JP2016152507A - Design device for array antenna, design method and design program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress power in a predetermined direction over a wide range, in the state where an in-phase composite gain in a desired direction is maintained, in a distributed array antenna technology.SOLUTION: A design device for an array antenna in which a plurality of antenna elements are arrayed in an end-fire direction comprises: an array factor calculation part which uses an interval of antenna elements forming the array antenna, the number of antenna elements and a center frequency to calculate an array factor defining an azimuth angle to a counter station as a parameter; and an offset angle calculation part for calculating an angle which is an angle of one grating lobe in the array factor and at which the other grating lobes in the array factor are not included within a range of a main lobe width in an antenna pattern of a single antenna element around the angle, setting this angle as an offset angle that is an angle formed from the end-fire direction and a main-lobe direction of the plurality of antenna elements, and reducing a main lobe width to a width of the one grating lobe.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an array antenna design apparatus, a design method, and a design program in which a plurality of antenna elements are arranged in an endfire direction.

  An array antenna improves antenna gain by using a plurality of antenna elements, and can change the main beam direction by electrically controlling the phase and amplitude. Among these advantages, there is a distributed array that uses a plurality of existing antennas to improve gain. In particular, this technique is effective in a situation where it is difficult to use a large antenna during communication. For example, the present invention can be applied to gain improvement when a temporary communication line is set up using a portable antenna.

  However, since a small antenna is used, the main lobe width and the side lobe level are increased, and interference with other systems is increased. With regard to the main lobe width, generally, the aperture can be increased by narrowing the antenna interval as in the case of a distributed array, and the lobe can be narrowed. However, on the other hand, a grating lobe generated by an increase in the antenna interval appears in the main beam, which may interfere with other systems when the array factor transmission power is improved. Regarding side lobes, adaptive beamforming can reduce interference from a desired outside direction, but the gain obtained is reduced compared to the in-phase combined gain. Even when the antenna arrangement is finely adjusted and the antenna interval is controlled so that a null point is provided in the vicinity of the predetermined side lobe, it is conceivable that the range of angles to be reduced becomes very narrow.

  It is desirable to reduce the interference in the vicinity of a predetermined direction over a wide range while maintaining the antenna gain improvement, which is a merit of the dispersion array.

Yoshinori Suzuki, et al., "Experimental verification of distributed array configuration technology applied to portable antennas for satellite communications," IEICE technical report, SAT2012-53 (2013): 35-40. Heimiller, R. C., J. E. Belyea, and P. G. Tomlinson. "Distributed array radar," IEEE Transactions on Aerospace and Electronic Systems, vol. AES-19, no. 6 (1983): 831-839. Kazufumi Hirata, et al., "Distribution method of distributed array antenna to suppress grating lobe," IEICE technical report, A / P2005-15, (2005): 35-40. Adaptive antenna technology, Ohm, 2003.

  Non-Patent Document 1 is a technique for obtaining an array gain by transmission and reception by performing phase compensation even with independent BUC and LNB aiming at application of a distributed array to a portable antenna. However, this technology does not mention interference suppression at the time of the distributed array.

  Non-Patent Documents 2 and 3 are techniques for smoothing and lowering a grating lobe by random or unequal intervals as a subarray arrangement method in a distributed array. However, the characteristics of this technology greatly depend on the number of antennas, and it is difficult to improve the characteristics with a small number of antennas. Furthermore, the characteristics of the present technology are not studied for reducing interference with respect to a predetermined position.

  Non-Patent Document 4 discusses null beam forming for canceling interference at a predetermined position. However, when such adaptive signal processing is performed, the gain in a desired direction is higher than that at the time of synthesizing transmission. It will decrease.

  It is an object of the present invention to provide an array antenna design apparatus, design method, and design program capable of suppressing power in a predetermined direction over a wide range in a distributed array antenna technology while maintaining a common-mode combined gain in a desired direction. Objective.

  According to a first aspect of the present invention, there is provided an array antenna design apparatus in which a plurality of antenna elements are arranged in the direction of the endfire. An array factor calculation unit for calculating an array factor and an angle of one grating lobe in the array factor, and within the range of the main lobe width in the antenna pattern of a single antenna element around the angle, An angle that does not include other grating lobes is calculated, the angle is set as an offset angle that is an angle between the endfire direction of the plurality of antenna elements and the main lobe direction, and the main lobe width is set to the one grating lobe. An offset angle calculator that reduces the width Obtain.

  According to a second invention, in an array antenna design apparatus in which a plurality of antenna elements are arranged in the endfire direction, the azimuth angle with respect to the opposite station is set as a parameter using the interval and number of antenna elements constituting the array antenna and the center frequency. An array factor calculation unit that calculates an array factor and an angle of an intermediate point of adjacent grating lobes that are closest to the angle of the side lobe to be reduced and calculate the angle between the end fire directions of a plurality of antenna elements. And an offset angle calculation unit that sets an offset angle that is an angle between the main lobe direction and the main lobe direction and reduces side lobes near the angle.

