JPH045285B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an array antenna in wireless communication. In particular, it relates to a shaped beam antenna in which the shape of the radiation beam has a fan-shaped spread in a certain plane, and in a plane orthogonal thereto, the beam shape differs from the plane. INDUSTRIAL APPLICABILITY The present invention is used for wireless communication between one master station and a plurality of slave stations. [Prior Art] In wireless communication, two radio stations face each other and communicate, so the antennas used generally have high gain and low sidelobe characteristics. However, when communicating between multiple slave stations scattered within a certain area and one master station, the antenna of the master station has a so-called shaped beam that efficiently illuminates the area where the slave stations are scattered. is necessary. FIG. 9 is a plan view in which a master station and a slave station for wireless communication are arranged, and FIGS. 10 and 11 are side views thereof, and the effect of beam forming will be explained using these. That is, with station A as the master station, B,
When stations C, D, and E are respectively slave stations, the shape of the beam of the antenna of the master station is 9th in the horizontal plane.
As shown by broken line 1 in the figure, it is desirable to have a fan-shaped spread that covers all slave stations. on the other hand,
In the vertical plane, as shown in Figures 10 and 11, due to the difference in ground height where slave stations are placed and the difference in distance from the master station, the beam beam is different from the normal pencil beam as shown by the broken line 2 in Figure 10. It is also desirable to have a shaped beam as shown by broken line 3 in FIG. FIG. 12 is a plan view when the communication ranges of the master station and slave station shown in FIG. 9 are arranged adjacent to each other. In such a case, in order to prevent shaped beams 1 and 1' from interfering, polarized waves orthogonal to each other are used, and the degree of orthogonality of the polarized waves, that is, the quality of the cross-polarized wave characteristics of beams 1 and 1' is determined. This will directly affect the quality of the line. Conventionally, methods for synthesizing such shaped beams include, for example, patent applications filed by the same applicant.
A shaped beam antenna such as No. 58-202372 (unpublished at the time of filing) was considered. Figures 13 and 14
15 and 16 respectively show a front view, a cross-sectional view in a horizontal plane, a cross-sectional view in a vertical plane, and an explanatory diagram of radiation characteristics in a vertical plane of this conventional antenna. The antenna has a primary radiator 20 and a main reflector 30
It consists of The main reflecting mirror 30 includes torus mirror surfaces 34, 37, and 38 at the center and parabolic mirror surfaces 35-1, 36-1, 39-1, and 35-1 at both ends.
2, 36-2, 39-2, the first mirror parts 34, 35-1, 35-2 are symmetrical with respect to the horizontal plane and the vertical plane, and the second mirror parts 37, 38, 36
-1, 36-2, 39-1, and 39-2 have asymmetric structures with respect to the horizontal plane. The radiation characteristics of this antenna in the horizontal plane are explained using FIG. 14.
is a torus mirror surface obtained by rotating the cutting line in Fig. 15 by an angle θ ₀ around the vertical axis, and numerals 35-1 and 35-2 have axes P35-1 and P35-2 as the center of rotation, respectively, and point F as the focal point. It is a parabolic mirror surface. The spherical wave emitted from the primary radiator 20 is reflected by the torus mirror surface part 34 in the horizontal plane, and the broken line 4,
It passes through a path as shown in 5, becomes a concentric radiation wavefront centered on the origin, and forms a parabolic mirror surface part 35-
The radio waves reflected by P35-1 and P35-2 pass through the path shown by broken lines 6 and 7, and are connected to the axes P35-1 and P35-2.
