JP2004080814A - Radio wave lens antenna apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio wave lens antenna apparatus capable of readily adjusting a plurality of antenna elements in position towards a plurality of stationary satellites. <P>SOLUTION: The radio wave lens antenna apparatus has a structure wherein the antenna apparatus having a hemispherical Luneberg lens 2 mounted on a reflecting plate 1 is provided with a support arm 4 that strides over the lens 2. A circular arc element holding section 4a along the spherical face of the lens 2 of the support arm 4 accompanied by an elevation angle adjuster 5 for adjusting an elevation angle, is provided with an antenna element 3 by way of a mounting means 6 at a gap corresponding to the gap of a stationary satellite to position a plurality of antenna elements in a batch by rotating the support arm 4 to a predetermined angle position. The structure includes a cover and the like, having a pointing map drawn thereon, which serves as an index for positioning the antenna elements enabling the setting points of the antenna elements to be checked through the map. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a radio wave lens antenna device using a Luneberg lens used for receiving radio waves from a plurality of geostationary satellites and transmitting radio waves to each geostationary satellite, and more specifically, the position of a radio wave transmitting / receiving antenna element. The present invention relates to a radio wave lens antenna device provided with a pointing map (a figure serving as an index for positioning) for making alignment accurate and simple.

The Luneberg lens known as one of the radio wave lenses is a dielectric lens having a sphere as a basic shape, and the relative permittivity εr of each part substantially follows the following equation (1).

εr = 2− (r / a) ² ... Equation (1)
However, a: the radius of the sphere r: the distance from the center of the sphere The antenna device using this Luneberg lens can capture radio waves from any direction by setting the focal point of radio waves at an arbitrary position on the hemisphere, and can also capture radio waves from any direction. Can send out radio waves.

ル ー Some Luneberg lens antenna devices have a function equivalent to a spherical lens by combining a hemispherical lens with a reflector. FIG. 8 shows an outline of the apparatus. In the figure, 1 is a reflector, 2 is a hemispherical Luneberg lens, and 3 is an antenna element (primary radiator).

With regard to an antenna device having this structure, an antenna device that transmits and receives radio waves to orbiting satellites by adding a tracking function to orbiting satellites has already been devised.

But it is just an antenna device for orbiting satellites.

For example, Japan has multiple geostationary satellites for satellite broadcasting. A parabona antenna is used to receive radio waves from the geostationary satellite, but the parabona antenna and the above-mentioned satellite tracking type radio wave lens antenna apparatus can cope with only one satellite or a satellite at the same point.

パ ラ In addition, the parabona antenna has a narrow range in which radio waves can be captured, and it is necessary to increase the number of antennas for satellites that are out of the capture area.

Accordingly, it is an object of the present invention to provide a radio wave lens antenna device capable of transmitting or receiving independently to a plurality of geostationary satellites.

In addition, the radio lens antenna device has a plurality of antenna elements corresponding to the number of satellites, but it is never possible to reliably position the plurality of antenna elements at a focal point of radio waves from a desired satellite. Not easy. Therefore, a radio wave lens antenna device that addresses this problem is provided.

In the case of a conventional parabolic antenna, as a method of adjusting the transmission / reception direction of radio waves to the direction in which the satellite exists, a spherical coordinate system at the antenna installation point is considered, and the satellite's azimuth (azimuth angle) φ and elevation angle (elevation angle) at the antenna installation point are considered. The direction is determined by using two orthogonal variables of the angle θ (see FIG. 9).

Since the azimuth and elevation at this time vary greatly depending on the area where the antenna is installed (strictly speaking, a point), for example, for a parabolic antenna for BS, CS broadcasting, etc., an equi-azimuth and an elevation are drawn. In this method, coarse adjustment is performed using a dedicated map as a guide, and then fine adjustment is performed while looking at a reception sensitivity value displayed on a television screen to search for an optimal direction.

方向 However, direction adjustment by this method is difficult for inexperienced people, and it takes time to work. An antenna device using a Luneberg lens adjusts the position of the antenna element, not the antenna itself, but attempts to enable independent transmission and reception to multiple geostationary satellites (multi-beam compatible type) ) Is provided with a plurality of antenna elements, so it is necessary to repeat complicated work, and it takes a long time to adjust.

