JP2655853B2 - Microwave antenna - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a microwave antenna suitable for transmission / reception of microwave relay, satellite broadcasting, radar, and the like, and more particularly, to an array-type microwave in which a plurality of radiators are arranged. Wave antenna.

[Prior Art] Conventionally, as this kind of microwave antenna, for example, there is an antenna as shown in FIGS. Each of the antennas shown in these figures includes a dipole 1 and a reflector 2.

FIG. 4 shows a dipole antenna with a reflector. In this antenna, the microwave radiated from the dipole antenna 1 is reflected by the reflector 2 by the action of the reflector, and is radiated by forming a beam on the front surface.

FIG. 5 shows an antenna in which the reflector 2 is replaced with a corner reflector. This antenna is
It is more efficient than the antenna shown in FIG. 4, and the radiation from the dipole antenna 1 can be radiated to the front surface with high efficiency.

Next, in the antenna shown in FIG. 6, the reflector 2 used in the antenna shown in FIGS. 4 and 5 is of a short back fire type, and a sub reflector 3 is provided on the front surface of the dipole antenna 1. The antenna is configured as follows. This antenna has a further improved radiation efficiency than that shown in FIG. 4 or FIG.

[Problems to be Solved by the Invention] However, the above-mentioned conventional antenna has the following problems.

There is a problem that the gain as a microwave antenna is low even if the efficiency is improved. That is, the antenna shown in FIG. 4 has a gain of about 6 dB, the antenna shown in FIG. 5 has a gain of about 10 dB, and the antenna shown in FIG. 6 has a gain of about 15 dB.

In addition, the above conventional microwave antennas have a problem that, when the structural form is set, the beam width and the gain are uniquely determined and cannot be changed.

The present invention has been made to solve the above problems,
It is an object of the present invention to provide a microwave antenna which can realize a high gain and has a degree of freedom in designing a beam width and a gain to some extent without largely changing the form.

[Means for Solving the Problems] The present invention provides, as means for solving the above-mentioned problems, a reflector disposed in a channel shape for reflecting electromagnetic waves, and an electromagnetic wave inside a channel formed by the reflectors. A plurality of radiators that radiate, and a sub-reflector that is disposed in the channel opening while leaving an electromagnetic wave radiation opening and reflects electromagnetic waves.

The reflectors are arranged in a channel shape and, together with a sub-reflector described later, form a rectangular space that resonates electromagnetic waves radiated from a radiator described later. In this case, in order to prevent the electromagnetic wave from leaking to the rear of the channel, it is preferable to form the channel integrally. Needless to say, it is sufficient that the channel can be formed in a state where the electromagnetic waves do not leak, and the channel may be formed by combining different members. The reflector may be a member having a surface that reflects electromagnetic waves, and examples thereof include a metal material and a synthetic resin material having a conductor layer formed on the surface.

The radiator is preferably a dipole radiator such as a half-wave dipole, and a plurality of radiators are arranged along the channel substantially at the center of the cross-sectional space of the channel. This arrangement interval can be set as appropriate, and is set to, for example, 3λ. Also,
Irregular intervals are also possible. The number of radiators arranged is determined by the arrangement interval and the channel length of the antenna.

The radiator only needs to be capable of radiating microwaves in the channel so as to resonate, and is not limited to the above-described embodiment. For example, a structure in which excitation is performed by a waveguide may be employed. In addition, the microwave antenna of the present invention, 1GHz ~
It is suitable for an antenna of an electromagnetic wave having a wavelength of 15 GHz. Of course, it is possible to apply to other wavelengths.

The sub-reflector may be a member having a surface that reflects electromagnetic waves, like the above-described reflector, and may be, for example, a metal material, a synthetic resin material having a conductor layer formed on the surface, or the like. The sub-reflector is disposed along the channel at the channel opening, preferably at the opening surface. Preferably, the channel opening is provided substantially at the center in the width direction of the channel opening so as to cover the channel opening, leaving the electromagnetic wave radiation openings on both sides in the width direction of the opening.