is converted into a plane wave traveling in the direction of . Therefore, the radiation characteristics in the horizontal plane are almost uniform within the angle range of ±θ ₀ from the mirror axis as a composite of each wavefront described above, and become sharp when the absolute value of the angle from the mirror axis is θ ₀ or more. It has a characteristic of attenuating to a large extent, and can be synthesized into a so-called fan-shaped beam. Next, to explain the radiation characteristics in the vertical plane using FIGS. 16 and 17, the cutting line of the first mirror surface section 34 in FIG. It is symmetrical about the mirror axis. The cutting lines of the second mirror surfaces 37 and 38 are parabolas having a focal point at point F and central axes at axes P37 and P38, respectively. Therefore, the radio wave reflected by the torus mirror surface 34 of the spherical wave emitted from the primary radiator 20 passes through the paths shown by broken lines 8-1 and 8-2, for example, as a wave front that travels in the mirror axis direction, that is, in the horizontal direction. radiated. Furthermore, the radio waves reflected by the mirror surfaces 37 and 38 are emitted as wavefronts that travel in the directions of axes P37 and P38, respectively, through paths indicated by broken lines 9 and 10, for example. The radiation characteristics in the vertical plane are determined as a combination of the above-mentioned wavefronts, and as shown by the solid line 12 in FIG. 16, a beam asymmetrical with respect to the plane at an angle of 0 degrees from the mirror axis, that is, the horizontal plane, is synthesized. In FIG. 16, broken lines 13 and 14 are the main polarization and cross polarization characteristics of the radio waves reflected by the first mirror surface part 34, and broken lines 15
is the main polarization component of the radio waves radiated from the second mirror portions 37 and 38. As shown by the broken line 14 in FIG. 16, the cross-polarized wave characteristics have good characteristics because the mirror surface portion 34 is symmetrical on the mirror axis with respect to this axis, so the cross-polarized wave components generated on the mirror surface are canceled out. . Furthermore, the cross-polarized components generated in the mirror surfaces 37 and 38, which are asymmetrical with respect to the mirror axis, do not have a large effect on the mirror axis because the maximum emission directions of the main polarized components are far from the mirror axis, and in the end the overall The cross-polarized wave characteristics are best on the mirror axis, as shown by the solid line 16. As is clear from the explanation of Fig. 14, the above characteristics in the vertical plane are as follows:
Since they are almost the same within the angular range of ±θ ₀ , this results in the best cross-polarization characteristics in the horizontal plane that includes the mirror axis. [Problems to be Solved by the Invention] However, in the conventional shaped beam antenna described above, as shown by the solid line 16 in FIG. The drawback was that a good cross-polarization characteristic could only be obtained in the vicinity of the horizontal plane. This drawback can be seen as a problem on the line, for example, in stations A and C in Figure 12, and
When selecting a station and A' station, the difference in ground height between each station may not be large enough, and if the actual terrain or height difference of buildings is taken into account, it may become impossible to select a station. To solve this problem, a special tower would have to be installed separately. That is, the 16th
In the figure, the angle range where good cross-polarization characteristics can be obtained is ±
When β ₀ is assumed, the difference in ground height that is allowed in line design is as follows: Allowable difference in ground height = (horizontal distance between each station) × tanβ ₀ ……(1) The size of angle β ₀ directly affects the line configuration. . The biggest factor that determines the size of the angle β ₀ above is the size of the cross-polarized components generated on the mirror surface. FIG. 17 is an explanatory diagram of cross-polarized components generated on a mirror surface. For convenience of explanation, only the first mirror surface section 34 of the mirror surfaces shown in FIG. Here is an example. As is well known, if this current component is the magnetic field vector component of the incident wave and the unit normal vector of the mirror surface, then the induced current vector on the mirror surface is as follows: 〓＝〓×〓...(2) Here, the magnetic field vector component 〓 is a spherical wave, and since the normal vector 〓 has the above configuration, each has three components in the rectangular coordinate system, so the induced current vector 〓 also has three components, and the When shown in the front view as shown in Figure 17, the main polarization component M ₁ ~
It can be expressed as M ₄ and cross polarization components C ₁ to C ₄ . That is, the current component itself induced on the mirror surface includes a cross-polarized component, and the amount of main polarization and cross-polarization of the radiation characteristics are each proportional to the magnitude of this induced current. As mentioned above, the mirror surface part 34 is symmetrical with respect to the horizontal plane and the vertical plane, so for example, when considering the horizontal plane, C ₁ and C ₂ have opposite directions and the same distance to the horizontal plane, and the relationship between C ₃ and C ₄ is also The same is true. Therefore, formula (1) holds true in the horizontal plane. However, in other than the horizontal plane, for example, C ₁ and C ₂
Since there is a distance difference from the component to the horizontal plane, Equation (1) does not hold and a cross-polarized component remains, resulting in the characteristics deteriorating in areas other than the horizontal plane, as shown by the broken line 14 in Figure 16. . In practice, conventional antennas with the configurations shown in Figures 13 to 15 have cross-polarization characteristics of, for example, 20 dB.
