JP2002107439A - Device and method for estimating arrival direction - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an arrival direction estimating device capable of accurately estimating the arrival direction of radio waves even in the case of using a receiver having a smaller number of elements in comparison with the number of directional antenna. SOLUTION: This arrival direction estimating device is provided with eight directional antennas 1 arranged in a circle, four receivers 2, a switch 4 for switching the eight directional antenna 8 and the four receivers 2, a control circuit 5 for switching the switch 4, and an arrival direction estimating unit 3 having an antenna selecting function and an arrival direction estimating function. The arrival direction estimating device roughly estimates the arrival direction in a first phase by using the four directional antennas 1 separated by 90 degree, and estimated the arrival direction in detail in a second phase by using the four directional antennas 1 close to an arrival direction showed by a result of the arrival direction estimation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an arrival direction estimating apparatus and an arrival direction estimating method applicable to a radar, a base station for mobile communication, and the like.

[0002]

2. Description of the Related Art In a radar or a base station for mobile communication, an arrival direction estimating apparatus capable of accurately estimating the direction of an incoming radio wave and realizing at low cost is desired.

As a method of estimating the direction of arrival with high accuracy,
MUSI based on received signals of each element of array antenna
C (Multiple Signal Classif)
ication) (RO Schmit, “Mu
little emitter location a
nd Signal Parameter Estim
ation ”, IEEE Trans. Anten
nas and Propagation, vol.
AP-34, no. 3, pp. 276-280,
March, 1986. ) And ESPRIT (Esti
nationof Signal Parameter
s via RotaryInvarianc
e Technologies) (R. Roy and
T. Keith, “ESPRIT-Estimat
ion of Signal Parameters
Via Rotational Innovation
Techniques ", IEEE Trans.
on Acoustics, Speech, an
d Signal Processing, vol. 3
7, pp. 984-995, July 198
6. ) Exists.

FIG. 6 shows an example of a conventional DOA estimating apparatus. This conventional direction-of-arrival estimation device uses MUSIC, and has a plurality of antennas 101 and a plurality of antennas 1.
01, and a direction-of-arrival estimating unit 103 connected to the plurality of receivers 102. The direction-of-arrival estimating unit 103 performs direction-of-arrival estimation by MUSIC using received signals from all antennas.

However, in the conventional direction-of-arrival estimation apparatus, the same number of receivers as the number of antenna elements are required in order to use the received signals of all elements as the direction-of-arrival estimation algorithm. For this reason, especially when the number of antenna elements is large, the number of receivers becomes enormous, and there is a problem that the cost is extremely high.

On the other hand, if the number of antenna elements is reduced to reduce the cost of the receiver, there is a problem that the estimation accuracy of the direction of arrival is deteriorated.

[0007]

As described above,
The conventional direction-of-arrival estimation device has a problem that it is impossible to achieve both high-accuracy direction-of-arrival estimation and cost reduction.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a low-cost direction-of-arrival estimating apparatus and a direction-of-arrival capable of reducing the number of receivers while maintaining high-precision direction-of-arrival estimation accuracy. It is intended to provide an estimation method.

[0009]

According to the present invention, there is provided an arrival direction estimating apparatus comprising: a plurality of directional antenna elements; a plurality of receivers having a number smaller than the number of the directional antenna elements; Switching means for switching the number of directional antennas selected from among the plurality of directional antennas equal to or less than the number of the receivers to be connected to the receiver, and a plurality of directional antennas selected in advance. Selection means for instructing the switching means so that the directional antenna element is connected to the receiver, and the plurality of directional antennas are connected by the switching means at the instruction of the first selection means. A first direction-of-arrival estimating means for roughly estimating the direction of arrival of radio waves based on the reception outputs of the plurality of receivers at that time, and an estimation result obtained by the first direction-of-arrival estimation means. Based on the direction of arrival of the radio wave, select a plurality of directional antenna elements to be used in the accurate direction of arrival estimation, so that the selected plurality of directional antenna elements are connected to the receiver, A second selection unit that issues an instruction to the switching unit, and based on reception outputs of the plurality of receivers when the plurality of directional antennas are connected by the switching unit at the instruction of the second selection unit, A second direction-of-arrival estimating means for precisely estimating the direction of arrival of the radio wave.

