JP5309290B2 - Array antenna - Google Patents

Description

  The present invention belongs to the technical field of a phased array antenna in which a large number of antenna elements are arranged on a plane and the directivity direction of a radiation beam is controlled by controlling the amplitude and phase with respect to the individual antenna elements.

The phased array antenna has a large number of antennas in which the distance between the feeding antenna elements is less than one half of the wavelength used in order to prevent a side lobe called a grating lobe that goes out of a desired direction during beam scanning. Elements are arranged.
In addition, since the phased array antenna is provided with an amplifier and a phase shifter for each antenna element in order to control the amplitude and phase in units of antenna elements as described above, in a phased array antenna having a large number of antenna elements, The number of phase shifters will be large, and the power supply system will be complicated and large.

Therefore, in order to reduce the number of amplifiers and phase shifters, for example, about half of the total number of antenna elements do not receive power, and thus are so-called parasitic elements that do not include amplifiers or phase shifters. A thinning power feeding method in which so-called feeding elements and parasitic elements connected to a phase shifter are alternately arranged has been proposed (for example, see Non-Patent Document 1).
However, in the case of power supply that is simply thinned out, a parasitic element is inserted between the power supply element and the power supply element, so that the interval between the power supply elements becomes larger than a half of the used wavelength, and a grating lobe is generated. There's a problem.

For example, as shown in FIG. 8, antenna elements are arranged at regular intervals of a half wavelength or less and the outlines are arranged in a hexagonal shape. FIG. 9 shows a plot of the number of power feeding elements with respect to each column position in the Y direction for the case of elements. This is called an excitation distribution.
Simulate the directivity in the YZ (Z is the direction perpendicular to the array plane) cross section when the excitation distribution exists in a period of more than one-half wavelength that is the interval between the feed element arrays as shown in FIG. Then, as shown in FIG. 7B, a grating lobe having a peak of about 25 dBi is generated around -10 deg.
Therefore, the following antennas that can suppress grating lobes have been proposed.

  The first grating lobe suppression array antenna is shown in FIG. 10, and a plurality of subarray antennas 12 and 13 are provided. Each subarray antenna 12 and 13 is an array antenna 11 composed of a plurality of element antennas 14. The plurality of subarray antennas 12 and 13 have the same planar shape as that of the Penrose tile and are aperiodically arranged on the plane, and the center position of the element antenna 14 is set in the subarray antennas 12 and 13. The plurality of element antennas 14 are arranged so that the center circles are in contact with each other and the circle is in contact with the outer shape of the Penrose tile (see, for example, Patent Document 1).

  The second grating lobe suppression array antenna is shown in FIG. 11, and includes a plurality of subarray units 17 in which a plurality of element antennas 16 are arranged in a line at predetermined intervals s. The subarray portions 17 are arranged in parallel to form an opening. Each subarray unit 17 is composed of at least one antenna module 18. The antenna module 18 includes, for example, four element antennas 16, and the opening shape is determined by adjusting the number of antenna modules 18. The subarray portion 17 is partially shifted along the direction in which the element antennas 16 are arranged, and the number of the element antennas 16 viewed from the right angle direction decreases from the center of the opening shape toward both sides by a predetermined interval s. (For example, refer to Patent Document 2).

  The third grating lobe suppression array antenna performs thinning power feeding to the array when it is desired to suppress power consumption and heat generation according to the usage status of the antenna. However, in order to reduce the frequency so that the grating can be used so that the grating lobe does not occur even in the interval, the frequency can be lowered so that frequency selection and excitation module selection can be performed. (For example, refer to Patent Document 3).

JP 2008-66936 A (paragraphs [0009] to [0018], FIG. 1) JP 2003-318647 A (paragraph [0017], FIG. 1) Japanese Patent Laying-Open No. 2005-269569 (paragraphs [0009] to [0011], FIG. 4)

Tadashi TAKANO and two others, "Simplification of an Array Antenna by Reducing the Fed Elements", IEICETRANS.COMMUN., The Institute of Electronics, Information and Communication Engineers, NO.9 SEPTEMBER 2005, VOL.E88-B P.3811-3814

  The first grating lobe suppression array antenna in the background art has two types of basic shapes of subarrays, but when the antenna elements are arranged in the subarrays, the polarization direction of each subarray is arranged for each subarray. Since it is necessary to change according to the angle, there is a problem that the number of types of subarrays becomes very large.