Japan (Japan) currently has a plurality of geostationary satellites in the range of 110 ° to 162 ° east longitude. Of these, one antenna element can handle only three satellites at 110 ° east longitude, and the other satellites are slightly shifted in direction. At present, even when targeting at least 10 satellites and half of the satellites, it is necessary to provide 4 to 6 antenna elements, which makes the adjustment considerably cumbersome.

The present invention provides a radio wave lens antenna device that can surely and easily position a plurality of antenna elements with respect to each satellite.

In order to solve the above problems, the present invention provides the following radio wave lens antenna devices (1) to (7).
(1) A reflector for radio waves, a hemispherical Luneberg lens provided on the reflector with a half-section of the sphere attached to the reflecting surface, an antenna element for transmitting, receiving or transmitting and receiving radio waves, and the antenna element A radio lens antenna device having a holding tool for holding in a fixed position, wherein a plurality of the antenna elements are provided corresponding to a plurality of stationary satellites of a communication partner,
It has a cover to cover the hemispherical Luneberg lens, and on the surface of the cover, the following equi-latitude line and equi-longitude difference line, which serve as an index for positioning of the antenna element, and a pointing mark indicating a reference orientation for attaching the cover to the lens. A radio wave lens antenna device configured by combining with a pointing map that draws an image.
(Record)
The longitude of the antenna installation point is φ, the latitude is θ, the longitude of the geostationary satellite is φs, and the longitude difference Δφ = φ-φs,
The equi-longitude difference line is a locus on the hemisphere obtained by changing θ while keeping Δφ constant,
The equilatitude line is a locus on a hemisphere obtained by changing Δφ while keeping θ constant.
(2) A reflector for radio waves, a hemispherical Luneberg lens provided on the reflector with a half-section of a sphere attached to the reflecting surface, an antenna element for transmitting, receiving or transmitting and receiving radio waves, and the antenna element A holding tool for holding the antenna at a fixed position, wherein a plurality of the antenna elements are provided in correspondence with a plurality of geostationary satellites of a communication partner, and
A film attached to the surface of the hemispherical Luneberg lens or a film attached to the surface of the lens is configured by combining a pointing map drawn by the following equilatitude line and equilongation difference line as an index for positioning the antenna element. Radio wave lens antenna device.
(Record)
The longitude of the antenna installation point is φ, the latitude is θ, the longitude of the geostationary satellite is φs, and the longitude difference Δφ = φ-φs,
The equi-longitude difference line is a locus on the hemisphere obtained by changing θ while keeping Δφ constant,
The equilatitude line is a locus on a hemisphere obtained by changing Δφ while keeping θ constant.
(3) The holding device for holding the antenna element of the antenna device of (1) or (2) is an arch-shaped support arm straddling a hemispherical Luneberg lens, and an arc-shaped element along the spherical surface of the lens of the support arm. The holding unit is provided with means for attaching antenna elements at intervals corresponding to the interval between geostationary satellites, and further provided with an elevation angle adjustment mechanism for rotating the support arm to an arbitrary position with an axis passing through the center of the lens as a fulcrum. Radio wave lens antenna device.
(4) The radio lens antenna device according to (3), further comprising a mechanism for finely adjusting the azimuth of the antenna element and the rotation angle for polarization adjustment between each antenna element and the support arm.
(5) The radio lens antenna device according to (3) or (4) above, wherein a plurality of support arms are provided, and a plurality of antenna elements are distributed and attached to the plurality of support arms rotatable around the same axis. (6) The above-mentioned (3), wherein the support arm is a deformed arm in which both ends are non-circular, and between the non-circular portions, there is an arc-shaped element holding portion which keeps a distance from the spherical surface of the lens substantially constant. The radio wave lens antenna device according to any one of (1) to (5).
(7) A hemispherical radome is used as the cover for covering the hemispherical Luneberg lens, and an antenna element is mounted on the element folder, including an element folder that can be mounted on the surface of the radome, and the antenna element is positioned with respect to the geostationary satellite. (1) is performed by selecting an attachment point in the folder.

(4) Since the radio wave lens antenna device of the present invention has the pointing map serving as an index for positioning the antenna element, the installation point of the antenna element can be confirmed by the map. Also, it is possible to add a mark at the confirmed position, and it is only necessary to position the element there. Therefore, it is possible to easily perform almost reliable alignment, and it is also easy to adjust the antenna device that performs the alignment of each element individually. Become.

