JP4662051B2 - Orthogonal polarization array antenna - Google Patents

Description

  In the present invention, when two array antennas having orthogonal planes of polarization are used at the same frequency, one as a transmitting antenna and the other as a receiving antenna, the isolation between the two antennas (the degree of separation of the amount of radio wave sneaking into adjacent antennas) ) Belongs to the technical field to enhance.

FIG. 4 is a diagram showing a configuration of a first example of a conventional orthogonal polarization array antenna.
(A) is the front view seen from the transmission / reception direction, (b) is the sectional drawing. In this example, a waveguide slot array antenna is used as the array antenna, and the slot is an antenna element.
A structure is such that a slot plate 12 provided with a slot 10 and a slot 11 is attached to a base body 9 provided in parallel with a plurality of waveguides 8 partitioned by a boundary wall 15. The first antenna unit 13 and the second antenna unit 14 are adjacent to each other with the straight line C as a boundary.

Since the longitudinal direction of the slot 10 of the first antenna unit 13 and the slot 11 of the second antenna unit 14 is symmetrically inclined by 45 degrees with respect to the straight line C, the angle formed by the slot directions of both antennas is exactly the same. 90 degrees, that is, a right angle.
Thereby, the main polarization plane by the first antenna unit 13 and the main polarization plane by the second antenna unit 14 are orthogonal (intersect).

Therefore, now, for example, when the first antenna unit 13 is used as a transmission antenna and the second antenna unit 14 is used as a reception antenna, the main polarized electromagnetic wave radiated from the first antenna unit 13 is the second antenna unit 14. Electromagnetic waves transmitted from the counterpart radio station in the same polarization plane as the main polarization plane of the second antenna section 14 are not received by the main polarization plane of the second antenna section. 14 is received by the main polarization plane of the first antenna unit 13 but is not received by the main polarization plane.
Therefore, bidirectional simultaneous parallel transmission / reception at one frequency is possible (for example, see Patent Document 1).

FIG. 5 is a diagram showing a configuration of a second example of a conventional orthogonal polarization array antenna.
In this example, the upper wide wall surface of the waveguide is formed by arranging slots in parallel and adjacent to each other. A waveguide 17 in which the slot 16 is cut at right angles to the tube axis direction, and a slot 18 is provided. The waveguides 19 cut in the tube axis direction are alternately arranged one by one.

  Two feeding waveguides are provided on the lower wide wall surface of the parallel waveguides in a direction orthogonal to the parallel waveguides, and one of the feeding waveguides 20 has a slot 16 in the tube axis. The other feed waveguide 21 is connected to every other waveguide 19 whose slots 18 are cut in the tube axis direction. Power supply coupling.

Therefore, every other waveguide 17 and the feeding waveguide 20 form a first antenna portion, and every other waveguide 19 and the feeding waveguide 21 are used as a second antenna. The part is formed. After all, since the direction of the slot of the first antenna unit and the direction of the slot of the second antenna unit are orthogonal, the main polarization planes of both antennas are orthogonal.
Therefore, an antenna capable of transmitting and receiving orthogonal polarized waves is configured (see, for example, Patent Document 2).
Japanese Unexamined Patent Publication No. 2004-15460 ([0018], [0019], FIG. 1) Japanese Unexamined Patent Publication No. 5-48323 ([0013] to [0015], FIG. 1)

However, the array antenna has a vertically polarized wave (cross-polarized wave) component with a small amplitude in a direction deviating from the principal axis direction even if the polarized wave (main polarized wave) is, for example, horizontal polarized wave in the azimuth direction. . Such an aspect is schematically shown in FIG.
(A) shows the directivity of the main polarization. The vertical axis represents amplitude, and the horizontal axis represents azimuth. The amplitude indicates that the polarity is inverted above and below the horizontal axis.

  It has the maximum amplitude in the main axis direction, goes down symmetrically in the left and right directions, reverses the polarity, increases to a certain value smaller than the amplitude value in the main axis direction, then decreases again, and then polarity again Is reversed on both sides in the main axis direction. This is the so-called main lobe and side lobe.

  (B) shows how the cross polarization component appears. That is, the amplitude level is zero in the main axis direction. However, in both directions of the main axis direction, the amplitude gradually increases as the distance from the main axis direction increases, and changes from a certain point again. The polarities are reversed on the left and right in the main axis direction.

Thus, cross polarization appears in the directions on both sides of the main axis direction.
For this reason, in the arrangement of the first antenna unit and the second antenna unit as in the conventional orthogonal polarization array antenna of FIG. 4, the first antenna unit is used as a transmission antenna because they are arranged side by side in the azimuth direction. In this case, no cross-polarization appears in the front direction, that is, in the direction perpendicular to the drawing sheet, but cross-polarization appears in the direction closer to the second antenna portion. Since this cross polarization is the main polarization of the second antenna unit, there is a problem that, when it is transmitted from the first antenna, wraparound to the second antenna occurs.

