JPH0356007B2 - - 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 to reduce the size and weight. The present invention relates to a slot array antenna device that achieves the following.

[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, with only a slotted waveguide, a directional beam can only be formed in a plane that includes the tube axis of the slotted waveguide (hereinafter referred to as the horizontal plane), and only in a plane that is perpendicular to the horizontal plane (hereinafter referred to as the vertical plane). Since a directional beam in the vertical plane cannot be formed, a horn is usually attached to obtain a directional beam in the vertical plane.
It is used. 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 to this, the present applicant has created a slot with a dielectric waveguide mechanism and a small reflector, and by replacing the horn with a small reflector and reducing the size, it is smaller and lighter, and the opening area is kept small.・Proposed an array antenna device (Japanese Patent Application Laid-open No. 56-31205
issue).

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 a channel member 2, and the slot array antenna device shown in FIG.
A slotted waveguide 1 is inserted and fixed in the slotted waveguide 1, and in front of the slotted waveguide 1, with a space in between, a pair of dielectric plates 3a whose thickness is sufficiently thin compared to the wavelength used. A dielectric waveguide mechanism 3 consisting of a dielectric waveguide mechanism 3b is protrudingly provided, and a reflection mechanism is provided on the outside of the pair of dielectric plates 3a and 3b to reflect electromagnetic waves transmitted through the vicinity of the bases of the dielectric plates 3a and 3b and emitted. A plate 4 is provided at the opening of the channel member 2.

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. The electromagnetic wave energy is increased to form a directional beam and the sidelobe level is reduced.

In this case, the reflector 4 only needs to reflect electromagnetic waves emitted from the dielectric base at a large angle, so it can be short and the opening area can be made smaller than in conventional horns. For example, in the case of a conventional horn type, the aperture height is 4
This slot array was more than twice as large.
In the case of an antenna device, it may be about twice the wavelength, and the aperture area can be made small.

[Problem to be solved by the invention] The slot shown in FIG. 1 and FIG.
Although the array antenna device itself is sufficiently practical, it may be required to further reduce the sidelobe level.

In contrast, changes in the material, length, etc. of the dielectric plate,
Possible solutions include changing the channel member, changing the length of the reflector, and changing the mounting angle.

However, with this method, it is necessary to prepare a variety of parts depending on the specifications, the production process is complicated, and the weight and opening area increase. Realization was not easy.

The present invention was made in view of the above problems, and it is possible to reduce the sidelobe level without increasing the weight or opening area by simply changing the shape and mounting condition of the dielectric plate. It is an object of the present invention to provide a slot array antenna device that can be formed without the need to prepare various parts other than the above, and without complicating the production process.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a pair of dielectric plates in front of the slotted waveguide, sandwiching a space in front of the slot waveguide, the plate thickness of which is sufficiently thin compared to the working wavelength. In the slot array antenna device, the body plates are arranged side by side with protrusions, and a reflecting plate for reflecting electromagnetic waves is provided outside the base of the pair of dielectric plates. The dielectric plates are arranged in such a manner that the parallel dielectric plates are inclined inwardly at an angle of 0.8 to 5 degrees.

[Function] In the above structure, the function of the present invention is not necessarily clear theoretically, but it can be thought of as follows.

When parallel plane dielectric plates are arranged non-parallelly,
Due to the inclination of the inward surfaces of the pair of dielectric plates, the angle of incidence of the electromagnetic waves on the dielectric plates becomes smaller than in the case of parallel arrangement, so the transmittance of the electromagnetic waves increases at the base of the dielectric plates and is reflected by the reflector. Being done,
Electromagnetic waves traveling forward increase. On the other hand, for the same reason, the electromagnetic waves reflected by the inward facing surfaces of the pair of dielectric plates make an extremely small angle with the horizontal plane and travel almost forward. As a result, the forward radiant energy increases, the lateral (vertical direction) radiant energy decreases, and the side lobe level is kept low.

In addition, when a wedge-shaped dielectric plate is used in a non-parallel arrangement, the electromagnetic waves that pass through the dielectric plate are largely refracted toward the thicker side, similar to the refraction of light by a prism. The amount of electromagnetic waves reflected increases. That is, among the electromagnetic waves that pass through the dielectric plate, even those waves that were not reflected in the past are significantly refracted, enter the reflector, and are reflected forward, increasing the forward radiant energy.

In either case, the reflector can be used effectively and the sidelobe level can be reduced without increasing the aperture area. Of course, since there is no need to increase the size of the reflector, the weight of the antenna does not increase.

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

In the first embodiment of the slot array antenna device of the present invention shown in FIGS. 3 and 4, 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 between, a pair of dielectric plates 3 whose thickness is sufficiently thin compared to the wavelength used.
A dielectric waveguide mechanism 3 consisting of a and 3b is provided protrudingly, and the electromagnetic waves transmitted through the vicinity of the bases of the dielectric plates 3a and 3b are reflected on the outside of the pair of dielectric plates 3a and 3b. A reflecting plate 4 is provided at the opening of the channel member 2. Note that, except for the dielectric waveguide mechanism 3, the other configurations are the same as those shown in FIG. 1 above.

The channel member 2 is made of a metal plate or a material with metal walls and acts similarly to a waveguide. An example of a material having a metal wall surface is a plastic plate with a metal layer applied thereto by plating or other means.