In a line that requires the above, β ₀ can only be about 0.5 degrees, which is a major constraint on the actual line configuration. Furthermore, as is clear from the configuration of the conventional antenna, a primary radiator 20 is present in the radio wave path, blocking a portion of the radio waves. For this reason, another drawback was that it was difficult to combine the horizontal and vertical beam shapes into a desired shape. As is clear from the explanation of FIGS. 14 and 15, beam shaping is performed by combining the reflected waves from each mirror surface, so the above-mentioned blocking prevents the necessary combining and deteriorates the degree of beam shaping. become. This effect has been particularly problematic in the vertical plane where beam shaping is desired to relatively low levels. Furthermore, creating a mirror surface with the configuration shown in Figures 13 to 15 is technically difficult to form a complex three-dimensional surface, and generally requires expensive jigs and tools. . Additionally, the molding itself required a large amount of man-hours, making the antenna as a whole expensive. SUMMARY OF THE INVENTION An object of the present invention is to provide an antenna with a new structure that has good beam shaping characteristics and cross-polarization characteristics. An object of the present invention is to provide an inexpensive antenna that does not require special jigs and tools for manufacturing, requires a small number of manufacturing steps, and is inexpensive. [Means for Solving the Problems] The present invention combines beam shaping in a vertical plane using an array antenna without using a reflector, and beam shaping in a horizontal plane by attaching the array antenna so as not to cause blocking. The antenna is synthesized by a main reflector composed of a plurality of flat conductor plates, and takes advantage of the radiation characteristics of the array antenna and the characteristics of the main reflector to obtain an antenna with good cross-polarization characteristics and beam shaping. shall be. That is, the present invention includes an array antenna in which a plurality of radiating elements are arranged on a rectangular plane, and a main reflecting plate disposed behind the radiating elements of the array antenna in the radiation direction of the radiating elements. In an array antenna with a reflector in which the main reflecting surface of the plate is composed of a plurality of flat conductor plates, the center of the rectangle of the array antenna is the origin, the X axis is defined in the longitudinal direction of the rectangle, and the plane of the rectangle is If the Z-axis is perpendicular to each other and passes through the origin and moves away from the main reflector, and the Y-axis is set to pass through the origin and perpendicular to the X-axis and the Z-axis, then All axes are parallel to the X-axis, symmetrical with respect to the XZ plane, and convex in the negative direction of the Z-axis. arranged so that the phase is antisymmetric with respect to the YZ plane,
Furthermore, the radiating elements of the array antenna are arranged so that the radiation beam formed by the main reflector is symmetrical about the Z-axis on the YZ plane and asymmetrical about the Z-axis on the YZ plane. Features. The main reflector preferably includes a conductor plate added to the end of the main reflector, and preferably the main reflector includes a mounting structure for attaching the array antenna. [Operation] A radiation beam that is symmetrical in the horizontal direction and asymmetrical in the vertical direction can be obtained by the array antenna and the reflector that shapes the radiation beam. [Embodiment] FIG. 1 is a perspective view showing the structure of an apparatus according to an embodiment of the present invention, and FIG. 2 is a front view thereof. In this embodiment, the array antenna 40 as a radiator is constituted by a waveguide slot antenna, and the main reflector is constituted by a reflector constituted by partial reflectors 50, 51, 52, and 53, which are conductive flat plates. ing. The main reflector is provided with a conversion section 42 as a mounting structure for mounting the array antenna. The array antenna 40 has a rectangular surface on which the radiating elements are arranged, and a terminator 41 is connected to one end of the rectangular surface. The orthogonal coordinate axes X, Y, and Z each have their origin at the center of the aperture where the slot of the array antenna is provided, the X-axis in the longitudinal direction of the array antenna, the Z-axis in the direction perpendicular to the aperture and away from the main reflector, The Y-axis is defined in a direction perpendicular to the Y-axis and the Z-axis. The partial reflectors 50, 51, 52, and 53 are arranged so that their reflector axes, that is, the axes along which the cutting lines of each partial reflector in a plane orthogonal to this axis are always the same, are parallel to the X axis, and the overall reflection is The plate is symmetrical about the XZ plane. FIG. 3 is an enlarged view of a part of the array antenna, in which a plurality of elliptical slots as shown in the figure are provided in the so-called magnetic interface of the waveguide parallel to the tube axis, that is, the longitudinal direction. Radio waves traveling through the waveguide are radiated from each slot. Each slot is excited by a current in the Y-axis direction flowing through the inner wall of the waveguide, and its amplitude is mainly determined by the dimension L in the X-direction between the slots shown in Fig. 3, and the relative excitation phase between each slot is It is mainly adjusted by the dimension S between the slot and the X axis shown in FIG. For example, in Figure 1, the YZ plane is a horizontal plane, and the
If we assume that the plane is a vertical plane, we will explain the case where asymmetrical beams are synthesized in the vertical plane around the Z-axis as shown by the solid line 60 shown in Fig. 5, that is, the axis at an angle of 0 degrees in Fig. 5. In this case, the excitation amplitude of each slot is symmetrical with respect to the YZ plane, but the excitation phase is
It is antisymmetric with respect to the plane. Here, antisymmetric means that the absolute value of the phase is the same but the sign is reversed. In the example of FIG. 5, the total number of slots is 21, and the amplitude and phase are as shown in the table up to the upper 10th slot, assuming that the example amplitude of the central slot is 1 and the example phase is 0 degrees. Up to the 10th slot at the bottom of the table, only the phase of the table value is reversed. Also, the numerical examples above are just a reminder that beam shaping can be achieved with an array antenna.