[0010] Further, the arrival direction estimating method according to the present invention comprises:
A plurality of directional antenna elements can be connected to a plurality of receivers, and a plurality of directional antenna elements selected from the number of directional antenna elements greater than the number of the receivers are connected to the plurality of receivers. Of the direction of arrival of the radio wave based on the received output of the receiver, and based on the direction of arrival of the radio wave obtained as a result of this estimation, a precise one of the number of directional antenna elements greater than the number of the receivers. Select a plurality of directional antenna elements to be used in the direction of arrival estimation, to the plurality of receivers,
Connecting these selected directional antenna elements,
The direction of arrival of the radio wave is accurately estimated based on the reception outputs of the plurality of receivers at this time.

Note that the present invention relating to the apparatus is also realized as an invention relating to a method, and the present invention relating to a method is also realized as an invention relating to an apparatus. Further, the present invention according to an apparatus or a method has a function of causing a computer to execute a procedure corresponding to the present invention (or causing a computer to function as means corresponding to the present invention, or a computer having a function corresponding to the present invention). The present invention is also realized as a computer-readable recording medium on which a program (for realizing the program) is recorded.

According to the present invention, a predetermined shape (for example, a circle)
When the direction of arrival estimation is performed using the directional antennas arranged in a plurality of directional antennas, even if the number of receivers is smaller than the number of antenna elements, the first
By performing a second direction-of-arrival estimation in detail using a plurality of directional antennas selected based on a predetermined selection criterion with respect to the direction of the first direction-of-arrival estimation result. The direction of arrival can be estimated with high accuracy. Also,
When the first arrival direction estimation result is two or more waves, for example, by selecting an antenna to be used by comparing gains in the estimated arrival direction, even if there are a plurality of arrival waves, one The wave arrival angle is estimated, and the estimation accuracy is improved. Also, for example, by selecting an antenna to use by comparing the angle difference between the estimated direction of arrival and the maximum gain direction of the directional antenna, even if there are multiple arriving waves, the arrival angle of one wave The estimation is performed, and the estimation accuracy is improved. Also, for example, the first
In the arrival direction estimation, the maximum gain direction of the directional antenna having the maximum received power is set as the arrival direction of the radio wave, so that the direction can be estimated by a simple algorithm and the cost of the device can be reduced. Also, for example, by realizing a directional antenna by feeding a phase difference between two sleeve monopole antennas, desired directivity can be easily realized. As described above, according to the present invention, it is possible to reduce the cost of the apparatus while realizing highly accurate arrival angle estimation.

[0013]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a configuration example of an arrival direction estimating apparatus according to an embodiment of the present invention.

As shown in FIG. 1, the direction-of-arrival estimating apparatus includes a predetermined number n (n is 2 ≦ n) arranged in a predetermined shape.
Directional antenna 1 and a predetermined number m (m is an integer of 2 ≦ m <n) of receivers 2 smaller than the number n of antenna elements
And a switch 4 for switching the connection between the plurality of antennas 1 and the plurality of receivers 2, and a switch for selecting a plurality of (m or less) directional antennas 1 and connecting them to the receiver 2 4, an arrival direction estimating unit 3 for estimating the direction of arrival of radio waves based on the outputs of (m or all of the m) receivers 2 to which the plurality of directional antennas 1 are connected. And a control circuit 5 for controlling switching of the switch 4 in accordance with an instruction from the arrival direction estimating unit 3. FIG. 1 does not always show the physical arrangement of the antenna.

With respect to the plurality of directional antennas 1 described above,
Various arrangements can be considered for the arrangement of the predetermined shape.For example, a plurality of directional antennas having the same characteristics are arranged on the circumference of one circle, and the position of a certain directional antenna and the position of the circle are determined. An arrangement is conceivable in which the angles formed from the center position and the position of the directional antenna adjacent to the directional antenna are all equal (see FIG. 3). Of course, other forms are possible, such as a form in which the characteristics of the antenna are not uniform, a form in which the antenna is arranged on the outer periphery in a shape other than a circle, and a form in which irregular arrangements are not made at equal angles or intervals. .

FIG. 2 shows an example of a schematic operation procedure of the DOA estimating apparatus.

