Claims
- 1. A slotted waveguide antenna assembly having a working wavelength in the microwave region including:
- a slotted waveguide for emitting a directive beam of microwaves;
- a holder member for supporting and fixing a rear portion of said slotted waveguide;
- a dielectric waveguiding arrangement formed of a pair of dielectric plate members, said dielectric plate members each being formed of a parallel planar plate and each having base and tip end portions, and each having a thickness which is one tenth or less of the working wavelength of said slotted waveguide antenna assembly, said dielectric plate members being supported at the base portions thereof by the holder member and disposed so that they are closer at the tip end portions thereof and being projected at the tip end portions thereof opposite said holder member, forwardly of the slotted waveguide, and arranged so as to define a space between them;
- a reflector, having two opposite walls, said reflector being provided outside of the dielectric plate members and supported by the holder member for reflecting microwaves emitted through the base portions of the respective dielectric plate members to form a radiated beam; and
- at least one fixing member having a thickness which is less than the working wavelength of the slotted waveguide antenna assembly provided at a position or positions spaced from the slotted waveguide, and disposed to extend between the opposite walls of the reflector connected thereto, said at least one fixing member having an end which extends outwardly from a wall of the reflector to form a mounting portion for mounting the slotted waveguide antenna assembly onto a place where the slotted waveguide antenna assembly is to be installed.
- 2. A slotted waveguide antenna assembly according to claim 1 further comprising an element for suppressing vertical polarization between the dielectric plate members.
Priority Claims (2)
| Number |
Date |
Country |
Kind |
| 59-35287[U] |
Mar 1984 |
JPX |
|
| 59-35288[U]JPX |
Mar 1984 |
JPX |
|
BACKGROUND OF THE INVENTION
This is a continuation of application Ser. No. 711,840, filed Mar. 14, 1985, which was abandoned upon the filing hereof.
1. Field of the Invention
This invention relates to a microwave antenna assembly suitable as an antenna for marine radars, and more particularly to a slotted waveguide antenna assembly fixed on a mounting portion and for mounting the assembly onto a rotary drive assembly.
2. Prior Art
A slot array antenna assembly comprising a slotted waveguide is already known. This type of antenna assembly is more compact in structure and lighter in weight than a parabolic reflector antenna and therefore it is widely used for marine radars or the like. However, the slotted waveguide can provide a beam directivity only in a plane including an axis of the slotted waveguide (hereinafter referred to as a horizontal plane) and cannot provide a beam directivity in a plane perpendicular to the horizontal plane (hereinafter referred to as a vertical plane). For this reason, the antenna assembly of this type is usually provided with a flared horn to obtain a directive beam in the vertical plane. Such an arrangement has been disclosed in U.S. Pat. No. 2,730,717.
FIG. 14 illustrates a flared horn type antenna assembly.
The antenna assembly of FIG. 14 is so constructed that a slotted waveguide 10 is fitted in a holder member 2 made of metal channel. A flared horn 5 functioning as a reflector is provided at an aperture portion of the holder member 2, and a grating 6 for suppressing vertical polarization and a radome 7 are placed at an aperture of the flared horn 5.
This antenna assembly is placed on a pedestal 50 encasing a rotary drive assembly therein and is rotated by the rotary drive assembly so as to be used as an antenna for a radar. The antenna assembly has a projection or rib 5a on a lower wall of the flared horn 5 and the antenna assembly is mounted on the pedestal in such a manner that it is fixed to an antenna support portion 52 of the pedestal 50 by the projection or rib 5a in cooperation with a portion of the holder member 2.
This mounting structure, however, has such problems that since the flared horn 5 is formed with the projection 5a, the shape of the horn 5 must be complicated and since the weight of the horn is supported by itself, the wall of the horn having the projection must be thick, thereby increasing manufacturing cost and time. This further increases the weight of the horn and increases the load applied to a portion of the pedestal where the antenna assembly is mounted.
The applicant of the present invention has previously proposed a slotted waveguide antenna assembly which comprises a dieletric waveguiding arrangement and a small-sized reflector which is used in place of the flared horn of the conventional antenna assembly for reducing an area of the aperture (U.S. Ser. No. 350,739, now U.S. Pat. No. 4,488,157).
In this slotted waveguide antenna assembly, the applicant has succeeded in suppressing the side lobe and reducing the aperture area of the reflector because of the effect of the dielectric waveguiding arrangement. As a result, the entire weight of the antenna assembly is reduced and wind pressure is minimized.
However, further reduction in weight is required according to use. In order to meet this requirement, the thickness of the reflector may be reduced and the material of the reflector may be selected from light weight materials. This however, presents another problem in that sufficient strength is not assured for the reflector of the antenna assembly which is used, for example, as a marine radar subjected to severe conditions.
