JP7285421B2 - antenna device - Google Patents

Description

The present invention relates to an antenna device, and more particularly to an antenna device used for estimating the direction of arrival of radio waves.

A radio wave direction-of-arrival estimation apparatus for estimating the direction of arrival of radio waves is one of devices using radio. This radio wave arrival direction estimating apparatus uses an antenna device for receiving incoming radio waves. Patent Documents 1 and 2 disclose examples of antennas used in a direction-of-arrival estimation apparatus for radio waves.

In the antenna device disclosed in Patent Document 1, the output terminal of the lower antenna element of the discone, that is, the lower output terminal, is connected to the core side of the coaxial feed line, and the output terminal of the upper antenna element, that is, the upper The output terminal is connected to the outer shield of the coaxial feeder line, which is completely opposite to the feeder line of the conventional discone antenna. connect to.

Further, the radio direction finder described in Patent Document 2 incorporates a plurality of antenna elements, a plurality of receivers connected to each of the plurality of antenna elements, and the outputs of the plurality of receivers, A / D A radio direction finder that detects the direction of an incoming radio wave by digitally processing the incoming radio wave received by each antenna element, the signal processing in the signal processing unit. Thus, a sum pattern having a main beam in the boresight direction and having a high sidelobe level to the extent that even a signal received with a sidelobe can obtain an S/N determined by the desired direction finding accuracy, and a null point in the boresight direction. and a difference pattern having a high sidelobe level to the extent that even a signal received with a sidelobe can obtain an S/N determined by a desired direction finding accuracy, and furthermore, the set of the sum pattern and the difference pattern is directed in the boresight direction. The direction of an incoming radio wave is detected by forming a plurality of different sets of .

Japanese Utility Model Laid-Open No. 06-077314 JP-A-08-166433

The antenna device used in the radio wave direction-of-arrival estimation device may be installed outdoors, and it is necessary to consider wind pressure resistance. Therefore, the pole of the antenna device must be made as thick as possible. However, the thickness of the strut deteriorates the pattern of received radio waves and disturbs the phase difference between the received radio waves. Patent Documents 1 and 2 do not disclose or suggest how to prevent the deterioration of the direction-of-arrival estimation performance due to the thickness of the strut.

One aspect of the antenna device according to the present invention includes a support and a plurality of directional antennas attached to the support, wherein the plurality of directional antennas are radially distributed at equal angles from the center of the support. The array radius, which is the distance from the center of the pillar to the center of the directional antenna, is set to 0.05λ or more, the lowest frequency used, and 2.5λ or less, the highest frequency used.

(Basis for correction: Paragraph 0018)
One aspect of the antenna device according to the present invention includes a support and a plurality of directional antennas attached to the support, wherein the plurality of directional antennas are radially distributed at equal angles from the center of the support. The array radius of the center of the directional antenna is set to 0.04λ or more, which is the lowest frequency used, and 2.5λ or less, which is the highest frequency used.

3 is a diagram for explaining the arrangement of antennas of the antenna device according to the first embodiment; FIG. FIG. 10 is a diagram for explaining the arrangement of antennas in the antenna device according to the second embodiment;

An antenna device according to an embodiment described below includes a plurality of antennas for receiving radio waves in a direction-of-arrival estimation device for radio waves. In the antenna device according to the embodiment described below, an example in which a plurality of directional antennas are provided will be described, but an omnidirectional antenna may be provided in addition to the directional antennas.

Embodiment 1
BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a diagram for explaining the arrangement of antennas in an antenna device 1 according to the first embodiment. FIG. 1 is a top view of the antenna device as seen from the tip direction of the column 10. FIG. As shown in FIG. 1, the antenna device 1 according to the first embodiment has a support 10 and a plurality of directional antennas (eg, antenna elements 21 to 27).

And the strut 10 has a cylindrical shape. The antenna elements 21 to 27 are distributed radially at equal angles (for example, angle θ) around the perimeter of the post 10 . The antenna elements 21 to 27 receive radio waves coming from respective radiation directions. At this time, in the antenna device 1 according to the first embodiment, the antenna elements 21 to 27 are arranged so that the center of the circle formed along the positions of the antenna centers of the antenna elements 21 to 27 is the center of the support 10. are arranged concentrically from the center CP of the Here, the antenna center means the center from the front end to the rear end of the antenna element. In FIG. 1, a concentric circle formed by the antenna centers of the antenna elements 21 to 27 is indicated by a dashed line. In the antenna device 1 according to the first embodiment, the distance between the approximate center of the length of the antenna elements in the radial direction and the center of the arrangement of the antenna elements is defined as the arrangement radius of the antenna elements. In the antenna device 1 according to the first embodiment, the array radius L is the distance from the center CP of the post 10 to the antenna centers of the antenna elements 21 to 27, and the array radius L is set to 2.5λ or less of the maximum frequency used. , this array radius L is more preferably 0.04λ or more, which is the lowest frequency used, and 2.0λ or less, which is the highest frequency used. Note that λ is the wavelength of the received radio wave.

If the array radius L is reduced, the gain of the antenna will decrease, the reception level of incoming radio waves will decrease, the signal-to-noise ratio (S/N) of the received radio waves will deteriorate, and the reception phase difference will decrease. , the deterioration of the direction finding performance becomes remarkable. Further, if the array radius L becomes too large, or if the reception phase difference becomes too large, the problem of large errors in azimuth calculation becomes conspicuous.