The direction-of-arrival estimating device is generally represented by (1)
The direction-of-arrival estimating unit 3 issues an instruction to the control circuit 5 so that n (or a predetermined smaller number (multiple)) directional antennas 1 selected in advance are connected to the receiver 2. The switch 4 is switched (step S1), and based on the reception output obtained from the directional antenna 1, the first
(2) The direction-of-arrival estimating unit 3 determines the direction of arrival of the directional antenna 1 according to a predetermined selection criterion for the (estimated) direction of arrival obtained as a result of the first direction-of-arrival estimation. (Or a predetermined number (however, a plurality thereof) smaller than n) are selected (step S3), and an instruction is issued to the control circuit 5 so that the selected directional antenna 1 is connected to the receiver 2. The switch 4 is switched (step S4), and the second direction of arrival is estimated based on the reception output obtained from the selected directional antenna 1 (step S5). When the first direction-of-arrival estimation has a function of outputting two or more arrival waves (directions of arrival) as estimation results, and when two or more direction-of-arrivals (directions of arrival) are output by the first direction-of-arrival estimation In the second direction-of-arrival estimation, if it is possible to estimate the direction of arrival for each of all or some of the plurality of incoming waves (arriving directions), in the above (2), the plurality of incoming waves (arriving directions) 2), the second direction of arrival estimation is performed.
In this case, in step S3, an antenna is selected for each arriving wave (direction of arrival), and a method of repeatedly performing steps S3 and S4 and a method of repeatedly performing steps S3 to S5 can be considered. Also, one arrival wave (direction of arrival) is obtained as an estimation result in the first direction of arrival estimation.
In addition to the case of outputting only the first direction of arrival, the first direction of arrival estimation has a function of outputting two or more arriving waves (directions of arrival) as estimation results, and the second direction of arrival estimation satisfies a predetermined condition ( For example, the largest received output,
Alternatively, in the case of estimating the arrival direction only for one arriving wave (arrival direction) (eg, closest to a predetermined direction), in the above (2), the one arriving wave (arrival direction) Only the second direction-of-arrival estimation is performed.

Next, an outline of the first direction-of-arrival estimation will be described.

Although various variations are conceivable for the first direction of arrival estimation, the simplest and most effective method uses the direction of arrival in the first direction of arrival estimation for the first direction of arrival estimation. This is a method of setting the maximum gain direction of the antenna having the largest received power among a plurality of antennas.

That is, according to the present embodiment, the first direction-of-arrival estimation may be a coarse direction-of-arrival estimation. Therefore,
Select the antenna with the highest received power. Here, it is considered that each element is a directional antenna, and the maximum gain direction of each element (as viewed from a certain reference point) is different.
Then, the maximum gain direction of the antenna having the maximum received power indicates the direction of arrival. Although the maximum gain direction of the antenna element having the maximum received power is different from the true direction of arrival, there is no problem because the first estimation may be a rough estimation.

In this case, the first direction-of-arrival estimation only needs to compare the received power, so that the algorithm is simple and the calculation device for the algorithm is simple.
This can contribute to further cost reduction. In addition, it has the effect of shortening the operation time required for the algorithm.

As described above, it is possible to provide the first direction-of-arrival estimation method capable of roughly estimating the direction of arrival only by comparing the reception powers of the antenna elements, thereby contributing to cost reduction of the apparatus.

It should be noted that the first direction of arrival estimation is interpolated by a simple interpolation algorithm, such as linear interpolation, based on the received power from each antenna element and the maximum gain direction used for the first direction of arrival estimation. You may do so.

Alternatively, there is a method in which antenna switching and reception are performed a plurality of times in the first direction-of-arrival estimation to double the number of antennas used for the first direction-of-arrival estimation to improve the azimuth resolution to some extent.

Further, the antenna characteristics may be the same in the first direction-of-arrival estimation and the second direction-of-arrival estimation, but a method of making them different (for example, in the first direction-of-arrival estimation,
A method in which the half-value angle of the antenna radiation pattern is set wider than the second DOA estimation is also possible.

Note that which antenna element is to be used in the first direction-of-arrival estimation is predetermined. However, instead, a plurality of patterns of a plurality of antenna elements used in the first DOA estimation are prepared in advance, and a pattern of the plurality of antenna elements to be used is appropriately selected from them. Such a configuration is also possible.

Next, the outline of the second direction-of-arrival estimation will be described.

