JP2018179553A - Array antenna device and method of estimating direction of arrival - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the accuracy of estimating the arrival direction of a radio wave while suppressing an increase in size. According to an embodiment, in an array antenna device including an antenna element group capable of receiving two orthogonal polarizations, the antenna element group is divided into a plurality of groups, and each of the plurality of groups is a sub-array antenna. Provided is an array antenna device provided with a received signal processing means for each sub-array antenna, which outputs a result of multiplying the received signals of the antenna elements belonging to each sub-array antenna by weights and synthesizing them. [Selection diagram] Fig. 1

Description

  Embodiments of the present invention relate to an array antenna apparatus and a direction of arrival estimation method.

  A radio wave arrival direction estimation technique using an array antenna of small antennas capable of receiving two orthogonal polarizations (horizontal polarization, vertical polarization) has been reported. A multiple signal classification method generally called MUSIC (Multiple Signal Classification) method is applied to the direction of arrival estimation algorithm. The MUSIC algorithm uses a steering vector of vertical polarization and a steering vector of horizontal polarization. These steering vectors represent the angular response of the amplitude and phase of each antenna.

Qiaowei Yuan, Qiang Chen, K. Sawaya, “MUSIC based DOA finding and polarization estimation using USV with polarization sensitive array antenna,” 2006 IEEE Radio and Wireless Symposium, pp. 339-342, 2006.

  In general, since a small antenna is used in the direction of arrival estimation, there is a limit to the accuracy of estimation of the direction of arrival. In order to improve the arrival direction estimation accuracy in the MUSIC method, it is necessary to either (1) use a large aperture array antenna or (2) sharpen the beam pattern of each antenna. These two points will be described below.

(1) When using a large aperture array antenna Although using a large aperture array antenna generally improves the direction of arrival estimation accuracy, this is analyzed from another viewpoint.

When a large aperture array antenna is used, the physical distance between the plurality of antennas increases. As the physical distance increases, the change with respect to the angle of the phase difference of the received signal between the antennas increases. When the change of the reception phase difference with respect to the angle is large, the error of the arrival direction estimation when the error such as the thermal noise is added is reduced.
The reception phase difference corresponds to the phase information of the steering vector.

  For example, when the element interval d, the wavelength of the radio wave is λ, the incident angle of the radio wave is θ, and the circumference ratio is π, the reception phase difference between the two antennas can be calculated by the following equation.

Δθ = −2πd sin θ / λ
Since the reception phase difference is proportional to the element spacing d, the larger the element spacing, the larger the fluctuation of the reception phase difference when the angle θ is changed, and the higher the arrival direction estimation accuracy when an error is added. it can.

  However, this method can not be applied to miniaturizing the array antenna because the element spacing must be increased.

(2) When sharpening the beam pattern of each antenna As another method, a method of sharpening the beam pattern of each antenna will be described.

  As the beam pattern of each antenna becomes sharper, the change with respect to the angle of the amplitude ratio of the received signal between each antenna becomes larger. As in the case of the reception phase difference, when the change of the reception amplitude ratio to the angle is large, the error of the arrival direction estimation when the error such as the thermal noise is added becomes small. The reception amplitude ratio corresponds to the amplitude information of the steering vector. In the direction of arrival estimation algorithm that does not use amplitude information for steering vectors, sharpening the beam pattern of each antenna does not improve the direction of arrival estimation accuracy.

  However, in the case of using a small antenna represented by a plate-like inverted F antenna or a monopole antenna as in the prior art, it is difficult to make the beam pattern sharp due to the restriction of the antenna size. This is a problem in an array antenna apparatus that requires the use of a small antenna.

  The problem to be solved by the invention is to provide an array antenna device and an arrival direction estimation method that make it possible to improve the estimation accuracy of the radio wave arrival direction while suppressing the increase in size.

  According to the embodiment, in the array antenna apparatus including antenna element groups capable of receiving two orthogonal polarized waves, the antenna element groups are divided into a plurality of groups, and each of the plurality of groups is regarded as a sub array antenna, and a sub array There is provided an array antenna apparatus comprising reception signal processing means for multiplying the reception signals of the respective antenna element groups belonging to each sub array antenna by weight and combining them for each antenna.

