JP3671896B2 - Offset parabolic antenna for broadcast wave relay - Google Patents

Description

【００１８】
この受信電界強度は、遮蔽板４のない−９０°方向の受信電界強度に比べて、低下している。この低下量も表１に示す。
表１によれば、９０°方向の受信電界強度は、０°方向の受信電界強度と比べて、それぞれ−４３ｄＢ，−４９ｄＢ，−５５ｄＢ，−５４ｄＢと十分に低下しているので、放送波の回り込みを防ぐことができる。
また、９０°方向の受信電界強度は、遮蔽板４のない−９０°方向の受信電界強度に比べて、それぞれ−１６ｄＢ，−１４ｄＢ，−１８ｄＢ，−８ｄＢと、十分低下している。これが遮蔽板設置の効果となる。
２. 遮蔽板の取り付け構造
次に本発明に関係する、放送波中継用オフセットパラボラアンテナの遮蔽板の取り付け構造を説明する。
【００１９】
図５は、放送波中継用オフセットパラボラアンテナの斜視図である。放送波中継用オフセットパラボラアンテナは、オフセットパラボラ反射板１を鉄塔に取り付けるための基体５と、遮蔽板４を固定したフレーム６とを有している。フレーム６は、基体５に設けられた支軸５ａ，５ｂを中心として、基体５に対して、回動可能に取り付けられる。そしてフレーム６の姿勢を保持するためのステー７が基体５の上端部とフレーム６との間に張られている。ステー７の先端部は、フレーム６の支軸６ａ，６ｂを通して回動可能となっている。ステー７の基端部は、基体５に対して取り外し可能にされている。
【００２０】
なお、図５では遮蔽板４を透明なものとして描いているが、実際には、前述したように複数本のグリッドにより形成されているものである。また、一次輻射器２を遮蔽板４に取り付ける部材の図示は省略している。
図６は、放送波中継用オフセットパラボラアンテナを鉄塔８に固定した状態を示す側面図であり,(a)はアンテナ使用時の状態を示し、(b)はフレーム６を跳ね上げた状態を示す。
【００２１】
アンテナ使用時には、図６(a)に示すように、ステー７の基端部を基体５に取り付ける。取り付け方法は限定されないが、例えばボルトによる嵌合などが採用できる。
一次輻射器２や２ダイポールアンテナ３のメンテナンス時には、ステー７の基端部の嵌合をはずして、フレーム６を支軸５ａ，５ｂの回りに回転させて跳ね上げる。この跳ね上げた状態が図６(b)である。図６(b)では、フレーム６の先端が鉄塔８に届くまで、フレーム６をほぼ９０度上方向に回動させている。この状態において、作業者は、鉄塔８に乗ったままの位置で、一次輻射器２や２ダイポールアンテナ３をメンテナンスできる。
【００２２】
以上で、本発明の実施の形態を説明したが、本発明の実施は、前記の形態に限定されるものではなく、例えばステー７の基端部を基体５でなく鉄塔８に取り付けるようにしてもよい。その他、本発明の範囲内において種種の変更を施すことが可能である。
【００２３】
【発明の効果】
以上のように本発明によれば、放送波中継用オフセットパラボラアンテナを鉄塔に取り付けた状態で一次輻射器をメンテナンスする時に、フレームごと回動させて、一次輻射器を作業者の近くに持って来ることができる。したがって、作業者がパラボラアンテナの前に回りこむ必要がなくなり、作業の安全と効率化に寄与することができる。
【図面の簡単な説明】
【図１】放送波中継用オフセットパラボラアンテナの正面図(a)及び側面図(b)である。
【図２】放送波中継用オフセットパラボラアンテナの斜視図である。
【図３】２ダイポールアンテナ３の正面図(a)及び側断面図(b)である。
【図４】受信電界強度を計算した結果を示すグラフである。
【図５】放送波中継用オフセットパラボラアンテナの遮蔽板の取り付け構造を示す斜視図である。
【図６】放送波中継用オフセットパラボラアンテナを鉄塔に固定した状態を示す側面図であり,(a)はアンテナ使用時の状態を示し、(b)は遮蔽板を跳ね上げた状態を示す。
【図７】中継機を搭載した鉄塔の概要図である。
【符号の説明】
１ オフセットパラボラ反射板
２ 一次輻射器
３ ２ダイポールアンテナ
４ 遮蔽板
５ 基体
６ フレーム
７ ステー７
８ 鉄塔[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an offset parabolic antenna for broadcast wave relay for performing retransmission at the same frequency.
