JPH0546721B2 - - Google Patents

Description

[Detailed Description of the Invention] "Industrial Application Field" This invention uses a polarization discrimination grid to allow radio waves with orthogonal polarizations to be transmitted without interfering with each other.
The present invention relates to a dual-polarization antenna used for transmission or reception, or for transmitting and receiving.

"Prior Art" Conventionally, as an example of a dual polarization antenna using a polarization discriminating grid, there is a literature (Bell Syst Tech.J.,
Vol. 56, No. 6, pp 977-986, July/Aug. 1977), and its configuration is shown in FIG. The reflecting mirror 1 constitutes a part of a paraboloid of rotation with the Z-axis as the axis, and the reflecting mirror 1 is located at the focal point 2 of the reflecting mirror 1.
A primary radiator 3 facing the radiator is provided. A plane polarization discriminating grid plate 5 is arranged between the reflecting mirror 1 and the primary radiator 3 and facing them. The polarization discrimination grid plate 5 has linear grids 6 parallel to each other.
It consists of This polarization discrimination grid plate 5
A primary radiator 8 is placed opposite the polarization discriminating grid plate 5 at the focal point 7 of the reflecting mirror 1 newly generated by the transmission or reflection of the beam.

Radio waves containing mutually orthogonal polarization components 9 _x and 9 _y arriving from the antenna's main radiation direction parallel to the Z-axis are reflected by a reflecting mirror 1 so as to converge on a focal point 2 . This reflected wave passes through the polarization discrimination grid plate 5, and the polarization component _9y perpendicular to the polarization discrimination grid plate 5 passes through the polarization discrimination grid plate 5 and reaches the primary radiator 3. On the other hand, the polarization component 9 _x parallel to the grid 6 in the reflected wave incident on the polarization discrimination grid plate 5 is reflected by the polarization discrimination grid plate 5 and is transmitted to the primary radiator 8.
leading to.

The above operation description has been given in the receiving state, but in the transmitting state, the polarized wave component perpendicular to the grid 6 of the radio wave emitted from the primary radiator 3 passes through the polarization discrimination grid plate 5, and the reflecting mirror 1 The polarized wave component parallel to the grid ₆ of the radio wave emitted from the primary radiator 8 is reflected by the polarization discrimination grid plate 5, It is further reflected by the reflecting mirror 1 and radiated in the main radiation direction to form a polarized wave component _9y .

In the known configuration shown in FIG. 1, the offset angle of the reflector 1 is ₀ , and the plane 12 perpendicular to the offset axis (the bisector of the antenna aperture angle _2a )
Let the angle formed by the polarization discrimination grid plate 5 be 〓,
By adding the restriction 〓=〓 ₀ /2, it is radiated from the primary radiators 3 and 8 to the antenna aperture surface 13.
The polarized waves 9 _x and 9 _y of the radio waves that have reached (the part facing the reflecting mirror 1 in the plane perpendicular to the Z axis) are due to the cross-polarized wave canceling effect between the polarization discrimination grid plate 5 and the reflecting mirror 1. It is explained that the entire area of the aperture surface 13 is approximately oriented in the X direction and the Y direction, respectively. Therefore, the polarization of the radio waves radiated from the antenna is approximately parallel to the X-axis or the Y-axis, and an antenna with excellent cross-polarization characteristics that generates a small amount of cross-polarization can be obtained.

"Problems to be Solved by the Invention" However, it is only an approximation that the polarized waves are aligned over the entire area of the antenna aperture 13, and in order to increase the approximation, the antenna aperture angle 2〓 _a is It is necessary to make it small, and numerically 〓a must be less than 20°.

Furthermore, since the angular relationship 〓=〓 ₀ /2 is uniquely set, the position of the primary radiator 8 on the reflecting side is inevitably determined. If the primary radiator 8 cannot be installed at the position determined by 〓=〓 ₀ /2 due to constraints from the surrounding environment of the antenna, the design should be changed after acknowledging the deterioration of the cross-polarized wave characteristics, for example 〓 〓
It must be changed from _0/2 .

Furthermore, in order to obtain good radiation characteristics of the antenna, for example, low sidelobe characteristics, the primary radiator 8
must not be on the radio wave path. FIG. 2 is an enlarged view of the vicinity of the primary radiators 3 and 8 in FIG. 1, and shows the case where the focal point 7 of the reflecting mirror 1 is at the end of the radio wave path. Here, since the angle of incidence and the angle of reflection of the radio waves must be equal, the following equation holds.

