JP2011249920A - Antenna unit and antenna system - Google Patents

Abstract

An antenna unit is reduced in size.
An antenna unit is attached to an attachment column. Two dipole antennas 31 and 32, a feed line connecting portion 35 to which the coaxial feed line 5 extending from the wireless device 4 is connected, and the feed line connecting portion 35 to the feed portions 31d and 32d of the dipole antennas 31 and 32, respectively. And a relay power feeding unit provided in parallel electrically. The relay power supply unit includes an internal conductor and an external conductor that are electrically connected to an internal conductor and an external conductor of the coaxial power supply line 5, respectively, and includes a coaxial pipe branched from the power supply line connection unit 35. The combined impedance of the two dipole antennas 31 and 32 is substantially the same as the impedance of the coaxial feeder 5.
[Selection] Figure 3

Description

  The present invention relates to an antenna unit having a dipole antenna and an antenna system.

  The dipole antenna is suitable as a VHF band transmission antenna, for example. For this reason, the dipole antenna has been used as a transmission antenna for terrestrial analog television broadcasting in the VHF band. Conventional transmission antennas for television broadcasting in the VHF band generally have four dipole antennas arranged in multiple stages in the height direction while ensuring omnidirectionality. Such a transmission antenna for terrestrial analog television broadcasting in the VHF band is described in Non-Patent Document 1, for example.

Yasada Shimizu, Antenna Learned with Photographs, Telecommunications Promotion Foundation, May 27, 2002

The conventional transmission antenna for television broadcasting has a weight of about 75 kg on the surface of the antenna 1 and the width of the surface of the antenna 1 is about 1 m. Therefore, in order to assemble such an antenna in multiple stages in the height direction, A huge steel tower was required, and it was difficult to simply install an antenna on the rooftop of a building or a small steel tower.
However, since a large number of transmission antennas for television broadcasting are not installed, even if the steel tower to which the antennas are assembled is huge, it is allowed.

On the other hand, when the VHF band is released to other uses as the television broadcast shifts from the terrestrial analog broadcast to the terrestrial digital broadcast, antennas may be installed in more places than in the case of the television broadcast. May be required. However, as described above, conventionally, there was only a large steel tower with an antenna assembled, and there was no technology for simply installing an antenna on a rooftop of a building or the like, or installing it on a small steel tower. .
Therefore, an object of the present invention is to provide a new technique for reducing the size of an antenna system.

(1) The present invention is an antenna unit that is attached to a mounting column, and includes a plurality of dipole antennas, a feed line connecting portion to which a coaxial feed line extending from a radio is connected, and a plurality of dipoles from the feed line connecting portion. A plurality of relay power supply portions provided in parallel to the respective power supply portions of the antenna, and each of the relay power supply portions is electrically connected to an inner conductor and an outer conductor of the coaxial power supply line, respectively. It has an inner conductor and an outer conductor to be connected, and is composed of a coaxial tube branched from the feeder line connecting portion, and the combined impedance of the plurality of dipole antennas is substantially equal to the impedance of the coaxial feeder line. And

According to the present invention, since the power supply line connecting portion to which the coaxial power supply line from the wireless device is connected is provided, even if the antenna unit has a plurality of dipole antennas, each dipole antenna has a coaxial power supply line. It is not necessary to connect the power supply line. Therefore, the number of coaxial feeders extending to the antenna unit can be reduced.
In addition, since the combined impedance of multiple dipole antennas is approximately the same as the impedance of the coaxial feeder, there is no need for a matching transformer for impedance matching even if there are multiple dipole antennas. It has been. In other words, in the present invention, the impedance of each dipole antenna is set to be larger than the impedance of the coaxial feed line, so that the combined impedance of a plurality of dipole antennas connected in parallel is the impedance of the coaxial feed line. It is small until it almost matches.
If the impedances of the plurality of dipole antennas are set to substantially the same value, assuming that the number of dipole antennas is n and the impedance of the coaxial feeder is Z, the impedance of each dipole antenna is approximately n times Z. And it is sufficient. In this case, the combined impedance of the plurality of dipole antennas is substantially Z, and substantially coincides with the impedance of the coaxial feeder.

  Further, the relay power feeding part is composed of a coaxial tube having an inner conductor and an outer conductor that are electrically connected to the inner conductor and the outer conductor of the coaxial feeding line, respectively, and the feeding part of each of the feeding line connecting part and the plurality of dipole antennas. Is connected by the coaxial pipe branched from the feed line connection section, and thus the power from the coaxial feed line is distributed in a coaxial state and supplied to the feed sections of each of the dipole antennas, and the antenna performance is improved. It becomes possible to improve.

(2) Moreover, this invention is an antenna unit attached to a mounting support | pillar, Comprising: A plurality of dipole antennas, a feed line connection part to which a coaxial feed line extending from a radio is connected, and a plurality of the feed line connection parts A plurality of relay feed portions provided in parallel to the feed portions of the respective dipole antennas, and each of the relay feed portions is electrically connected to an internal conductor of the coaxial feed line. The parallel impedance of the conductive member and the conductive member electrically connected to the outer conductor of the coaxial feeder line, and the combined impedance of the plurality of dipole antennas substantially match the impedance of the coaxial feeder line. It is characterized by being.