〔Effect of the invention〕

As described above, by implementing the present invention, it is possible to realize an antenna with a good degree of beam forming and an excellent degree of cross-polarization discrimination. Moreover, since the reflective surface is planar, it has the advantage that it can be manufactured at a lower cost than the conventional mirror surface. The present invention can be used to great effect in antennas of master stations that need to perform wireless communications with a plurality of stations scattered in a certain area.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing the structure of an apparatus according to an embodiment of the present invention.
FIG. 2 is a front view of the above embodiment. FIG. 3 is an enlarged view of a portion of the array antenna. FIG. 4 is a perspective view of another structural example of the array antenna. FIG. 5 is an explanatory diagram of the radiation characteristics in the vertical plane of the antenna according to the above embodiment.
FIG. 6 is a horizontal sectional view of the above embodiment. FIG. 7 is an explanatory diagram of radiation characteristics in the horizontal plane of the antenna according to the above embodiment. FIG. 8 is a plan view of another embodiment of the invention. FIG. 9 is a plan layout diagram of a master station and slave stations that perform wireless communication. FIG. 10 is a vertical cross-sectional view of FIG. 9 using a pencil beam. Figure 11 shows the 9th beam formed by the shaped beam.
A vertical cross-sectional relationship diagram of the figure. FIG. 12 is a plan layout diagram when the communication areas shown in FIG. 9 are adjacent to each other. FIG. 13 is a front view of a shaped beam antenna with a conventional structure. 1st
FIG. 4 is a horizontal sectional view of the conventional example. FIG. 15 is a vertical sectional view of the conventional example. FIG. 16 is an explanatory diagram of the radiation characteristics in the vertical plane of the above-mentioned conventional antenna. FIG. 17 is an explanatory diagram of the polarization characteristics of the above-mentioned conventional antenna. 1, 1', 2, 3, 12 to 16, 60, 61...
...Radiation characteristics, 4-7, 8-1, 8-2, 9, 1
0,70-75... Radio wave path, 20... Primary radiator, 30... Main reflector, 34, 37, 38...
Torus mirror surface part, 35-1, 35-2, 36-
1, 36-2, 39-1, 39-2... Parabolic mirror surface, 40... Array antenna having a waveguide slot, 41... Terminator, 42... Conversion unit, 4
3, 46, 47...Metal strip, 44...Dielectric substrate, 45...Metal conductor, 48, 49...Connector, 50-53...Partial reflection plate, 54...
Conductor side plate, P35-1, P35-2, P37,
P38, P50, P51, P52, P53... Central axis of parabola, A, A'... Master station, B, B', C,
C', D, D', E, E'...Slave station, F...Focus, S,
L...Dimension indicating slot spacing and position.

Claims (1)

[Claims] 1. An array antenna in which a plurality of radiating elements are arranged on a rectangular plane, and a main reflecting plate disposed behind the radiating elements of the array antenna in the radiation direction, In an array antenna with a reflector in which the main reflection surface of the main reflector is constituted by a plurality of flat conductor plates, the origin is the center of the rectangle of the array antenna, the X axis is defined in the longitudinal direction of the rectangle, and If the Z-axis is perpendicular to the plane and passes through the origin and moves away from the main reflector, and the Y-axis is set in the direction that passes through the origin and is perpendicular to the X-axis and the Z-axis, then the main reflector is formed by each conductor plane plate. The central axes of both are parallel to the X axis, symmetrical with respect to the XZ plane, and convex in the negative direction of the Z axis, and the excitation amplitude of the radiating element of the array antenna is symmetrical with respect to the YZ plane. The excitation phase is
The radiating elements of the array antenna are arranged so as to be antisymmetric with respect to the YZ plane, and the radiating elements of the array antenna are arranged such that the radiation beam formed by the main reflector is
An array antenna with a reflector, characterized in that it is arranged symmetrically with respect to the Z-axis on a plane and asymmetrically with respect to the Z-axis on a YZ plane. 2. The array antenna with a reflector according to claim 1, wherein the main reflector includes a conductor plate added to an end of the main reflector. 3. The array antenna with a reflector according to claim 1, wherein the main reflector includes a mounting structure for attaching the array antenna.