FIG. 1 is a diagram showing an example of the configuration of an array antenna apparatus according to an embodiment. The figure which shows the relationship between a sub array antenna and an arrival direction estimation part. FIG. 7 is a diagram showing an example of a configuration in which three or more antenna elements are associated with one sub array antenna. The figure which shows an example in the case of arranging an antenna element group circularly.

  Embodiments will be described below with reference to the drawings.

FIG. 1 is a diagram showing an example of the configuration of an array antenna apparatus according to an embodiment.
The array antenna apparatus shown in FIG. 1 includes antenna element groups 101a, 101b, 102a, 102b, 103a, 103b capable of receiving two orthogonal polarized waves, and a received signal processing unit 11 that processes received signals of the antenna element group. And the arrival direction estimation unit 12 performing processing of estimating the arrival direction of the radio wave using the MUSIC method based on the signal processed by the reception signal processing unit 11, and the arrival of the radio wave estimated by the arrival direction estimation unit 12 And an output device 13 for outputting information indicating a direction.

  Each of the antenna element groups is, for example, a small antenna. The type of the small antenna may be any type, for example, various antennas such as a monopole antenna, a loop antenna, and an inverted F antenna, or a modification or combination of these antennas may be applied. The two orthogonal polarizations are not limited to the vertical polarization and the horizontal polarization, and may be any two polarizations such as right-handed circular polarization and left-handed circular polarization, as long as they are orthogonal.

  The received signal processing unit 11, the arrival direction estimation unit 12, and the output device 13 constitute an information processing unit 10. The functions of all or part of the information processing unit 10 can be realized by a computer.

  The configuration of the array antenna apparatus is not limited to the example shown in FIG. For example, the arrival direction estimation unit 12 may be configured to include the received signal processing unit 11. Also, the arrival direction estimation unit 12 and the output device 13 may be realized as separate devices different from the array antenna device.

  In this embodiment, the antenna element group is divided into a plurality of groups, and each of the plurality of groups is regarded as a sub array antenna, and for each sub array antenna, a weight is given to each received signal of the antenna element group belonging to each sub array antenna. The received signal processing unit 11 outputs the result of the multiplication and combination to the arrival direction estimation unit 12. Thereby, in the arrival direction estimation unit 12, based on the output of each sub array antenna from the reception signal processing unit 11, processing is performed to estimate the arrival direction of radio waves using steering vectors of two orthogonal polarizations. It will be. The steering vectors of each of the two orthogonal polarizations represent the angular response of the amplitude and phase of each sub-array antenna.

  In the example of FIG. 1, the antenna element groups 101a and 101b constitute a subarray antenna 101, the antenna element groups 102a and 102b constitute a subarray antenna 102, and the antenna element groups 103a and 103b constitute a subarray antenna 103.

  The received signal processing unit 11 performs weight multiplication and their combination on each received signal of the antenna element group belonging to each sub array antenna in units of sub array antenna.

  Specifically, for the sub-array antenna 101, the received signal processing unit 11 multiplies each of the received signals of the antenna element groups 101a and 101b belonging to the sub-array antenna 101 by weights W11 and W12, respectively, The signals multiplied by the weights are combined by the combiner and output. Further, with regard to the subarray antenna 102, the received signal processing unit 11 multiplies weights W21 and W22 by the respective multipliers with the respective received signals of the antenna element groups 102a and 102b belonging to the subarray antenna 102, and multiplies the weights. The synthesized signals are synthesized by the synthesizer and output. Similarly, as for the sub array antenna 103, the received signal processing unit 11 multiplies the received signals of the antenna element groups 103a and 103b belonging to the sub array antenna 103 by weights W31 and W32 respectively with a multiplier, and the weights are calculated. Each signal after multiplication is synthesized by a synthesizer and output.

  The multiplication of weights corresponds to phase shift for phase rotation of the received signal, or amplitude adjustment for adjusting the amplitude of the received signal, or both of phase rotation and amplitude adjustment. The phase shift may be performed by a phase shifter. The amplitude adjustment may be performed by an attenuator.