[0002]
[Prior art]
When performing wireless relay for digital television broadcasting, it has been proposed to set the frequency of the relay wave to the same frequency as the broadcast wave (SFN: Single Frequency Network). This relay using the same frequency eliminates the need for a frequency conversion device, and can realize a simple and low-cost repeater.
FIG. 7 is a schematic diagram of a steel tower 12 on which the repeater 11 is mounted. A signal received by the reception antenna 13 of the relay wave is supplied to the repeater 11 through the cable 14. Here, the signal is amplified to a predetermined level, and is fed through the cable 14 to the broadcast transmitting antenna 15 installed in the upper part of the steel tower.
[0003]
Since the relay wave receiving antenna 13 installed in the repeater is required to have a high gain, it is difficult to realize it with a Yagi antenna or the like.
Therefore, it is conceivable to use a parabolic antenna. However, the parabolic antenna has a high back lobe at an angle of 90 degrees or more from the main beam direction, and prevents the broadcast radio wave radiated from the broadcasting transmission antenna of the steel tower from wrapping around. I can't.
Moreover, since the offset parabolic reflector is usually a single plate, the wind receiving area is large and the weight is large. For this reason, it becomes difficult to endure the wind, and the load on the steel tower is required to be sufficient.
[0004]
Therefore, the applicant filed a patent application for an offset parabolic antenna for broadcast wave relay that can suppress directivity from a predetermined direction different from the main beam direction, and can reduce the wind pressure load and weight. (Japanese Patent Application No. 2001-45410).
[0005]
[Problems to be solved by the invention]
The broadcast wave relay offset parabolic antenna is provided with an offset parabolic reflector facing the primary radiator, and is incident on a side where the offset parabolic reflector is not disposed from a predetermined direction different from the radio wave receiving direction. It has a structure in which a shielding plate that blocks incoming radio waves is installed.
In this structure, there is a problem in that it is dangerous to implement and the efficiency of maintenance is low because it is necessary to hang it on the front side of the offset parabolic reflector plate during maintenance of the primary radiator or the like.
[0006]
Therefore, the present invention provides an offset parabola antenna for broadcast wave relay that can perform maintenance of a primary radiator, etc. without having to rotate in front of an offset parabola reflector, and thus has high safety and high maintenance efficiency. Objective.
[0007]
[Means for Solving the Problems]
The offset parabolic antenna for broadcast wave relay according to the present invention is provided with an offset parabolic reflector facing the primary radiator, and is incident on a side where the offset parabolic reflector is not disposed from a predetermined direction different from the radio wave receiving direction. A shielding plate for blocking the retransmitted radio wave, the offset parabolic reflector is fixed to a steel tower, and the primary radiator and the shielding plate are integrally attached to the frame. The frame is pivotable so as to open in the direction of arrival of the retransmitted radio wave with a pivot axis set in a stationary state with respect to the steel tower .
[0008]
According to the above configuration, when the primary radiator is maintained with the offset parabolic antenna for broadcasting wave relay attached to the steel tower, the entire frame is rotated, and the primary radiator is held near the operator. Can come. Therefore, it is not necessary for the operator to go around in front of the parabolic antenna, which can contribute to work safety.
Previous SL frame while being maximally rotated, it is preferable tip of the frame is contactable to a part of the tower. If the rotation angle can be increased until the tip of the frame comes into contact with a part of the steel tower, the operator can maintain the primary radiator and the like while riding on the steel tower.
[0009]
The “predetermined direction” is the arrival direction of the sneak radio wave, and is determined by the installation state of the offset parabolic antenna for broadcast wave relay and the broadcast wave retransmission antenna. For example, in a typical installation state as shown in FIG. 7, the elevation angle is 90 °.
The offset parabolic reflector or shielding plate may be constituted by a grid of metal bars. As a result, it is possible to reduce the wind pressure load and the weight of the offset parabolic antenna for broadcasting wave relay. If the grid pitch is set to about one-tenth or less of the wavelength of the radio wave used, reflection loss can be prevented.
