JPH02237203A - Offset antenna - Google Patents

Abstract

PURPOSE:To obtain an offset antenna without the deterioration cause of electric and mechanical characteristics at low cost by setting a side board a specified conical enveloping body. CONSTITUTION:The external form of a radome 11 is set to be two semiellipsoidal assembled forms, and the internal face form of the side board 10 is constituted by the conical enveloping body in which the outer peripheral of a main reflecting mirror is composed of a conductor and respective points on the outer periphery of the radome 11 are set to be vertexes. An auxiliary reflecting mirror 2 and a primary radiator 3 are installed in the conical enveloping body, namely, the side board 10. Since the side board 10 can cover a transmission path 8 without cutting or blocking a radio wave radiated from the primary radiator 3, a hole through which the radio wave passes is eliminated in the side board 10, and the deterioration of a side lobe characteristic due to the edge of the hole and the deterioration of mechanical strength around the hole do not exist. Thus, the inexpensive offset antenna without the deterioration cause of the electric/mechanical characteristics can be obtained.

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention relates primarily to an aperture antenna used for microwave band communication or radar. More specifically, it relates to the improvement of an offset antenna having a circular aperture. [Prior Art] Fig. 4 is a side view showing a conventional offset antenna disclosed in, for example, Japanese Patent Publication No. 53-31345. Figure 5 is a front view. Figure 6 is a partial oblique view, and in the figure (1)
is a paraboloid of revolution with F2 as the focal point and AA as the rotation axis. ! :Plane P forming an angle of φ
The main reflecting mirror obtained by cutting at (2) is F1 and F2
A sub-reflector that is a part of an ellipsoid of revolution that focuses both BB and BB as the axis of rotation. (3) is, for example, a primary radiator of a conical horn.1 The phase center of the radiated radio waves of this primary radiator (3) coincides with one of the focal points F1 of the sub-reflector r21. {4)
is a cylindrical side plate that covers the main reflector. (
5) is a hole (6) made by cutting a part of the side plate (4).
is a box body that covers the primary radiator (3) and the hole (5) in the side plate (4), a radome made of a dielectric plate that covers the opening on the side of the side plate (the force is the sub-reflection boundary 12 of the side plate (4)), (8) The transmission path 1 (9) of the radio waves radiated from the primary radiator (3) is a hole (5). The conventional offset antenna is configured as above,
When considering this as a transmitting antenna, the primary radiator (3
) The lightning waves radiated from the line follow the transmission path (8). The phase center of the radiated radio wave of the primary radiator (3). That is, the focal point F1
is emitted as a spherical wave centered at the sub-reflector (2)
When raindrops or snow adhere to the aperture of this primary radiator (3), it is reflected by the main reflector (1) and forms a sharp beam in front of the antenna. ．Because the root width distribution of the sleep wave emitted from the primary radiator (3) changes.The original sharp beam may deteriorate,
Since radio waves are emitted in unnecessary directions, the radome +7L
ld main reflecting mirror (1), side plate (4). Together with the box body (6), a sealed groove structure is formed to prevent rain and snow from entering the interior and adhering to the primary radiator 13). The holes (5) in the side plate (4) are arranged so that the radio waves will not be blocked on the way to the transmission line f8) that passes through the main reflector fil and reaches the front of the antenna, and the radome (7) is also The dielectric material is sufficiently thin compared to the radome (7) and the transmission line (8) are made at an angle ψ which is not a right angle to reduce the reflection force when the radio waves pass through. With the above considerations in mind, offset antennas. Compared to parabolic antennas and Cassegrain antennas that inherently have blocking, there is no side rope deterioration or gain reduction due to blocking. As an antenna with good characteristics, it is used in high-density communications and satellite communications [a problem that the invention aims to solve]. Regarding the hole (5) in the side plate f41 required in the conventional O'7 set antenna mentioned above. There are a few points to consider in terms of electrical properties and mechanical strength. Firstly, in terms of electrical properties, when considering the hole 15) from a geometric optics perspective, its shape has a focal point F2 at its apex and a main reflection. @(1
) can be used as a line of mutual penetration between the cone that carries the conductor and the side plate (4), but in reality K is a heart wave with a wavelength of several degrees, so the cone formed by this radio wave is a wave expansion. The hole (5) must be larger than the above-mentioned intersecting line.
)4? It is necessary to make it sufficiently large near the focal point F2. In practical use, the hole (5) is usually the same size as the box (6), as shown in Figure 6. Furthermore, the hole (5) forms an edge (9) between it and the side plate (4). In addition to the edges of the main reflector (1) and sub-reflector (2), the antenna has an unavoidable edge (edge 19), which increases the deterioration of the sidelobe characteristics due to edge diffraction or edge scattering. Therefore, it is necessary to install a radio wave absorber.Secondly, in terms of mechanical strength, the hole (5) breaks up the continuity of the first side plate (4) as a cylindrical well. Furthermore, since the curvature b as a shell changes its direction at an angle, an out-of-plane bending moment is generated here at the point where the side plate (5) and the box body 16) are joined, so the plate thickness is increased or reinforcement is added. Such measures may be necessary, or when strong winds such as typhoons act on the antenna. The box body (6) disturbs the flow lines of the wind and adds to the wind load. In order to reduce turbulence, we searched for a shape with less impact through wind tunnel experiments. Based on the results, it is necessary to improve the strength of each part. All of these are done to prevent deterioration of the original electrical and mechanical characteristics of the offset antenna, but to improve this, it is necessary to use radio wave absorbers. As the plate thickness increases, manufacturing costs increase. The shape of the hole and the mounting position of the radio wave absorber. The development procedure for experimental elements, such as selecting the shape of the box, was thoroughly explained. As a result, it has become difficult to realize an offset antenna that is inexpensive and has good characteristics.This invention was made to solve this problem. The objective is to obtain an inexpensive offset antenna that does not have the above characteristics deterioration factors [Means for solving the problem] The offset antenna according to the present invention is as follows. The outer circumferential shape of the radome is a collection of two semi-inverted circles. The inner surface of the side plate is composed of a pyramidal envelope whose vertices are each point on the radome's outer periphery, with the outer periphery of the main reflecting mirror being the conducting wire. This envelope, that is, the side plate contains the sub-reflection boundary and the primary radiator. [Function] In this invention, the zero plate allows the radio waves emitted from the primary radiator to be connected to the transmission path without dividing or blocking. The things that cover it will be there for a long time. There is no need for holes in the four-rule plate for passing radio waves, and there is no deterioration in side lobe characteristics caused by the edges of the holes or deterioration in mechanical strength around the holes. In addition, there is a secondary reflective bell. The side plate of this invention also serves as the primary radiator and the box that covers the hole. [Embodiment] Fig. 1 is a side view showing an embodiment of the present invention. Figure 2 is a front view. In the figure, (1) is the main reflector, and (2) 1 is the sub-reflector. (3) is the primary radiator. (8) is the transmission line, and these are the same as the conventional device described above. , 01 is the side plate, and D is the radome. A cone with the outer periphery of the main reflecting mirror (1) as a conducting wire and a point on the outer center of the radome OB as its apex is elliptical and uniquely defined. As you move the apex on the outer circumference of the radome [lI, cones are formed one after another, but as the apex goes around the outer circumference of the radome a1, a chromatic body is formed as a collection of these cones. . The shape of this envelope is. The external solid shape of Radomero 9. Once the relative position between the main reflective bell (1) and the radome an is determined, it is uniquely determined with respect to the main reflective bell fi+. Therefore, when the outer 11 shape of the L/tome Qη is projected onto the aperture surface of the antenna, that is, when viewed from the direction of rotational transport AA in Fig. 2, the area above the aperture center 0 is the reflector (the outer periphery of The shape is a semicircle with a radius r.The area below the aperture center O contains the sub-reflector (2) and the primary radiator (3).The extended dimension fl is the short radius r, the long radius R= Radome Ql on half beak circle of r+l
When the outer circumferential shape of the radome (1) and its position is determined as described above, the envelope is uniquely defined, and the shape of the side plate Ill with this as the inner shape is determined. !=0, that is, it is not possible to open it unless the side plate α1 is cylindrical.As shown in Fig. It can be approximated numerically by calculating the cumulative shape of a triangle from the actual length of one river at a point.In the offset antenna configured as above, the primary radiator (3) causes the sub-reflection @(2), and the main reflection. The radio waves emitted to the chain (1) propagate through the transmission path (8) as in the conventional device and form a sharp beam in front of the antenna, but the cone formed by these radio waves is located on the side plate ^■
It is included in There is no need for holes or edges created by holes that existed in conventional mountings. The side plate (I) has no tendency to cut or block the transmission line (8), which is a cause of deterioration of electrical characteristics). ! : Secondary reflection @(2) only external station. Sidelobe deterioration due to the wave-like behavior of radio waves is extremely limited.Also, mechanically, this side plate (11 minute portions) is a conical shell and is continuous and smooth along the circumference. .It is approximated to a shell with a Gaussian curvature of 0, which is the same as the cylindrical shell of the side plate (4) of the conventional device,
The strength and properties are almost the same, and unlike conventional equipment, there are no holes, so the continuity of the shell is maintained. The strength of the shell can be maximized and no reinforcing measures are required.The box body (6) of the conventional device also serves as the side plate (11) of this invention, so the box body (6) is unnecessary and the number of parts is reduced. do.
! : The wind streamlines are smooth, and the wind load does not increase.As stated above, this side plate 11 can be directly approximated, and its manufacture Since it can be made by sheet metal processing, it is possible to construct an off-set antenna at an extremely low cost.Therefore, an off-set antenna with no characteristics deterioration factor can be realized at an extremely low cost.[Effects of the Invention] This invention is as explained above. By making the side plate of the offset antenna a predetermined pyramidal envelope, it is possible to realize an offset antenna at a low cost without any deterioration factors in its electrical and mechanical properties.