Various variations can be considered for the predetermined selection criterion for selecting an antenna element in the second DOA estimation. For example, the arrival direction and the antenna element estimated in the first DOA estimation are considered. (E.g., n in descending order of gain in the DOA obtained as a result of the first DOA estimation)
A method of selecting the number of antennas, a method of selecting n as an upper limit on condition that the gain is equal to or more than a certain value), a direction of arrival estimated by the first direction of arrival estimation, and a maximum gain direction of the antenna (antenna (E.g., the order of arrangement of the antennas) (for example, a method of selecting n pieces in ascending order of the angle difference between the arrival direction obtained as a result of the first arrival direction estimation and the maximum gain direction of the antenna). A method in which the angle difference is selected in ascending order with n being the upper limit under the condition that the angle difference is equal to or less than a certain value).

When there are a plurality of arriving waves (arriving directions) obtained as a result of the first arriving direction estimation, the influence of the arriving waves in one arriving direction from the arriving waves in the other arriving directions is considered. Then, it is preferable to adopt a method of selecting an antenna.

In the case where two or more arriving waves (arrival directions) may be output as the estimation result in the first arriving direction estimation, the arriving waves (arriving directions) obtained as a result of the first arriving direction estimation may be output. ) May be changed in accordance with the number of antennas.

Hereinafter, the present embodiment will be described in more detail.

(First Specific Example) First, the antenna 1 will be described. The antenna 1 is assumed to be constituted by a directional antenna. The directional antenna may be a horn antenna, a patch antenna, a Yagi-Uda antenna, or any antenna as long as it is designed to operate at a desired frequency.

Next, the first direction-of-arrival estimation and the second direction-of-arrival estimation will be described.

Here, for the following description, as shown in FIG. 3, the number of antenna elements is 8, the antenna radiation pattern has a half-value angle of 90 degrees, and the maximum gain direction is 180 degrees opposite to the center of the circular array. The direction (that is, the direction of radiation outside the circle) and the number of receivers will be described as an example.

The first direction-of-arrival estimation performs a coarse direction-of-arrival. In the first direction-of-arrival estimation, a combination of directional antennas having a certain degree of gain in all directions at an azimuth of 360 degrees may be selected. Here, since the directional antenna has a beam half-value angle of 90 degrees, it is possible to obtain a directivity of a level fluctuation of 3 dB at an angle of 360 degrees by combining four elements selected every other.

In this state, the direction of arrival is estimated.
The direction-of-arrival estimation algorithm may be based on any algorithm. That is, any method may be used as long as the direction can be estimated. However, in the first direction-of-arrival estimation, with a small number of antenna elements, 36
Since all directions at 0 degrees are evaluated, the estimation accuracy is degraded, resulting in coarse arrival direction estimation.

Therefore, the second direction-of-arrival estimation performs highly accurate direction-of-arrival estimation. Here, as an example, in the second direction-of-arrival estimation, a directional antenna is selected in descending order of gain with respect to the direction of arrival obtained as a result of the first direction-of-arrival estimation (and connected to the receiver by a switch). It shall be. As a result, the radio wave is received only by the antenna having a high gain in the direction of arrival obtained as a result of the first direction of arrival estimation. That is, the S / N is equivalently improved, and the DOA estimation accuracy is improved.

By selecting an antenna in this manner, the DOA is estimated only within the range where the DOA can exist. That is, referring to the example of FIG. 3, by selecting four continuous elements, it is possible to obtain a directivity of a level fluctuation of 3 dB at an angle of 225 degrees. That is, the direction of arrival in the range of 225 degrees is estimated by four elements.

In the second direction-of-arrival estimation, although the number of antenna elements is small, the direction-of-arrival estimation range is limited, so that the direction can be estimated with high accuracy. Note that the arrival direction estimation algorithm may be of any type.

As described above, in this embodiment, even if the number of receivers is small, the direction of arrival can be estimated with high accuracy by changing the antenna used by the switch.

In the above description, all the elements have the same directivity, but may of course be different. The elements may be arranged at irregular intervals.

Although the antenna element itself is non-directional, it is also effective when the antenna element has directivity due to the influence of an adjacent antenna element or other structure.