[0010]
In order to obtain a sufficient shielding effect, the length L with which the shielding plate shields the primary radiator is preferably ½ wavelength or more, and more preferably 2/3 wavelength or more.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
1. Structure of Offset Parabolic Antenna for Broadcasting Wave Relay FIG. 1 shows a front view (a) and a side view (b) of an offset parabolic antenna for broadcasting wave relay. FIG. 2 is a perspective view of a broadcast wave relay offset parabolic antenna.
The format of the offset parabolic antenna for broadcasting wave relay is an offset parabolic antenna. The offset parabolic reflector 1 forms part of a paraboloid of revolution whose center line is c. A primary radiator 2 is disposed at the focal point p of the offset parabolic reflector 1, and a 2 (two) dipole antenna 3 is disposed so as to face the reflecting surface of the primary radiator 2.
[0012]
The offset parabolic reflector 1 is formed by a plurality of grids (metal bars) processed into a curved shape according to the paraboloid of revolution.
In addition, a shielding plate 4 is installed horizontally above the offset parabolic reflector 1 in order to prevent broadcast waves from wrapping around. The shielding plate 4 is rectangular and is formed by a plurality of straight grids.
The length of the part of the shielding plate 4 protruding from the focal point p is represented by L (see FIG. 1B). This protrusion length L is a parameter representing the ability to prevent broadcast waves from wrapping around. The illustrated angle α represents the directivity angle of the received radio wave.
[0013]
Here, a specific numerical example is given. The broadcast wave frequency is the UHF broadcast wave band (470 to 770 MHz). The protruding length L is 440 mm. The diameter of one grid of the offset parabolic reflector 1 and the shielding plate 4 is 25 mm, and the installation interval s between the grids is 80 mm. The lateral width r of the offset parabolic reflector 1 is 2400 mm, the distance d from the center line c to the end of the offset parabolic reflector 1 is 2440 mm, the distance e from the bottom of the paraboloid to the focal point p is 1000 mm, and the center line c is shielded. The distance g to the plate 4 is 160 mm. The installation angle θ of the primary radiator 2 disposed at the focal point p is 55 °, the vertical length m is 480 mm, and the horizontal length n is 760 mm.
[0014]
FIG. 3 is a front view (a) and a side sectional view (b) of the two-dipole antenna 3. The two-dipole antenna 3 includes one antenna element 3a connected to the inner conductor of the feeder line and the other antenna element 3b connected to the outer conductor of the feeder line. Each element is formed of a metal plate and is attached to the insulating plate 3c. Each element is provided with two radiation plates, and the distance between the radiation plates is represented by h. Specifically, h = 240 mm.
[0015]
FIG. 4 shows the calculation result of the received electric field strength of the broadcast wave relay offset parabolic antenna described above.
The horizontal axis of FIG. 4 is the directivity angle α of the broadcast wave relay offset parabolic antenna, the plus side indicates the elevation angle, the minus side indicates the depression angle, and 0 ° indicates the front. The received electric field strength on the vertical axis represents a relative value when the received electric field strength at 0 ° is 1 (0 dB). The frequency is calculated with four types of 470 MHz, 570 MHz, 670 MHz, and 770 MHz.
[0016]
The protrusion length L = 440 mm described above becomes 0.69λ, 0.84λ, 0.98λ, and 1.13λ (λ is a wavelength in free space), respectively, when converted into a wavelength.
From the graph of FIG. 4, the relative values of the received electric field strength in the 90 ° direction are as shown in Table 1 below.
[0017]
[Table 1]

[0018]
The received electric field strength is lower than the received electric field strength in the −90 ° direction without the shielding plate 4. This reduction amount is also shown in Table 1.
According to Table 1, the received electric field strength in the 90 ° direction is sufficiently reduced to −43 dB, −49 dB, −55 dB, and −54 dB, respectively, compared with the received electric field strength in the 0 ° direction. The wraparound can be prevented.
Also, the received electric field strength in the 90 ° direction is sufficiently reduced to −16 dB, −14 dB, −18 dB, and −8 dB, respectively, compared with the received electric field strength in the −90 ° direction without the shielding plate 4. This is the effect of installing the shielding plate.
2. Shielding plate mounting structure Next, a shielding plate mounting structure of an offset parabolic antenna for broadcast wave relay related to the present invention will be described.
