protrudes upward and includes a helical coil and receives a vertical linearly polarized ground wave is disposed at the center position of the planar radiating element 12. The vertically linearly polarized wave receiving antenna element 18 is in an insulated state from the planar radiating element 12.
[0004]
The directivity characteristics of the conventional composite antenna having such a configuration are as shown in FIGS. FIG. 10 is a vertical in-plane directivity characteristic diagram in which a satellite wave is received by the circularly polarized wave receiving patch antenna 16. FIG. 11 is a vertical in-plane directivity characteristic diagram in which a terrestrial wave is received by the vertical linearly polarized wave receiving antenna element 18. FIG. 12 is a horizontal plane directivity characteristic diagram in which a terrestrial wave is received by the vertical linearly polarized wave receiving antenna element 18.
[0005]
[Problems to be solved by the invention]
In the conventional composite antenna shown in FIG. 9, as shown in FIG. 12, the directional characteristic in the horizontal plane shows omnidirectionality with respect to the ground wave. Moreover, although not shown in the drawing, it is a matter of course that the directivity characteristic in the horizontal plane shows omnidirectionality with respect to the satellite wave. However, as shown in FIG. 10, the gain in the vertical direction is the largest with respect to the satellite wave, and the gain decreases as the elevation angle decreases. This causes a change in reception sensitivity depending on the place where the reception is performed and the posture where the composite antenna is installed. And as shown in FIG. 11, the gain in the low elevation angle of a horizontal direction is small with respect to a terrestrial wave. In order to obtain good reception sensitivity for terrestrial waves, it is desirable that the gain of the low elevation angle in the horizontal direction is large.
[0006]
Since the present invention has been made in view of the circumstances of the prior art as described above, the gain change is small due to the difference in elevation angle with respect to the satellite wave, the gain is large even at a low elevation angle, and the low elevation angle with respect to the ground wave. It is an object of the present invention to provide a composite antenna improved so that the gain becomes larger.
[0007]
[Means for Solving the Problems]
In order to achieve such an object, the composite antenna of the present invention is a composite antenna that receives a circularly polarized satellite wave and a vertical linearly polarized terrestrial wave, and has an upwardly convex cone shape and a substantially constant thickness. A conical radiating element is disposed on the surface of the dielectric member with the conical apex as a center, a ground plate is disposed on the back surface of the dielectric member, and a feed line is connected to the conical radiating element. The circularly polarized wave receiving patch antenna capable of receiving the circularly polarized wave is formed by the conical radiating element and the ground plate, and the vertical linearly polarized wave is projected upward from the cone-shaped apex of the dielectric member. A linearly polarized wave receiving antenna element capable of receiving a signal is disposed in an insulated state from the conical radiating element, and a coaxial central conductor is connected to the base end of the vertically linearly polarized wave receiving antenna element . .
[0008]
The dielectric member may be conical, the conical radiating element may be disposed on the surface of the dielectric member, and the vertical linearly polarized wave receiving antenna element may include a helical coil.
[0009]
Further, a central conductor of the first coaxial structure as the feeder line is electrically connected to the conical radiating element from the ground plate side through the dielectric member, and the outer conductor of the first coaxial structure is electrically connected. Is electrically connected to the ground plate, the base end of the vertical linearly polarized wave receiving antenna element is electrically connected to the center conductor of the second coaxial structure, and the outer conductor of the second coaxial structure is connected to the ground plate. It can also be configured by electrical connection.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1A and 1B are external views of a first embodiment of a composite antenna according to the present invention. FIG. 1A is a plan view and FIG. 1B is a side view. 2 is an AA cross-sectional arrow enlarged view of FIG. FIG. 3 is a vertical in-plane directivity characteristic diagram in which satellite waves are received by a circularly polarized wave receiving patch antenna. FIG. 4 is a vertical in-plane directivity characteristic diagram in which terrestrial waves are received by the vertical linearly polarized wave receiving antenna element. FIG. 5 is a horizontal plane directivity characteristic diagram in which the terrestrial wave is received by the vertical linearly polarized wave receiving antenna element. FIG. 6 is a longitudinal sectional view in which the composite antenna of FIG. 1 is accommodated in an antenna housing case.