  According to a third aspect of the present invention, in the array antenna design method in which a plurality of antenna elements are arranged in the endfire direction, the azimuth angle with respect to the opposite station is set as a parameter using the interval and number of antenna elements constituting the array antenna and the center frequency. And an offset angle that is an angle formed between the endfire direction of the plurality of antenna elements and the main lobe direction, and the angle of one grating lobe in the array factor, and the angle The main lobe width is set to an angle that does not include other grating lobes in the array factor within the range of the main lobe width in the antenna pattern of the single antenna element with the center at the center, and the main lobe width is reduced to the width of the one grating lobe. 2 steps.

  According to a fourth aspect of the present invention, in the array antenna design method in which a plurality of antenna elements are arranged in the endfire direction, the azimuth angle with respect to the opposite station is set as a parameter using the interval and number of antenna elements constituting the array antenna and the center frequency. As an offset angle that is an angle formed between the endfire direction of the plurality of antenna elements and the main lobe direction, the closest step to the sidelobe angle to be reduced is adjacent, and the array factor is adjacent to the array factor. A second step of setting the angle of the intermediate point of the grating lobe to reduce the side lobe.

  According to a fifth aspect of the invention, there is provided an array antenna characterized by causing a computer to execute the processing of each step executed by the array antenna design method of the third aspect of the invention and calculating an offset angle for reducing the main lobe width. Design program.

  According to a sixth aspect of the present invention, there is provided an array antenna characterized by causing a computer to execute the processing of each step executed by the array antenna design method according to the fourth aspect of the invention, and calculating an offset angle for reducing side lobes. Design program.

  In the distributed array antenna technology, the main lobe width can be sufficiently reduced by setting the offset angle or the power in a predetermined direction can be suppressed over a wide range even with a small number of antennas while maintaining the in-phase combined gain. .

It is a figure which shows the structural example of the design apparatus of the array antenna of this invention. It is a flowchart which shows the example of a process sequence which performs main lobe width reduction. It is a flowchart which shows the example of a process sequence which performs a side lobe reduction. It is a figure which shows the example of arrangement | positioning (offset angle 0) of an array antenna. It is a figure which shows the evaluation function F ((theta)) and a grating lobe generation | occurrence | production position. It is a figure which shows an array factor. It is a figure which shows the example of arrangement | positioning (offset angle (phi)) of an array antenna. It is a figure which shows the evaluation function F ((theta)) and offset lobe generation | occurrence | production position in offset angle (phi) =-11.89 degree. It is a figure which shows the array factor in offset angle (phi) =-11.89 degree. It is a figure which shows the antenna pattern of an antenna element single-piece | unit. It is a figure which shows the antenna pattern (azimuth angle (theta) = +/- 30 degree) in offset angle (phi) =-11.89 degree. It shows an antenna pattern (azimuth angle θ = ± 5 °) at an offset angle φ = −11.89 °. It is a figure which shows the evaluation function F ((theta)) and offset lobe generation | occurrence | production position in offset angle (phi) =-14.36 degrees. It is a figure which shows the array factor in offset angle (phi) =-14.36 degrees. It is a figure which shows the side lobe to reduce. It is a figure which shows offset angle (phi) corresponding to the side lobe to reduce. It is a figure which shows the array factor in offset angle (phi) =-18.74 degrees. FIG. 5 is a diagram showing an antenna pattern (azimuth angle θ = ± 30 °) at an offset angle φ = −18.74 °. It is a figure which shows the antenna pattern (azimuth angle = 15 to -22 degrees) in offset angle (phi) =-18.74 degrees.

FIG. 1 shows a configuration example of an array antenna design apparatus of the present invention.
In FIG. 1, an array antenna design apparatus according to the present invention includes an array factor calculation unit 11 and an offset angle calculation unit 12, and uses an array factor to reduce the main lobe width or the side lobe. In this configuration, the angle is calculated and set.

FIG. 2 shows a processing procedure example for reducing the main lobe width.
In FIG. 2, the array factor calculation unit 11 calculates an array factor using the azimuth angle with respect to the opposite station as a parameter, using the interval and number of antenna elements constituting the array antenna and the center frequency (S1). The offset angle calculation unit 12 includes the angle of one grating lobe in the array factor, and includes other grating lobes in the array factor within the range of the main lobe width in the antenna pattern of the single antenna element with the angle as the center. Is calculated as an offset angle that is an angle formed between the endfire direction of the plurality of antenna elements and the main lobe direction (S3), and the main lobe width is set to the one grating lobe. Reduce to width.