In the above description, all receivers are used in the second direction-of-arrival estimation, but the directivity in which the absolute gain in the direction of arrival obtained as a result of the first direction-of-arrival estimation is sufficiently large is used. When the number of antenna elements is smaller than the number of receivers, the switch may control to use only a directional antenna having a large absolute gain. That is, the received signal from the directional antenna having a small received power is considered to have a large error due to the influence of noise and measurement error.
By not using the signal having a large error, it is possible to perform accurate direction-of-arrival estimation.

(Second Concrete Example) The second concrete example differs from the first concrete example in the second direction of arrival estimation. In the following, a description will be given focusing on differences from the first specific example.

Here, if the number of arriving waves obtained as a result of the first direction-of-arrival estimation is k (k is 2 or more) (the (estimated) direction of arrival of the first to k-th arriving waves) To the first to k-th
), The first direction of arrival is in descending order of “the difference between the gain for the first direction of arrival and the maximum value of the gains for the other second to k-th directions of arrival”. A plurality of directional antennas are selected (and connected to a receiver by a switch) to perform a second DOA estimation.

The same applies to the case where the second direction of arrival estimation is performed for the second and subsequent directions of arrival. That is, the second
Similarly, the directional antennas are selected in descending order of the difference between the gain in the second direction of arrival and the maximum value of the gains in the other first, third to kth directions of arrival. . The same applies to the third to k-th arrival directions.

As described above, by selecting the antenna used in the second direction of arrival estimation, the number of waves to be estimated can be reduced to one. Conventionally, as the number of waves to be estimated increases, the estimation accuracy deteriorates. However, according to the present embodiment, the direction of arrival can be estimated with high accuracy by always using one wave to be estimated.

The details will be described below. Here, a direction-of-arrival estimation device as shown in FIGS. 1 to 3 is considered. And
As a result of the first direction-of-arrival estimation, it is assumed that the directions of arrival of two arriving waves are 112.5 degrees and 0 degrees (112.5 degrees is the first direction of arrival, and 0 degrees is the first direction of arrival). 2).

At this time, selection of an antenna used for estimating the arrival direction of the first arriving wave with high accuracy will be described.

Here, the description will be made on the assumption that the gain of each element decreases as the angle increases from the front of the antenna. In this case, the gain difference can be treated as an angle difference.

FIG. 4 shows an angle difference α between the first arrival direction and the front direction of each antenna, an angle difference β between the second arrival direction and the front direction of each antenna, and β-α. β-
As α is larger, the difference between the gain in the first direction of arrival and the gain in the second direction of arrival is larger. When β-α is negative, the second arrival direction has a higher gain than the first arrival direction.

As shown in FIG. 4, the antennas are selected in the descending order of β-α. The remaining antennas are not selected because β-α is negative and the gain in the second direction of arrival is high.

It should be noted here that the gain of the antenna is higher than that of the antenna in the first direction of arrival. However, according to the present embodiment, by selecting an antenna, the direction of arrival can be estimated with high accuracy without being affected by the second arriving wave.

Note that the arrival direction estimation algorithm may be of any type. In particular, it is particularly effective for an algorithm (for example, MUSIC, ESPRIT, etc.) in which estimation accuracy is degraded when there is a correlation between a plurality of arriving waves, and high-accuracy estimation can be performed. ing.

FIG. 4 shows an example in which k = 2.
In the above case, the gain in the first direction of arrival and the second to k-th
In the direction of arrival of the target is calculated. When the angle is treated as shown in FIG. 4 based on the above assumption, for each antenna, the angle difference between the second arrival direction and the front direction,..., The k-th arrival direction and the front direction And the minimum value of the angle difference is β, β-α
Should be obtained.

As described above, in the present embodiment, even if the number of receivers is small, the antenna used by the switch is changed and the angle is estimated under the condition of one arriving wave. The direction can be estimated.

Although the description has been made on the assumption that the angle difference and the gain are proportional for the sake of explanation, when the beam width of the directional antenna used differs depending on the element, the antenna to be used cannot be selected depending on the angle difference. At this time, the determination may be made based on the gain.

Further, by controlling with a switch so as to use a smaller number of elements than the number of receivers, the influence of the second and subsequent arriving waves can be reduced when the angle difference between the arriving waves is small, etc. It can be estimated with high accuracy.

(Third Specific Example) The first and second examples of the third specific example
The second embodiment differs from the second embodiment in the second direction of arrival estimation. The following description focuses on the differences from the first and second specific examples.

