JP2023102306A - array antenna - Google Patents

Abstract

To suppress the occurrence of a grating lobe in an array antenna.SOLUTION: An array antenna 1 includes at least four sub-arrays 11 each including a plurality of radiation elements 111. Each center position of the four sub-arrays 11 is arranged at four vertexes of a square S. A direction of a straight line connecting each of the plurality of radiation elements 111 and the other radiation element 111 that is nearest to each of the plurality of radiation elements 111 is different from direction of four sides of the square S.SELECTED DRAWING: Figure 1

Description

The present invention relates to array antennas.

2. Description of the Related Art Conventionally, there is known an array antenna configured by a plurality of subarray antennas (hereinafter referred to as "subarrays") each including a plurality of radiating elements (see Patent Document 1, for example).

JP 2018-186337 A

In an array antenna, by feeding different phases to a plurality of subarrays, radio waves can be radiated in directions corresponding to the feeding phases. However, depending on the feed phase, strong radio waves may be radiated in a specific direction other than the direction in which radio waves are desired to be radiated (main radiation direction). This is called a grating lobe. It is required to suppress such grating lobes.

In conventional array antennas, a plurality of subarrays are arranged in a straight line. When power is supplied in the same phase to a plurality of sub-arrays arranged on a straight line, a problem arises that grating lobes are likely to occur.

Accordingly, the present invention has been made in view of these points, and it is an object of the present invention to suppress the generation of grating lobes in an array antenna.

The array antenna of the present invention has at least four subarrays each including a plurality of radiating elements, and the center positions of the at least four subarrays are arranged at the vertexes of a polygon having a number of sides equal to or less than the number of subarrays included in the array antenna, and the direction of a straight line connecting each of the plurality of radiating elements and another radiating element closest to each of the plurality of radiating elements is different from the direction of the sides of the polygon.

Each of the at least four sub-arrays may include four radiating elements arranged at vertices of a square as the plurality of radiating elements.

The four sub-arrays included in the at least four sub-arrays are a first sub-array, a second sub-array, a third sub-array and a fourth sub-array, and when the distance between the first radiating element among the plurality of radiating elements and the second radiating element closest to the first radiating element is d, the center position of the first sub-array and the center position of the second sub-array are separated by d in the first direction and by 2d in the second direction orthogonal to the first direction. the center position of the second sub-array and the center position of the third sub-array are separated by 2d in the first direction and the center position of the third sub-array are separated by d in the second direction; the center position of the third sub-array and the center position of the fourth sub-array are separated by d in the first direction and the center position of the fourth sub-array are separated by 2d in the second direction; They may be separated by d in said second direction.

A distance d between the first radiation element and the second radiation element may be 0.5λ or more and less than 0.8λ, where λ is the wavelength of radio waves emitted by the array antenna.

When the reference value of the phase difference of the signals fed to the subarrays is τ, the feeding phase of one of the four subarrays may lead the feeding phase of the other three subarrays by τ, 2τ, and 3τ, respectively.

Each of the at least four sub-arrays may further have a feed port co-located with respect to the plurality of radiating elements.

The feeding port of at least one of the subarrays may be provided in an area surrounded by a line connecting a plurality of radiating elements closest to the other subarray among the plurality of radiating elements of each of the four subarrays.

ADVANTAGE OF THE INVENTION According to this invention, it is effective in the ability to suppress generation|occurrence|production of the grating lobe in an array antenna.

It is a figure which shows the structural example of 1 A of array antennas which concern on 1st Embodiment. It is a figure which shows the structural example of 1 A of array antennas which concern on 1st Embodiment. It is a figure for demonstrating the parameter used by this simulation. It is a figure which shows a 1st simulation result. It is a figure which shows a 2nd simulation result. FIG. 10 is a diagram showing first simulation results of an array antenna of a comparative example; FIG. 10 is a diagram showing a second simulation result of the array antenna of the comparative example; FIG. 10 is a diagram showing configurations of an array antenna 1B and an array antenna 1C according to a second embodiment; FIG. 10 is a diagram showing the configuration of an array antenna 1D according to a third embodiment; FIG. FIG. 11 is a diagram showing the configuration of an array antenna 1E according to a fourth embodiment; FIG. FIG. 14 is a diagram showing the configuration of an array antenna 1F according to a fifth embodiment;