According to the present invention, since the power supply line connecting portion to which the coaxial power supply line from the wireless device is connected is provided, even if the antenna unit has a plurality of dipole antennas, each dipole antenna has a coaxial power supply line. It is not necessary to connect the power supply line, and it is sufficient to connect the coaxial power supply line to the power supply line connection part. Therefore, the number of coaxial feeders extending to the antenna unit can be reduced.
In addition, since the combined impedance of multiple dipole antennas is approximately the same as the impedance of the coaxial feeder, there is no need for a matching transformer for impedance matching even if there are multiple dipole antennas. It has been. In other words, in the present invention, the impedance of each dipole antenna is set to be larger than the impedance of the coaxial feed line, so that the combined impedance of a plurality of dipole antennas connected in parallel is the impedance of the coaxial feed line. It is small until it almost matches.
If the impedances of the plurality of dipole antennas are set to substantially the same value, assuming that the number of dipole antennas is n and the impedance of the coaxial feeder is Z, the impedance of each dipole antenna is approximately n times Z. And it is sufficient. In this case, the combined impedance of the plurality of dipole antennas is substantially Z, and substantially coincides with the impedance of the coaxial feeder.

  Furthermore, the relay power supply unit is composed of two parallel lines of a conductive member electrically connected to the inner conductor of the coaxial power supply line and a conductive member electrically connected to the outer conductor of the coaxial power supply line. And the feeding parts of each of the plurality of dipole antennas are connected by the parallel two lines. As described above, the relay power feeding portion is formed of two parallel wires, so that the structure is simplified and it is possible to contribute to the weight reduction of the antenna unit.

(3) Also, holding the plurality of dipole antennas so that the plurality of dipole antennas are positioned around the mounting column at substantially the same height as the mounting column when mounted to the mounting column. It is preferable to further include a member.
In this case, since the plurality of dipole antennas are positioned around the mounting column at the same height of the mounting column, directivity in multiple directions around the mounting column is ensured.

(4) Each of the antenna units further includes a holding member that attaches a plurality of the dipole antennas to a periphery of a mounting column, and each of the plurality of dipole antennas includes a first antenna element, a second antenna element, A first terminal portion that is electrically connected to the inner conductor of the coaxial feed line connected to the feed line connection portion via the relay feed portion and feeds power to the first antenna element, and is connected to the feed line connection portion. A second terminal portion that is electrically connected to the outer conductor of the coaxial feeder via the relay feeder and feeds power to the second antenna element; a first parallel conductor extending from the first terminal portion; A second parallel conductor extending in parallel with the first parallel conductor and extending from the second terminal portion, and a short-circuit conductor short-circuiting the first parallel conductor and the second parallel conductor Preferably it has.

A dipole antenna is a load in balanced mode. However, if a coaxial feed line that is an unbalanced system is connected directly to this dipole antenna, a lot of unwanted radiation is generated due to the difference in transmission mode, and the cross-polarized wave component becomes large. The antenna performance may not be obtained.
Therefore, in each of the plurality of dipole antennas, the first parallel conductor extending from the first terminal portion, the second parallel conductor extending from the second terminal portion in parallel with the first parallel conductor, and the first parallel conductor By providing a short-circuit conductor that short-circuits the second parallel conductor, the inner conductor and the outer conductor of the coaxial feeder are connected to the dipole antenna by a balanced transmission line. It has been found that this configuration makes it possible to reduce cross polarization and obtain desired antenna performance.
As a result, there is no need to provide a conventionally known balanced / unbalanced conversion circuit section between each of the plurality of dipole antennas attached to the periphery of the mounting column by the holding member and the feeder connection section. The dipole antenna can be installed close to the feeder connection portion, and the antenna unit can be downsized while obtaining desired antenna performance.

(5) Further, the present invention is an antenna system in which a plurality of antenna units are arranged side by side in the height direction of the mounting column, and the antenna unit is any one of (1) to (4). It is the antenna unit described.
According to the present invention, since each antenna unit is reduced in size, the antenna system can also be reduced in size. Further, a plurality of antenna units are arranged in the height direction of the mounting column to be multi-staged, so that the gain can be increased.

  According to the present invention, a miniaturized antenna unit and antenna system can be obtained.