=2 = (1) If the intersection of the polarization discrimination grid plate 5 and the offset axis 11 is a point C, then the angle formed by the line 7 and the offset axis 11 is =. Distance between C-2 and C-7
Since the distances between C-2-7 are equal, the triangle consisting of C-2-7 is an isosceles triangle. The sum of interior angles of a triangle is 〓
Since it is in radians, (〓−〓)+2〓 _a =〓, and the following formula holds true.

〓=2〓 _a ...(2) From equations (1) and (2), 〓=〓 _a . This is focus 7
The condition is when is at the end of the radio wave path, and when it is not on the radio wave path, the following equation must be satisfied.

〓＞〓 _a ……(3) Here, in order to minimize the occurrence of cross polarization, 〓=〓 ₀ /2 must be satisfied, so 〓 ₀ > 2〓 _a ……(4) is satisfied. There must be. In this way, due to the condition that the primary radiator 8 must not be placed on the radio wave path, as shown in equation (4), there are important issues regarding the off-set angle 〓 ₀ and the aperture angle 〓 _a , which are the basic parameters in antenna design. It has become clear that there are limitations.

``Means for Solving the Problems'' According to the present invention, the grids constituting the polarization discriminating grid plate are not straight lines parallel to each other, and when the grids are projected onto the antenna aperture plane through a reflecting mirror, the antenna aperture is Select the grid alignment so that the lines on the surface are straight lines parallel to each other.

"Embodiment" Overview FIG. 3 shows an embodiment of the present invention, with the same reference numerals attached to parts corresponding to those in FIG. 1. First in appearance
Although it is similar to the conventional one shown in the figure, the shape and position of the grids constituting the polarization discrimination grid plate 14 are different from the conventional one shown in FIG. 1, and they are parallel to each other although not shown in the figure. It is not a straight line; its specific shape will be shown later.

FIG. 4 shows another embodiment of the present invention, in which a curved polarization discriminating grid plate 15 is disposed opposite the reflecting mirror 1 and the primary radiator 3. The curved polarization discriminating grid plate 15 is made of a part of a hyperboloid of revolution or an ellipsoid of revolution, and one focal point of the curved polarization discriminating grid plate 15 is made to coincide with the focal point 2 of the reflecting mirror 1, and the other focal point is made to coincide with the focal point 2 of the reflecting mirror 1. 16, the primary radiator 8 is connected to the polarization discrimination grid plate 1.
It is arranged opposite to 5. Polarization discrimination grid plate 15
Since the radio waves reflected by the polarization discriminating grid plate 15 converge at a focal point 16, the focal point 16 is herein referred to as the focal point of the reflecting mirror 1 newly generated by the reflection action of the polarization discriminating grid plate 15.

Polarization discrimination grid plate 14 in FIGS. 3 and 4,
Each of the 15 grids is determined by the positional relationship between the reflecting mirror 1 and the polarization discriminating grid plates 14 and 15, and each consists of conductor wires oriented in directions that are not parallel to each other. The following describes how these grids are obtained.

Determination of the grid Basically, by projecting parallel straight lines on the antenna aperture 13 that match the polarization direction of the radio waves onto the polarization discrimination grid plate 14 or 15 through the reflector 1. can get. That is, when the grid of the polarization discrimination grid plate 14 or 15 is projected onto the antenna aperture surface 13 through the reflecting mirror 1, the lines on the antenna aperture surface 13 become straight lines parallel to each other.

The procedure for determining the grid will be explained below with reference to FIG.

(a) Relationship between the position X, Y of the blind 17 on the antenna aperture surface 13 in the XY coordinate system and the position in the polar coordinate system with the focal point 2 as the center and the Z axis as the polar axis.

