JPH0342723B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a slot array antenna device suitable as an antenna for a marine radar, a relay device, etc., and in particular, it is equipped with a dielectric waveguide mechanism and is small and lightweight. The present invention relates to a slot array antenna device that is designed to

[Prior Art] Slot array antenna devices are smaller and lighter than parabolic antennas and the like, so they are often used in marine radars that need to be mounted on a mast or the like. However, the slot waveguide alone can only form a directional beam within a plane (hereinafter referred to as the horizontal plane) that includes the tube axis of the slot waveguide.
A plane perpendicular to the horizontal plane (hereinafter referred to as a vertical plane)
Since a directional beam in the vertical plane cannot be formed, a horn is usually mounted and used to obtain a directional beam in the vertical plane. Therefore, even though it is not as sharp as a parabolic antenna, when trying to obtain a sharp beam, the weight increases and the aperture area becomes large, which has the drawback of increasing the influence of wind pressure when used outdoors. In particular, the issue of wind pressure is extremely important for marine radars used on windy seas, as this has a great effect on not only the strength of the radar itself but also the rotational drive system.

In response, the applicant has developed a slot-type device that is equipped with a dielectric waveguide mechanism and a small reflector, and by replacing the horn with a small reflector to reduce the size and weight and reduce the opening area. He proposed an array antenna device (Japanese Patent Application Laid-Open No. 56-31205).

FIGS. 1 and 2 show an example of this slot array antenna device. The slot array antenna device shown in these figures has a groove 2a provided in the web of the channel member 2, and the groove 2a
A slot waveguide 1 is inserted and fixed in the slot waveguide 1, and a space in front of the slot waveguide 1 is sandwiched between the slot waveguide 1 and the slot waveguide 1.
A dielectric waveguide mechanism 3 consisting of a pair of dielectric plates 3a and 3b whose plate thickness is sufficiently thin compared to the wavelength used is provided protrudingly,
Further, on the outside of the pair of dielectric plates 3a, 3b, a reflection plate 4 is provided at the opening of the channel member 2, which reflects electromagnetic waves transmitted through the vicinity of the bases of the dielectric plates 3a, 3b and emitted. configured.

Of the electromagnetic waves radiated from the slot waveguide 1, this slot array antenna device detects those radiated at a small angle with respect to the horizontal plane.
It is reflected by the inward surfaces (opposing surfaces) of the dielectric plates 3a and 3b and guided forward, and the radiation emitted at a large angle is reflected forward by the reflection plate 4, thereby radiating it forward. increasing the electromagnetic energy transmitted to form a directional beam, and
It reduces the sidelobe level.

In this case, the reflector plate 4 may be short because it only needs to reflect electromagnetic waves emitted from the dielectric base at a large angle. Therefore, the opening area can be made smaller than that of conventional horns. for example,
In the case of conventional horn type antennas, the aperture height is more than four times the wavelength used, but in the case of this slot array antenna device, the height of the aperture is only about twice the wavelength, making it possible to reduce the aperture area. .

[Problem to be solved by the invention] The slot shown in FIG. 1 and FIG.
Although the array antenna device is fully usable on its own, considering that it will be used outdoors, it is preferable to attach a radome.

However, conventionally, no consideration has been given as to what kind of radome should be installed. In particular, a radome is desired that can contribute to sharpening the beam in terms of directional characteristics, that is, increasing the maximum gain.

The present invention has been made in view of the above-mentioned problems, and provides a slot array antenna device in which a radome is attached to suppress the increase in side lobes as much as possible and sharpen the main lobe beam. The purpose is to

[Means for Solving the Problems] In order to achieve the above object, the present invention has a structure in which a pair of plates are installed in front of the slot waveguide, sandwiching a space in front of the slot waveguide, and the plate thickness is sufficiently thin compared to the wavelength used. In a slot array antenna device, a dielectric waveguide mechanism is formed by protruding dielectric plates, and a reflecting plate for reflecting electromagnetic waves is provided outside near the base of the pair of dielectric plates, A radome made of a dielectric plate is attached to the outside of the pair of dielectric plates, and a spacer is arranged between the tips of the pair of dielectric plates and the inner surface of the tip of the radome. do.