(4) For an antenna element holder that uses, for example, an arch-shaped rotatable support arm that straddles a lens, the positioning of a plurality of antenna elements with respect to each geostationary satellite can be performed collectively, which greatly simplifies the operation.

(4) For those having the support arm, the antenna elements are first attached to the element holding portion of the support arm at intervals corresponding to the intervals between the geostationary satellites by using element attachment means.

(4) Next, determine the elevation angle from a table or map prepared in advance based on the latitude and longitude of the antenna installation point, and lock the position by rotating the support arm at the angle.

Then, install the antenna device in the specified direction. Thus, the orientation of each antenna element is collectively adjusted, and each element is placed at a position corresponding to the satellite at an interval corresponding to the satellite.

With the above, the antenna element is positioned at a position where all of the target satellites can be captured substantially.

(4) Since the focal point of the radio wave from the satellite is approximately along the arc-shaped element holding portion of the support arm, the antenna element is almost aligned near the focal point of the radio wave. Here, the reason was roughly stated because only when the observation point is on the equator, the focal point is completely along the arc-shaped element holding part, and if the latitude changes, a shift occurs between the focal point and the arc of the holding part. is there. The deviation from the focal point of the element due to the change in latitude is not so large and can be ignored. For example, when using a lens antenna having a diameter of about 40 cm (commercially available BS and CS broadcasting parabolic antennas have a diameter of about 45 cm), the half width of the radio wave beam is about 4 degrees, and a deviation of about 1 degree is sufficient. It is within the range that can be used. Of course, it is better that there is no such shift. If a fine adjustment mechanism for elevation and azimuth is provided for each antenna element, the shift can be corrected.

Further, the azimuth and elevation of the satellite viewed from the antenna installation point vary depending on the antenna installation point, but if a fine adjustment mechanism for the azimuth and the polarization adjustment rotation angle is provided (the device of (3) above) Also, it is possible to cope with an angle change due to a difference in installation point.

誤差 By using regional support arms with element mounting intervals that match the satellite spacing in each region and using them, errors can also be reduced.

As described above, the antenna device of the present invention can collectively perform positioning of a plurality of antenna elements corresponding to a plurality of satellites, and can facilitate, secure, and speed up the adjustment.

If the distance between the elements is reduced, a problem of mutual interference between the elements occurs. In the device of the above (5) in which a plurality of support arms are provided, by separating and mounting elements on each support arm, the element interval on the same arm can be widened, and the mounting restriction due to mutual interference can be eased.

静止 In addition, geostationary satellites are, for example, in a limited range of 110 to 162 degrees east longitude in Japan. Therefore, the support arm may be one having both ends straightened to reduce the distance between both ends for compactness, or one having both ends bent in a side view so that the element holding portion can be easily aligned with the positioning point of the antenna element. You can use it. These arms are referred to as deformed arms to distinguish them from semicircular arms.

Hereinafter, an embodiment of the antenna device according to the present invention will be described with reference to FIGS.

The radio wave lens antenna apparatus shown in FIGS. 1 to 3 has a configuration in which a hemispherical Luneberg lens 2 is fixed on a reflector 1 and a plurality of antenna elements 3 are attached to a support arm 4 provided on the reflector 1. Is done.

The Luneberg lens 2 is made of a dielectric material, and the relative dielectric constant of each part is approximated to the value obtained by the above-described equation (1) by making the whole a multilayer structure.

(4) The antenna element 3 may be an antenna only, or may be an element that is set with a circuit board including a low-noise amplifier, a frequency converter, an oscillator, and the like.

The support arm 4 is an arched arm that straddles the lens 2, has an element holding portion 4 a along the arc surface of the lens 2, and further has a support shaft 4 b serving as a rotation fulcrum at both ends. The support shafts 4b at both ends are rotatably attached to the angle adjuster 5. In the illustrated device, the support shaft 4b is on the axis passing through the center of the lens. However, the rotation center of the arm may be intentionally shifted from the axis passing through the center of the lens in order to increase the positioning accuracy of the element.