It is a perspective view which shows the antenna system installed on the roof of a building. It is a figure which shows the wiring of the main electric power feeding line to several antenna units. It is a perspective view of an antenna unit. It is the perspective view which showed a part of folding | turning dipole antenna. FIG. 4 is a side view of a folded dipole antenna on the right side of FIG. 3. It is sectional drawing which looked at the antenna unit from the top. It is a front view which shows a part of antenna unit. It is explanatory drawing which shows the balance-unbalance conversion circuit part using a branch conductor. It is a schematic diagram of the structure corresponding to the dipole antenna of this embodiment. It is a graph which shows the horizontal surface directivity of the antenna of this embodiment. It is a graph which shows the horizontal surface directivity by the structure of a comparative example. It is a graph which shows the relationship between a frequency and VSWR. It is a polar chart which shows the relationship between a short circuit position and the change of an impedance. It is a figure which shows the XY orthogonal coordinate system of the horizontal surface which uses an attachment support | pillar as a coordinate center. It is a perspective view which shows other embodiment of an antenna unit. It is the figure which showed the simulation result about horizontal plane directivity, (a) is the case where it supplies with a coaxial pipe | tube, (b) is the case where it supplies with two parallel lines. It is the figure which showed the simulation result of VSWR, (a) is a case where it supplies with a coaxial pipe | tube, (b) is a case where it supplies with two parallel lines.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[1. Overall configuration of antenna system]
FIG. 1 shows an example in which an antenna system 1 according to the present invention is installed on the roof of a building B. This antenna system 1 is a vertically polarized omnidirectional antenna in the VHF band, and is configured by providing a plurality of antenna units 3 in the height direction of the mounting column 2 in order to increase the gain.

The mounting column 2 is a cylindrical metal pole having a diameter of about 40 to 114.3 mm and a height of about 5 to 6 m, and is smaller than a conventional television tower. Note that the shape of the support is not limited to a circle, and may be a quadrangular prism or the like.
This support | pillar 2 is comprised by connecting several division | segmentation support | pillars 2a and 2b in the height direction. Therefore, it is possible to transport the antenna to the installation site of the antenna system in a state where the plurality of split columns 2a and 2b are separated.

  In the present embodiment shown in FIG. 1, the antenna unit 3 is provided on the mounting column 2 in four steps in the vertical direction (four pieces). As shown in FIG. 2, the antenna system 1 includes a feeder (main feeder) that connects the antenna units 3 in parallel from the feeder terminal (coaxial cable terminal) 4 a of the radio (transceiver) 4. 5a, 5b, 5c, 5d. Each of these main feed lines 5a, 5b, 5c, 5d is configured by a coaxial feed line (hereinafter also referred to as a coaxial cable). When representatively explaining using one of the main power supply lines 5a, 5b, 5c, and 5d, the reference numeral of the main power supply line is 5.

  The plurality of main power supply lines 5 a, 5 b, 5 c, 5 d are connected to the power supply line terminal 4 a of the wireless device 4 by connecting one end sides of the plurality of main power supply lines 5 a, 5 b, 5 c, 5 d together. 6e and the other end side of each of the main feed lines 5a, 5b, 5c, 5d are connected to feed line connection parts (coaxial cable terminals) 35 provided in each of the plurality of antenna units 3. Antenna unit side end portions 6a, 6b, 6c, and 6d. In the present embodiment, a plurality of main feed lines 5a, 5b, 5c, 5d extend from the input origin 6e in a star shape (radial), but one main feed line extends from the input origin 6e, Further, a tournament type may be used in which the main power supply lines are branched into two main power supply lines, and the two main power supply lines are further branched into two to form a total of four main power supply lines.

[2. Configuration of antenna unit]
As shown in FIG. 3, each antenna unit 3 has a plurality (two in the present embodiment) of folded dipole antennas 31 and 32. The folded dipole antennas 31 and 32 have dipole body portions 31a and 32a and folded portions (folded elements) 31b and 32b, respectively, arranged in parallel. The dipole main body portions 31a and 32a and the folded portions 31b and 32b are connected to each other at both longitudinal ends (upper and lower ends) via connection portions (first connection members) 31c and 32c.
The dipole main body portions 31a and 32a, the folded portions 31b and 32b, and the connection portions 31c and 32c are made of a bar material or a plate material made of a copper alloy such as aluminum or brass, or a metal material (conductor) such as iron.

The length of the folded dipole antennas 31 and 32 in the longitudinal direction (vertical direction) is set to a length of 0.37λ (where λ is the wavelength of the transmission radio wave). For example, in the case of 214 MHz which is the VHF band, the wavelength λ is about 1400 mm (1400.9), and therefore the length of the folded dipole antennas 31 and 32 in the longitudinal direction is about 520 mm.
Each of the folded dipole antennas 31 and 32 has a longitudinal direction oriented in the vertical direction (vertical direction), and functions as a vertically polarized antenna.

The dipole main body portions 31a and 32a have power feeding portions 31d and 32d at the longitudinal center (vertical center), respectively.
In FIG. 3, the left power feeding portion 31 d has a pair of first and second terminal portions 31 d-1 and 31 d-2 connected to the main power feeding line side arranged at intervals in the longitudinal direction of the dipole main body portion 31 a. Is made up of. In the right power supply portion 32d, a pair of first and second terminal portions 32d-1 and 32d-2 connected to the main power supply line side are arranged with a gap in the longitudinal direction of the dipole main body portion 32a. Is made up of.

