JPH06334434A - Planar antenna system - Google Patents

Abstract

PURPOSE:To facilitate the manufacture of the planar antenna comprising plural patch antenna elements and to uniformize power supply to each antenna element by adjusting a coupling position of a coupling probe (feeding point) with respect to a patch to adjust the supplied power to each antenna element. CONSTITUTION:Plural antenna elements 24 are arranged to an upper H plane of a waveguide 10. Each element 24 is provided a metallic plate (patch) 28 provided on the upper H plane of the waveguide 10 acting like a ground plate via a dielectric layer 26 and a leg (coupling probe) 30 extended downward from the patch 28. The probe 30 is projected in the waveguide 10 through a small hole 32 provided on the H plane and coupled electromagnetically with the waveguide 10 thereby. The coupling coefficient of power of a predetermined frequency sent from the waveguide 10 to the patch 28 depends on a ratio of an impedance of the probe 30 and an impedance of the patch 28. The difference from the power supplied to the elements 24 caused by a difference from the installed position with respect to the probe 20 is corrected by setting a coupling degree of each antenna element 24 in response to a distance from the feeding probe 20 to excite all the elements 24 at an equal amplitude.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flat antenna device for receiving radio waves such as satellite communication, and more particularly to a flat antenna device having a plurality of patch antennas.

[0002]

2. Description of the Related Art In recent years, satellite communications using satellites, mobile communications in automobiles, etc. have become widespread with the progress of communications technology. Therefore, receiving satellite broadcasts in mobile units is also being considered.

In order to receive satellite broadcasting, the antenna must have a high gain because the radio waves from the satellite are weak. On the other hand, it is preferable that the antenna mounted on the moving body be as small as possible. Particularly in an automobile or the like, the antenna is often placed on the roof and is required to have a low posture.

As such an antenna, a plane antenna for receiving circularly polarized waves is considered preferable. For example, Japanese Patent Application Laid-Open No. 2-235409 discloses an antenna element that uses a patch element, a slot element, or the like, and a feeding line that uses a microstrip line or a triplate line. According to such an antenna,
The antenna can have a low profile, that is, a horizontally long structure,
Suitable for in-vehicle use. Further, since the element and the power feeding line can be manufactured by printing or etching, there is an advantage that the manufacturing is easy and the assembly is easy.

In such a planar antenna, a plurality of antenna elements are provided to obtain a high gain. However, as the number of antenna elements increases, there is a problem that the loss of the feeder line increases and the efficiency of the antenna decreases. On the other hand, Japanese Unexamined Patent Publication No. 4-35401 discloses a planar antenna using a waveguide in which a plurality of helical antenna elements or patch antenna elements are arranged. In this planar antenna, the legs of each antenna element are projected into the waveguide to couple the feeding point of the waveguide to each antenna element. Then, by changing the leg length of the plurality of antenna elements into the waveguide according to the distance from the feeding point of the waveguide, the coupling coefficient of each antenna element to the waveguide is changed, and the electric field distribution of the planar antenna is changed. Is uniform.
With such a configuration, it is possible to obtain a planar antenna using a waveguide, which has a reduced number of feed lines and high efficiency.

[0006]

However, according to the above conventional example, the leg length of each antenna element must be precisely adjusted according to the distance from the feeding point. Therefore, in the helical antenna element, it is necessary to set the length of the leg portion to a predetermined length and then accurately fix it so that the amount of protrusion into the waveguide is as set. Further, in the case of a patch element, it is necessary to create leg portions each having a predetermined length and attach them to a metal flat plate. Then, such work has to be performed for each antenna element, which is a troublesome and difficult task.

[0007]

The present invention is a planar antenna device in which a plurality of antenna elements are coupled to a waveguide fed by one feeding probe, and at least one of the antenna elements is A patch consisting of a metal plate and a rod-shaped coupling probe whose one end is joined to this patch and extends in the vertical direction, and the distance from the center of the metal plate at the junction point between the patch and the coupling probe is from the feeding probe of each patch antenna. It is set according to the position of.