Assuming a path where the light enters the reflecting mirror 1 through positions X and Y, is reflected by the reflecting mirror 1, and reaches the focal point 2,
At that time, the path length between the focal point 2 and the reflector 1 is determined by the coordinate system with the focal point 2 as the center and the Z axis as the polar axis.
As shown in p.261, Baifukan), it is expressed as 〓=2f/(1+cos〓)...(5). However, 〓 is the angle made by the line 〓 with respect to the Z axis, and 〓 is the angle made by the z〓 plane with respect to the zx plane.
f indicates the focal length of the reflecting mirror 1. On the other hand, arbitrary points X and Y on the XYZ coordinates that define the antenna aperture surface 13 can be found from 〓, 〓, as shown in the following equation.

X=〓sin〓cos Y=−〓sin〓sin ……(6) Conversely, 〓 can be found from equations (5) and (6) using X and Y as follows.

tan=-Y/X tan〓/2=X/2fcos ……(7) (b) Relationship between the position of the polar coordinate system〓 and point G on the plane polarization discrimination grid plate 14 Polarization discrimination grid plate 14 Let the angles made by the normal vector ng of the plane with the x, y, and z axes, respectively, be 〓, _〓 , 〓 _, respectively.
z _a ), the following equation holds true for each point (x, y, z) on the plane of the polarization discrimination grid plate 14 in the xyz coordinate system.

x cos 〓 + y cos 〓 + z cos 〓 = x _a cos 〓 + y _a cos 〓 + z _a cos 〓 ...(8) On the other hand, the point where the line segment directed from the focal point 2 to the position 〓 and direction intersects the plane of the polarization discrimination grid 14 is Point G
(x _g , y _g , z _g, variables in the x, y, z coordinate system that defines the primary radiation system of the antenna), and point G-2
Letting the distance between them be 〓g, then x _g ＝〓 _g sin〓cos y _g ＝〓 _g sin〓 sin z _g ＝〓 _g cos〓 ...(9). Since point G is naturally a point on the plane shown by equation (8), equation (8) holds even if x _g , y g , and _{z g} are substituted for x, y, and z in equation (8). . Therefore, by substituting equation (9) into equation (8), we get 〓 _g = (X _a cos〓 + y _a cos〓 + z _a cos〓) / (sin〓coscos〓＋sin〓sincos〓 +cos〓cos〓) ……(10 ) is obtained. Equation (10) shows that since x _a , y _a , z _a and 〓, 〓, 〓 are known, if 〓, is given, the distance 〓g from the focal point 2 to the point G can be found.

(c) Relationship between the position X, Y of one of the blinds 17 on the antenna aperture surface 13 and the corresponding point G of the polarization discrimination grid plate 14 Now, in equation (7), (X, Y) is (〓, ), and 〓g can be found in equation (10). That is, for (X, Y), the polarization discrimination grid plate 14
The position of the upper point C is determined by the angle 〓 with respect to the focal point 2 and the distance 〓g.

Therefore, if the steps (a) to (c) are repeated for each point on all blinds 17 on the aperture surface 13 to find the corresponding point G, the line formed by each point G will be the polarization discrimination grid. This becomes the grid 18 on the plate 14.

Grid setting of a curved polarization discrimination grid plate When using a curved polarization discrimination grid plate 15 as shown in Fig. 4, the above procedure (b) can be changed to the following (b)'.
You can replace it with For this explanation, FIG. 6, in which the vicinity of the primary radiators 3 and 8 is enlarged, will be used. 6th
In the figure, the curved surface formed by the curved polarization discriminating grid plate 15 is assumed to be an ellipse or a hyperboloid for convenience, and the axis z'' passing through the two focal points 2 and 16 of the curved surface is at an angle 〓 Assume that the angle is tilted.

(b) Relationship between the position 〓 in the coordinate system xyz and the point G on the curved polarization discrimination grid plate 15.

In a polar coordinate system with focus 2 as the center and the z″ axis as the polar axis, so-called quadratic surfaces such as ellipses and hyperboloids are described in the literature (Iwakiri, Essays on Algebraic Geometry, p. 261,
As shown in Baifukan), (〓″,″) is displayed as the following formula.

〓g=l/(1+e cos〓″)...(11) 〓g is the distance between the point G on the quadratic curved surface 15 and the focal point 2, and e and l are each determined by the shape of the curved surface 15. It is a constant.