The angle adjuster 5 supports the support shaft 4b with the bracket 5b having the angle scale 5a. The adjuster 5 has a lock mechanism (not shown) for fixing the support arm 4 at each rotational position. The lock mechanism may be one in which a long hole is formed in the bracket that is concentric with the support shaft 4b, a screw attached to the support shaft 4b is passed therethrough, and tightened with a wing nut.

素 子 An element mounting means 6 is provided on the element holding portion 4 a of the support arm 4. The element mounting means 6 is provided with a concave portion, a convex portion, a mark, and the like for designating a setting position of the holder on the support arm 4 and is fitted into the designated position to position the fitting type holder or the slide type holder. A structure in which the element 3 is mounted is conceivable, and the space between the antenna elements is made to correspond to the space between the satellites by using the element mounting means 6.

取 付 け The mounting interval of the antenna element 3 by the element mounting means 6 is determined as follows. For example, in Japan, geostationary satellites that are mainly used are located at 110, 124, 128, 132, 136, 144, 150, 154, 158, and 162 degrees east longitude. is there. Among them, for example, when capturing satellites of 124 degrees and 128 degrees east longitude, the difference between the longitudes of the two satellites is 4 degrees, but from the antenna installation point in Japan, the satellite interval is about 4.4 degrees. Therefore, in this case, the antenna elements 3 should be mounted on the element holding portion 4a at an interval of 4.4 degrees (+ correction angle if necessary).

Further, as described above, the focal point of the radio wave shifts from an arc concentric with the element holding unit due to the change in latitude due to the rotation of the support arm 4, and the azimuth facing the satellite also shifts depending on the installation point of the antenna. It is desirable to provide a mechanism for fine adjustment of the azimuth angle and the rotation angle for polarization adjustment between the element 3 and the support arm 4. Alternatively, it is also possible to prepare a regional support arm having a structure in which the antenna elements are positioned and mounted at intervals matching the average satellite interval in each region, and the arm may be used properly. The region-specific support arms referred to here include those in which a part of the arm is made replaceable, and only a part of the arm is replaced to position the antenna element at the optimum point for each region.

Hereinafter, a method of installing the radio wave lens antenna device of FIG. 1 will be described.
1) A mark for azimuth alignment at the time of installing the apparatus (for example, S indicating true south direction or N indicating true north when used in the southern hemisphere) is attached to the reflector 1. This mark may be attached in advance, but it is necessary that the positional relationship between the mark and the mounting point of the antenna element be determined.
2) Prepare antenna elements for the desired number of satellites and attach them to the corresponding locations on the arm.
3) Based on the latitude and longitude of the antenna installation point, determine the elevation angle from a table or map, and adjust the arm to that angle.
4) Install the antenna so that the south mark is facing south.
In this state, almost all satellites have been captured.
5) Adjust the rotation angle of the antenna element while receiving radio waves from each satellite, and set so that the reception level is maximized. Further, the position of the antenna element is finely adjusted (azimuth and elevation), and the setting is fixed so that the reception level is maximized. Perform this operation for all satellite antenna elements.

で By doing so, a plurality of satellites can be easily and collectively captured, and positioning of the antenna elements can be facilitated.

FIG. 2 shows a second embodiment. The above-mentioned 4.4-degree satellite interval is quite narrow, and if antenna elements are mounted on the same support arm at the interval, a small antenna element is required. If the required miniaturization cannot be realized, mutual interference between adjacent antenna elements occurs, and one satellite must be abandoned. The apparatus shown in FIG. 2 is provided with two support arms 4 having a rotation fulcrum on the same axis. If a plurality of arms are provided and the antenna element 3 is separately mounted on each support arm 4 as described above, it is possible to widen the interval between adjacent antenna elements, thereby solving the above-mentioned problem.

FIG. 3 shows an example of using a deformable support arm. The element holding portion 4a of the support arm is formed in an arc shape concentric with the lens 2 in order to keep the focal length of the radio wave constant. The area outside the element holding portion 4a has no effect on the focal length, and therefore, both ends of the support arm 4 may be shaped as shown in FIG. With the shape shown in FIG. 3, the distance between both ends of the arm is reduced, and compactness can be achieved. Further, as shown by a chain line in FIG. 3A, both ends of the arm 4 may be bent in a side view, and this shape is effective for making the element holding portion 4a ideally along the positioning point of the antenna element. It is.