FIG. 3 shows an example of a processing procedure for performing side lobe reduction.
In FIG. 3, the array factor calculation unit 11 calculates an array factor using the azimuth angle with respect to the opposite station as a parameter, using the interval and number of antenna elements constituting the array antenna and the center frequency (S1). The offset angle calculation unit 12 calculates the angle of the intermediate point of adjacent grating lobes in the array factor closest to the angle of the side lobe to be reduced (S4), sets the calculated angle as the offset angle (S5), and sets the side lobe. Reduce.

FIG. 4 shows an arrangement example (offset angle 0) of the array antenna.
In FIG. 4, it is assumed that the transmitting station has a distributed array including a plurality of antennas, and is a receiving station existing on the x-axis. Note that the distance between transmission and reception is sufficiently long so that the traveling direction of radio waves from each antenna of the transmitting station can be regarded as the same. The antenna arrangement is assumed to be a linear array. When the array antenna interval is d, the azimuth angle is θ, the number of antennas is K, and the wavelength is λ, when the transmitting station antennas are arranged in the end-fire direction with respect to the receiving station as shown in FIG. The array factor D (θ) with the angle θ as a parameter is as follows.

となる。 Summarizing equation (1):

It becomes.

The conditions for generating grating lobes in the array factor are as follows:
(k-1) d / λ (1-cosθ)
Is an integer. Since (k-1) is an integer, it is a condition that d / λ (1-cos θ) is an integer. This is an evaluation function F (θ).

  The following description is based on an array factor when Ku-band satellite communication is assumed, the frequency is 14 GHz, the wavelength λ is 0.0214 m, and the array antenna interval d is 1 m.

  The array factors of 2 and 3 antennas under this condition are shown in FIGS. 6 (a) and 6 (b). As shown in the figure, by configuring a linear array, the position of the grating lobe is fixed even when the number of antennas is changed.

FIG. 7 shows an arrangement example (offset angle φ) of the array antenna.
In FIG. 7, in the present invention, an offset angle φ is given to the receiving station in the azimuth direction with the relative position of the linear array fixed. That is, the offset angle φ is an angle formed between the endfire direction of the plurality of antenna elements and the main lobe direction. Since the same phase synthesis is performed on the receiving station, the array factor D (θ) is as follows.

式(3) をまとめると、

Summarizing equation (3):

となる。

It becomes.

  In the present invention, as will be described below, the main lobe width and the side lobes can be reduced by setting the offset angle φ to an appropriate value.

(Reduction of Main Lobe Width) Here, the offset angle φ is set to the grating lobe position calculated in FIG. Here, the evaluation function F (θ) at the offset angle φ = −11.89 ° corresponding to the first grating lobe angle is as shown in FIG. 8, and the array factors of the number of antennas 2 and 3 are as shown in FIGS. ) become that way. Thus, it can be seen that the pattern has shifted by the offset angle φ = −11.89 ° while maintaining the same antenna pattern as that in FIG. 5 in which the linear array is formed in the endfire direction. The robe that has become the main robe. By utilizing this, the main lobe width can be reduced by setting the offset angle φ such that no other grating lobe enters the main lobe width of the single antenna pattern.

  As an example, in the array antenna shown in FIG. 9, if the thick line frame is the main lobe width of the single antenna, it can be seen that the first grating lobe is located at the center of the thick line frame. By superimposing this on the single antenna pattern, the main lobe width can be reduced. However, if another lobe enters the thick line frame, a grating lobe is generated in the main lobe, leading to an increase in interference. However, it can be seen in FIG. 9 that no other grating lobes are contained within the bold frame. If this condition can be satisfied, there may be a grating clove other than the first grating clove. As a result, only the main lobe width can be reduced.

  Here is a specific example. A single-directional pattern of a 0.6 m diameter circular aperture antenna shown in FIG. 10 is used. The main lobe width is about 5 °, and the offset angle φ = −11.89 ° with respect to the main lobe width is a value at which no other grating lobe intersects. As an antenna pattern when the offset angle φ = −11.89 ° is set, FIG. 11 shows the case of the azimuth angle θ = ± 30 °, and FIG. 12 shows the case of θ = ± 5 °. As shown in FIGS. 11 and 12, it can be seen that the width of the main lobe can be reduced as compared with the single pattern. At θ = 2 °, which can be in the direction of other satellites in Ku-band satellite communication, 4 dB for 2 antennas and 3 antennas for 3 antennas. A 20dB lobe reduction effect is seen, and its effectiveness can be confirmed. In FIG. 11, the pattern of two antennas is omitted.