The antenna elements are aligned on the upper surface of the rectangular waveguide, for example. The waveguide can have a shape in which two rectangular waveguides are joined, a window is provided in the center thereof, and a feeding probe is arranged therein, whereby power is supplied to the two rows of antenna elements. be able to. The patches are preferably formed at once by photoetching or the like.

[0009]

Operation: The impedance of the coupled probe changes depending on the length and thickness of the probe. On the other hand, the input impedance of the patch differs depending on the junction point (position of the feeding point) of the coupling probe. Then, when the impedance of the coupled probe and the impedance of the patch are equal, the coupling between the two becomes maximum, and the coupling becomes smaller in other cases.

In the present invention, by changing the position of the junction point, the degree of coupling in each antenna element is adjusted while keeping the length and thickness of the coupling probe in the antenna element the same. Then, by setting the degree of coupling in each antenna element according to the distance from the feeding probe, the difference in the power supplied to the antenna element caused by the difference in the distance from the feeding probe is corrected, and all antenna elements are equalized. Amplitude can be excited.

Therefore, the patch and the coupling probe can be made of the same material, are easy to manufacture, and can accurately adjust the power between the antenna elements. Also, the manufacturing cost can be suppressed.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. Although a transmission antenna device will be described here, the same applies to a reception antenna device.

First Embodiment FIG. 1 is a perspective view showing a structure of a waveguide and a feeding probe according to a first embodiment. A rectangular waveguide 10 is made of metal, and a partition 12 made of metal is used. Two waveguides 14,
It is divided into 16. Therefore, the two waveguides 14, 1
6 has a shape in which one narrow surface (hereinafter referred to as E surface) is joined. And the central part of the partition part 12 is cut off and the window 12a is provided. In the vicinity of the central portion of the window 12a, the feeding probe 20 is projected from the back side (lower side) of the wide surface (hereinafter referred to as H surface) of the waveguide 10.
The feeding probe 20 is composed of an extension of the central conductor of the feeding coaxial line 22, and has a thickened tip portion 22a as shown in FIG. 2 (A) or as shown in FIG. 2 (B). In addition, it is preferable to cover the circumference with a dielectric sleeve 22b. By configuring the power feeding probe 20 in this way, the impedance here can be adjusted, and impedance matching between the waveguide 10 and the power feeding probe 20 can be achieved in a wide band. The window 12
The position of a is near the center of the partition 12, but it does not necessarily have to be near the center. Further, it is preferable to chamfer the end portion of the partition portion 12 generated by providing the window 12a. The outer conductor of the coaxial line 22 is the waveguide 10.
It is connected to the. Further, both ends of the waveguide 10 are subjected to treatment such as short-circuiting, opening, matching termination, etc. depending on the situation.

On the upper surface H of the waveguide 10, a plurality of antenna elements 24 are arranged in line, as shown in FIG. That is, the antenna elements 24 are arranged in one row in each of the waveguides 14 and 16. This antenna element 24 is
As shown in FIG. 4, this is a microstrip patch antenna element, and a metal plate (patch) 28 provided on the upper H surface of the waveguide 10 functioning as a ground plate via a dielectric layer 26, and this patch 28. It consists of a leg portion (coupling probe) 30 extending downward from the. This coupling probe 30 has a small hole 3 provided on the upper surface H of the waveguide 10.
It penetrates 2 and protrudes in the waveguide 10, and thereby is electromagnetically coupled to the waveguide 10. The patch 28 is formed on the dielectric layer 26 by a method such as photo etching or printing.
Therefore, a plurality of patches 28 can be formed simultaneously.

The patch 28 has a circular shape as a whole and has a pair of notches at symmetrical positions. Then, the binding probe 30 is joined to a predetermined position (joint point) of the patch 28. The line connecting the joining point and the patch center is set at 45 degrees with respect to the line connecting the notches. And
In the present embodiment, the distance from the patch center of this junction is set according to the installation position of the antenna element 24.