[0011]
In the composite antenna of the present invention, the conical conical radiating element 22 made of a conductive metal plate, a conductive metal thin film, or the like is formed on the surface of the dielectric member 20 having a convex conical shape and a substantially constant thickness t. Is disposed. A conical radiating element 22 is disposed around the apex of the dielectric member 20, and the apexes coincide. The edge of the conical radiating element 22 is provided with notch-like perturbing elements 22a and 22a at two radially opposing positions. In addition, a ground plate 24 made of a conductive metal thin film or the like is disposed on substantially the entire back surface of the dielectric member 20. Further, the central conductor 26a of the first coaxial line 26 penetrates the dielectric member 20 from the back side and is appropriately electrically connected to the conical radiating element 22 on the surface by soldering 28 or the like. Further, the outer conductor 26b of the first coaxial line 26 is electrically connected to the ground plate 24 by appropriate soldering or the like. Accordingly, a conical circularly polarized wave receiving patch antenna is formed by the conical radiating element 22 and the ground plate 24 provided with the dielectric member 20 in between. As an example, the cone-shaped radiating element 22 for receiving a 2.3 GHz circularly polarized satellite wave having a transmission frequency of XM satellite radio broadcasting has an apex angle of 125 ° and a dimension from the apex to the edge. Is 25 mm. Of course, the external dimensions of the conical radiating element 22 with respect to the reception frequency should be appropriately set according to the dielectric constant of the dielectric member 20.
[0012]
Furthermore, a vertical linearly polarized wave receiving antenna element 30 is provided at the conical apex of the dielectric member 20 so as to protrude upward, and the helical coil portion 30a and the base end side thereof are a straight portion 30b. The straight line portion 30b penetrates the apex of the dielectric member 20 in the vertical direction and is electrically connected to the center conductor 32a of the second coaxial line 32 provided on the back surface side. The outer conductor 36b of the second coaxial line 32 is appropriately electrically connected to the ground plate 24 on the back surface of the dielectric member 20 by soldering or the like. The vertical linearly polarized wave receiving antenna element 30 is insulated from the conical radiating element 22. The vertical linearly polarized wave receiving antenna element 30 functions as an antenna at a portion above the ground plate 24. As an example, the vertical linearly polarized wave receiving antenna element 30 is set to an electrical length of ¼ wavelength of 2.3 GHz of the broadcast transmission frequency so as to resonate. Is done.
[0013]
In the composite antenna of the present invention having such a configuration, as shown in FIG. 3, the vertical in-plane directivity received by the conical radiating element 22 with respect to the satellite wave has a low elevation angle of approximately ± 70 ° from vertically above. The reception sensitivity is substantially the same as 5 dB, and even at a low elevation angle of ± 90 °, the gain is improved by about 3 dB as compared with the conventional composite antenna shown in FIG. . Therefore, there is little change in the reception sensitivity with respect to the satellite wave depending on the location where the satellite wave is received and the posture where the composite antenna of the present invention is installed. In addition, the reception sensitivity at a low elevation angle is improved. Thus, the satellite wave can be reliably received. In addition, although the directivity characteristic in the horizontal plane with respect to the satellite wave is not illustrated, it is a matter of course that it is non-directional.
[0014]
As shown in FIG. 4, the vertical directivity characteristic received by the vertical linearly polarized antenna element 30 with respect to the terrestrial wave is approximately 1 dB at a low elevation angle of ± 90 °, compared with the conventional composite antenna shown in FIG. Thus, the gain is improved by about 3 dB. Thereby, the reception sensitivity is improved by about 3 dB with respect to the ground wave.
[0015]
Here, since the conical radiating element 22 acts as a reflecting plate with respect to the vertical linearly polarized antenna element 30, a gain of a low elevation angle of ± 90 ° is obtained by making the reflecting plate into a conical shape having a small apex angle. However, even when the apex angle of the conical radiating element 22 is simply reduced from 180 °, the gain of the low elevation angle of ± 90 ° of the vertical linearly polarized antenna element 30 is uniformly improved. Rather, the increase and decrease occur alternately. Therefore, the inventors set the apex angle of the conical radiating element 22 as the reflecting plate to 125 ° by experiment.