The dielectric waveguide mechanism 3 includes two dielectric plates 3
a, 3b, and the dielectric plates 3a, 3b are
Each is made of a plate-shaped dielectric material slightly bent near the base, and the base is fixed to the inside of the parallel piece of the channel member 2 so that the extension lines of the outward surfaces approach each other at the tip side. Become.

The bending of the dielectric plate varies depending on the length of the plate, the length of the reflecting plate, and the opening angle, but the bending angle is extremely small, not exceeding 5 degrees. 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 too large, the main lobe pattern will deteriorate, so the above angle range is preferable.

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.

Projection length L of dielectric plates 3a and 3b in the forward direction
It is considered that the longer the wavelength, the better, but considering the inward inclination, a value several times the wavelength λ is appropriate. 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 is suppressed, so the dielectric plate mounting structure as in this embodiment is In this case, 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 of the outward facing surface is set to 0.78λ.
On the other hand, the distance d at the tip is the dielectric plates 3a, 3
It is determined by the length of b and the inclination angle, and in 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 the 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. In addition, the opening angle θ of the reflector plate is determined by considering the incident angle of the electromagnetic waves passing through the dielectric plate and the wind pressure.
Determined by experiment. In this example, it is 25 degrees.

In such a configuration, when an electromagnetic wave is emitted from the slot waveguide 1, the angle of incidence on the dielectric plates 3a and 3b becomes smaller by the inclination angle of the dielectric plates 3a and 3b. The transmittance becomes larger than that of the dielectric plates 3a and 3b.
Electromagnetic waves traveling at a large angle with respect to the horizontal plane near the base end, as shown by W1 in FIG.
Most of the light passes through the dielectric plate 3a, is reflected by the reflection plate 4, and travels forward.

Furthermore, the electromagnetic waves that are incident on the dielectric plate at an angle larger than the above W1 do not enter the reflecting plate 4, but spread slightly forward and travel, as shown by W2 in the figure.

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.

Here, the specifications of the slot array antenna device that provides the radiation pattern shown in FIG. 6 will be shown.

Wavelength used λ=31.9mm Distance between outward facing surfaces (non-opposing surfaces) of dielectric plates D≒25.0mm Distance between plates at the tip d≒22.0mm Plate thickness t≒2.49mm Forward protrusion length L≒108mm Relative permittivity ε〓 ≒2.8 Inclination angle ψ≒0.80° Reflector length l≒60.0mm Opening angle θ≒25° Set the dielectric plate spacing parallel to each other (D=d=0.78λ)
The first example has the same dimensions as this example except for
When compared with the radiation pattern of the slot array antenna device shown in the figure (Figure 7), the latter shows -
In the former case, that is, in this embodiment, the sidelobe level which was larger than 20 dB has become an extremely small level of -24 dB or less.

In the above embodiment, a parallel plane plate was used as the dielectric plate, but a wedge-shaped plate may also be used. 8th
The example shown in the figure is one such example.

A second embodiment of the present invention shown in FIG. 8 uses wedge-shaped plates as the dielectric plates 3a and 3b, and a groove 2a is provided on the non-projecting side of the parallel pieces of the channel member 2. The slot waveguide 1 is fixed to the channel member 2a, and the bases of wedge-shaped dielectric plates 3a and 3b are attached to the outer side of the parallel pieces of the channel member 2, and the reflector plate 4 is attached to the outer side of the wedge-shaped dielectric plates 3a and 3b. It is something.

The reflecting plate 4 is provided separately from the channel member 2. However, a wedge-shaped dielectric plate 3 is added to the channel member 2 and the reflecting plate 4, which have the same structure as the first embodiment.
a and 3b may be attached. Further, the channel member 2 and the reflecting plate 4 are formed of a metal plate or a plate having a metal wall surface, as in the case of the first embodiment.

Also in this embodiment, the sidelobe level is reduced as in the first embodiment described above.

Since the wedge-shaped dielectric plates 3a and 3b have their tips gradually tapered, electromagnetic waves trapped inside are radiated to the outside, which has the advantage of reducing back lobe due to reflection at the tips.

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

[Effects of the Invention] As explained above, the present invention provides a slot array antenna device equipped with a dielectric waveguide mechanism, in which a pair of dielectric plates are arranged such that the outward surfaces of the dielectric plates are
By configuring the dielectric plates to be installed in opposite directions at a slight angle with the corresponding surfaces of other dielectric plates, weight and opening area can be increased simply by changing the shape and mounting condition of the dielectric plates. It is possible to reduce the sidelobe level without having to bend the dielectric plate, and there is no need to prepare many different parts other than preparing a bent dielectric plate or a wedge-shaped dielectric plate, and the production process does not become complicated. This has the effect of forming an antenna.

[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. FIG. 7 is a characteristic diagram showing an actually measured radiation pattern of the example shown in FIG. 1, and FIG. 8 is a sectional view showing a second 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.

Claims (1)

[Claims] 1. In front of the slotted waveguide, a pair of dielectric plates whose thickness is sufficiently thin compared to the wavelength to be used are protruded and arranged side by side with a space in front of the slotted waveguide in between, and In a slot array antenna device configured by providing a reflector for reflecting electromagnetic waves on the outside of the base of a pair of dielectric plates, each of the pair of dielectric plates arranged in parallel has the following characteristics: The slots are arranged so as to be inclined inwardly in the range of 0.8 to 5 degrees.
Array antenna device. 2. The slot array antenna device according to claim 1, wherein the dielectric plate is a parallel plane plate. 3. The slot array antenna device according to claim 1, wherein the dielectric plate is a wedge-shaped plate.