Here, a log-periodic antenna, a Vivaldi antenna, or the like can be used as the antenna elements 21 to 27 having directivity of received radio waves. In the example shown in FIG. 1, the number of antenna elements to be arranged is 7, but it can be changed between 5 and 9 according to the estimation accuracy required for the direction-of-arrival estimation device. Two or more antenna elements are feasible.

As described above, in the antenna device 1 according to the first embodiment, by using a plurality of antenna elements having directivity of received radio waves, the influence of the reflected waves reflected by the support 10 is reduced to prevent deformation of the horizontal plane pattern. be able to. The horizontal pattern is the electric field characteristic of horizontal electric field directivity (electric field=electric field intensity) or horizontal power directivity. The power directivity is the square of the electric field directivity.

Here, the antenna device 1 is used when estimating the direction of arrival of radio waves arriving from a horizontal direction with respect to the ground. Such an antenna device 1 is required to be able to stably receive radio waves in a horizontal radio wave arrival range. For this purpose, it is required that the directivity of the antenna is generally uniform (so-called wide beam) and that there is no sharp drop (null) in the directivity. An omnidirectional antenna is an antenna that satisfies such requirements. directional distortion and nulls occur at frequencies of On the other hand, the direction-of-arrival estimation device for radio waves is a device for estimating the direction of arrival of radio waves from the phase difference of the radio waves received by each antenna. Therefore, when an omnidirectional antenna is used as an antenna for an antenna device used in a direction-of-arrival estimation device, the reception level decreases, and the phase detection accuracy decreases due to the decrease in the reception level, resulting in direction finding accuracy. decreases.

On the other hand, in the antenna device 1 according to the first embodiment, the antenna elements having directivity are arranged so that the antenna centers of the antenna elements are on the same circle, and the angular range mainly covered by each antenna (depending on the number of arranged elements By having a substantially uniform directivity in the variable), it is possible to reduce the influence of reflections from the poles 10 and the like, and obtain stable reception level and phase detection.

Further, in the antenna device 1 according to the first embodiment, the array radius L, which is the distance from the center CP of the support 10 to the antenna centers of the antenna elements 21 to 27 , is 0.04λ or more, which is the lowest frequency used, and the highest frequency used 2.5 λ or less (more preferably, the lowest frequency used 0.05 λ or more, and the highest frequency used 2.0 λ or less), the magnitude of the phase difference of the received signal between the antenna elements Errors due to (for example, too small and too large phase difference) can be suppressed. As a result, in the radio wave direction-of-arrival estimation apparatus using the antenna apparatus 1 according to the first embodiment, the direction detection accuracy can be improved by sending the error-suppressed received signal to the subsequent-stage direction-of-arrival estimation apparatus.

In addition, in the antenna device 1 according to the first embodiment, the radius of the struts 10 can be increased to a thickness allowed by the arrangement radius L. FIG. By increasing the thickness of the support in this way, the wind pressure resistance when the antenna device 1 is installed outdoors can be increased.

When the horizontal bar on which the antenna element is attached (orientation of the antenna radiation element with respect to the ground) is horizontal, it is called horizontal polarization, and when it is vertical, it is called vertical polarization. However, any polarization can be considered in the same way as the horizontal polarization.

Embodiment 2
In Embodiment 2, an antenna device 2 that is another form of the antenna device 1 will be described. FIG. 2 shows a diagram for explaining the arrangement of the antennas of the antenna device according to the second embodiment. As shown in FIG. 2, the antenna device 2 according to the second embodiment has a support 11 instead of the support 10 of the antenna device 1 according to the first embodiment. The column 11 is a column having a polygonal cross section. In the example shown in FIG. 2, since seven antenna elements are arranged on the support, the support 11 is made heptagonal. In this way, the shape of the post is not limited to a cylinder, and even if a polygonal tube is used, a plurality of directional antennas can be arranged so that the centers of the antennas are arranged on concentric circles so that they can be oriented in the same direction as in the first embodiment. It is possible to obtain the effect of improving detection accuracy. This is because the array radius of the antenna elements is defined as "the distance between the approximate center of the radial length of the antenna elements and the center of the antenna element array" regardless of the shape of the support.

It should be noted that the present invention is not limited to the above embodiments, and can be modified as appropriate without departing from the scope of the invention.

1, 2 antenna device 10, 11 pillar 21 to 27 antenna element

Claims (5)

a stanchion;
a plurality of directional antennas attached to the support and used for estimating the direction of arrival of radio waves;
The plurality of directional antennas,
Distributed radially at equal angles from the center of the support,
An antenna device in which an array radius, which is the distance from the center of the support to the center of the directional antenna, is set to 0.04λ or more, the lowest frequency used, and 2.5λ or less, the highest frequency used. 2. The antenna device according to claim 1, wherein said directional antenna is a log-periodic antenna or a Vivaldi antenna. 3. The antenna device according to claim 1, wherein the number of said plurality of directional antennas is set to any one number from 5 to 9. 4. The antenna device according to any one of claims 1 to 3, wherein the post has a polygonal shape having angles corresponding to the number of the directional antennas. 5. The antenna device according to any one of claims 1 to 4, wherein the array radius is 0.05λ or more of the lowest frequency used and 2.0λ or less of the highest frequency used.

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