Between (〓,) and (〓″,″), (〓,
) and (〓″,″) point in the same direction, and the coordinate system xyz is the coordinate system x″y″z″ rotated by 〓 around the y″ axis. , can be expressed as follows using the well-known coordinate rotation formula.

cos〓 0 −sin〓0 1 0sin〓 0 cos〓 sin〓cos sin〓sin cos〓＝sin〓″cos″ sin〓″sin″ cos〓″ ...(12) From equation (12), 〓″ is as follows. It is expressed as 〓,, 〓, as shown below.

cos〓″＝−sin〓sin〓cos＋cos〓cos〓 ……(13) Eventually, from equations (13) and (12), between the focal point 2 given (〓,) and the point G on the curved surface 15 It can be seen that the distance g can be found.

By the above procedure, the desired shape and position of the grid can be determined whether the polarization discrimination grid plate is a plane or a quadratic curved surface. Even if the polarization discrimination grid plate 15 is a curved surface other than a quadratic curved surface, if the distance 〓g between the focal point 2 and the point G on the curved surface 15 is expressed by some relation to 〓, the same procedure can be applied. The shape and position of the grid can be found using (b)′
It is clear from the explanation in .

Example of Grid Design Next, a design example of the grids 18 of the polarization discriminating grid plate 14 will be shown, and it will be made clear that the orientations of the grids 18 are not parallel to each other. Figure 7 shows the third
FIG. 2 is a view of the planar polarization discriminating grid plate 14 in the embodiment shown in the figure, viewed from a direction perpendicular to the plate surface. As antenna parameters, reflector 1
When the offset angle = ₀ is 30°, the half-aperture angle _a is 25°, and the installation angle of the polarization discrimination grid plate 14 is 30°, that is, the conventional antenna = = ₀ /2,
〓 ₀ > 2〓 Even if the condition deviates from _a , the occurrence of cross-polarized waves can be sufficiently reduced by forming each grid 18 in the shape shown in FIG. 7 clearly shows that the grids 18 are not parallel to each other.

Also, Figure 8 shows the case using typical antenna parameters when minimizing the generation of cross-polarized waves with a conventional configuration: 〓 ₀ to 50 degrees, 〓 _a to 20 degrees,
Let 〓 be 25° (=〓 ₀ /2), and 〓 =〓 ₀ /2,〓 ₀ /2
〓 It satisfies the condition of _a . A grid 18 shown by a solid line is a grid to which the present invention is applied, and a grid 6 shown by a broken line is a conventional grid that is straight and parallel to each other. As can be seen from this diagram, applying the present invention will cause the grids 18 to deviate slightly from parallel lines, which will further reduce the generation of cross-polarization than would be the case if the conventional configuration attempted to minimize the generation of cross-polarization. It is understood that it is possible to make it smaller.

In the case of a curved polarization discriminating grid plate 15, it is clear that the grids 19 are not parallel to each other, although there is no need to specifically show them.

The above determination of the grids 18 and 19 was explained based on the reception state in which the radio waves go from the aperture 13 of the antenna to the focal point 2, but if this antenna is used for transmission,
Grid 1 on polarization discrimination grid plate 14 or 15
If 8 or 19 is projected onto the aperture surface 13 of the antenna, it will become a linear blind that is all parallel, so it is possible to transmit polarized waves that are correctly parallel to the blind and polarized waves that are correctly perpendicular to the blind. Effects of the embodiment shown in FIG. 4 Since the antenna of the present invention uses a polarization discrimination grid plate having such characteristics, the radio waves radiated from the primary radiator 3 or 8 are directed to the aperture 13 of the antenna. When this is reached, the polarization will be uniform throughout the aperture surface 13, resulting in excellent cross-polarization characteristics. In addition, when using a plane polarization discrimination grid plate 14, there are no restrictions on the setting angle of the grid plate, so it is possible to set the angle at any angle according to the situation of the antenna installation location. In addition, since the condition 〓=〓 ₀ /2 is unnecessary, the condition regarding the antenna parameter〓>2
〓 This has the effect that there is no need to consider _a as well. When using a polarization discriminating grid plate 15 having a curved surface, when viewed from the primary radiator 8 on the reflecting side, an offset Gregorian antenna or a hyperboloid can be created by using, for example, an elliptical surface as the curved surface of the grid plate 15. By using it, it is possible to construct an offset Cassegrain antenna, which has the effect of being able to apply various antenna techniques such as beam forming, high efficiency, and low side lobe.