  The second grating lobe suppression antenna can prevent a grating lobe from occurring in a vertical plane in one direction within a plane in which antenna elements are arranged, but has a grating lobe in a vertical plane perpendicular to that direction. There is a problem that it cannot be suppressed.

  The third grating lobe suppression antenna has a problem that the antenna gain fluctuates because the number of excitation modules increases or decreases depending on the frequency.

  In view of the above-mentioned problems of the prior art, the object of the present invention is to reduce the frequency to one half of the total number of antenna elements without changing the number of excitation elements (feeding elements), and to determine the total orientation on the array plane. It is to realize a phased array antenna capable of suppressing a grating lobe in a vertical cross section.

As described above, in a phased array antenna that scans all directions in the plane of the array, in order to prevent grating lobes from being generated in the directivity in the vertical plane passing through the center of the array plane, The intersecting line of the vertical plane is the Y axis, and there is no valley in the distribution of the number of feeding elements existing on the line orthogonal to the Y axis at a position on the Y axis with a period of one-half or more of the wavelength used, It is necessary that the distance on the Y-axis is the largest at the center (0) of the Y-axis, so that the distance decreases monotonously or stepwise in each of the + and − directions.
With such an arrangement, generation of grating lobes can be avoided even if half of the total number of antenna elements is a parasitic element.

In order to achieve the above-mentioned object, the present invention has the following configuration.
That is, the inner angles of the corners are 60 degrees, 120 degrees, 60 degrees, and 120 degrees, and the length d of one side is one side on the surface of the rhomboid substrate of the four equilateral sides whose length is less than or equal to 4/3 times the wavelength used. Four lines parallel to the one side with a distance of d / 8, d / 4, d / 4, d / 4 at a distance on the adjacent side from the same, and d / Virtually intersecting lines intersecting four lines parallel to the adjacent side at intervals of 8, d / 4, d / 4, d / 4, and from the end of the four intersecting points on one line Two parasitic elements are arranged in succession at two intersections, then two feeding elements are arranged in succession, and at the four intersections on the adjacent line, the feeding elements are continued from the end on the same side to the two intersections. Next, two parasitic elements are arranged in succession, and the tips of the corners of 60 degrees of the subarray substrate on which eight feeder elements and eight parasitic elements are arranged at a total of 16 intersections are arranged. Is an array antenna, characterized in that the antenna element arrays each other along what was collected against a plurality thereof rhombus sides on each side has a hexagonal throughout arranged as shifted by half a pitch in a plane with one another.

FIG. 1A shows a subarray substrate referred to in the problem solving means.
The basic shape of the substrate is a quadrilateral rhombus with an inner angle of the upper left and lower right corners including the cut portion 4 of 60 degrees, an inner angle of the lower left and upper right corners of 120 degrees, and a side length of d.
d is 4 / √3 or less of the operating wavelength λ. A circle is an antenna element, a black circle is a feeding element 2, and a white circle is a parasitic element 3. The arrangement position is on the intersection of four imaginary lines virtually imaginary in the vertical and horizontal directions at the intervals shown.
Therefore, the three adjacent antenna elements are at the positions of the three vertices of an equilateral triangle having one side of d / 4.

Now, if the array of antenna elements in (a) is regarded as a column structure, there are three main columns as shown in (b).
Then, looking at the interval between these rows, it can be seen that it is equal to the height h of the equilateral triangle as shown in (b).
By the way, one side of the equilateral triangle is d / 4 as described above, and the height of the equilateral triangle is √3 / 2, so it becomes √3d / 8.

  However, since d is 4 / √3 or less of the operating wavelength λ as described above, the height of the equilateral triangle, that is, the interval between the antenna element arrays is λ / 2 or less, and is an interval for suppressing the grating lobe. become.