The beam width and / or the antenna gain of this sub-reflector are set by appropriately selecting the width, that is, the area of the sub-reflector with respect to the area of the channel opening. For example, the width is selected in the range of 1/3 to 1/2 of the channel opening width. In this case, the longitudinal direction matches the length of the channel.

Further, the sub-reflection plate may be formed so as to be able to expand and contract in the width direction. For example, by arranging two metal plates so that one side thereof is slidably overlapped with each other, the overall width of the two metal plates stacked can be made variable.
In this case, the width of the sub-reflector is set to expand and contract in accordance with the desired beam width and / or antenna gain.

The electromagnetic wave radiation apertures provided on both sides of the aperture in the width direction do not necessarily have to have the same aperture area (aperture width). However, in consideration of the symmetry and side lobes of the formed beam, they have the same area (aperture width). (Opening width).

Further, in the present invention, a flare that expands toward free space may be provided in the electromagnetic wave radiation opening provided in the channel opening.

Note that the microwave antenna of the present invention can be applied to any of horizontal polarization, vertical polarization, and circular polarization.

[Operation] In the antenna of the present invention configured as described above,
When electromagnetic waves are radiated from the plurality of radiators, the electromagnetic waves resonate in a rectangular space formed by the channel formed by the reflector and the sub-reflector, and a part is radiated outside from the electromagnetic wave radiation aperture. When exciting multiple radiators,
When they are arranged at equal intervals, the excitation amplitude of each radiator is changed, while when they are arranged at unequal intervals, the side lobes are suppressed by exciting each radiator at equal amplitude. can do.

When the electromagnetic wave from each radiator resonates in the rectangular space, if the electromagnetic wave radiation aperture is large, the electromagnetic field distribution on the channel opening surface is concentrated only near each radiator.
Therefore, the directivity in the antenna axis plane (in the electric field plane) becomes broad, and the gain does not become so large.

On the other hand, if the width of the sub-reflector is increased and its area is increased, the radiation aperture becomes narrower and the electromagnetic field is more likely to be confined in the channel space. Spread. That is, the electromagnetic field distribution spreads in the lateral direction of the opening surface. Then, the electromagnetic field distribution of each adjacent radiator overlaps, the directivity in the antenna axis plane is sharpened, and the gain is increased.

Here, the relationship between the half width of the beam and the directivity gain with respect to the width of the sub-reflector when the opening width of the channel opening is constant, according to experiments performed by the present inventors, is based on the electric field surface (hereinafter referred to as E). In this case, it was confirmed that as the width of the sub-reflector was increased, the half-value width of the beam was reduced and the directivity gain was increased. On the other hand, with respect to the magnetic field plane perpendicular to the E plane (hereinafter referred to as the H plane), it was confirmed that the half width of the beam and the directivity gain did not change much with the change in the width of the sub-reflector.

Therefore, according to the present invention, the total gain can be made larger than the gain obtained with a conventional antenna of this type. For example, the maximum gain is about 15 dB in the past, but a high gain of about 20 dB or more is possible in the present invention.
Moreover, by changing the width of the sub-reflector, the gain can be set to a desired value within a certain range. For example, 12dB ~ 20
The desired value can be obtained in the range of dB. That is, the present invention can be designed to some extent arbitrarily in beam width and gain without significantly changing the format.

According to this operation, it is possible to adjust the gain of the antenna without using an expensive attenuator or the like. Therefore, the present invention is suitable for, for example, gain setting in a relay antenna or the like.

In the present invention, if a flare is provided in the electromagnetic wave radiation aperture, radiation impedance matching can be achieved, and a higher gain can be realized as compared with an antenna having the same configuration but without a flare. Lobes can be reduced.

Example An example of the present invention will be described with reference to the drawings.

<Configuration of First Embodiment> FIGS. 1A and 1B show a configuration of a microwave antenna according to a first embodiment of the present invention.