ポ Attach a pointing map described later to these antenna devices. FIG. 4 shows an embodiment of the pointing map.

(4) In the present invention, a diagram depicting a locus of equal latitude and equal longitude difference as shown in FIG. 4 is called a pointing map.

For example, if the longitude of the antenna installation point is φ, the latitude is θ, the longitude of the satellite is φs, and the longitude difference Δ = φ−φs,
The equi-longitude difference line is a locus on the hemisphere obtained by changing θ while keeping Δφ constant,
The equilatitude line is a locus on the hemisphere obtained by changing Δφ while keeping θ constant,
Is drawn.

This pointing map 7 is drawn on, for example, a radome 8 and placed on a hemispherical lens, and the satellite capture position is determined from the difference between the latitude of the antenna installation point, the longitude of the antenna installation point, and the longitude of the desired satellite. I do.

A specific antenna element installation method using the pointing map of FIG. 4 will be described with reference to FIG.
1) Install the lens antenna 2 on the reflector 1 and cover the radome 8.
2) In addition to the pointing map 7, a pointing mark 9 is drawn on the radome.
3) The radome 8 is oriented so that the pointing mark 9 matches an azimuth mark 10 described later. 4) The reflector 1 is provided with an azimuth mark (here, S) 10 indicating the true south direction (when installed in the southern hemisphere, the mark N indicating the true north direction is provided).
5) If necessary, the satellite direction may be marked in accordance with the longitude of the target satellite with reference to S (N).
6) In this state, the satellite antenna element 3 (primary radiator) is temporarily fixed to the antenna installation point on the pointing map 7.
7) The same operation is performed for the antenna elements 3 of all necessary satellites.
8) Confirm that the pointing mark 9 is aligned with the azimuth mark 10, and move the reflector 1 so that the azimuth mark 10 faces south (north).
9) Adjust the rotation angle of the antenna element while receiving radio waves from each satellite, and set so that the reception level is maximized. Further, the position of the antenna element is finely adjusted, and the setting is fixed so that the reception level is maximized. Perform this operation for all satellite antenna elements.

と Using the pointing map 7, the satellite can be reliably and easily captured, and the positioning of the antenna element can be simplified.

描 く Further, by drawing the pointing map 7 on the surface of a radome or the like, a special tool for adjusting the azimuth becomes unnecessary, which is advantageous in terms of economy and the like.

Although the pointing map 7 is drawn on the radome 8 and has a function as the original antenna cover of the radome, the pointing map 7 is a primary jig used only for positioning the antenna element. It may be. In that case, a structure is required that allows the pointing map cover to be removed after the antenna is installed. For example, it is desirable to draw the map on a 1/4 sphere cover, leaving only the side on which the map is drawn.

If the lens does not require a radome, a pointing map may be printed on the surface of the lens, or a sticker or the like on which the map is printed may be attached to the lens for use.

Although FIG. 5 shows one antenna support pole 12 for one antenna element 3, an arm system as shown in FIGS. 1 to 3 may be used. Further, as shown in FIG. 6, a support tool in which a support pole 12 and a small arm 13 supporting a plurality of antenna elements 3 are combined may be employed. In this case, since the shape of the arm may not completely match the locus of the map, it is preferable to provide a fine adjustment mechanism for the azimuth and elevation angles for each antenna element. Meets the advantage of secure installation.

Further, as shown in FIG. 7, an element folder 14 which is attachable to the surface of the radome 8 or is formed integrally with the radome 8 has a size covering the pointing map 7 or a size including only the existence range of the antenna element. And a surface-mounted lens antenna device that fixes the individual antenna elements 3 at an arbitrary position in the folder 14 (a position corresponding to the position marked on the map). In the folder 14, if a large number of insertion holes or the like for elements or element mounting tools are provided at a minute pitch, a hole at an arbitrary position can be selected and the element or element mounting tool can be mounted at a desired position. In this case, if an element mounting tool is used, a fine adjustment mechanism for the azimuth and rotation angle can be provided.

The antenna device (1) of the present invention may be either an antenna device that individually holds antenna elements or an antenna device that holds several antenna elements collectively.