Accordingly, the dipole main body portions 31a and 32a have the first antenna elements 31a-1 and 32a-1 on one side in the longitudinal direction and the second antenna on the other side in the longitudinal direction with the power feeding portions 31d and 31d interposed therebetween, respectively. Antenna elements 31a-2 and 32a-2 are provided.
The first antenna elements 31a-1, 32a-1 and the second antenna elements 31a-2, 32a-2 are electrically connected to the folded portions 31b, 32b through the connection portions 31c, 32c, respectively.
The first terminal portions 31d-1 and 32d-1 are provided at the end portions of the first antenna elements 31a-1 and 32a-1 on the second antenna elements 31a-2 and 32a-2 side, The first antenna elements 31a-1, 32a-1 and the first terminal portions 31d-1, 32d-1 are electrically connected, and the first antenna elements 31a-2, 32a-2 are the first antennas. Second terminal portions 31d-2 and 32d-2 are provided at the end portions of the elements 31a-1 and 32a-1, and the second antenna elements 31a-2 and 32a-2 and the second terminal portion 31d- are provided. 2 and 32d-2 are electrically connected.

  Insulating members (synthetic resin materials) 31e and 32e are attached between the first terminal portions 31d-1 and 32d-1 and the second terminal portions 31d-2 and 32d-2. Since the insulating members 31e and 32e are provided, the dipole body portion is secured while the space is secured between the first terminal portions 31d-1 and 32d-1 and the second terminal portions 31d-2 and 32d-2. Each of 31a and 32a has a single continuous bar shape, and the folded dipole antennas 31 and 32 as a whole have a closed loop shape with no open portion, and high strength can be obtained with a simple structure.

Reinforcing members (second connecting members) 31f and 32f are provided between the insulating members 31e and 32e and the longitudinal center portions 31h and 32h of the folded portions 31b and 32b. The reinforcing members 31f and 32f are made of a bar material or a plate material of a metal material (conductor) such as aluminum, copper alloy such as brass, or iron like the dipole main body portions 31a and 31b, and the folded dipole antennas 31 and 32. Are disposed at right angles to the folded portions 31d and 32d at the longitudinal center portions 31h and 32h, and are electrically connected.
The reinforcement members 31f and 32f further improve the strength of the folded dipole antennas 31 and 32, and will be described later. The reinforcement members 31f and 32f are holding members made of a metal material (conductor) bar or plate material. It is electrically connected to the mounting column 2 through 33 and has a lightning protection function.
The reinforcing members 31f and 32f are conductive, but are located in the center in the longitudinal direction of the folded dipole antennas 31 and 32, so that the presence of the reinforcing members 31f and 32 has little influence on the antenna performance.

A holding member 33 is attached to the insulating members 31e and 32e, and the holding member 33 holds the first and second folded dipole antennas 31 and 32.
The holding member 33 is for fixing the two folded dipole antennas 31 and 32 integrally and attaching the antenna unit 3 to the attachment column 2 integrally. In the present embodiment, the holding member 33 is a rod-like member extending in the horizontal direction (lateral direction) when attached to the attachment column 2, and the insulating members 31 e and 32 e of the folded dipole antennas 31 and 32 at both ends in the longitudinal direction. Is attached.
Therefore, when the antenna unit 3 is mounted on the mounting column 2 by the holding member 33, the plurality of folded dipole antennas 31 and 32 are mounted around the mounting column 2 and at the same height of the mounting column 2. Located in. Note that the holding member 33 is fixed to the mounting support 2 by, for example, welding or a fastener such as a bolt (U bolt).

Since the holding member 33 made of metal is attached to the folded dipole antennas 31 and 32 via the insulating members 31e and 32e, the holding member 33 is electrically insulated from the dipole main body portions 31a and 31b. Yes, adverse effects on antenna performance are avoided.
The reinforcing members 31f and 32f are electrically (DC-like) connected to the longitudinal center portions 31h and 32h of the folded portions 31b and 32b at one end in the longitudinal direction, and the other end in the longitudinal direction is held. The member 33 is electrically (DC-like) connected. And since the holding member 33 contacts the metal part of the attachment support | pillar 2 when attached to the attachment support | pillar 2, the reinforcement members 31f and 32f will be in the state earth | grounded by the attachment support | pillar 2. For this reason, the folded dipole antennas 31 and 32 are electrically connected to the mounting column 2 via the reinforcing members 31 f and 32 f and the holding member 33, and are grounded to the mounting column 2. Thereby, the lightning resistance is improved.

  FIG. 4 is a perspective view showing a part of the left and right folded dipole antennas 31 and 32. In FIG. 4, the first antenna elements 31 a-1 and 32 a-1 are removed from the first terminal portions 31 d-1 and 32 d-1 for explanation. Although the left and right folded dipole antennas 31 and 32 are symmetrical, but have the same configuration, the folded dipole antenna 32 on the right side in FIG. 3 will be described as a representative. FIG. 5 is a side view of the folded dipole antenna 32 on the right side.

