JP2003218630A - Antenna system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an antenna system capable of suppressing decreasing the amount of diffracting scattering waves and reflected waves propagated along a radome. <P>SOLUTION: In the antenna system provided with a radiation element, a reflection mirror and the radome, a radiation electromagnetic field adjustment sheet member is placed in parallel with a slope to an outer edge of the slope of the radome. In this case, it is desirable that the inner circumference of the radiation electromagnetic field adjustment sheet member should be substantially non-circular. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna device mainly used for wireless communication.

[0002]

2. Description of the Related Art FIG. 8 shows an example of the basic structure of an antenna device having a radiating element, a reflecting mirror and a radome. In FIG. 8, 1 is a primary radiator, 2 is a reflecting mirror for directing electromagnetic waves emitted from the primary radiator 1 in a desired direction, and 3 is a radome for protecting the primary radiator 1 and the reflecting mirror 2. The orientation of the surface of the radome 3 forms an angle of about 120 ° with the directivity of the electromagnetic wave determined by the reflecting mirror 2.

Another example of the basic structure of an antenna device having a radiating element, a reflecting mirror and a radome is shown in FIGS. 9 and 10. 9 and 10 are different from FIG. 8 in that
This is the point where the sub-reflecting mirror 4 is provided. In this case, the reflecting mirror 2 is called the main reflecting mirror.

An antenna device in which the sub-reflecting mirror 4 is a convex mirror as shown in FIG. 9 is called a Cassegrain type, and an antenna device in which the sub-reflecting mirror 4 is a concave mirror as shown in FIG. 10 is called a Gregorian type.

Only the basic structure of the antenna device shown in FIGS. 8 to 10 is that of the electromagnetic wave radiated from the primary radiator 1, the electromagnetic wave component not reflected by the reflecting mirror or the main reflecting mirror 2 and the diffraction scattering propagating along the radome 3. There is a problem in that the waves are emitted from the radome 3 to the outside as they are, and the wide-angle directivity characteristic, particularly the directivity characteristic on the rear side with respect to the main directivity, is adversely affected.

A means for solving this problem is disclosed, for example, in Japanese Utility Model Publication No. 57-117810. A specific example thereof is shown in FIG.

In FIG. 11, the radome 3 is provided so as to project from the reflecting mirror 2, and a radio wave absorber 9 is loaded in the projecting portion 8 of the radome 3. Here, the portion loaded with the radio wave absorber 9 is only the protruding portion 8.

With the configuration shown in FIG. 11, of the electromagnetic waves emitted from the primary radiator 1, the electromagnetic wave components not reflected by the reflecting mirror or the main reflecting mirror 2 are absorbed and attenuated by the electromagnetic wave absorber 9,
It is said that the diffracted and scattered wave from the edge of the reflecting mirror or the main reflecting mirror 2 is also attenuated.

[0009]

By the way, in recent years, the use of electromagnetic waves has progressed, and the need for suppressing unnecessary electromagnetic waves is increasing from the viewpoint of effective use of electromagnetic waves. However, even with the antenna device of FIG. 11, it is difficult to reduce the emission of unnecessary electromagnetic waves to a level below the level currently required, and new measures are required.

Therefore, an object of the present invention is to provide an antenna device capable of sufficiently reducing diffracted and scattered waves and reflected waves propagating along a radome.

[0011]

[Means for Solving the Problems] Claim 1 in the present invention
The invention of, in an antenna device comprising a radiating element, a reflecting mirror, and a radome, at the outer edge of the inclined portion of the radome,
A sheet-shaped radiation electromagnetic field adjusting member is arranged in parallel with the inclined portion.

The invention of claim 2 is characterized in that, in the invention of claim 1, the inner circumference of the radiation electromagnetic field adjusting member is substantially non-circular.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing an example of a part of an antenna device according to a first embodiment of the present invention. In FIG. 1, 2 is a reflecting mirror or main reflecting mirror, 3 is a radome, 5
Is a sheet-shaped radiation electromagnetic field adjusting member provided on the outer edge of the inclined portion of the radome 3 in parallel with the inclined portion, and 6 is a radome mounting portion.

In the case of FIG. 1, the radiation electromagnetic field adjusting member 5 is
Although an example is shown in which the antenna device is arranged on the outer surface of the radome 3 in a state where the antenna device is configured, the present invention is not limited to this, and it may be arranged on the inner surface of the radome 3 as shown in FIG. Needless to say, it may be embedded in the radome 3 as shown in FIG. Further, as shown in FIG. 4, between the reflecting mirror or the main reflecting mirror 2 and the radome 3,
It is also possible to provide the shield plate 7.

As the radiation electromagnetic field adjusting member 5, a radio wave absorber or an object that reflects radio waves (hereinafter referred to as a radio wave reflector) can be applied. As the radio wave absorber, a conductor such as carbon or a magnetic body is preferably used,
As the radio wave reflector, a conductor, a high dielectric constant dielectric material, a high magnetic permeability magnetic material, or the like is preferably used.