Here, if the number of arriving waves obtained as a result of the first arriving direction estimation is k (k is 2 or more) (the (estimated) arriving directions of the first to k-th arriving waves) To the first to k-th
) And the first direction of arrival, for each antenna, “the difference (α) between the first direction of arrival and the maximum gain direction of the directional antenna” and “the second to kth Βi (i = i) between the arrival direction of the directional antenna and the maximum gain direction of the directional antenna.
2,..., K) ”, and“ βi−α ”is calculated therefrom, and a plurality of directional antennas are selected in descending order of“ minimum value of βi−α ”. Then, they are connected to a receiver by a switch to perform a second direction-of-arrival estimation.

The same applies to the case where the second direction of arrival is estimated for the second and subsequent directions of arrival. That is, the second
Similarly, for the arrival direction of “βi−α (i = 1,
, K), a plurality of directional antennas are selected in descending order of “minimum value among values of 3). The same applies to the third to k-th arrival directions.

The details will be described below. In the second specific example, the directional antenna is selected by comparing the gains in the directions of arrival. Here, the antenna to be used is selected using the concept of the angle difference.

Here, as in the second specific example, FIGS.
Considering the direction-of-arrival estimating apparatus shown in (1), as a result of the first direction-of-arrival estimation, it is assumed that the directions of arrival of two arriving waves are 112.5 degrees and 0 degrees (112.5 degrees).
Degree is defined as a first direction of arrival, and 0 degree is defined as a second direction of arrival).
In this case, the result of the antenna selection for the arrival direction of the first arriving wave is the same as that of FIG. 4 of the second specific example.

That is, the antennas,..., Are selected in descending order of β-α.

The direction-of-arrival estimation algorithm may be any algorithm. In particular, it is particularly effective for an algorithm (for example, MUSIC, ESPRIT, etc.) in which estimation accuracy is degraded when there is a correlation between a plurality of arriving waves, and high-accuracy estimation can be performed. ing.

According to such a method, it is only necessary to calculate only the angle difference, so that the antenna to be used can be easily selected.

As described above, according to the present embodiment, even if the number of receivers is small, the antenna used by the switch is changed and the angle is estimated under the condition of one arriving wave. Be able to estimate.

Hereinafter, the antenna will be described.

FIG. 5 shows an example of the directional antenna according to the present embodiment.

In this example, the directional antenna is configured by feeding two sleeve monopole antennas 6 with a phase difference.

The sleeve monopole antenna is an omnidirectional antenna and has a wide frequency bandwidth, and thus has a wide application range such as radar. However, in order to form a directional antenna as in this embodiment, it is necessary to use a two-element sleeve monopole antenna as an antenna array.

Here, radiation patterns of various shapes can be obtained by changing the distance between the two element antennas and the feeding phase difference. The various shapes include the magnitude of the beam half-value angle, the F / B ratio, the side lobe level, and the maximum gain. Here, a desired pattern can be easily realized by the inter-element distance and the feeding phase difference. In particular, the F / B ratio and the side lobe level are important parameters in estimating the direction of arrival, and a desired radiation pattern can be easily realized by using this embodiment.

As described above, according to this embodiment, the directional antenna for estimating the direction of arrival is realized by feeding the phase difference between the two sleeve monopole antennas. As a result, various directivities can be easily realized by the distance between the two elements and the power supply phase difference.

The directional antenna according to the present embodiment has, for example, a maximum gain direction in a direction 180 degrees opposite to the center direction of the circular array. Hereinafter, the effect of such an arrangement will be described in detail.

The fact that the directivity of the circular array antenna is directed toward the inside of the circle of the array means that the antenna radiates with high gain to other antennas. That is, the fact that the radiation amount of one antenna is larger than that of the other antenna means that the coupling between the antennas is large.

This coupling between antennas not only changes the antenna performance, but also significantly degrades the DOA estimation accuracy. That is, as in the present embodiment, by setting the maximum gain direction of the directional antenna to be 180 degrees opposite to the center direction of the circular array, the coupling between antennas can be reduced most. That is, it is possible to suppress the performance deterioration of each element of the antenna and to simultaneously improve the accuracy of estimation of the direction of arrival.

As described above, in this embodiment, since the coupling between antennas can be reduced, it is possible to provide an arrival direction estimating apparatus capable of estimating the direction of arrival with high accuracy.