In the microwave antenna of the first embodiment shown in these figures, a plurality of half-wavelength dipole antennas are arranged as radiators 11 inside a reflector 12 forming a channel 10 having a U-shaped cross section. In addition, the sub-reflector 13 is arranged in the channel opening 10a.

The reflection plate 12 is made of a metal material such as aluminum,
It comprises a vertical piece 12a and two parallel parallel pieces 12b sandwiching the vertical piece 12a. The vertical piece 12a and the two parallel parallel pieces 12b are integrally connected and formed to form the channel 10.

The channel 10, together with the sub-reflector 13, constitutes a rectangular space that resonates the electromagnetic wave radiated from the radiator 11. In this embodiment, the channel 10 is formed such that the wavelength of the electromagnetic wave to be used is λ, the width D is 1.5λ, and the depth r is 0.5λ. The length 1 is determined by the number of radiators 11 arranged, and if the arrangement interval is k and the arrangement number is n, then approximately l = k (2n + 1). Needless to say, it is only necessary that the interval is such that the electromagnetic waves resonate, so the specific size is not limited to this.

A plurality of the radiators 11 are arranged on a line substantially at the center of the cross-sectional space of the channel 10 at an interval of 3λ in the longitudinal direction of the channel 10. That is, a plurality of radiators 11 are arranged at the center in the width direction of the vertical piece 12a of the reflection plate 12 constituting the channel 10 with its dipole parallel to the channel 10. The radiator 11 only needs to be able to radiate microwaves resonably in the channel 10, and is not limited to the above embodiment.

The sub-reflection plate 13 is formed of a band-shaped metal plate, and is arranged in the channel opening 10a along the longitudinal direction of the channel 10 and substantially at the center of the channel opening 10a in the width direction. At this time, the sub-reflector 13 leaves the electromagnetic wave radiation openings 14a and 14b on both sides in the width direction of the channel opening 10a,
It is arranged so as to cover the channel opening 10a. In this embodiment, the electromagnetic wave radiation openings 14a and 14b have the same area (opening width).

The sub-reflection plate 13 is arranged in parallel with the vertical piece 12a of the reflection plate 12, and the interval between them is set so as to be substantially equal to the depth of the channel 10. That is, the wavelength is set to about の of the wavelength of the electromagnetic wave used. However, the interval is not limited as long as the size of the channel 10 is sufficient as long as the interval is such that the electromagnetic waves resonate.

The width of the sub-reflector 13, that is, the channel opening
The area of the sub-reflection plate 13 with respect to the area of 10a is appropriately selected according to the intended beam width and / or antenna gain. For example, 1/3 of the opening width of the channel opening 10a
Select the width in the range of ~ 1/2. In this case, the longitudinal direction matches the length of the channel 10. Specifically, 0.5
A plurality of types of sub-reflectors 13 having different widths in the range of λ to 0.8λ may be prepared, and may be appropriately selected as needed.

<Operation of First Embodiment> Next, the operation of the antenna according to the present embodiment configured as described above will be described.

First, when an electromagnetic wave is radiated from each radiator 11, the electromagnetic wave resonates in a rectangular space formed by the channel 10 composed of the reflector 12 and the sub-reflector 13, and a part of the electromagnetic wave radiation aperture is formed.
It is radiated from 14a and 14b to the outside. At this time, channel 10
The central portion of the opening 10a is covered with the sub-reflection plate 13, so that the radiation opening of the electromagnetic wave becomes narrow, and the electromagnetic field becomes
It becomes easy to be confined in the space of 10, this electromagnetic field,
It is dispersed in the width direction of the antenna, and the electromagnetic field distribution spreads in the lateral direction of the aperture surface. Then, the electromagnetic field distribution of each adjacent radiator overlaps, the directivity in the antenna axis plane is sharpened, and the gain is increased.