For this reason, it has been a long task to develop an antenna assembly which is of reduced weight but without deteriorating strength.
The present invention has been made with a view to overcoming the problems involved in the conventional antenna assembly.
It is a first object of the present invention to provide a slotted waveguide antenna assembly which can be formed without making the shape of a reflector (including a horn) complicated or increasing the weight of the reflector, can save the manufacturing time and cost, and can minimize the effect of a load which is applied to a portion of a pedestal where the antenna assembly is mounted.
It is a second object of the present invention to provide a slotted waveguide antenna assembly which is capable of reducing the weight without reduced strength of the reflector.
The present invention relates to a slotted waveguide antenna assembly which comprises a slotted waveguide having a plurality of slots, a reflector which opens in front of the slotted waveguide for reflecting an electromagnetic wave radiated from the slotted waveguide so as to form a directive beam, and a mounting portion for mounting the antenna assembly onto a pedestal or the like.
In such a slotted waveguide antenna assembly, this invention is characterized by a fixing member which is sufficiently thin as compared with the working wavelength and provided on the reflector at a position spaced from the radiation source in such a manner that it extends between and through the opposite walls of the reflector and is fixed to the respective walls of the reflector. The fixing member has an end which is projected outwardly from the wall of the reflector so as to be used as a mounting portion for mounting the antenna assembly onto the pedestal or the like.
The present invention is also applicable to a slotted waveguide antenna assembly which comprises a slotted waveguide held, at the rear portion thereof, by a holder member, a dielectric waveguiding arrangement formed of a pair of dielectric plate members sufficiently thin as compared with the working wavelength, supported, at the respective base portions thereof, by the holder member and projected, at the respective tip end portions, forwardly of the slotted waveguide so as to define a space therebetween, and a reflector disposed outside of the base portions of the dielectric plate members and held by the holder member for reflecting electromagnetic waves radiated through the base portions of the dielectric plate members.
In such a slotted waveguide antenna assembly, the present invention is characterized, by a fixing member, sufficiently thin as compared with the working wavelength, disposed on the reflector at a position spaced from the slotted waveguide so as to extend between and through the walls of the reflector and is fixed to the respective walls. The fixing member has an end which is projected outwardly through the wall of the reflector so as to form a mounting portion for mounting the antenna assembly onto a pedestal or the like.
Heretofore, it has been generally considered that metal material scatters electromagnetic waves and should not be placed in front of an electromagnetic wave radiation source (such as a slotted waveguide). The inventors of the present invention, however, have experimentally found that the conventional understanding is not always true. More particularly, they experimentally have found that there is hardly any scattering of electromagnetic wave when the member placed in front of the radiation source is sufficiently thin as compared with the wavelength of the working electromagnetic wave and disposed at a position spaced from the radiation source; and that the scattering of the electromagnetic wave, if any, is within such a negligible range that the obtained radiation pattern satisfies the requirement for the radiation pattern for radars in practical use. The present invention has been made on the basis of such findings and according to the invention, a fixing member which is sufficiently thin as compared with the wavelength of the working electromagnetic wave is provided at a position spaced from the radiation source in such a manner that it extends between and through opposite walls of a reflector and is fixed thereto so that the weight of the reflector may be supported by the fixing member. Thus, no loads is applied onto the reflector. Therefore, it is not necessary to form the reflector in a special shape and to make the walls of the reflector thicker, and accordingly, the reflector can be simpler in structure and lighter in weight.
Furthermore, one end of the fixing member is projected outwardly from the reflector to form a mounting portion so that the antenna assembly of the present invention can be mounted, at the mounting portion, onto a rotary drive assembly.
Further, according to the present invention, a projection which is formed on one of the walls of the reflector in the conventional antenna assembly may be omitted so that the walls of the reflector can be formed symmetrically. Therefore, the upper and lower walls may be used in common and the number of parts may be reduced.
In addition, according to the present invention, when it is embodied into a slotted waveguide antenna assembly with a dielectric waveguiding arrangement, sufficient strength can be obtained even if the reflector is made of a light weight material such as a synthetic material. As a result, the present invention may be applied to various forms of antenna assembly as described in connection with the following embodiments and modifications.
US Referenced Citations (7)
Foreign Referenced Citations (1)
| Number |
Date |
Country |
| 241847 |
Jul 1960 |
AUX |
Non-Patent Literature Citations (1)
| Entry |
| Telco Electronics Mfg. Co., Cat. No. A-55, Sep. 1957, p. 19. |
Continuations (1)
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Number |
Date |
Country |
| Parent |
711840 |
Mar 1985 |
|
Patent Grant
4829312