The folded dipole antenna 32 has the first terminal portion 32d-1 that feeds power to the first antenna element 32a-1, and this first terminal portion 32d-1 is connected to the feed line connecting portion 35. The main conductor 5 (coaxial cable) 5 is electrically connected to the inner conductor 5i via a feeder unit 34 (inner conductor 34i) described later.
The folded dipole antenna 32 includes the second terminal portion 32d-2 that feeds power to the second antenna element 32a-2. The second terminal portion 32d-2 is connected to the feed line connecting portion 35. Are electrically connected to the outer conductor 5o of the main feeder line (coaxial cable) 5 connected to the via via a feeder unit 34 (outer conductor 34o) described later.

Further, the folded dipole antenna 32 extends in a direction away from the feeder line connecting portion 35 from the first terminal portion 32d-1, and is parallel to the first parallel conductor 12a. The first parallel conductor has a second parallel conductor 12b extending from the second terminal portion 32d-2 and a short-circuit conductor 12c short-circuiting the first parallel conductor 12a and the second parallel conductor 12b. 12b and the second parallel conductor 12b constitute a balanced transmission line.
The first parallel conductor 12a and the second parallel conductor 12b have the same shape (the same cross-sectional shape and the same length), and in the present embodiment, as shown in FIG. The first terminal portion 32d-1 is made of a single member, and the second parallel conductor 12b and the second terminal portion 32d-2 are made of a single member, so that the dipole antenna 32 can be easily assembled.

The first parallel conductor 12a that is a linear member is disposed between the first antenna element 32a-1 and the folded portion 32b, and the second parallel conductor 12b that is a linear member is the second antenna element 32a−. 2 and the folded portion 32b. The first parallel conductor 12a and the second parallel conductor 12b extend in a direction orthogonal to the longitudinal direction of the first and second antenna elements 32a-1 and 32a-2.
The first parallel conductor 12a, the second parallel conductor 12b, and the short-circuit conductor 12c are made of a metal material (conductor) such as aluminum, a copper alloy such as brass, or iron, like the dipole main body 32a.

The short-circuit conductor 12c is a linear member oriented in a direction parallel to the longitudinal direction of the first and second antenna elements 32a-1 and 32a-2 arranged on the same straight line. The second antenna elements 32a-1, 21a-2 and the folded portion 32b are disposed.
Therefore, as shown in FIG. 4, a hole (long hole) 32g is formed in the reinforcing member 32f, and the short-circuit conductor 12c passes through the hole 32g. With this configuration, the short-circuit member 12c is movable along the hole 32g and is supported by the midway portion of the reinforcing member 32f. The short-circuit conductor 12c and the reinforcing member 32f are in contact with each other and are electrically connected.

According to the folded dipole antenna 32, the first parallel conductor 12a, the second parallel conductor 12b, and the short-circuit conductor 12c are on the same plane as the folded dipole antenna 32, and are within the range of the folded dipole antenna 32 (within the frame). ) And can contribute to the miniaturization of the antenna unit.
As will be described later, the inner conductor 5i and the outer conductor 5o of the main feeder (coaxial cable) 5 are connected to the antenna 32 by a balanced transmission line by the first parallel conductor 12a, the second parallel conductor 12b, and the short-circuit conductor 12c. Therefore, it can have the same function as the balance-unbalance conversion circuit (balun).

Further, in the present embodiment, the short-circuit conductor 12c is configured to be changeable in position, and the short-circuit position 12a-1 with the first parallel conductor 12a and the short-circuit position 12b with the second parallel conductor 12b by the short-circuit conductor 12c. -1 can be changed in the longitudinal direction of the first parallel conductor 12a and the second parallel conductor 12b. For this purpose, the first parallel conductor 12a and the second parallel conductor 12b are formed with a long hole 12a-2 and a long hole 12b-2, and both ends of the short-circuit conductor 12c are connected to the long holes 12a-2, It is movable along 12b-2.
Furthermore, the short-circuit conductor 12c is fixed to the first parallel conductor 12a and the second parallel conductor 12b by fastening both ends thereof with, for example, screw members, and the short-circuit conductor 12c is fixed to the first parallel conductor 12a and the second parallel conductor. It is positioned at 12b and can be moved by loosening this screw member.

  In the present embodiment, the short-circuit conductor 12c is configured to be able to continuously change the position along the first parallel conductor 12a and the second parallel conductor 12b, but the long holes 12a-2 and 12b-2 Instead, although not shown, a configuration in which independent holes are intermittently formed and the position of the short-circuit conductor 12c can be changed in stages is also possible.