  With such a configuration, the arrival direction estimation unit 12 estimates the arrival direction of radio waves based on the signal output of each of the plurality of sub array antennas 101, 102, and 103 as shown in FIG. It can be seen as going.

  Although the direction of arrival estimation unit 12 uses the MUSIC method to estimate the direction of arrival of radio waves based on the reception signals of each subarray antenna, the same algorithm as in the prior art can be applied to the MUSIC method used here. it can. The combined beam pattern of each sub array antenna corresponds to the steering vector of vertical polarization and the steering vector of horizontal polarization, and the direction of arrival can be estimated by the MUSIC method using the combined beam pattern of each sub array antenna. For example, it is estimated that the peak value of the spectrum that changes according to the steering vector of vertical polarization and the steering vector of horizontal polarization corresponds to the arrival direction.

  By this configuration, it is possible to make the beam pattern of each sub array antenna sharper while suppressing an increase in the overall size, and to improve the arrival direction estimation accuracy.

  Also, in this embodiment, a case is illustrated where a part of the antenna element group belonging to another sub array antenna is arranged in the space between two adjacent antenna elements in the antenna element group belonging to a certain sub array antenna. ing. However, not all subarray antennas need to have such a configuration, and there may be subarray antennas not having such a configuration.

  In the example of FIG. 1, a part of each of the three sub array antennas 101, 102, and 103 is disposed so as to spatially overlap. For example, while the antenna element 101b which is a component of the subarray antenna 101 is disposed in the space between the antenna element 102a and the antenna element 102b which constitute the subarray antenna 102, the antenna element which is a component of the subarray antenna 103. 103a is arranged.

  With this configuration, while the size of the entire array antenna apparatus is restricted, the distance between the antenna elements constituting each subarray antenna can be made as wide as possible, whereby the beam pattern of each subarray antenna can be obtained. It is possible to make it more sharp and to improve the arrival direction estimation accuracy more effectively.

  Further, the number of sub-array antennas with sharp directivity can be increased while reducing the overall size of the antenna device. As the number of subarray antennas increases, the effect of increasing the number of radio waves that can be estimated simultaneously and the effect of improving the accuracy of estimation of the direction of arrival can be obtained.

  In the example of FIG. 1, although the case where two antenna elements were matched with respect to one sub array antenna was illustrated, it is not limited to this. For example, as shown in FIG. 3, three or more antenna elements may be associated with one sub array antenna.

Further, in the example of FIG. 1, the case where two antenna elements belonging to another sub-array antenna are arranged in the space between the antenna element 102 a and the antenna element 102 b constituting the sub-array antenna 102 is exemplified. For example, three or more may be arranged, or only one may be arranged, and such arrangement may not be necessary in some cases (with respect to the other sub array antennas 101 and 103). The same is true).
Further, in the example of FIG. 1, the number of sub-arrays is three, but it is not limited to this. The number of subarrays may be four or more.

  Further, although an example in which the antenna element groups are linearly arranged is shown in the example of FIG. 1, the present invention is not limited to this. For example, the antenna elements may be arranged circularly. .

FIG. 4 is a diagram showing an example in which the antenna element groups are arranged in a circle.
In the example of FIG. 4, the antenna element groups 101a, 101b, 102a, 102b, 103a, 103b,... Are arranged in a circle.

  As each antenna element, for example, a square loop antenna which is a kind of small antenna is applied. In this example, the antenna element groups 101a and 101b constituting the subarray antenna 101 described in FIG. 1, the antenna element groups 102a and 102b constituting the subarray antenna 102, and the antenna element groups 103a and 103b constituting the subarray antenna 103, ... are arranged in a circle on the ground (not shown).

  The antenna elements are arranged in different orientations. For example, each antenna element is installed in an inclined state so that the directions of inclination with respect to the ground (not shown) are different.