Coupling coefficient α of the power of a predetermined frequency (which is assumed to be at resonance) transmitted from the waveguide 10 to the patch 28.
Is determined by the ratio of the impedance of the coupling probe 30 itself inserted in the waveguide 10 from the patch 28 and the impedance of the patch 28. Here, the impedance of the coupling probe 30 can be set to an arbitrary impedance depending on, for example, the length and thickness of the coupling probe 30. In addition, from the shape of the entire antenna
There is a predetermined restriction on the size of the above, and the impedance of the coupling probe 30 that can be actually changed is about several tens Ω to several hundreds Ω. The input impedance of the patch 28 is
The value varies depending on the relative permittivity and the thickness of the dielectric layer 26. Therefore, there are innumerable combinations of the coupling coefficients α for exciting each antenna element 24 with equal amplitude.

Here, examples of the relationship between the position of the feeding point with respect to the patch 28 and the coupling coefficient α are shown in FIGS. 5 and 6 show that the impedance of the coupling probe 30 is 1/2 of the input impedance at the edge of the patch 28, respectively.
And the coupling coefficient α when 1/3 is shown. In this way, the coupling coefficient α can be set to a desired value by changing the position of the feeding point.

That is, when the impedance of the coupling probe 30 and the impedance of the patch 28 are equal, the degree of coupling between the two becomes maximum, and otherwise the degree of coupling becomes small. Therefore, in this embodiment, by changing the position of the joining point, the coupling probe 30 in the antenna element 24 is changed.
Each antenna element 24 with the same length and thickness
Adjust the degree of coupling at.

Then, as shown in FIG. 7, by setting the degree of coupling in each antenna element 24 according to the distance from the feeding probe 20, the antenna element 24 is supplied to the antenna element 24 caused by the difference in the installation position with respect to the feeding probe 20. It is possible to correct the difference in the electric power to be generated and to excite all the antenna elements 24 with an equal amplitude.

Furthermore, the phase of the current in each antenna element differs depending on the distance from the feeding probe 20. In this example, the phase is adjusted by changing the orientation of the antenna element 24 (arranged by rotating mechanically), and the phases at the time of power combining of the antenna elements are matched. That is, the direction of the line connecting the notches in the patch 28 of each antenna element 24 is changed according to the distance from the power supply probe 20, and the phase is adjusted.

The antenna element 2 for generating the circularly polarized wave
As the shape of the patch 28 of No. 4, as shown in FIG. 8, it is possible to adopt a notch in a circular shape or a square shape, a projection provided with both, an ellipse, or the like.

As described above, in the antenna of this embodiment, the power and phase of the plurality of antenna elements can be adjusted. Therefore, combining the power of multiple antenna elements,
A highly sensitive antenna for satellite communication can be configured. Further, since the rectangular waveguide is used, it is possible to realize an array antenna with a small power loss in the waveguide and a high aperture efficiency. Furthermore, since a rectangular waveguide is used, a horizontally long structure can be obtained, and a low-profile antenna suitable for vehicle mounting can be realized. Since all the binding probes have the same length and thickness, there is no need to make a plurality of binding probe materials, the variation in characteristics is reduced, the production cost is reduced, and the productivity is excellent.
Further, the patch 28 can be formed at once by photoetching or the like, and the rotation angle can be set easily and accurately. In addition, by creating a mark of the feeding point position at this time, the joining position of the coupling probe 30 can be easily and accurately set.

The shape of the waveguide is not limited to the above-mentioned one. For example, when increasing the number of antenna elements 24 for one feeding probe 20, as shown in FIG. 9, the waveguide 10 having a linear shape is used.
Can be folded and doubled in length. Even in this case, the feeding point position of each antenna element 24 is
The powers of all the antenna elements 24 are adjusted to be the same. However, in the case of this embodiment, since the difference in power is large, the thickness and / or the length of the coupling probe 30 are set to two types, which are arranged in each row, and the position of the feeding point is changed in each row. Then, the power in each antenna element 24 may be made uniform. 9A shows an example in which the waveguide 10 is bent on both sides of the feeding probe 20, and FIG. 9B shows an example in which only one side is bent.