The antenna of the present embodiment has the electromagnetic wave radiation apertures 14a and 14b.
A beam is formed by combining the electromagnetic waves radiated from and. This beam has different characteristics depending on the width of the sub-reflector 13, as described above.

Here, the relationship between the opening areas of the electromagnetic wave radiation openings 14a and 14b and the characteristics of the formed electromagnetic wave beam will be described with reference to FIGS. 2 (A) to 2 (C). In the present embodiment, the opening area of the electromagnetic wave radiation openings 14a and 14b is
Therefore, here, it is indicated by the width of the sub-reflection plate 13. Also, in FIGS. 2 (A) and (B),
As shown in FIG. 1, the E plane is a plane orthogonal to the channel opening plane at the center thereof and parallel to the channel depth.
The H plane is a plane orthogonal to the channel opening plane and the E plane.

FIG. 2 (A) shows the sub-reflector 13 having a width of 0.5λ, 0.6
The half-width characteristics on the E-plane and the H-plane of the microwave antenna of the present embodiment in which four types of λ, 0.7λ and 0.8λ are selected and mounted are shown. In the figure, the horizontal axis represents the width d (λ) of the selected sub-reflection plate 13, and the vertical axis represents the actual value (゜) of the half-width realized thereby. As is clear from this figure, the half-value width on the E-plane indicated by the dot in the figure is
Decreases as the width d (λ) increases. For example,
When the width d (λ) of the sub-reflector 13 is 0.8λ, the angle is 19 °. This indicates that the beam is narrowed and sharpened as the width d (λ) of the sub-reflection plate 13 increases, that is, as the width of the electromagnetic wave radiation apertures 14a and 14b decreases.

On the other hand, on the H plane indicated by a cross in the figure, the half-width of the beam slightly changes with respect to the change in the width of the sub-reflector 13.
That is, as the width d (λ) of the sub-reflector 13 increases, the half-value width of the beam decreases within a range of several degrees.

FIG. 2 (B) shows the same as FIG. 2 (A).
As the sub-reflector 13, the width is 0.5λ, 0.6λ, 0.7λ and 0.8.
The directional gain on the E-plane and the H-plane of the microwave antenna of the present embodiment in which four types of λ are selected and mounted are shown. In the figure, the horizontal axis is the width d (λ) of the selected sub-reflector 13
And the vertical axis is the directional gain (dB) achieved by it.
Are respectively shown. As is apparent from this figure, the directivity gain on the E-plane indicated by the point 中 in the figure increases as the width d (λ) of the sub-reflector 13 increases. For example, the width d of the sub-reflector 13
When (λ) is set to 0.8λ, it becomes 12 dB. this is,
The directional gain increases as the width d (λ) of the sub-reflector 13 increases, that is, as the width of the electromagnetic wave radiation apertures 14a and 14b decreases.

On the other hand, on the H plane indicated by a cross in the figure, the directivity gain of the beam slightly decreases with the change in the width of the sub-reflector 13. That is, as the width d (λ) of the sub-reflector 13 increases, it decreases within a range of several dB.

Note that the total gain can be obtained from the directivity gains of the E plane and the H plane shown in FIG. 2B, and is about 20 dB in the antenna of this embodiment.

FIG. 2C shows an electromagnetic wave radiation pattern on the E-plane when the width d (λ) of the sub-reflector 13 is 0.8λ. As is clear from this figure, the antenna of the present embodiment has a small side lobe, and has a preferable radiation pattern as the antenna.

As described above, in the present embodiment, the half-width and the directivity gain can be set to some extent freely only by selecting the width of the sub-reflector 13 and without changing the other components. Therefore, unlike conventional antennas of this type,
The beam width and gain in the E plane can be designed arbitrarily arbitrarily without largely changing the format.

<Configuration of Second Embodiment> FIGS. 3A and 3B show a configuration of a microwave antenna according to a second embodiment of the present invention.