  In addition, in the orthogonal polarization array antenna as shown in FIG. 5, the waveguides constituting the first antenna and the waveguides constituting the second antenna are alternately arranged one by one. At the position shifted by the width of one wave tube, it is equivalent to the first antenna and the second antenna being adjacent to each other, and a wraparound problem occurs for the same reason as in FIG.

  In short, in the conventional orthogonal polarization array antenna, the isolation due to the orthogonal main polarization can be taken, but since there is a wraparound due to the cross polarization component and the arrangement of the two antennas, only that much remains. There is a problem that the isolation is insufficient.

  Enough isolation is a big issue because weak reception radio waves can be identified and received without being masked by the local transmission radio waves.

The present invention has the following configurations in order to solve the above problems.
In the first configuration (basic configuration) of the present invention, a plurality of antenna elements are arranged in a plane along one plane and symmetrically with respect to a plane orthogonal to the plane, and specified in the normal direction of the one plane. A first array antenna having directivity in the plane of polarization, and a plurality of antenna elements that are planar and orthogonal to each other along an extended surface that does not overlap with the first array antenna or a surface parallel to this surface. A second array antenna having a directivity in a plane of polarization orthogonal to a specific plane of polarization of the first array antenna is arranged in the same direction as the normal direction of the one plane arranged symmetrically with respect to the plane. This is an orthogonally polarized array antenna.

  A second configuration of the present invention is an orthogonal polarization array antenna according to the first configuration, wherein the antenna element is a slot provided on a wide surface of a rectangular waveguide.

  A third configuration of the present invention is an orthogonal polarization array antenna according to the first configuration, wherein the antenna element is a patch antenna.

  A fourth configuration of the present invention is an orthogonal polarization array antenna according to the first configuration, wherein the antenna element is a circular waveguide opening.

As described in the problem solving means, the orthogonally polarized array antenna of the present invention has two array antennas at two positions that share one central line when viewed from the front in the direction of direction, and each array antenna includes a plurality of array antennas. Antenna elements are arranged in a plane symmetrically on both sides with respect to the center line, and the main polarizations of the antennas are orthogonal to each other.
Since the antenna elements are arranged symmetrically on both sides with respect to the center line in this way, the main polarization directivity characteristic of each array antenna is left-right symmetric with respect to the main axis direction as shown in FIG. As shown in (b), the directivity characteristics are symmetrical in absolute amplitude on the left and right in the main axis direction, but the polarity is reversed.

  Now, if one antenna is the transmitting antenna and the other antenna is the receiving antenna, the center line of the antenna element array matches, so the antenna element on the right side of the receiving antenna center line is the cross polarization of the transmitting antenna. The signal is received with the characteristic on the right side of the characteristic (FIG. 3B), and the left antenna element is received with the characteristic on the left side of FIG. As described above, the cross polarization characteristic of FIG. 3B is a characteristic that the amplitude is the same and the polarity is opposite on both sides in the main axis direction.

On the other hand, the antenna elements of the receiving antenna are arranged symmetrically with respect to the center line, the right antenna element receives with the right characteristic, and the left antenna element receives with the left characteristic. The reception of the antenna element and the reception of the left antenna element have the same amplitude and opposite polarity.
Since the antennas are combined so that the signals received by the respective antenna elements in the same phase are added, the signals received in the opposite phase are canceled and do not appear in the output of the antenna.

  Eventually, even if each of the two antennas has a cross-polarized component in addition to the main polarization, the cross-polarization is caused by the arrangement of the antenna elements that are symmetric with respect to the center line and the arrangement of both antennas that match the center line. The effect of eliminating the influence of waves and obtaining high isolation is obtained.

Regardless of whether a patch antenna, waveguide slot, or circular waveguide opening is used as an antenna element, it is best from the economical viewpoint to construct an orthogonally polarized antenna with the same array antenna vertically and horizontally. It is an embodiment.
For this purpose, it is necessary to determine the arrangement of the antenna elements so that the center line is determined in both the vertical and horizontal directions.
Also, it is best to fix the two array antennas to one structure with the directions of the opening surfaces being coincident. Direction setting adjustment is simplified in installation work.

Embodiments of the antenna of the present invention will be described below with reference to the drawings.
FIG. 1 is a front view of an antenna when the antenna element is a patch antenna as viewed from the front of the opening.
In the first antenna unit 1, the patch antennas 7 are arranged in a plane so as to be symmetric with respect to the center line CC. The power supply path is not shown.
As a result, the first antenna unit 1 can transmit and receive electromagnetic waves on a specific main polarization plane (for example, horizontal polarization). The second antenna unit 6 is tilted 90 degrees in the longitudinal direction of the first antenna unit 1 by two patch antennas so that the arrangement of the patch antennas 7 is symmetrical with respect to the center line CC. The first antenna unit is disposed below the first antenna unit. By rotating 90 degrees, the polarization planes of the first antenna unit 1 and the second antenna unit 6 are orthogonal (for example, vertically polarized waves).