Further, FIG. 10 shows the waveguide 10
This is an example in which four antennas are joined, and the antenna of the above-described embodiment is
The two are joined together. That is, the same antenna element 24 is assigned to each of the four feeding probes 20. Further, FIG. 11 shows an example in which the rows of the antenna elements 24 (rows of the waveguide 10) fed by one feed probe are three rows or more. In this case, the electric power supplied to the central row becomes larger than that of the other rows unless some measures are taken. Therefore, FIG. 11 (A)
, The entrance (window) 12a of the waveguide 10 in the central row is
Is small. Further, in the example of (B), the windows 12a of each row are arranged concentrically with respect to the power feeding probe 20. The power supply probe 2 is also used in these examples.
The power supplied from 0 to each column can be the same.

Also in these examples, the coupling probe 30 for the patch 28 of the antenna element 24 in each row is used.
The joint position (feeding point) is changed according to the distance from the feeding probe 20 to make the power in each antenna element 24 uniform. Therefore, the same effect as that of the above-described embodiment can be obtained.

FIG. 12 shows still another embodiment. In this example, a director 32 made of a metal layer that is sufficiently thinner than the wavelength of the radio wave to be transmitted is provided above the antenna element 24 via a dielectric material (air in this example) having a low dielectric constant. In addition, a dielectric substrate 34 having mechanical strength is installed on the upper portion of the waveguide 10 at a predetermined interval and is formed thereon. The dielectric substrate 34 is supported by a predetermined number of dielectric spacers 36 according to the strength of the dielectric substrate 34.
The director 32 is provided above each antenna element 24,
For example, a shape such as a circle, a square, or a cross as shown in FIG. 13 is suitable. Further, the size of the director 32 and the height from the antenna element 24 are appropriately set based on the wavelength of radio waves to be handled and the like. The director 32 may be formed on the dielectric substrate 34 by etching or the like.

As described above, by providing the director 32 on each antenna element 24, the directivity of each antenna element 24 can be sharpened, and high sensitivity can be obtained without increasing the size of the antenna. .

[0028]

As described above, according to the planar antenna device of the present invention, the power supplied to each antenna element is adjusted by adjusting the joint position (feeding point) of the coupling probe to the patch. So the patch,
The coupled probes can be made of the same material, are easy to manufacture, and allow accurate power adjustment between the antenna elements. Also, the manufacturing cost can be suppressed.

[Brief description of drawings]

FIG. 1 is a partially cutaway perspective view showing a schematic configuration of an embodiment.

FIG. 2 is a cross-sectional view showing a configuration of a power supply probe 20.

FIG. 3 is a partially cutaway perspective view showing the overall configuration of the embodiment.

FIG. 4 is a diagram showing a configuration of an antenna element 24.

FIG. 5 is an example of a characteristic diagram showing a relationship between a feeding point position and a coupling coefficient.

FIG. 6 is an example of a characteristic diagram showing a relationship between a feeding point position and a coupling coefficient.

FIG. 7 is a diagram showing an arrangement of antenna elements 24 and a power supply state.

FIG. 8 is a diagram showing an example of the shape of a patch 28.

FIG. 9 is a diagram showing a bent example of a waveguide.

FIG. 10 is a diagram showing an example in which four antennas are joined.

FIG. 11 is a diagram showing an example of a waveguide in which three or more rows are joined.

FIG. 12 is a diagram showing an example in which a director 32 is provided.

FIG. 13 is a diagram showing an example of the shape of a director 32.

[Explanation of symbols]

 10 Waveguide 20 Feed probe 28 Patch 30 Coupling probe 32 Waveguide

Claims (1)

[Claims] 1. A planar antenna device in which a plurality of antenna elements are coupled to a waveguide which is fed by one feeding probe, wherein at least one of the antenna elements is a patch made of a metal flat plate. A rod-shaped coupling probe with one end joined to the patch and extending in the vertical direction is included.The distance from the center of the metal plate at the junction between the patch and the coupling probe is set according to the position of each patch antenna from the feeding probe. A planar antenna device characterized in that.