Thus, by moving the short-circuit conductor 12c, the impedance of the folded dipole antenna 32 can be adjusted as will be described later.
As described above, the short-circuit conductor 12c can be moved closer to or away from the power feed portion 32d, but it is preferable that the short-circuit conductor 12c is not too close to the power feed portion 32d. More specifically, for example, when the operating frequency is 214 MHz (wavelength λ is about 1400 mm), the end of the balanced transmission line (connected to the power feeding unit 32d) by the first parallel conductor 12a and the second parallel conductor 12b. The length L (see FIG. 5) from the short-circuit conductor 12c to the short-circuit positions 12a-1 and 12b-1 is preferably λ / 35 (40 mm) or more.
This is the same whether the short-circuit conductor 12c is movable as in the present embodiment or is a fixed type. In the embodiment of FIG. 3, the maximum value of the length L (see FIG. 5) is limited as a position where the short-circuit conductor 12 c does not contact the folded portion 32 b, but the maximum value of the length L is the short-circuit member The position can be up to a position where 12c contacts the folded portion 32b.
Further, in order to obtain the maximum value of the length L, the first parallel conductor 12a and the second parallel conductor 12b may be extended until they contact the folded portion 32b. In addition, the long hole (long hole 12a-2, long hole 12b-2, and long hole 32g: refer FIG. 4) for moving the short circuit member 12c is extended and formed in the folding | returning part 32b. And it is set as the structure which can remove the short circuit member 12c, and when the said short circuit member 12c is removed, the maximum value of the said length L can be obtained. That is, in this case, a part of the folded portion 31b also serves as the short-circuit member 12c.

  That is, the distance (length L) from the end on the first terminal portion 32d-1 side of the first parallel conductor 12a to the short-circuit position 12a-1 by the short-circuit conductor 12c is not less than λ / 35 (40 mm). Similarly, the distance (length L) from the end on the second terminal portion 32d-2 side of the second parallel conductor 12b to the short-circuit position 12b-1 by the short-circuit conductor 12c is less than λ / 35 (40 mm). The end positions of the long holes 12a-2 and 12b-2 (or the holes 32g) in FIG. The technical significance of this configuration will be described later.

  Further, as shown in FIG. 5, the first parallel conductor 12a and the second parallel conductor 12b are centered on the power feeding part 32d constituted by the first terminal part 32d-1 and the second terminal part 32d-2. As shown in FIG. That is, the first parallel conductor 12a and the second parallel conductor 12b are vertically symmetrical with respect to a horizontal plane passing through the center point in the longitudinal direction (vertical direction) of the folded dipole antenna 32. The reinforcing member 32f is arranged along the horizontal plane. According to this configuration, the current distribution in the folded dipole antenna 32 is vertically symmetric, and efficient radio wave radiation is possible.

  Further, in the present embodiment, the first parallel conductor 12a is connected to the first terminal portion 32d-1 such that the vertical distance between the first parallel conductor 12a and the second parallel conductor 12b is λ / 6 or less. The second parallel conductor 12b extends from the second terminal portion 32d-2. Thereby, the 1st parallel conductor 12a and 2nd parallel conductor 12b used as a balanced transmission line can be closely approached, and the function similar to a balance-unbalance conversion circuit part (balun) can be exhibited effectively as mentioned above. Can do.

  In the present embodiment, the first terminal portion 32d-1 (second terminal portion 32d-2) and the first parallel conductor 12a (second parallel conductor 12b) are arranged on the same plane. When it is difficult to bring the first parallel conductor 12a and the second parallel conductor 12b close to each other, the first terminal portion 32d-1 (second terminal portion 32d-2) and the first parallel conductor 12a (second parallel conductor 12b) A step (bending portion) may be provided in the vertical direction between them.

FIG. 6 is a cross-sectional view of the antenna unit 3 as viewed from above. The two folded dipole antennas 31 and 32 are attached to the attachment strut 2 by the holding member 33 so as to be arranged symmetrically across a virtual vertical plane F passing through the center line O of the attachment strut 2. .
The left and right first parallel conductors 11a and 12a of the pair of folded dipole antennas 31 and 32 adjacent to the left and right across the virtual vertical plane F are arranged symmetrically with respect to the virtual vertical plane F. The second parallel conductors 11b and 12b are arranged symmetrically with respect to the virtual vertical plane F.
According to this configuration, the directivity of the pair of adjacent folded dipole antennas 31 and 32 can be made equal, and the directivity of the horizontal plane can be easily made non-directional. Note that the arrangement of the left and right short-circuit conductors 11c and 12c is adjusted in the X-axis direction in FIG. 6 and therefore may not be symmetrical with respect to the virtual vertical plane F.

[2.1 Configuration of feeding unit of antenna unit (first form)]
FIG. 7 is a front view showing a part of the antenna unit 3. The antenna unit 3 includes a feeding unit 34 between the antennas 31 and 32 for feeding power to the two folded dipole antennas 31 and 32, respectively.
The power supply unit 34 is branched from the power supply line connection portion 35 to which the antenna unit side end portion 6 of the main power supply line (coaxial cable) 5 extending from the wireless device 4 (see FIG. 1) is connected. And a branch feed line 36 extending in parallel to the feed parts 31d and 32d of the plurality of dipole antennas 31 and 32, respectively. By connecting the main power supply line (coaxial cable) 5 to the power supply line connection part 35, power can be supplied to the folded dipole antennas 31 and 32 in cooperation with the branch power supply part 36.

  In the present embodiment, one antenna unit 3 includes two dipole antennas 31 and 32. However, since the antenna unit 3 includes a common feeder connection portion 35 for the dipole antennas 31 and 32, wireless communication is performed. The number of feed lines (main feed lines) extending in parallel from the machine 4 is not necessarily the number corresponding to the total number of dipole antennas 31 and 32 (eight in this embodiment). A corresponding number (four in this embodiment) is sufficient.