<Outline of the array antenna of this embodiment>
The inventors of the present application have diligently studied methods for suppressing grating lobes in an array antenna having a plurality of subarrays. As a result, it was found that grating lobes can be suppressed by making the direction of a straight line connecting each of the plurality of radiating elements included in each subarray and the other radiating element in the same subarray that is closest to each of the plurality of radiating elements different from the direction of a straight line that connects the center positions of the plurality of subarrays that are closest to each other.

That is, the inventor of the present application has found that the array antenna has at least four subarrays each including a plurality of radiating elements, the center positions of the at least four subarrays are arranged at the vertexes of a polygon having sides equal to or less than the number of subarrays included in the array antenna, and the direction of a straight line connecting each of the plurality of radiating elements and each of the plurality of radiating elements and the other nearest radiating element is desirably different from the direction of the sides of the polygon. In this specification, configuration examples of array antennas satisfying this condition are shown, and results of comparison of radio wave radiation characteristics of an array antenna satisfying this condition and an array antenna not satisfying this condition are also shown.

<First Embodiment>
[Configuration of array antenna 1A]
1 and 2 are diagrams showing a configuration example of an array antenna 1A according to the first embodiment. The array antenna 1A has four subarrays 11 from a first subarray 11-1 to a fourth subarray 11-4. FIG. 1(a) schematically shows the shape and arrangement of four sub-arrays 11 in the array antenna 1A, and FIG. 1(b) schematically shows the configuration of each sub-array 11. FIG.

As shown in FIG. 1(b), each of the four subarrays 11 includes four radiating elements 111 arranged at the vertices of a square. That is, each subarray 11 has four radiating elements 111 (111-1 to 111-4) and feed ports 112. FIG.

The four radiating elements 111 are arranged so as to be positioned at the vertices of the square. That is, among the four radiating elements 111, the distances between the closest radiating elements 111 are the same. The direction of the straight line connecting the first radiation element 111-1 and the second radiation element 111-2 and the direction of the straight line connecting the third radiation element 111-3 and the fourth radiation element 111-4 are the same X direction. The direction of the straight line connecting the first radiation element 111-1 and the fourth radiation element 111-4 and the direction of the straight line connecting the second radiation element 111-2 and the third radiation element 111-3 are the Y direction orthogonal to the X direction.

In FIG. 1B, center positions C of four radiating elements 111 are shown. The center position C corresponds to the center position of the polygon (that is, the quadrangle) formed by the four radiating elements 111 . In the example shown in FIG. 1B, the center position C is the position of the intersection of a straight line connecting the first radiating element 111-1 and the third radiating element 111-3 and a straight line connecting the second radiating element 111-2 and the fourth radiating element 111-4.

The feeding port 112 is an input terminal for supplying transmission power to the four radiating elements 111 and an output terminal for outputting received power, and is coupled to a waveguide connected to an external circuit. The feeding port 112 of each of the four subarrays 11 is arranged in a region that does not overlap with other subarrays 11 . Further, in the array antenna 1A shown in FIG. 1A, the feeding ports 112 of each of the four subarrays 11 are arranged at the same positions with respect to the plurality of radiation elements 111 of each subarray 11. As shown in FIG.

Further, at least one feeding port 112 among the plurality of feeding ports 112 of the plurality of subarrays 11 is provided within a region surrounded by lines connecting the plurality of radiating elements 111 closest to the other subarrays 11 among the plurality of radiating elements 111 of each of the four subarrays 11. In the example shown in FIG. 1(a), the feeding port 112 of the fourth subarray 11-4 is provided in a region within a rectangle having four radiating elements 111 indicated by symbols a, b, c, and d as vertices. By arranging the feeding port 112 in such a region, the size of the array antenna 1 can be reduced.