Next, when looking at the number of power feeding elements for the columns in each direction of (b), b-1 is 2 in each column. b-2 is also each row 2. In b-3, the numbers are 1, 1, 1, 2, 1, 1, 1 from the left column.
A plurality of such sub-array substrates 1 are in contact with their rhombus sides, and a hexagon is formed so that the antenna element arrays along the contact sides are shifted by a half pitch, and the direction parallel to one side of the hexagon When the number of feeding elements for each column from the one side is viewed, the number of antenna elements increases by one for each column. If this increased antenna element is a feeding element, the number of feeding elements is increased by one. If the increased antenna element is a parasitic element, the number of feeding elements in that column is the same as the previous column. Same thing.

Thus, the number of feeding elements in a row between one side of the hexagon and the maximum width does not decrease by the same or one increase when the row advances by one.
That is, there is no trough of the number of feeding elements on the way through the row.
After reaching the maximum width column, the number of feeding elements in the column is the same as the previous column or decreases by one as the column progresses to the side opposite to the one side of the start. It means that there is no valley.
A plot of the position of each column and the number of feeding elements in that column with the former as the horizontal axis and the latter as the vertical axis is called an excitation distribution.

The above is not only between the first focused side of the hexagon and its opposite side, but also between the left adjacent side of the focused side and its opposite side, and between the right adjacent side and its opposite side. But it is exactly the same.
The reason is that the hexagon is made of only a combination of diamond-shaped sub-array substrates as shown in FIG. 1. This means that the hexagon is rotated 120 degrees or 240 degrees. This is because the arrangement of the feeding element and the parasitic element is exactly the same as the first.
In addition, the column spacing is also less than or equal to half the wavelength used as described above.

  Thus, the hexagonal array antenna formed by arranging the sub-array substrates shown in FIG. 1 has gratings in directivity in three planes that pass through the center, are perpendicular to the two opposite sides, and have different directions by 120 degrees with respect to the center. The effect is that the lobes are suppressed.

Furthermore, when the direction perpendicular to the intermediate angle, for example, a line connecting one corner of the hexagon and the opposite corner is viewed as the column direction, the column spacing is d / 8, where d is as described above. In addition,
Since it is 4λ / √3 or less, the column spacing is λ / 2√3, which is sufficiently smaller than λ / 2, so that the grating lobe is suppressed regardless of the change in the number of feed elements for each column.

  Further, since the column spacing is further reduced at the angle between them, the grating lobe is suppressed for the same reason as above, and eventually the grating lobe is suppressed in the omnidirectional vertical plane through the center of the hexagonal array plane. There is an effect.

It is a top view of the subarray board | substrate which comprises the array antenna of this invention. FIG. 2 is a plan view of an array antenna of the present invention configured using three subarray substrates of FIG. 1 and its excitation distribution diagram. It is a top view of the array antenna of this invention comprised using 12 subarray board | substrates of FIG. FIG. 4 is an excitation distribution diagram of the array antenna of FIG. 3. It is a top view of the array antenna of this invention comprised using 27 subarray board | substrates of FIG. 6 is an array antenna excitation distribution diagram of FIG. 5. FIG. FIG. 4A is a simulation diagram of Y1 direction center vertical plane directivity when all elements of the array antenna of FIG. FIG. 9B is a simulation diagram of the Y-direction vertical cross section directivity of the array antenna of FIG. FIG. 5C is a simulation diagram of the Y1 direction center vertical plane directivity of the array antenna of FIG. FIG. 5 is a plan view of an antenna element array of an array antenna that performs thinning feeding with a parasitic element array every other antenna element array having a column interval of a half wavelength or less. FIG. 9 is an excitation distribution diagram in which the column number of each column in the Y direction in the antenna element array of FIG. 8 is taken on the horizontal axis, and the number of feed elements in each column is plotted on the vertical axis. It is a perspective view of the 1st example of the conventional grating lobe suppression array antenna. It is an array top view of the 2nd example of the conventional grating lobe suppression array antenna.