In the above configuration, although the operation of the present invention is not necessarily theoretically clear, it can be thought of as follows.

A portion of the electromagnetic waves emitted from the pair of dielectric plates and the electromagnetic waves reflected from the reflector are reflected by the dielectric plates that constitute the radome on the outside.
This is thought to be because what is originally radiated laterally (in the vertical direction) to spread the beam is focused in the forward direction, contributing to sharpening the beam.

Further, by using the spacer, positioning when installing the radome can be easily performed. By the way, according to the inventor's experiments, it was found that the relative distance between the dielectric waveguide mechanism and the radome affects the radiation pattern of electromagnetic waves. This is considered to be more pronounced at the tip of the dielectric waveguide mechanism. When a spacer is used, at the tip of the dielectric waveguide mechanism,
The relative spacing with the radome can be maintained, and the radiation pattern can be maintained constant.

Note that the inside of the radome and the space between the dielectric plates constituting the dielectric waveguide mechanism may be filled with a support member such as a foam material. In this case, it functions as a positioning member in the process of filling the support member,
As a result, at the tip of the dielectric waveguide mechanism,
The relative spacing with the radome can be maintained.

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

FIGS. 3, 4 and 9 show the structure of a first embodiment of the slot array antenna device of the present invention. Note that FIG. 9 shows a state in which a spacer, which will be described later, is attached, and FIG. 4 shows a state in which a spacer is not attached.

3 and 4, in the slot array antenna device of this embodiment, a groove 2a is provided in the web of the channel member 2, and the slot waveguide 1 is inserted and fixed into the groove 2a. In front of the slotted waveguide 1, with a space in front of it in between, is a first dielectric waveguide mechanism 3 consisting of a pair of dielectric plates 3a and 3b whose thickness is sufficiently thin compared to the wavelength used.
are provided protrudingly, and the pair of dielectric plates 3a, 3b
A reflecting plate 4 is provided outside the opening of the channel member 2 to reflect electromagnetic waves transmitted through the vicinity of the bases of the dielectric plates 3a and 3b and emitted. Further, on the outside of the pair of dielectric plates 3a, 3b, dielectric plates 5a, 5b, which are sufficiently thin compared to the wavelength used, are provided to form a radome, as will be described later.
are arranged in parallel. These dielectric plates 5a and 5b are
A dielectric waveguide mechanism 5 is constructed.

Further, as shown in FIG. 9, in this embodiment, spacers 7 are attached to the tips of the dielectric plates 3a and 3b,
The dielectric plates 5a, 5b and the covering member 6 are positioned and attached by the outer periphery of the spacer 7 and the opening 4a of the reflecting plate 4.

For example, as shown in FIG. 10, the spacer 7 has a curved surface portion 7a corresponding to the tip shape of the covering member.
and a recess 7b into which the tips of the pair of dielectric plates 3a and 3b are fitted. This spacer 7 is
In order to avoid scattering of electromagnetic waves, it is made of a material that reflects less electromagnetic waves used, that is, a substance with a dielectric constant of approximately 1.

The spacers 7 are attached to the dielectric plates 3a, 3b by arranging a plurality of them at appropriate intervals in the longitudinal direction. In this case, if a cushion material is interposed at the part where the recess 7b and the tips of the dielectric plates 3a and 3b come into contact, excessive force will not be applied to the dielectric plates 3a and 3b during positioning work, and the work will be carried out smoothly. I can do it.

In addition, in this embodiment, the dielectric plates 3a and 3b are
The tips are placed close together and non-parallel. Of course,
It can also be applied when they are arranged in parallel. According to such a non-parallel arrangement configuration, side lobes can be suppressed smaller than when the dielectric plates 3a and 3b are arranged in parallel.

The channel member 2 is made of a metal plate or a material with metal walls and acts similarly to a waveguide. Materials with metal walls include, for example, plastic plates with a metal layer applied by plating or other means.