As shown in FIGS. 1(a) and 1(b), the distance between the two closest radiating elements 111 (ie, the first radiating element and the second radiating element) among the four radiating elements 111 is d. Here, the distance d is preferably 0.5λ or more and less than 0.8λ, where λ is the wavelength of the radio wave radiated by the array antenna 1 . When the distance d is within this range, it becomes easier to suppress grating lobes.

When the distance between the first radiation element 111-1 and the second radiation element 111-2 is d, the center position C1 of the first subarray 11-1 and the center position C2 of the second subarray 11-2 are separated by d in the X direction (corresponding to the first direction) and by 2d in the Y direction (corresponding to the second direction) perpendicular to the X direction. Here, the center of the subarray indicates the center of gravity obtained from the positions of the plurality of radiating elements forming the subarray as described above.

Similarly, the center position C2 of the second subarray 11-2 and the center position C3 of the third subarray 11-3 are separated by 2d in the X direction and by d in the Y direction. The center position C3 of the third subarray 11-3 and the center position C4 of the fourth subarray 11-4 are separated by d in the X direction and by 2d in the Y direction. The center position C4 of the fourth subarray 11-4 and the center position C1 of the first subarray 11-1 are separated by 2d in the X direction and by d in the Y direction.

As shown in FIG. 2, the center positions C1 to C4 of the four subarrays 11 are arranged at the four vertices of the quadrangle S. As shown in FIG. That is, the positional relationship of the four subarrays 11 is equivalent to the positional relationship of the blades of the windmill.

Among the plurality of radiation elements 111, the direction of the straight line connecting the first radiation element and the second radiation element closest to the first radiation element is different from the direction of the four sides of the quadrangle S. That is, the direction of the sides of the polygon formed by the plurality of radiation elements 111 forming the subarray 11 and the direction of the four sides of the quadrangle S are different.

Specifically, the directions of the four sides of the quadrangle S are different from the X direction and the Y direction. More specifically, the directions of the four sides of the quadrangle S are the directions of the straight line connecting the first radiation element 111-1 and the second radiation element 111-2, the direction of the straight line connecting the second radiation element 111-2 and the third radiation element 111-3, the direction of the straight line connecting the third radiation element 111-3 and the fourth radiation element 111-4, and the direction of the straight line connecting the fourth radiation element 111-4 and the first radiation element 111-1. They are different from each other.

The center positions C1 to C4 of the four sub-arrays 11 are arranged in a direction different from the direction of the straight line connecting the closest plurality of radiating elements 111 included in each sub-array 11, thereby suppressing grating lobes as shown by simulation results to be described later.

By feeding signals of different phases to each of the four sub-arrays 11, it is possible to change the radiation direction of radio waves. When the reference value of the phase difference of the signals fed to the plurality of subarrays 11 is τ, the feed phase of one of the four subarrays 11 is preferably advanced by the feed phase of the other three subarrays 11 by τ, 2τ, and 3τ, respectively.

[simulation result]
Simulation results of the radio wave radiation characteristics of the array antenna 1A and the radio wave radiation characteristics of the array antenna of the comparative example will be described below. In the simulation, the distance d=0.5λ.

FIG. 3 is a diagram for explaining parameters used in the simulation. Assuming that the surface of the array antenna 1 is on the XY plane, the angle between the radiation direction and the Z direction is θ, and the angle between the radiation direction and the X direction is Φ.

FIG. 4 is a diagram showing the results of the first simulation of the array antenna 1A shown in FIGS. 1 and 2, that is, the simulation results of the radio wave radiation characteristics when the direction of the main radiation beam is changed within the XZ plane. FIG. 4(a) is a diagram showing the feeding phases of each of the four radiating elements forming the subarrays 11-1, 11-2, 11-3 and 11-4 of the array antenna 1A. In FIG. 4A, the feeding phase of the first sub-array 11-1 is advanced by τ, the feeding phase of the third sub-array 11-3 is advanced by τ, the feeding phase of the third sub-array 11-3 is advanced by 2τ, and the feeding phase of the fourth sub-array 11-4 is advanced by 3τ with respect to the feeding phase of the second sub-array 11-2. By changing τ, the direction of the main radiation beam changes. As for the feeding phase of the radiation elements constituting each subarray, only the changes of τ, 2τ, and 3τ are shown, and the fixed phase difference between the radiation elements is not shown. The same applies to the following examples.