  Since the main feed line 5 is a coaxial cable, the feed line connecting portion 35 has a coaxial terminal 35a to which the connection terminal (antenna unit side end portion 6) of the coaxial cable can be connected, and the coaxial terminal 35a. The main power supply line 35 b extends from the power supply line to the branch power supply line. The main feeder 35b has an inner conductor 35bi and an outer conductor 35bo like the coaxial cable 5, and is formed as a coaxial tube in which the inner conductor 35bi and the outer conductor 35bo are coaxially arranged. The inner conductor 5bi and the outer conductor 35bo of the main feeder line 35b are connected to the inner conductor 5i and the outer conductor 5o of the main feeder line 5 via a coaxial terminal 35a, respectively.

  The impedance of the main power supply line 35b is set so as to substantially match the impedance of the main power supply line 5. For example, if the impedance of the main power supply line 5 is 50Ω, the main power supply line 35b is also 50Ω. . Therefore, the main power supply line 35b and the main power supply line 5 are impedance matched, and no matching transformer is required between them. For this reason, the main feeder 35b can be shortened regardless of the wavelength, and can be shortened to the minimum dimension required for attachment. In general, the impedance of the coaxial cable is 50Ω or 75Ω.

  The branch power supply line 36 is bifurcated from the main power supply line 35 b via a branch part 37. The branch feed line 36 includes a first branch feed line 36a that branches to the first folded dipole antenna 31 side and a second branch feed line 36b that branches to the second folded dipole antenna 32 side. The first and second branch power supply lines 36a and 36b have internal conductors 36ai and 36bi and external conductors 36ao and 36bo, respectively, like the main power supply line 35b, and these internal conductors 36ai and 36bi and external conductors, respectively. 36ao and 36bo are formed as coaxial tubes arranged coaxially. Each of the first branch feeder line 36a and the second branch feeder line 36b includes a relay feeder section provided in parallel from the feeder line connection section 35 to the feeder sections 31d and 32d of the antennas 31 and 32, respectively. Become.

  The impedance of each of the first and second branch power supply lines 36 a and 36 b is set to approximately twice the impedance of the main power supply line 35 b or the main power supply line 5. For example, as described above, if the impedances of the main feeder 5 and the main feeder 35b are 50Ω, the impedances of the first and second branch feeders 36a and 36b are 100Ω.

Here, when viewed from the main power supply line 35b or the main power supply line 5, the first and second branch power supply lines 36a and 36b are connected in parallel. Therefore, the combined impedance of the first and second branch power supply lines 36a and 36b viewed from the main power supply line 35b or the main power supply line 5 is 50Ω.
Therefore, impedance matching is established between the main feeder 35b and the branch feeder 36, and a matching transformer is not required between them.
Note that the impedance of the coaxial pipe (the main feeder 35b and the branch feeders 36a and 36b) is determined by the ratio between the diameter of the inner conductor and the diameter of the outer conductor. Therefore, the desired impedance as described above can be obtained by appropriately setting the diameter of the inner conductor or the outer conductor.

  The tips of the first and second branch feeders 36a and 36b are connected to the feeders 31d and 32d of the two folded dipole antennas 31 and 32, respectively. Specifically, the inner conductors 36ai and 36bi of the first and second power feeding portions 36a and 36b are connected to the first terminal portions 31d-1 and 32d-1 of the power feeding portions 31d and 32d, respectively. The outer conductors 36ao and 36bo of the two power feeding portions 36a and 36b are connected to the second terminal portions 31d-2 and 32d-2 of the power feeding portions 31d and 32d.

The length (electrical length) of the first branch power supply line 36a and the length (electrical length) of the second branch power supply line 36b are set to substantially coincide. Thus, by making the lengths substantially coincide, both antennas 31 and 32 have the same phase.
Further, since the impedance of the first branch feed line 36a (first folded dipole antenna 31) and the impedance of the second branch feed line 36b (second folded dipole antenna 32) are equal, the first branch feed line 36a and the first branch feed line 36a Electric power is evenly distributed to the two-branch power supply line 36b. In order to change the power distribution ratio, the impedance of the first branch feed line 36a (first folded dipole antenna 31) and the second branch feed line 36b are set so that the reciprocal of the ratio to be distributed and the combined impedance is 50Ω. The impedance of the (second folded dipole antenna 32) may be set.
Note that the number of the folded dipole antennas 31 and 32 is not limited to two in the present embodiment, but two is advantageous to ensure equal distribution to the plurality of branch feeders 36a and 36b. is there.

The impedances of the first folded dipole antenna 31 connected to the first branch feed line 36a and the second folded dipole antenna 32 connected to the second branch feed line 36b are respectively the first branch feed line 36a to the second branch feed line 36a. It is set so as to substantially coincide with the branch feeder line 36b. For example, as described above, if the impedances of the first and second branch feeders 36a and 36b are 100Ω, the impedances of the first and second folded dipole antennas 31 and 32 are also 100Ω.
Accordingly, the folded dipole antennas 31 and 32 and the branch feed lines 36a and 36b are impedance matched, and no matching transformer is required between them.