[0016]
The composite antenna of the present invention as described above is housed in an antenna housing case as shown in FIG. 6 so that it can be mounted on the roof of a car as an example. In FIG. 6, a circuit board 40 is disposed on the base side of the dielectric member 20, and a low noise amplification circuit (not shown) for amplifying satellite wave and ground wave reception signals is mounted on the circuit board 40. The other ends of the first and second coaxial lines 26 and 32 are appropriately electrically connected to the circuit board 40, and the received signal is input to the low noise amplifier circuit. The amplified output of the low noise amplifier circuit is derived by the output cable 42. A radome 44 made of a substantially conical dielectric is provided so as to cover the composite antenna from above, and a base 46 is disposed below the composite antenna. The radome 44 and the base 46 constitute an antenna housing case 48 capable of housing the composite antenna in a watertight manner. Furthermore, the base 46 can be appropriately fixed to the roof of the vehicle by sticking or the like.
[0017]
Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 7 is an external perspective view of a second embodiment of the composite antenna of the present invention. In the second embodiment shown in FIG. 7, the pyramid-shaped radiating element 52 made of a conductive metal plate, a conductive metal thin film, or the like with the apex coincident with the surface of the dielectric member 50 having a quadrangular pyramid and a substantially constant thickness. Is disposed. A vertical linearly polarized wave receiving antenna element 30 including a helical coil is provided so as to protrude upward from the apex of the dielectric member 50. A ground plate (not shown) is provided on the back surface of the dielectric member 50, and an appropriate feeding line is electrically connected to the quadrangular pyramid radiating element 52 to form a circularly polarized wave receiving patch antenna.
[0018]
Even in the second embodiment of the present invention shown in FIG. 7, the gain of the low elevation angle can be improved for both the satellite wave and the ground wave as in the first embodiment.
[0019]
Furthermore, a third embodiment of the present invention will be described with reference to FIG. 8A and 8B are external views of a third embodiment of the composite antenna of the present invention. FIG. 8A is a plan view and FIG. 8B is a front view. The third embodiment shown in FIG. 8 differs from the first embodiment in that a feeding line for the conical radiating element 22 is provided on the surface of the dielectric member 20 in place of the first coaxial line 26. This is formed by a microstrip line 60 made of a conductive metal thin film. Needless to say, the same effects as those of the first embodiment can be obtained.
[0020]
In the first embodiment, the first and second coaxial lines 26 and 32 are used. However, any structure may be used as long as a coaxial structure is formed. Further, as in the first embodiment, the planar projection shape is not limited to the one in which the conical radiating element 22 having a circular planar projection shape is provided on the surface of the conical dielectric member 20, and the planar projection shape is rectangular (including squares and rectangles). Or one with a square corner cut out. Further, as in the second embodiment, the quadrangular pyramid radiating element 52 having a rectangular planar projection shape is not provided on the surface of the quadrangular pyramid-shaped dielectric member 50, and the conical radiating element having a circular planar projection shape is provided. It may be. In the second embodiment, the dielectric member and the cone-shaped radiating element disposed on the surface thereof are not limited to a quadrangular pyramid, and may be any pyramid shape such as a pentagonal pyramid or a hexagonal pyramid. Further, the dielectric member may be an elliptical cone or a rectangular quadrangular pyramid. The conical radiating elements provided on the surfaces of the dielectric members 20 and 50 may have any patch shape whose planar projection shape can receive circularly polarized waves. Further, in the embodiment, the vertical linearly polarized wave receiving antenna element 30 is formed to include a helical coil in order to shorten the physical length. However, if the physical length can be long, it is formed from a pole antenna. Of course, any structure may be used as long as the antenna has a non-directional horizontal plane directivity.
[0021]
【The invention's effect】
Since the composite antenna of the present invention is configured as described above, the following special effects can be obtained.
[0022]
In the composite antenna according to claim 1, the radiation element forming the circularly polarized wave receiving patch antenna has a conical shape, so that the vertical in-plane directivity characteristic of the satellite wave received by the circularly polarized wave receiving patch antenna is low. The gain is improved both at the elevation angle and at the low elevation angle of the vertical in-plane directivity when the ground wave is received by the vertical linearly polarized wave receiving element. In addition, the gain is substantially constant over a wide range from vertically above to a low elevation angle of approximately ± 70 ° with respect to the satellite wave. Therefore, the reception sensitivity of the satellite wave does not change significantly due to a change in the location where the satellite wave is received or the attitude of the composite antenna.