The part for performing the processing such as the arithmetic operation in the above configuration can also be realized as software. According to the present embodiment, a computer-readable recording of a program for causing a computer to execute predetermined means (or for causing a computer to function as predetermined means or for causing a computer to realize predetermined functions) It can also be implemented as a possible recording medium.

The configuration illustrated in each embodiment is merely an example, and is not intended to exclude other configurations. Some of the illustrated configuration may be replaced with another one, or one of the illustrated configurations. Another configuration obtained by omitting a part, adding another function to the illustrated configuration, or combining them is also possible. In addition, another configuration that is logically equivalent to the illustrated configuration, another configuration including a portion that is logically equivalent to the illustrated configuration, another configuration that is logically equivalent to the main part of the illustrated configuration, and the like are also possible. is there. In addition, another configuration that achieves the same or similar purpose as the illustrated configuration,
Another configuration that has the same or similar effect as the illustrated configuration is also possible. In addition, various variations of various components can be implemented in appropriate combinations. In addition, each embodiment is an invention as an individual device, an invention about two or more related devices, an invention as a whole system, an invention about components inside the individual device, an invention of a method corresponding thereto, and the like. It encompasses and implies inventions relating to various aspects, stages, concepts or categories. Therefore, the present invention can be extracted from the contents disclosed in the embodiments of the present invention without being limited to the illustrated configuration.

The present invention is not limited to the above-described embodiments, but can be implemented with various modifications within the technical scope.

[0082]

According to the present invention, first, a rough estimation of the direction of arrival of a radio wave is performed with a number of directional antenna elements whose upper limit is the number of receivers, and then the arrival direction obtained by the rough estimation is obtained. , The precise direction of arrival is estimated by the number of directional antenna elements with the number of receivers as the upper limit, so that the cost of the apparatus can be reduced and the angle of arrival can be estimated with high accuracy.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of an arrival direction estimation device according to an embodiment of the present invention.

FIG. 2 is an exemplary flowchart illustrating an example of an operation procedure of the DOA estimation apparatus according to the embodiment.

FIG. 3 is a view for explaining an eight-element circular array and a radiation pattern according to the embodiment;

FIG. 4 is a diagram for describing selection of an antenna used in second direction-of-arrival estimation;

FIG. 5 is a diagram illustrating a sleeve monopole antenna.

FIG. 6 is a diagram showing a configuration example of a conventional DOA estimation device.

[Description of Signs] 1 directional antenna 2 receiver 3 arrival direction estimation unit 4 switch 5 control circuit 6 sleeve monopole antenna

Claims (12)