The first dielectric waveguide mechanism 3 is, for example,
It is composed of two dielectric plates 3a and 3b made of FRP (fiber reinforced plastic). Dielectric plate 3
a and 3b are each made of a plate-shaped dielectric material that is slightly bent near the base, and the bases are connected to the parallel pieces of the channel member 2 so that the extension lines of the outward surfaces approach each other on the tip side. It is fixed on the inside.

The dielectric plate is bent at an extremely small angle of about 1 to 5 degrees, although it varies depending on the length of the plate, the length of the reflecting plate, and the opening angle. However, if the parallel pieces of the channel member 2 are provided with an inclination, there is no need to bend the dielectric plate. Further, the parallel plane dielectric plate may be bent when attached to the channel member 2.

The inclination angle of the dielectric plates 3a and 3b has an effect on the sidelobe level, and according to the inventor's experiments, the larger the angle, the smaller the sidelobe level. However, if the angle is made too large, the radiation pattern of the main lobe will deteriorate, so the above angle range is desirable.

Further, the dielectric plates 3a and 3b are those having a sufficiently thin thickness compared to the wavelength, for example, plates having a thickness of 1/10 wavelength or less. In the case of this example, this plate thickness t is
It is set as 0.078λ. The plate thickness needs to be made thinner as the dielectric constant increases, and in this example, a plate with a dielectric constant of about 2.8 is used. The reason for reducing the plate thickness is to prevent deterioration of the radiation pattern due to electromagnetic waves being trapped within the dielectric plate.

It is considered that the longer the length L of the dielectric plates 3a and 3b in the front-rear direction, the better; however, considering the inward inclination, it is appropriate that the length L be several times the wavelength λ. In this example, it is 3.4λ.

Further, as the distance between the dielectric plates 3a and 3b becomes narrower, the side lobe level decreases. However, at the bases of the dielectric plates 3a and 3b, if the opening width of the channel member 2 is made smaller than 1/2λ, power radiation from the slot waveguide 1 is suppressed. In the case of a structure, it will inevitably be 1/2 wavelength or more. However, if the structure of the channel member 2 is different, the present invention is not limited to this. In this embodiment, the distance D between the outward facing surfaces is 0.78λ.

On the other hand, the distance d at the tip is the dielectric plate 3a,
It is determined by the length and inclination angle of 3b, and in the case of this example,
It is 0.69λ.

The reflecting plate 4 is made of a metal plate or a plate having a metal wall surface, like the channel member 2, and in this embodiment, it is integrally provided at the opening of the channel member 2, like the one in FIG. There is. The side lobe level of this reflecting plate 4 decreases as its length l increases, but as l increases, the wind pressure increases accordingly. Therefore, it is desirable that the wavelength be about twice the wavelength used, and in this embodiment, it is set to 1.9λ.

Further, the opening angle θ of the reflection plate 4 is determined by the dielectric plate 3a.
Alternatively, it is determined through experiments, taking into consideration the incident angle of the electromagnetic waves passing through 3b and the wind pressure. In this example, it is 25 degrees.

The second dielectric waveguide mechanism 5 has the base ends of dielectric plates 5a and 5b made of, for example, FRP (fiber-reinforced plastic) fixed to the opening 4a of the reflecting plate 4, and the dielectric plates 3a, They are arranged in parallel on the outside of 3b so as to cover these. That is, the second dielectric waveguide mechanism 5 is formed to sandwich the first dielectric waveguide mechanism 3 with an appropriate space between them. In this embodiment, the dielectric plates 3a, 3b are
Although it is made of the same material as , it may be made of a different material.

The dielectric plates 5a and 5b are the dielectric plates 3 and 3.
Similar to a and 3b, a plate having a sufficiently thin thickness compared to the wavelength λ, for example, 1/10λ or less, is used. In the case of this embodiment, the plate thickness t is set to 0.05λ.
The plate thickness is not limited to this value, but the dielectric plate 3
For the same reason as in cases a and 3b, it is necessary to make the material thinner as the dielectric constant increases.