Next, a second embodiment of the present invention will be described. FIG. 5: is a front view which shows an example of a part of antenna device which is the 2nd Embodiment of this invention. In FIG.
An example in which the inner circumference of the radiation electromagnetic field adjusting member 5 has a sawtooth shape is shown.

The shape of the inner circumference of the radiation electromagnetic field adjusting member 5 is not limited to the shape shown in FIG. 5, but may be wavy as shown in FIG. 6, for example. Further, the radiation electromagnetic field adjusting member 5 shown in FIGS. 5 and 6 may be arranged on the radome 3 at the positions illustrated in FIGS. 1 to 3 as described in the first embodiment. .

As shown in FIGS. 5 and 6, since the radiation electromagnetic field adjusting member 5 has a substantially non-circular inner circumference, the diffracted scattered wave and the reflected wave propagating along the surface of the radome 3 are radiated. When reflected on the inner circumference of the electromagnetic field adjusting member 5, it is not reflected in a specific direction, so that it is possible to minimize the influence on the wide-angle directivity characteristic.

Here, a comparison between the second embodiment of the present invention and the prior art will be made. In this comparison, the used frequency was 7.5 GHz (wavelength about 40 cm), and each element of the antenna device is shown in Table 1.

[0021]

[Table 1]

In the example according to the second embodiment of the present invention, as shown in FIG. 7, the wide-angle directivity characteristic, particularly the rearward directivity characteristic is excellent, and the directivity of the conventional example 1 without the shielding plate is provided. The improvement of about 10 to 15 dB is shown in FIG. 12 showing the directional characteristic, and the improvement of about 5 dB is shown in FIG. 13 showing the directional characteristic of the conventional example 2 having a shield plate and no radiation electromagnetic field adjusting member.

The characteristic diagram shown in FIG. 7 is merely an example, and the antenna device according to each embodiment of the present invention is shown in FIG.
It is possible to obtain a wide-angle directivity characteristic equal to or higher than that of the characteristic diagram of FIG.

It is needless to say that there are embodiments of the present invention other than these embodiments, and the embodiments can be freely modified within the scope of the invention described in the claims. Nor.

As described above, in the antenna device of the present invention, since the sheet-shaped radiation electromagnetic field adjusting member is arranged in parallel with the inclined portion at the outer edge of the inclined portion of the radome, the wide-angle directivity characteristic, particularly the rear The directivity characteristics of are excellent.

[0026]

As described above, according to the present invention, since the sheet-shaped radiation electromagnetic field adjusting member is arranged at the outer edge of the inclined portion of the radome in parallel with the inclined portion, it propagates along the radome. It is possible to sufficiently reduce the diffracted and scattered wave and the reflected wave.

Further, by making the inner circumference of the radiation electromagnetic field adjusting member substantially non-circular, the diffracted scattered wave and the reflected wave propagating along the radome are reflected on the inner circumference of the radiation electromagnetic field adjusting member. In this case, it is possible to minimize the influence on the wide-angle directivity characteristic.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a part of an antenna device according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view showing another example of a part of the antenna device according to the first embodiment of the present invention.

FIG. 3 is a sectional view showing still another example of a part of the antenna device according to the first embodiment of the present invention.

FIG. 4 is a cross-sectional view showing an example of a part of the antenna device according to the first embodiment of the present invention, showing an example in which a shield plate is provided between a reflecting mirror or a main reflecting mirror and a radome. is there.

FIG. 5 is a front view showing an example of a part of an antenna device according to a second embodiment of the present invention.

FIG. 6 is a front view showing another example of a part of the antenna device according to the second embodiment of the present invention.

FIG. 7 is a wide-angle directivity characteristic diagram of the antenna device according to the second embodiment of the present invention.

FIG. 8 is a cross-sectional view showing an example of a basic configuration of an antenna device including a radiating element, a reflecting mirror, and a radome.

FIG. 9 is a cross-sectional view showing another example of the basic configuration of the antenna device including the radiating element, the reflecting mirror, and the radome.

FIG. 10 is a cross-sectional view showing another example of the basic configuration of the antenna device including the radiating element, the reflecting mirror, and the radome.

FIG. 11 is a cross-sectional view showing an example of a part of an antenna device in which a radio wave absorber is loaded on a protruding portion of a radome.

12 is a characteristic diagram showing an example of wide-angle directivity characteristics of the antenna device shown in FIG.

FIG. 13 is a characteristic diagram showing an example of wide-angle directivity characteristics of an antenna device in which a radio wave absorber is loaded on a protruding portion of a radome.

[Explanation of symbols]

1 Primary radiator 2 Reflector or main reflector 3 radome 4 Sub-reflector 5 Radiation electromagnetic field adjustment member 6 radome mount 7 Shield 8 protrusion 9 Radio wave absorber

Claims (2)

[Claims] 1. An antenna device comprising a radiating element, a reflecting mirror, and a radome, wherein a sheet-shaped radiating electromagnetic field adjusting member is arranged at an outer edge portion of the inclined portion of the radome in parallel with the inclined portion. An antenna device characterized by. 2. The antenna device according to claim 1, wherein an inner circumference of the radiation electromagnetic field adjusting member is substantially non-circular.