  The array antenna of the present invention is formed by arranging a subarray substrate as shown in FIG. 1 in a hexagonal shape so that antenna element rows along each side are in contact with each other and shifted by a half pitch from each other. The The minimum number to be arranged is 3, which is as shown in FIG. Next, 12 pieces are as shown in FIG. Furthermore, 27 pieces are as shown in FIG. Similarly, a larger array antenna can be configured.

The size to be selected is selected depending on the antenna gain required for the antenna and the size of the aperture surface.
Since the number of feed elements and parasitic elements is 8 and 8 on the sub-array substrate, the parasitic elements are half of the total number of antenna elements for any size of array antenna. The ratio is the same as in the case where parasitic elements are used every other row of the element array.
Therefore, the number of phase shifters and amplifiers can be halved.
These phase shifters and amplifiers are provided together with the power supply network on the back side of the array substrate.

FIG. 2A shows an example of 48 elements of 3 subarrays.
(B) is a diagram in which the number of feed elements in each column when the arrangement of (a) is viewed from three directions is plotted, and is called an excitation distribution. Looking at the column number Y1 in (a), the number on the scale indicates the number of the element column through which a line drawn laterally penetrates. As described in the section “Effects of the Invention”, the interval between the element rows is ½ wavelength or less, and the excitation distribution in (b) is flat, monotonically increasing, or monotonically decreasing, and has no valleys. Therefore, it can be seen that the grating lobe is suppressed.

FIG. 3 shows an embodiment in the case of 12 subarrays 192 elements.
As shown in FIG. 4, the excitation distribution has no valleys in any of the directions Y1, Y2, and Y3, indicating that the grating lobe is suppressed.
When directional characteristics in the Y1 cross section passing through the center of the array antenna are simulated, the result is as shown in FIG. According to this, a grating lobe having a peak of about 7 dBi appears in the vicinity of -62 deg.

As shown in FIG. 8, the directivity when the feeding element rows and the parasitic element rows are arranged every other row is as shown in FIG. 7B, so that the peak value of the grating lobe is suppressed by about 18 dBi. You can see that.
Incidentally, when the directivity of the cross section in the Y1 direction passing through the center of the array when all the elements in the element arrangement of FIG. 3 are used as power feeding elements (no thinning power feeding), the result is as shown in FIG.

  According to this, a grating lobe of less than 10 dBi appears in the vicinity of about −67 deg. When this is compared with Example 2 of the present invention ((c) in FIG. 7), (c) is 2 to 3 dB lower than (a), and even if thinning power feeding is performed, the present invention Accordingly, it can be seen that the level of the grating lobe is suppressed to the same level or less as compared with the case where no thinning power feeding is performed.

DESCRIPTION OF SYMBOLS 1 Subarray board | substrate 2 Feeding element 3 Parasitic element 4 Cut part 5 Virtual line 11 Array antenna 12 Subarray antenna 13 Subarray antenna 14 Element antenna 15 Phase shifter 16 Element antenna 17 Subarray part 18 Antenna module

Claims (1)

Adjacent from one side to the surface of a rhomboid substrate with four equal sides whose inner angles are 60 degrees, 120 degrees, 60 degrees, and 120 degrees and the length d of one side is less than 4/3 times the wavelength used. Four lines parallel to the one side at intervals of d / 8, d / 4, d / 4, and d / 4 in the distance on the side, and d / 8 in the same distance from the adjacent side, Virtually intersecting lines intersecting four lines parallel to the adjacent side at intervals of d / 4, d / 4, d / 4, and two from the end of four intersections on one line Two parasitic elements are arranged in succession at the intersection, then two feeding elements are arranged in succession, and at the four intersections on the adjacent line, feeding elements are arranged at the two intersections from the end on the same side. Then, two parasitic elements are arranged in succession, and the tip of a 60-degree corner of the sub-array substrate on which eight feeding elements and eight parasitic elements are arranged at a total of 16 intersections is cut. Array antenna, wherein a plurality that the contact of the rhombus sides antenna element arrays each other along each side and hexagonal throughout arranged in a plane so as to deviate by a half pitch from each other things.

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