The microwave antenna according to the second embodiment shown in these figures is configured by including flares 15a and 16a, 16b and 16b and 15b in the electromagnetic wave radiation openings 14a and 14b of the antenna configured in the same manner as the first embodiment. You. The configuration of the present embodiment is the same as that of the first embodiment except for the flare portion, and therefore the description will be made focusing on the differences.

The flares 15a and 15b are provided at the tip of the parallel piece 12b of the reflection plate 12, and are mounted as a flare of the entire channel 10 with the tip expanding outward. Also,
Flares 16a and 16b are connected to both sides of the sub-reflector 13,
The cross section is configured to be triangular in a state where these are connected. Of course, the arrangement of the flares 16a and 16b and the sub-reflector 13 does not necessarily have to have a triangular cross section.

Similarly to the antenna of the first embodiment, the antenna of this embodiment forms a rectangular space in which the channel 10 and the sub-reflector 13 resonate the electromagnetic wave radiated from the radiator 11.
In this embodiment, the channel 10 is formed such that the wavelength of the electromagnetic wave to be used is λ, the width D is 1.5λ, the depth r is 0.5λ, and the length 1 is k (2n + 1). . The width d of the sub reflector 13 is 0.5λ, 0.6λ, 0.7λ and
It is appropriately selected from 0.8λ. The distance S from the position of the sub-reflector 13 to the tip of the flare 16a, 16b is selected to be 1.0λ, and the distance F from the channel opening 10a to the tip of the flare 15a, 15b is set to 1.5λ. . In this state, Flare 1
The opening end width W of 5a and 15b is 3λ. Needless to say, it is only necessary that the interval is such that the electromagnetic waves resonate, so the specific size is not limited to this.

<Operation of Second Embodiment> The operation of the antenna of this embodiment is basically the same as that of the first embodiment.
Although the same as the embodiment, the side lobe can be reduced by the presence of the flare. That is, as described above, on the H plane, the directivity gain of the beam with respect to the change in the width of the sub-reflector 13 is several dB as the width d (λ) of the sub-reflector 13 is increased. Decrease in range. This means an increase in side lobes. However, in the present embodiment, the side lobe is suppressed by the flare, and as a result, an increase in the side lobe caused by increasing the directivity gain of the beam is suppressed.

Further, in the present embodiment, the radiation impedance can be matched, and a higher gain can be realized than in the first embodiment.

In this embodiment, the width of the sub-reflector 13 is selected, flare is added, and the other values are not changed at all. Can be set freely.

Incidentally, when the antenna of the present embodiment was actually measured,
The overall gain was 23 dB, the H beam width was 20 °, and the E-plane beam width was 10 °. FIG. 3C shows an electromagnetic radiation pattern characteristic on the E plane of the microwave antenna according to the present embodiment.

<Other Embodiments> In each of the above embodiments, an example was described in which a half-wavelength dipole was used as the radiator. However, the present invention is not limited to this, and another radiator can be used. For example, a structure in which excitation is performed by a waveguide may be employed. In each of the above embodiments, the dipoles are arranged in parallel to the channel extending direction. However, the dipoles may be arranged vertically.

In each of the above embodiments, an example in which the reflection plate is formed of metal is shown. However, the reflection plate in the present invention is not limited to this, and a conductive layer such as a metal film is formed on the surface of a synthetic resin material such as fiber-reinforced plastic. Any material can be used as long as it reflects electromagnetic waves, such as those adhered.

Further, the sub-reflection plate 13 may have a structure capable of expanding and contracting in the width direction. For example, by arranging two metal plates so that one side thereof is slidably overlapped with each other, the overall width of the two metal plates stacked can be made variable. With such an extendable structure, it is possible to easily adjust the half width of the beam, the gain, and the like at the installation site of the antenna. Therefore, the gain can be adjusted without using an expensive attenuator or the like.
It is suitable for setting an optimum gain in a relay antenna or the like.