[0019]
FIG. 5 is a perspective view of a broadcast wave relay offset parabolic antenna. The broadcast wave relay offset parabolic antenna has a base 5 for attaching the offset parabolic reflector 1 to a steel tower and a frame 6 to which the shielding plate 4 is fixed. The frame 6 is attached to the base 5 so as to be rotatable about the support shafts 5 a and 5 b provided on the base 5. A stay 7 for holding the posture of the frame 6 is stretched between the upper end portion of the base 5 and the frame 6. The tip of the stay 7 can be rotated through the support shafts 6 a and 6 b of the frame 6. The base end portion of the stay 7 is detachable from the base body 5.
[0020]
In FIG. 5, the shielding plate 4 is depicted as being transparent, but actually, it is formed of a plurality of grids as described above. Moreover, illustration of the member which attaches the primary radiator 2 to the shielding board 4 is abbreviate | omitted.
FIGS. 6A and 6B are side views showing a state where an offset parabolic antenna for relaying a broadcast wave is fixed to a steel tower 8. FIG. 6A shows a state when the antenna is used, and FIG. 6B shows a state where the frame 6 is flipped up. .
[0021]
When the antenna is used, the base end portion of the stay 7 is attached to the base 5 as shown in FIG. The attachment method is not limited, but for example, fitting with a bolt can be employed.
At the time of maintenance of the primary radiator 2 and the two-dipole antenna 3, the base end portion of the stay 7 is detached, and the frame 6 is rotated around the support shafts 5a and 5b to jump up. FIG. 6 (b) shows the state of the jump. In FIG. 6 (b), the frame 6 is rotated approximately 90 degrees upward until the tip of the frame 6 reaches the steel tower 8. In this state, the operator can maintain the primary radiator 2 and the 2-dipole antenna 3 at a position on the steel tower 8.
[0022]
Although the embodiment of the present invention has been described above, the embodiment of the present invention is not limited to the above-described embodiment. For example, the base end portion of the stay 7 is attached to the steel tower 8 instead of the base 5. Also good. In addition, various changes can be made within the scope of the present invention.
[0023]
【The invention's effect】
As described above, according to the present invention, when maintaining the primary radiator with the offset parabolic antenna for broadcasting wave relay attached to the steel tower, the entire frame is rotated and the primary radiator is held near the operator. Can come. Therefore, it is not necessary for the worker to go around in front of the parabolic antenna, which can contribute to the safety and efficiency of the work.
[Brief description of the drawings]
FIGS. 1A and 1B are a front view and a side view of a broadcast wave relay offset parabolic antenna. FIGS.
FIG. 2 is a perspective view of a broadcast wave relay offset parabolic antenna.
3 is a front view (a) and a side sectional view (b) of a two-dipole antenna 3. FIG.
FIG. 4 is a graph showing the result of calculating the received electric field strength.
FIG. 5 is a perspective view showing a structure for attaching a shielding plate of a broadcast wave relay offset parabolic antenna.
FIGS. 6A and 6B are side views showing a state where an offset parabolic antenna for broadcasting wave relay is fixed to a steel tower, where FIG. 6A shows a state when the antenna is used, and FIG. 6B shows a state where a shielding plate is flipped up.
FIG. 7 is a schematic diagram of a steel tower equipped with a repeater.
[Explanation of symbols]
1 Offset parabolic reflector 2 Primary radiator 3 2 Dipole antenna 4 Shield plate 5 Base 6 Frame 7 Stay 7
8 steel tower

Claims (2)

An offset parabolic reflector is installed opposite to the primary radiator, and a shielding plate is installed on the side where the offset parabolic reflector is not placed to block retransmitted radio waves incident from a predetermined direction different from the radio wave reception direction. Is an offset parabolic antenna for broadcast wave relay,
The offset parabolic reflector is fixed to a steel tower,
A frame in which the primary radiator and the shielding plate are integrally attached, and the frame is directed toward the arrival direction of the retransmitted radio wave with a rotation axis set to be stationary with respect to the steel tower . An offset parabolic antenna for broadcast wave relays, which is pivotable so as to open . Previous SL frame in a state of maximally rotated, broadcasting wave relay for offset parabolic antenna according to claim 1, wherein a distal end portion of the frame is contactable to a part of the tower.

Images