The dielectric plates 5a and 5b are arranged so that their tips are close to each other. The reason for this is to avoid increasing side lobes, such as back lobes, that occur at angles far away from the main beam. However, even if they are provided in parallel, there is a beam focusing effect.

Furthermore, a curved covering member 6 is provided at the tips of the dielectrics 5a and 5b. In this embodiment, the covering member 6 is integrally provided with the same material as the dielectric plates 5a and 5b. Therefore, the dielectric waveguide mechanism 5 of this embodiment is provided by molding one dielectric plate into a substantially U-shaped shape that expands toward the opening, and the opening is connected to the reflecting plate 4. It is fixedly formed in the opening 4a of.

The covering member 6 and the dielectric plates 5a and 5b constitute a radome, and by covering both sides of the antenna device with appropriate side plates (not shown), the internal dielectric waveguide mechanism 3 and slot guide can be protected. Seal the wave tube 1.

In addition, in the present invention, in order to improve the radiation pattern of electromagnetic waves, the dielectric plate 3 of the dielectric waveguide mechanism 3 is
Plate-shaped dielectric plates 5a and 5b arranged in parallel with a and 3b
This covering member 6 does not necessarily need to be provided. However, the covering member 6 is essential to construct the radome. If a radome is provided, the influence of wind pressure can be reduced and water and dust can be prevented from entering.

In the above-described configuration, when an electromagnetic wave is emitted from the slot waveguide 1, the angle of incidence on the dielectric plates 3a and 3b, which are arranged in a non-parallel manner, becomes smaller by the inclination angle of the dielectric plates 3a and 3b. 1
The transmittance is higher than in the case of the parallel arrangement shown in the figure, and the electromagnetic waves traveling at a large angle with respect to the horizontal plane near the base ends of the dielectric plates 3a and 3b are
As shown by W1 in the figure, most of the dielectric plate 3a
and is reflected by the reflection plate 4. This electromagnetic wave W1 travels in a direction slightly away from the front, enters the dielectric plate 5a, is reflected inward here, enters the dielectric plate 3a again, is reflected, and advances forward. do.

Furthermore, the electromagnetic waves that are incident on the dielectric plate at an angle larger than W1 above do not enter the reflecting plate 4, but spread out slightly in front, and then enter the dielectric plate 5a, as shown by W2 in the figure. Some of it is transmitted and the rest is reflected. Then, it is reflected by the dielectric plate 3a,
Proceed forward.

On the other hand, the electromagnetic waves incident on the dielectric plate 3a at an angle larger than W2 are reflected by the inward surface of the dielectric plate and travel forward, as shown by W3 in the figure. In this case, the electromagnetic waves that are reflected are only those that have a large incident angle, so the radiant energy is focused and becomes a beam with little spread.

When the electromagnetic waves traveling like W1, W2, and W3 are superimposed, the radiation pattern shown in FIG. 6 is obtained.

Comparing this with the radiation pattern of the antenna device of the above embodiment except for the second dielectric waveguide mechanism 5 (see Fig. 7), it is found that in the former, that is, the antenna device of the above embodiment, the sidelobes are slightly smaller. Although it is higher, the beam half-width, that is, the −3 dB beam width is 22 degrees, which is sharper than the latter 24 degrees, and the antenna gain increases.

Next, a second embodiment of the present invention shown in FIG. 8 will be described.

In this embodiment, a flat plate-shaped covering member 6 is attached to the tip openings of dielectric plates 5a and 5b constituting a dielectric waveguide mechanism 5. The other configurations are the same as those in the first embodiment, so the description will not be repeated.

The covering member 6 of this embodiment includes dielectric plates 5a and 5b.
Although it is provided separately from the above, it may be provided integrally as in the first embodiment. Further, the material of the covering member 6 does not have to be the same as that of the dielectric plate, and it is sufficient that the material reflects less emitted electromagnetic waves.

In addition, when using the flat plate-shaped covering member 6 shown in the said 2nd Example, the curved surface part 7b of the said spacer 7 shown in FIG. 10 is used as a spacer in the flat form.