FIG. 4(b) is a diagram showing radio wave radiation characteristics of the array antenna 1A having such a feeding phase. The horizontal axis of FIG. 4(b) indicates the angle θ between the radiation direction and the Z direction, and the vertical axis indicates the gain (dB) corresponding to the intensity of the radiated radio wave.

The solid line in FIG. 4(b) indicates the radio wave radiation characteristics when τ=0° (that is, when the feeding phases of all the subarrays 11 are the same). The dashed line indicates the case of τ=50°, the one-dot chain line indicates the case of τ=100°, and the two-dot chain line indicates the case of τ=150°. In all cases, the gain of the grating lobes is suppressed sufficiently low with respect to the gain of the main radiation beam.

FIG. 5 is a diagram showing the results of the second simulation of the array antenna 1A, that is, the simulation results of the radio wave radiation characteristics when the direction of the main radiation beam is changed within the YZ plane. FIG. 5(a) is a diagram showing feeding phases of each of the four radiating elements forming the subarrays 11-1, 11-2, 11-3 and 11-4 of the array antenna 1A. In FIG. 5A, the feeding phase of the second sub-array 11-2 is 2τ, the feeding phase of the third sub-array 11-3 is 3τ, and the feeding phase of the fourth sub-array 11-4 is advanced by τ with respect to the feeding phase of the first sub-array 11-1. As shown in FIG. 5B, the grating lobes are sufficiently suppressed in this case as well.

FIG. 6 is a diagram showing first simulation results of the array antenna of the comparative example. In the array antenna of the comparative example, as schematically shown in FIG. 6A, a plurality of subarrays are arranged on the same straight line in the X direction. In other words, the subarrays 21-1 and 21-2, and the subarrays 21-3 and 21-4 are arranged on a straight line, respectively, and are arranged so as to be shifted from each other by the distance of the radiating elements of the subarrays. The feeding phase of the subarray 21-4 is advanced by τ, the feeding phase of the subarray 21-2 is advanced by 2τ, and the feeding phase of the subarray 21-3 is advanced by 3τ with respect to the feeding phase of the subarray 21-1. In this case, the radiation direction changes in the XZ plane (Φ=0°), and the grating lobes are suppressed to some extent.

FIG. 7 is a diagram showing a second simulation result of the array antenna of the comparative example. The feed phase of the subarray 21-1 and the feed phase of the subarray 21-2 are equal, and the feed phase of the subarray 21-3 and the feed phase of the subarray 21-4 are advanced by τ. In this case, the direction of the main beam of radiation changes in the YZ plane (Φ=90°). In FIG. 7B, it can be seen that large grating lobes are generated.

From the above comparison results, it was confirmed that the array antenna 1A according to the present embodiment can widely change the radiation direction and can sufficiently suppress the grating lobe compared to the conventional array antenna.

<Second embodiment>
FIG. 8 is a diagram showing configurations of an array antenna 1B and an array antenna 1C according to the second embodiment. Array antenna 1B and array antenna 1C differ from array antenna 1A shown in FIG. 1 in that each subarray 11 has two radiating elements 111 . The direction of the side of the square connecting the center positions of the two radiating elements 111 in the array antennas 1B and 1C is different from the direction of the straight line connecting the two radiating elements 111 . Grating lobes are also suppressed in such a configuration.

<Third Embodiment>
FIG. 9 is a diagram showing the configuration of an array antenna 1D according to the third embodiment. Array antenna 1D differs from array antenna 1A shown in FIG. 1 in that each subarray 11 has three radiating elements 111. FIG. The directions of the sides of the quadrangle connecting the center positions of the three radiating elements 111 in the array antenna 1D are different from the directions of the sides of the triangle formed by the three radiating elements 111 . Grating lobes are also suppressed in such a configuration.