Further, in the above embodiment, the sub-reflector 13 is provided at the center of the channel opening in the width direction, and the electromagnetic wave radiation openings 14a and 14b have the same opening width. However, depending on the direction of the beam to be formed, it is not always necessary to make them equal. Instead, both may be different according to the intended beam. Also, the opening width
It is not limited to the values shown in the above embodiments.

[Effects of the Invention] As described above, the present invention can improve the gain, and has a degree of freedom in designing the beam width and the gain in the E-plane to some extent without largely changing the form. There is an effect that can be realized.

[Brief description of the drawings]

FIG. 1A is a perspective view showing the configuration of a first embodiment of the microwave antenna of the present invention, FIG. 1B is a side view thereof, and FIG.
FIG. 2A is a graph showing the half-width characteristic on the E-plane of the microwave antenna of the present embodiment. FIG. 2B is a graph showing the directivity gain characteristic on the E-plane of the microwave antenna of the present embodiment. FIG. 2 (C) is a graph showing the radiation pattern characteristics on the E-plane of the microwave antenna of the present embodiment. FIG. 3 (A) is a perspective view showing the configuration of the microwave antenna of the second embodiment of the present invention. 3 (B) is a side view thereof, FIG. 3 (C) is a graph showing electromagnetic wave radiation pattern characteristics on the E-plane of the microwave antenna of the present embodiment, and FIGS. 4 to 6 are conventional microwave antennas. 4 (A), 5 (A) and 6 (A) are front views thereof, and FIGS. 4 (B), 5 (B) and 6 (B) are It is sectional drawing of them. 10 Channel 10a Channel opening 11 Radiator 22 Reflector 13 Subreflector 14a, 14a Electromagnetic radiation aperture 15a, 15b, 16a, 16b Flare

Claims (6)

(57) [Claims] 1. A reflecting plate having a surface for reflecting an electromagnetic wave having a channel shape with a concave cross section and having both ends opened in a channel extending direction, and a concave shape of a channel formed by the reflecting plate. A plurality of radiations arranged in the space surrounded by the channel along the extension direction of the channel, each having a beam axis of an electromagnetic wave radiated in a plane orthogonal to the channel extension direction. And a sub-reflector that is disposed at a position that covers an opening of a space surrounded by the concave shape of the channel formed by the reflector and reflects electromagnetic waves. Between at least one of the two parallel pieces along the channel extension direction, disposed to leave a gap constituting an electromagnetic wave radiation aperture, the reflector and the sub-reflector, the channel bottom of the reflector, and A microwave antenna, wherein one surface of the sub-reflector is disposed in a relative positional relationship to face each other, and forms a rectangular space for resonating electromagnetic waves radiated from the radiator. 2. The microwave antenna according to claim 1, wherein said sub-reflector is configured to cover the whole of said plurality of radiators. 3. The distance between the opposing surfaces of the reflection plate is:
3. The microwave antenna according to claim 1, wherein said microwave antenna has a length corresponding to 3/2 of a wavelength of an electromagnetic wave radiated from said radiator. 4. The microwave antenna according to claim 1, wherein said sub-reflector has a width corresponding to 1/3 to 1/2 of a width of said channel opening. 5. The microwave antenna according to claim 1, wherein said radiators are arranged at intervals corresponding to a length three times the wavelength of an electromagnetic wave radiated from said radiators. 6. The electromagnetic wave radiation aperture is formed between each of two parallel pieces of the reflector along the channel extension direction, and each of the two parallel pieces of the reflector along the channel extension direction. Two first flare members extending in the channel extension direction respectively adjacent to the electromagnetic wave radiation apertures respectively formed between the two ends, each of which expands toward the free space from each of the two ends; Two sides respectively extending toward the free space with the two sides along the electromagnetic wave radiation opening of the sub-reflection plate as base ends, and forming two inclined surfaces respectively reducing the distance from the base end toward the free space. The microwave antenna according to any one of claims 1 to 5, further comprising a second flare member.