[Brief explanation of drawings]

Figure 1 is a side view showing one embodiment of this invention. Fig. 2 is a front view, Fig. 3 is a developed view of the side plate, Fig. 4 is a side view showing a conventional offset antenna, Fig. 2g5 is a front view, and Fig. 6 is a partial oblique view. In the figure. CI) is the main reflector, (2) is the sub-reflector, (
3) ID primary radiator, (4) is the side plate, (5) is the hole, j6
) is a box body. (7) is a radome. t8) is the transmission line, (9)
is the edge, (1■ is the old side plate} is the radome. In each figure, the same σ sign indicates the same -1 or equivalent part.

Claims (1)

[Claims] A main reflecting mirror obtained by cutting a paraboloid of revolution with a plane, a side plate attached to the outer periphery of the main reflecting mirror, and a sub-reflection of a part of the ellipsoid of revolution whose focal point is the focal point of the main reflecting mirror. In an offset antenna consisting of a mirror, a primary radiator whose radio wave phase center is at the focus of the other sub-reflector, and a radome covering the opening side of the side plate, the outer circumferential shape is a collection of two semi-ellipses. A radome is provided, and a side plate is provided, the inner surface of which is a pyramidal envelope with the outer periphery of the main reflecting mirror as a conducting wire and each point on the outer periphery of the radome as the apex. An offset antenna characterized by comprising: and the above primary radiator.