Another Embodiment FIG. 9 shows another embodiment of the invention. In this example, in addition to the polarization discrimination grid plate 21a that corresponds to the polarized waves between the reflector 1 and the focal point 2 of the reflector, this grid plate 21a also corresponds to the polarized waves orthogonal to the assumed polarized waves. Polarization discrimination grid plate 21
b are provided, and these polarization discrimination grid plates 21
Primary radiators 8a and 8b are respectively formed at the focal points 22a and 22b of the reflecting mirror 1 newly generated by a and 21b.
will be arranged. Polarization discrimination grid plates 21a, 21b
The polarization discriminating grid plate 14 may be a plane as described above, or may be the polarization discriminating grid plate 15 having a curved surface.

This antenna has a reflector 1- for a certain polarized wave.
The antenna is composed of a polarization discrimination grid plate 21a and a primary radiator 22a, and for polarized waves perpendicular to this, it is an antenna composed of a reflector 1, a polarization discrimination grid plate 21b, and a primary radiator 22b. Both of these antennas have two reflectors (i.e. reflector 1 and polarization discrimination grid 21a or 21).
b) Therefore, antenna technologies such as beam forming, high efficiency, and low sidelobe reduction can be applied independently to each other. Needless to say, in this case as well, the cross-polarized wave characteristics are excellent.
Furthermore, the cross-polarization characteristics of this antenna are mainly determined by the polarization discrimination grid plate 21a on the reflecting mirror 1 side, that is, the side that transmits radio waves of one polarization, and the polarization discrimination grid plate 21b has polarization discrimination characteristics. It is also possible to use a conductive plate that does not have a

``Effects of the Invention'' As explained above, the antenna of the present invention has low generation of cross-polarized waves and can share polarized waves, and can increase communication capacity by introducing it into congested wireless communication lines or increase the number of installed antennas. It has the advantage of contributing to an increase in communication capacity and number of channels in limited communication and broadcasting satellites.

[Brief explanation of the drawing]

FIG. 1 shows an antenna using a conventional polarization discriminating grid plate, where A is a configuration diagram, B is a front view of the antenna aperture 13, C is a plan view of the polarization discriminating grid plate 5, and FIG. Figure 1 is an enlarged view of the vicinity of the primary radiators 3 and 8, Figure 3 is a configuration diagram showing an embodiment of the present invention using a plane polarization discrimination grid plate, and Figure 4 is a curved polarization discrimination grid plate. A configuration diagram showing an embodiment of this invention using a plate, FIG. 5 is a diagram used to explain the determination of the grid on the polarization discrimination grid plate used in the antenna of this invention, and FIG. 6 is a diagram showing polarization discrimination on a curved surface. Figures used to explain the determination of grids on the grid plate, Figure 7 is a plan view showing an example of a design of a polarization discrimination grid plate, and Figure 8 is a diagram according to the present invention that corresponds to a conventional polarization discrimination grid plate. FIG. 9 is a diagram showing a design example of a polarization discriminating grid plate. FIG. 9 is a configuration diagram showing an embodiment of the present invention using two polarization discriminating grid plates. 1...Reflector, 2, 7, 16, 22a, 22b
...focal point, 3,8,8a,8b...primary radiator,
5, 14, 15, 21a, 21b... polarization discrimination grid plate, 6, 18, 19... grid.

Claims (1)

[Claims] 1. A reflecting mirror that forms part of a paraboloid of rotation and whose focal point is off the main radiation path; and a first reflecting mirror that is disposed at the focal point of the reflecting mirror so as to face the reflecting mirror. a first primary radiator that emits a linearly polarized wave; and a plurality of mirrors that are provided between the reflecting mirror and the first primary radiator and facing away from the main radiation path and that do not intersect with each other. A polarization discriminating grid is constructed by arranging conductive grid lines consisting of curves of plate, and a second primary radiator that emits a second polarized wave at a focal point newly generated by the reflection action of the polarization discriminating grid plate, which is arranged to face the polarization discriminating grid plate, The linear shape of the conductive grid wires arranged on the polarization discrimination grid plate discriminates polarization of a plurality of straight lines parallel to each other at the antenna aperture surface on the main radiation path of the reflector through the reflector. A polarization-discriminating antenna characterized in that the antenna is selected so as to match a line shape formed by projecting it onto a grid plate.