That is, the cross polarization plane of the first antenna unit 1 is the same as the main polarization plane of the second antenna unit 6, and the cross polarization plane of the second antenna unit 6 is the same as the main polarization plane of the first antenna unit 1. become.
Now, assuming that the first antenna unit 1 is a transmitting antenna and the second antenna unit 6 is a receiving antenna, the main polarized wave is radiated from the first antenna unit 1 with the directivity shown in FIG. The wave component is radiated with the directivity shown in FIG. The azimuth angle is an angle in the left-right direction with the center line CC as the central axis.

  The electromagnetic wave radiated by the main polarization is not received by the main polarization plane of the second antenna unit 6 because it is orthogonal to the main polarization of the second antenna unit 6, but the directivity shown in FIG. The electromagnetic wave radiated with the characteristic is received by the second antenna unit 6 because the plane of polarization is the same as the main polarization plane of the second antenna unit. However, the patch antenna on the left side of the center line CC is received with the characteristics on the left side of the main axis direction of FIG. 3B, and the patch antenna on the right side of the center line CC has the main axis direction of FIG. Received with the characteristics on the right. That is, the signals are received with the same amplitude and opposite polarity on the left and right of the center line CC.

  By the way, since the patch antenna 7 of the second antenna unit 6 is arranged symmetrically with respect to the center line CC, when signals received by all the patch antennas are combined, the cross polarization of the first antenna unit 1 is received. The signal received on the left side of the center line CC and the signal received on the right side cancel each other, and do not appear in the output of the second antenna unit 6. As a result, the cross polarization component from the first antenna unit 1 is the same as it was not received, and the isolation between the two antennas becomes very high.

  The above description has been made in the case where the cross polarization component of the first antenna unit 1 for transmission is received by the main polarization characteristic of the second antenna unit 6 for reception. Even when the main polarization component is received with the cross polarization characteristic of the second antenna unit 6 for reception, the cross polarization characteristic of the second antenna unit 6 is also centered as in FIG. Since signals are received with equal amplitude and reverse polarity in the left-right direction around the line C-C, when signals received by all patch antennas are combined, they are canceled out to zero, which is the same as no cross-polarization reception. become.

  In addition, in the example of FIG. 1, the 1st antenna part 1 and the 2nd antenna part 6 have touched, but it does not need to contact. In addition, the antenna element array surfaces of both antennas may be flush or may be shifted back and forth. The same applies to the following embodiments.

The embodiment of FIG. 2 is a case where the antenna element is a slot.
The first antenna unit 1 and the second antenna unit 6 are configured such that the same antenna passing through the feeding path in the center is vertically and horizontally so as to be orthogonally polarized between both antennas.
Both antennas are positioned so that the arrangement of slots as antenna elements is symmetrical with respect to the center line CC in both the first antenna unit 1 and the second antenna unit 6.
In this embodiment, the slot is shown as a simple rectangle, but the slot is not limited to this, and the slot corresponding to one slot in the above drawings may be a combination of a plurality of slots. It may be a long or short series, or may not be a simple long hole. Various types of unit slots can be considered from various other design conditions.
The isolation between the two antennas actually measured in the arrangement of the embodiment of FIG. 2 is very good at about 80 dB or more.

In addition, a circular waveguide opening can be used as the antenna element.
Basically, any antenna element may be used as long as it can be used as an element, and is not particularly limited.

It is a front view of the 1st example of the present invention whose antenna element is a patch antenna. It is a front view of the 2nd example of the present invention in which an antenna element is a slot cut in the wide surface of a waveguide. It is an azimuth | direction directivity figure of the main polarization and cross polarization of an array antenna. It is a block diagram which shows the 1st example of the conventional orthogonal polarization array antenna. It is a block diagram which shows the 2nd example of the conventional orthogonal polarization array antenna.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st antenna part 2 Feeding path 3 Slot 4 Waveguide 5 Waveguide boundary 6 2nd antenna part 7 Patch antenna 8 Waveguide 9 Base body 10 Slot 11 Slot 12 Slot plate 13 1st antenna part 14 2nd antenna part 15 Boundary Wall 16 Slot 17 Waveguide 18 Slot 19 Waveguide 20 Feeding waveguide 21 Feeding waveguide

Claims (4)

A first array antenna having a plurality of antenna elements arranged in a plane along one plane and symmetrically with respect to a plane orthogonal to the plane and having directivity in a specific polarization plane in a normal direction of the one plane; Similarly, a plurality of antenna elements are arranged in a plane along an extended surface that does not overlap the first array antenna or a plane parallel to this plane and symmetrically with respect to the orthogonal plane, and the normal of the one plane An orthogonal polarization array antenna, wherein a second array antenna having directivity in a polarization plane orthogonal to a specific polarization plane of the first array antenna is arranged in the same direction as the direction .   2. The orthogonally polarized array antenna according to claim 1, wherein the antenna element is a slot provided on a wide surface of a rectangular waveguide.   The orthogonally polarized array antenna according to claim 1, wherein the antenna element is a patch antenna.   The orthogonally polarized array antenna according to claim 1, wherein the antenna element is a circular waveguide opening.

Images