Next, the third embodiment of the present invention shown in FIG.
Dielectric plate 5a of the antenna device of the second embodiment,
A support member 8 is loaded inside the support member 5b.

The support member 8 is made of a material that is transparent to the electromagnetic waves used, that is, a material with a dielectric constant of approximately 1. For example, a foamed material such as expanded polystyrene is loaded between dielectric plates 5a and 3a, between dielectric plates 3a and 3b, and between dielectric plates 3b and 5b.

For example, in the case of the support member 8 made of a foamed material, the filling is carried out by fitting the foamed material that has been foam-molded in advance into each of the above-mentioned spaces, or by foaming and filling the foamed material raw material in each of the above-mentioned spaces. Do by doing.
In this case, the material between the dielectric plates 3a and 3b and the outside thereof do not necessarily have to be the same.

When foaming is performed in the dielectric plates 5a and 5b,
Because of the spacer 7, a space is created in which the foam material is not filled, and electromagnetic waves may be scattered in this space, which may cause an inconvenience. Therefore, as shown in FIG. 11, if a through hole 7c is provided in the spacer 7, the foam material will move through the through hole 7c, filling the unfilled portion, and the above-mentioned problem will not occur.

In each of the above embodiments, the dielectric plate constituting the second dielectric waveguide mechanism is attached to the inside of the reflection plate, but it may be attached to the outside. Alternatively, it may be provided outside the reflector so as to cover the entire antenna device without being fixed to the reflector.

In each of the above embodiments, the reflecting plate 4 is made of a flat plate, but it may be a curved plate such as a paraboloid.

[Effects of the Invention] As explained above, according to the present invention, the positional relationship between the dielectric waveguide mechanism and the radome can be maintained by the spacer, so even if the radome is attached to the outside of the pair of dielectric plates. This has the effect of suppressing the increase in side lobes to a minimum and sharpening the main lobe beam.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing an example of a slot array antenna device equipped with a dielectric waveguide mechanism, Fig. 2 is a sectional view thereof, and Fig. 3 is a slot array antenna device of the present invention.
FIG. 4 is a perspective view showing the first embodiment of the antenna device, FIG. 4 is a sectional view thereof, FIG. 5 is an explanatory diagram showing the operation of the first embodiment, and FIG. 6 is an actually measured radiation pattern of the first embodiment FIG. 7 is a characteristic diagram showing the measured radiation pattern of the antenna device of the first embodiment from which the second dielectric waveguide mechanism is removed.
The figure is a cross-sectional view showing a second embodiment of the slot array antenna device of the present invention, FIG. 9 is a cross-sectional view showing the first embodiment of the slot array antenna device of the present invention, and FIG. 10 is a cross-sectional view showing the first embodiment of the slot array antenna device of the present invention. FIG. 11 is a perspective view showing an example of a spacer used in this example, and FIG. 11 is a sectional view showing a third embodiment of the slot array antenna device of the present invention. 1... Slot waveguide, 2... Channel member,
3... Dielectric waveguide mechanism, 3a, 3b... Dielectric plate, 4... Reflection plate, 4a... Opening, 5... Second
dielectric waveguide mechanism, 5a, 5b... dielectric plate, 6
... Covering member, 7 ... Spacer, 8 ... Supporting member.

Claims (1)

[Claims] 1. A dielectric waveguide mechanism is constructed by protruding a pair of dielectric plates whose thickness is sufficiently thin compared to the wavelength used, with a space in front of the slotted waveguide in between. In the slot array antenna device, a radome made of a dielectric plate is provided on the outside of the pair of dielectric plates. What is claimed is: 1. A slot array antenna device which is attached to a slot array antenna device and further comprises spacers arranged at a plurality of locations between the tip portions of the pair of dielectric plates and the inner surface of the tip end of the radome. 2. The spacer has a curved surface corresponding to the shape of the tip of the member constituting the radome, and a recess into which the tip of the pair of dielectric plates is fitted. The slot array antenna device according to item 1. 3. The slot array antenna device according to claim 1, wherein a cushion material is interposed at a portion where the concave portion of the spacer contacts the tips of the pair of dielectric plates.