(About side lobe reduction)
A processing procedure for reducing an arbitrary side lobe using an array factor will be described. The condition for the appearance of the grating lobe is when the phases of all the elements of the array antenna are the same as in the main lobe. Therefore, in the array factor shown in FIG. 6, if the in-phase synthesis is performed on the receiving station in the direction other than the angle at which the grating lobe appears, the lobe in the end fire direction does not become a grating lobe. It is assumed that a wide low-level lobe is formed.

  4 and 5, FIG. 13 shows the evaluation function F (θ) in the case where the offset angle φ = −14.36 ° is set to the angle that is the intermediate point between adjacent grating lobes. Thus, it can be seen that no grating lobe is generated in the endfire direction representing the maximum value of the evaluation function. The array factors of the number of antennas 2 and 3 under this condition are shown in FIGS. As shown in the figure, it can be seen that a wide lobe valley is formed.

  Using this, as an example, the offset angle φ in the case of reducing the side lobe around −18 ° of the 0.6 m diameter circular aperture antenna shown in FIG. 15 is obtained. As shown in FIG. 16, it can be seen that the point near −18 ° at the intermediate point between adjacent grating lobes is −18.74 °. Accordingly, FIGS. 17A and 17B show the array factors of the number of antennas 2 and 3 when the offset angle φ = −18.74 ° is applied. Thus, it can be seen that the lobes near −18 ° are greatly reduced. As an antenna pattern when the offset angle φ = −18.74 ° is set, FIG. 18 shows the case of the azimuth angle θ = ± 30 °, and FIG. 19 shows the case of θ = −15 to −22 °. As shown in the figure, a -18 ° lobe has a reduction effect of 21 dB when the number of antennas is 2, and a reduction effect of 10 dB when the number of antennas is 3, and the effect can be confirmed. In FIG. 18, the pattern of two antennas is omitted.

  The array antenna design apparatus and design method of the present invention can be realized by a computer and a program that execute the processing shown in FIG. 2 or FIG. 3, and can be recorded on a recording medium or provided through a network. is there.

11 Array factor calculation unit 12 Offset angle calculation unit

Claims (6)

In an array antenna design apparatus in which a plurality of antenna elements are arranged in the endfire direction,
An array factor calculation unit that calculates an array factor using the azimuth angle with respect to the opposite station as a parameter, using the interval and the number of the antenna elements constituting the array antenna, and the center frequency;
Calculate the angle that is the angle of one grating lobe in the array factor and that does not include other grating lobes in the array factor within the range of the main lobe width in the antenna pattern of a single antenna element centered on the angle An offset angle calculation unit that sets the angle as an offset angle that is an angle formed by the endfire direction and the main lobe direction of the plurality of antenna elements, and reduces the main lobe width to the width of the one grating lobe; An array antenna design apparatus comprising: In an array antenna design apparatus in which a plurality of antenna elements are arranged in the endfire direction,
An array factor calculation unit that calculates an array factor using the azimuth angle with respect to the opposite station as a parameter, using the interval and the number of the antenna elements constituting the array antenna, and the center frequency;
An angle of an intermediate point of adjacent grating lobes in the array factor that is closest to the angle of the sidelobe to be reduced is calculated, and this angle is an angle formed by the endfire direction and the main lobe direction of the plurality of antenna elements. An array antenna design apparatus comprising: an offset angle calculation unit configured to set an offset angle and reduce a side lobe near the angle. In the design method of an array antenna in which a plurality of antenna elements are arranged in the endfire direction,
A first step of calculating an array factor using the azimuth angle with respect to the opposite station as a parameter, using the spacing and number of the antenna elements constituting the array antenna and the center frequency;
Calculate the angle that is the angle of one grating lobe in the array factor and that does not include other grating lobes in the array factor within the range of the main lobe width in the antenna pattern of a single antenna element centered on the angle A second step of setting the angle as an offset angle that is an angle formed between the endfire direction and the main lobe direction of the plurality of antenna elements, and reducing the main lobe width to the width of the one grating lobe; An array antenna design method characterized by comprising: In the design method of an array antenna in which a plurality of antenna elements are arranged in the endfire direction,
A first step of calculating an array factor using the azimuth angle with respect to the opposite station as a parameter, using the spacing and number of the antenna elements constituting the array antenna and the center frequency;
An angle of an intermediate point of adjacent grating lobes in the array factor that is closest to the angle of the sidelobe to be reduced is calculated, and this angle is an angle formed by the endfire direction and the main lobe direction of the plurality of antenna elements. And a second step of reducing a side lobe near the angle, which is set as an offset angle.   An array antenna design program for causing a computer to execute the processing of each step executed by the array antenna design method according to claim 3 to calculate the offset angle for reducing a main lobe width.   An array antenna design program for causing a computer to execute the processing of each step executed by the array antenna design method according to claim 4 to calculate the offset angle for reducing side lobes.

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