<Fourth Embodiment>
FIG. 10 is a diagram showing the configuration of an array antenna 1E according to the fourth embodiment. Array antenna 1E differs from array antenna 1A shown in FIG. In the array antenna 1E, the direction of the straight line connecting the center positions of the plurality of subarrays 11 is different from the direction of the straight line connecting the two closest radiating elements 111 among the plurality of radiating elements 111 included in the subarray 11. Grating lobes are also suppressed in the array antenna 1E having such a configuration.

<Fifth Embodiment>
FIG. 11 is a diagram showing the configuration of an array antenna 1F according to the fifth embodiment. Array antenna 1F differs from array antenna 1A shown in FIG. In the array antenna 1F, the direction of the straight line connecting the center positions of the plurality of subarrays 11 is different from the direction of the straight line connecting the two closest radiating elements 111 among the plurality of radiating elements 111 included in the subarray 11. Grating lobes are also suppressed in the array antenna 1F having such a configuration.

<Other embodiments>
The form of the array antenna 1 according to the present invention is not limited to the forms exemplified above, and various modifications are possible. As an example, in the above description, the distance in the first direction and the distance in the second direction between the center positions of the closest subarrays 11 are either d or 2d, and the center positions of the four subarrays 11 are arranged at the vertices of a square.

In the embodiment illustrated above, the plurality of radiating elements 111 of the subarray 11 are arranged at the vertices of the square, but the positional relationship of the plurality of radiating elements 111 may be arranged at positions other than the vertices of the square as long as the direction of the straight line connecting the center positions of the plurality of subarrays 11 does not coincide with the direction of the straight line connecting the nearest plurality of radiating elements 111. For example, the array antenna may have five or more subarrays, and the direction of the sides of the polygon connecting the center positions of the five or more subarrays may be different from the direction of the straight line connecting the closest radiating elements included in the subarrays.

Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of the gist. For example, all or part of the device can be functionally or physically distributed and integrated in arbitrary units. Further, new embodiments resulting from arbitrary combinations of multiple embodiments are also included in the embodiments of the present invention. The effect of the new embodiment caused by the combination has the effect of the original embodiment.

1 array antenna 11 subarray 21 subarray 111 radiation element 112 feeding port

Claims (7)

an array antenna,
having at least four sub-arrays each containing a plurality of radiating elements;
center positions of the at least four subarrays are arranged at the vertices of a polygon having a number of sides equal to or less than the number of subarrays included in the array antenna;
a direction of a straight line connecting each of the plurality of radiating elements and another radiating element closest to each of the plurality of radiating elements is different from a direction of a side of the polygon;
array antenna. each of the at least four sub-arrays includes, as the plurality of radiating elements, four radiating elements arranged at vertices of a square;
The array antenna according to claim 1. The four sub-arrays included in the at least four sub-arrays are a first sub-array, a second sub-array, a third sub-array, and a fourth sub-array, and when the distance between the first radiating element among the plurality of radiating elements and the second radiating element closest to the first radiating element is d,
the center position of the first sub-array and the center position of the second sub-array are separated by d in a first direction and separated by 2d in a second direction orthogonal to the first direction;
the center position of the second sub-array and the center position of the third sub-array are separated by 2d in the first direction and separated by d in the second direction;
the center position of the third sub-array and the center position of the fourth sub-array are separated by d in the first direction and separated by 2d in the second direction;
The center position of the fourth sub-array and the center position of the first sub-array are separated by 2d in the first direction and separated by d in the second direction,
The array antenna according to claim 1 or 2. A distance d between the first radiating element and the second radiating element is 0.5λ or more and less than 0.8λ, where λ is the wavelength of radio waves radiated by the array antenna.
The array antenna according to claim 3. When the reference value of the phase difference of the signals fed to the sub-arrays is τ, the feeding phase of one of the four sub-arrays is advanced by τ, 2τ, and 3τ in the feeding phases of the other three sub-arrays, respectively.
The array antenna according to any one of claims 1 to 4. each of the at least four sub-arrays further having a feed port co-located with respect to the plurality of radiating elements;
The array antenna according to any one of claims 1 to 5. At least one feed port of the sub-array is provided in an area surrounded by lines connecting a plurality of radiating elements closest to other sub-arrays among the plurality of radiating elements of each of the four sub-arrays.
The array antenna according to claim 6.

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