(A) The radio lens antenna of the present invention is a side view of an embodiment of the device, and (b) is a plan view of the device. (A) A side view of another embodiment of the radio wave lens antenna device, (b) a plan view of the same device as above (A) A side view of still another embodiment of the radio wave lens antenna device, and (b) a plan view of the same device. (A) Top view of an embodiment of a pointing map, (b) Side view of the same map (A) A plan view showing an example of using the map of FIG. 4, and (b) a side view of the same. A perspective view showing another example of the use of the pointing map. Perspective view showing yet another example of using a pointing map. Conceptual diagram of hemispherical Luneberg antenna device Illustration of the azimuth and elevation of the satellite viewed from the antenna installation point

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Reflector 2 Luneberg lens 3 Antenna element 4 Support arm 4a Element holding part 4b Support shaft 5 Angle adjuster 6 Element mounting means 7 Pointing map 8 Radome 9 Pointing mark 10 Direction mark 11 Satellite direction mark 12 Antenna support pole 13 Small arm 14 Element folder

Claims (7)

A reflector for radio waves, a hemispherical Luneberg lens provided on the reflector with a half-section of the sphere attached to the reflecting surface, an antenna element for transmitting, receiving or transmitting and receiving radio waves, and the antenna element in place A holding tool for holding, a radio wave lens antenna device in which a plurality of the antenna elements are provided corresponding to a plurality of geostationary satellites of a communication partner,
A cover that covers the hemispherical Luneberg lens, and the following equi-latitude and equi-longitude difference lines that serve as indices for positioning the antenna elements on the surface of the cover, and a pointing mark that indicates a reference orientation for attaching the cover to the lens. A radio wave lens antenna device configured by combining with a pointing map that draws an image.
(Record)
The longitude of the antenna installation point is φ, the latitude is θ, the longitude of the geostationary satellite is φs, and the longitude difference Δφ = φ-φs,
The equi-longitude difference line is a locus on the hemisphere obtained by changing θ while keeping Δφ constant,
The equilatitude line is a locus on a hemisphere obtained by changing Δφ while keeping θ constant. A reflector for radio waves, a hemispherical Luneberg lens provided on the reflector with a half-section of the sphere attached to the reflecting surface, an antenna element for transmitting, receiving or transmitting and receiving radio waves, and the antenna element in place A holding tool for holding, a radio wave lens antenna device in which a plurality of the antenna elements are provided corresponding to a plurality of geostationary satellites of a communication partner,
A film attached to the surface of the hemispherical Luneberg lens or a film attached to the surface of the lens is configured by combining a pointing map drawn by the following equilatitude line and equilongation difference line as an index for positioning the antenna element. Radio wave antenna antenna device.
(Record)
The longitude of the antenna installation point is φ, the latitude is θ, the longitude of the geostationary satellite is φs, and the longitude difference Δφ = φ-φs,
The equi-longitude difference line is a locus on the hemisphere obtained by changing θ while keeping Δφ constant,
The equilatitude line is a locus on a hemisphere obtained by changing Δφ while keeping θ constant. The holder is an arch-shaped support arm straddling a hemispherical Luneberg lens, and means for attaching antenna elements to the arc-shaped element holding portion along the spherical surface of the lens of the support arm at an interval corresponding to the interval between the geostationary satellites. The radio wave lens antenna device according to claim 1, further comprising an elevation angle adjustment mechanism provided to rotate the support arm to an arbitrary position around an axis passing through the center of the lens. 4. The radio wave lens antenna device according to claim 3, further comprising a fine adjustment mechanism of the azimuth angle of the antenna element and the rotation angle for polarization adjustment between each antenna element and the support arm. 5. The radio wave lens antenna device according to claim 3, wherein a plurality of the support arms are provided, and a plurality of antenna elements are distributed and attached to the plurality of support arms rotatable around the same axis. 6. The deformable arm according to claim 3, wherein the support arm has a non-circular shape at both ends, and an arc-shaped element holding portion in which a distance from the spherical surface of the lens is kept substantially constant between the non-circular portions. The radio wave lens antenna device according to any one of the above. A hemispherical radome is used as the cover for covering the hemispherical Luneberg lens. An antenna element is mounted on the element folder, including an element folder that can be mounted on the surface of the radome. 2. The radio wave lens antenna device according to claim 1, wherein the radio wave lens antenna device is operated by selecting an attachment point.

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