[0023]
In the composite antenna according to claim 2, the whole is formed in a substantially conical shape, and a vertically linearly polarized wave receiving antenna element including a helical coil having a short physical length is provided at the apex thereof. It is suitable for a small configuration.
[0024]
In the composite antenna according to claim 3, since the received signal by the circularly polarized wave receiving patch antenna and the vertical linearly polarized wave receiving antenna element is derived by the first and second coaxial structures, Does not cause attenuation.
[Brief description of the drawings]
1A and 1B are external views of a first embodiment of a composite antenna of the present invention, where FIG. 1A is a plan view and FIG. 1B is a side view;
FIG. 2 is an enlarged view taken along the line AA in FIG.
FIG. 3 is a vertical in-plane directivity characteristic diagram in which satellite waves are received by the circularly polarized wave receiving patch antenna of the composite antenna of the present invention.
FIG. 4 is a vertical in-plane directivity characteristic diagram in which terrestrial waves are received by the vertically linearly polarized wave receiving antenna element of the composite antenna of the present invention.
FIG. 5 is a directional characteristic diagram in a horizontal plane in which terrestrial waves are received by the vertically linearly polarized wave receiving antenna element of the composite antenna of the present invention.
6 is a longitudinal sectional view in which the composite antenna of FIG. 1 is housed in an antenna housing case.
FIG. 7 is an external perspective view of a second embodiment of the composite antenna of the present invention.
8A and 8B are external views of a third embodiment of the composite antenna of the present invention, where FIG. 8A is a plan view and FIG. 8B is a front view.
FIG. 9 is a perspective view of an example of a conventional composite antenna.
FIG. 10 is a vertical in-plane directivity characteristic diagram in which satellite waves are received by a circularly polarized wave receiving patch antenna of a conventional composite antenna.
FIG. 11 is a vertical in-plane directivity characteristic diagram when a ground wave is received by a vertical linearly polarized wave receiving antenna element of a conventional composite antenna.
FIG. 12 is a horizontal plane directivity characteristic diagram in which terrestrial waves are received by a vertical linearly polarized wave receiving antenna element of a conventional composite antenna.
[Explanation of symbols]
14, 24 Ground plates 18, 30 Vertically linearly polarized wave receiving antenna elements 20, 50 Dielectric member 22 Conical radiating element 26 First coaxial line 32 Second coaxial line 52 Square pyramidal radiating element 60 Microstrip line

Claims (3)

A composite antenna that receives a circularly polarized satellite wave and a vertical linearly polarized ground wave, and is centered on the top of the cone-shaped apex on the surface of a dielectric member that is convex upward and has a substantially constant thickness. A conical radiating element is disposed, a ground plate is disposed on the back surface of the dielectric member, a feed line is connected to the conical radiating element, and the circularly polarized wave is generated by the conical radiating element and the ground plate. A circularly polarized wave receiving patch antenna that can be received is formed, and a vertically linearly polarized wave receiving antenna element that can receive the vertically linearly polarized wave by protruding upward from the apex of the cone of the dielectric member is formed into the cone shape. A composite antenna comprising a radiating element and an insulating state, and a coaxial central conductor connected to a base end of the vertical linearly polarized wave receiving antenna element . 2. The composite antenna according to claim 1, wherein the dielectric member has a conical shape, the conical radiating element is disposed on a surface of the dielectric member, and the vertical linearly polarized wave receiving antenna element includes a helical coil. A composite antenna characterized by that. 3. The composite antenna according to claim 1, wherein the central conductor of the first coaxial structure as the feed line is electrically connected to the conical radiating element through the dielectric member from the ground plate side, The outer conductor of the first coaxial structure is electrically connected to the ground plate, the proximal end of the vertical linearly polarized wave receiving antenna element is electrically connected to the center conductor of the second coaxial structure, and the second conductor A composite antenna comprising an outer conductor having a coaxial structure electrically connected to the ground plate.

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