[Claims] A plurality of directional antenna elements; a plurality of receivers having a number smaller than the number of the directional antenna elements; and a number equal to the number of the receivers selected from the plurality of directional antennas. Or a switching means for switching so that a smaller number of directional antennas are connected to the receiver, and a plurality of pre-selected directional antenna elements are connected to the receiver. First selecting means for issuing an instruction to the switching means, and based on reception outputs of the plurality of receivers when the plurality of directional antennas are connected by the switching means according to the instruction of the first selecting means. First arrival direction estimating means for roughly estimating the arrival direction of the radio wave, and precise arrival direction estimating based on the arrival direction of the radio wave obtained as a result of the estimation by the first arrival direction estimating means. Selecting a plurality of directional antenna elements to be used in, the selected plurality of directional antenna elements, so as to be connected to the receiver, a second selection means for instructing the switching means, The second arrival which estimates the direction of arrival of the radio wave precisely based on the reception outputs of the plurality of receivers when the plurality of directional antennas are connected by the switching means according to the instruction of the second selection means. An arrival direction estimating device comprising: a direction estimating unit. 2. The method according to claim 1, wherein said first direction-of-arrival estimating means includes a first arrival direction estimation means.
Among the plurality of directional antennas connected to the plurality of receivers by the switching unit at the instruction of the selection unit, the maximum gain direction for the directional antenna that maximizes the reception output of the plurality of receivers, The direction-of-arrival estimation device according to claim 1, wherein the direction-of-arrival is estimated. 3. The second selecting means is used for the precise direction-of-arrival estimation by the second direction-of-arrival estimating means for the direction of arrival of the arriving wave estimated by the first direction-of-arrival estimating means. The direction-of-arrival estimating apparatus according to claim 1, wherein a plurality of directional antennas are selected as the directional antennas based on a maximum gain direction or a gain / direction characteristic of each directional antenna. 4. The method according to claim 1, wherein the second selecting means comprises k pieces (k is 2 or more) from first to k-th by the first direction-of-arrival estimating means.
When the direction of arrival of the arriving wave is estimated, each directional antenna is used as the directional antenna used for the precise direction of arrival estimation by the second direction of arrival estimating means for the direction of arrival of the first arriving wave. Selecting a plurality of directional antennas based on the difference obtained by subtracting the maximum value of the gain in the direction of arrival of the second to kth incoming waves from the gain in the direction of arrival of the first incoming wave in The direction-of-arrival estimation apparatus according to claim 1, wherein: 5. The apparatus according to claim 1, wherein the second selecting means comprises k pieces (k is 2 or more) from first to k-th by the first direction-of-arrival estimating means.
When the direction of arrival of the arriving wave is estimated, each directional antenna is used as the directional antenna used for the precise direction of arrival estimation by the second direction of arrival estimating means for the direction of arrival of the first arriving wave. I (i = 2, ...,
The value βi−α obtained by subtracting the difference α between the arrival direction of the first arriving wave and the maximum gain direction of the directional antenna from the difference βi between the arrival direction of k) and the maximum gain direction of the directional antenna.
The direction-of-arrival estimating apparatus according to claim 1, wherein a plurality of directional antennas are selected based on a minimum value among the directional antennas. 6. The method according to claim 1, wherein said second direction-of-arrival estimating means is MUSI.
The direction-of-arrival estimation apparatus according to claim 1, wherein the direction-of-arrival estimation is performed by a C algorithm. 7. The apparatus according to claim 1, wherein the plurality of directional antennas are arranged in a circle. 8. The direction-of-arrival estimation apparatus according to claim 7, wherein the directional antenna has a maximum gain direction in a direction 180 degrees opposite to a center direction of the circular array. 9. The direction-of-arrival estimating apparatus according to claim 1, wherein said directional antenna comprises two sleeve monopole antennas fed with a phase difference. 10. A method in which a plurality of directional antenna elements selected from a plurality of directional antenna elements greater than the number of receivers are connected to a plurality of receivers to which a plurality of directional antenna elements can be connected. Based on the reception outputs of the plurality of receivers, the direction of arrival of the radio wave is roughly estimated, and based on the direction of arrival of the radio wave obtained as a result of the estimation, the number of directional antenna elements greater than the number of the receivers is estimated. From among them, a plurality of directional antenna elements to be used in precise DOA estimation are selected, and the plurality of receivers are connected to the selected plurality of directional antenna elements. A method of estimating a direction of arrival, wherein the direction of arrival of a radio wave is accurately estimated based on the reception output of the device. 11. A computer-readable recording medium storing a program for causing a computer constituting a base station to estimate a direction of arrival of a radio wave, comprising: a plurality of directional antenna elements connected to a plurality of receivers. Connecting a plurality of directional antenna elements selected from among a greater number of directional antenna elements than the number of the receivers, and roughly estimating a direction of arrival of a radio wave based on reception outputs of the plurality of receivers at this time. Based on the direction of arrival of the radio wave obtained as a result of this estimation, a plurality of directional antenna elements to be used in precise direction-of-arrival estimation are selected from among a greater number of directional antenna elements than the number of receivers. The plurality of directional antenna elements are connected to the plurality of receivers, and based on the reception outputs of the plurality of receivers at this time, the direction of arrival of the radio wave is precisely determined. Computer-readable recording medium storing a program for estimation. 12. A program product for causing a computer constituting a base station to estimate a direction of arrival of a radio wave, wherein a plurality of receivers to which a plurality of directional antenna elements can be connected have more than the number of receivers. A plurality of directional antenna elements selected from among a plurality of directional antenna elements are connected, and the direction of arrival of radio waves is roughly estimated based on the reception outputs of the plurality of receivers at this time. Based on the direction of arrival of the radio wave, from the number of directional antenna elements greater than the number of the receivers, to select a plurality of directional antenna elements to be used in accurate arrival direction estimation, the plurality of receivers A program product for connecting the selected plurality of directional antenna elements, and for accurately estimating the direction of arrival of radio waves based on the reception outputs of the plurality of receivers at this time.