  In the example of FIG. 4, focusing on the sub-array antenna 101, for example, the installation directions of the two antenna elements 101a and 101b constituting the sub-array antenna 101 are different. Thus, antenna element groups 101a and 101b can receive both vertical polarization and horizontal polarization. Further, the orientations of installation of the two antenna elements 102 a and 102 b constituting the sub array antenna 102 are also different for the sub array antenna 102 as well. Thus, antenna element groups 102a and 102b can receive both vertical polarization and horizontal polarization. Similarly for the sub-array antenna 103, the directions of installation of the two antenna elements 103a and 103b constituting the sub-array antenna 103 are different. Thereby, antenna element groups 103a and 103b can receive both vertical polarization and horizontal polarization.

  More specifically, for example, the antenna element groups 101a, 101b, 102a, 102b, 103a, 103b,... Are arranged such that, for example, the upper part (part far from the ground) of each antenna element approaches the central part of the circular array , The lower part (the part close to the ground) is installed in an inclined state about the line on the circle so that each lower part is away from the center of the circular array.

By configuring in this way, it is possible to prevent the angles of nulls that do not receive radio waves from overlapping. That is, a general square loop antenna forms a beam pattern of a figure of eight, and there is a null angle at which radio waves are not received. However, as in this example, the installation direction of each antenna element constituting the subarray antenna device is By arranging in a different manner, it is possible to prevent the angles at which radio waves can not be received, that is, the angles at which the directions of arrival of radio waves can not be estimated, and reduce the angles at which the direction of arrival of radio waves can not be estimated. .
Further, by arranging the antennas in different orientations, a plurality of antennas can be arranged at the same place. This makes it possible to configure a smaller array antenna.

  As described above, according to the embodiment, it is possible to improve the estimation accuracy of the arrival direction of radio waves while suppressing the increase in size.

  The present invention is not limited to the above embodiment as it is, and at the implementation stage, the constituent elements can be modified and embodied without departing from the scope of the invention. In addition, various inventions can be formed by appropriate combinations of a plurality of constituent elements disclosed in the above embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, components in different embodiments may be combined as appropriate.

  DESCRIPTION OF SYMBOLS 10 ... Information processing part, 11 ... Reception signal processing part, 12 ... Arrival direction estimation part, 13 ... Output device, 101, 102, 103 ... Subarray antenna, 101a, 101b, 102a, 102b, 103a, 103b ... Antenna element group.

Claims (7)

An array antenna apparatus comprising an antenna element group capable of receiving two orthogonal polarized waves,
The antenna element group is divided into a plurality of groups, and each of the plurality of groups is regarded as a sub-array antenna, and for each sub-array antenna, the received signal of each of the antenna element groups belonging to each sub-array antenna is multiplied and synthesized. An array antenna apparatus comprising: received signal processing means for outputting   It further comprises arrival direction estimation means for performing processing of estimating the arrival direction of a radio wave using steering vectors of two orthogonal polarizations based on the output of each sub array antenna from the reception signal processing means. The array antenna apparatus of 1.   3. The array antenna apparatus according to claim 2, wherein said arrival direction estimation means performs a process of estimating the arrival direction of a radio wave using a multiple signal classification (MUSIC) method.   4. A part of an antenna element group belonging to another sub array antenna is arranged in a space between two adjacent antenna elements in an antenna element group belonging to a certain sub array antenna. The array antenna apparatus as described in a term.   The array antenna device according to any one of claims 1 to 4, wherein the antenna element group is arranged in a circular shape.   The array antenna apparatus according to any one of claims 1 to 5, wherein the antenna element group is installed in a state of being inclined so that the directions of inclination are different from each other. An arrival direction estimation method applied to an array antenna apparatus comprising an antenna element group capable of receiving two orthogonal polarizations, comprising:
The antenna element group is divided into a plurality of groups, and each of the plurality of groups is regarded as a sub-array antenna, and for each sub-array antenna, the received signal of each of the antenna element groups belonging to each sub-array antenna is multiplied and synthesized. Output
An arrival direction estimation method comprising performing processing of estimating an arrival direction of a radio wave using steering vectors of two orthogonal polarizations based on an output of each sub array antenna.