Further, when the folded dipole antennas 31 and 32 are viewed from the main feed line 5 side, the impedance (100Ω) of the folded dipole antennas 31 and 32 is substantially twice the impedance (50Ω) of the main feed line. .
Therefore, the combined impedance of the two folded dipole antennas 31 and 32 connected in parallel is 50Ω, and substantially matches the impedance (50Ω) of the main feeder 5. For this reason, no matching transformer is required between the main feeder 5 and the folded dipole antennas 31 and 32.

  The impedances of the folded dipole antennas 31 and 32 can be adjusted by adjusting the size of the members constituting the antenna or adjusting the interval. Specifically, by adjusting the diameter and interval of the dipole main bodies 31a and 32a and the folded portions 31b and 32b, the respective lengths, and the positions of the connection portions 31c and 32c (positions in the height (longitudinal direction of the antenna)), Impedance can be adjusted. Moreover, the adjustment of the impedance is further facilitated by individually adjusting the lengths of the dipole main bodies 31a and 32a and the folded portions 31b and 32b.

[2.2 Functions of the first parallel conductor, the second parallel conductor, and the short-circuit conductor]
Here, FIG. 8 is an explanatory diagram showing a general balance-unbalance conversion circuit unit using the branch conductor 81. The balance-unbalance conversion circuit section is parallel to the coaxial power supply line (coaxial cable) 82, and a branch conductor 81 having the same diameter as the coaxial power supply line 82 is disposed. One end side of the branch conductor 81 is short-circuited by the outer conductor 82o of the coaxial feed line 82 and the first short-circuit line 83, and the other end side of the branch conductor 81 is short-circuited with the inner conductor 82i of the coaxial feed line 82. The configuration is short-circuited by the wire 84. An antenna element 85 is connected as a load to the other end of the branch conductor 81, and an antenna element 86 is connected to the end of the outer conductor 82 o of the coaxial feeder 82.
By using this circuit unit, the unbalanced mode that is the transmission mode of the coaxial line is converted to the balanced mode that is the transmission mode of the dipole antenna, so that unnecessary radiation can be suppressed. As for the balance-unbalance conversion function by this circuit section, the literature [Keiji Endo, Gensada Sato, Atsushi Nagai, "Antenna Engineering", page 257, General Electronic Publishing Company, March 21, 1984 (3rd edition) )]It is described in.

  FIG. 9 is a schematic diagram of a configuration corresponding to the dipole antenna 32 of this embodiment (the folded dipole antenna 32 on the right side of FIG. 5). In FIG. 9, a branch feeder line 36b (hereinafter referred to as a coaxial feeder line portion 36b) made of a coaxial tube of the feeder unit 34, a first terminal portion 32d-1, a second terminal portion 32d-2, and a first parallel conductor 12a. The 2nd parallel conductor 12b, the short circuit conductor 12c, and the structure of the circumference | surroundings are shown. Note that the inner conductor 36bi of the coaxial feeder line portion 36b is electrically connected to the inner conductor of the coaxial cable 5 at the feeder line connecting portion 35 (see FIG. 7), and is also external to the coaxial feeder line portion 36b. The conductor 36bo is electrically connected to the outer conductor of the coaxial cable 5 at the feeder connection portion 35.

  In FIG. 9, the first parallel conductor that is parallel to the second parallel conductor 12b, which is the portion where the outer conductor 36bo of the coaxial feeder line portion 36b is electrically extended, has the same shape as the second parallel conductor 12b. 12a is arranged. One end side of the first parallel conductor 12a is connected to the outer conductor 36bo of the coaxial feeder line portion 36b and the short-circuit conductor 12c (and the second parallel conductor 12b), and the other end side of the first parallel conductor 12a is coaxial. This is a configuration connected to the inner conductor 36bi of the feeder line portion 36b. The first antenna element 32a-1 is connected as a load to one end of the first parallel conductor 12a, and the second antenna element 32a-2 is connected to the end of the outer conductor 36bo of the coaxial feeder line portion 36b. Has been. The first parallel conductor 12a is grounded via a reinforcing member 32f and the like.

  Thus, in FIG. 8 and FIG. 9, the balance-unbalance conversion circuit portion shown in FIG. 8 and the portion P surrounded by the two-dot chain line in FIG. 9 are considered to be substantially equivalent. In this case, the portion P surrounded by the two-dot chain line in FIG. 9 can have substantially the same function as the balanced-unbalanced conversion circuit unit in FIG.

The folded dipole antennas 31 and 32 included in the antenna system 3 of the present embodiment (FIG. 3) are balanced mode loads, and the dipole antennas 31 and 32 are branched feed lines made of coaxial tubes that are unbalanced. When 36a and 36b are directly connected, a lot of unnecessary radiation is generated due to the difference in the transmission mode, the cross polarization component becomes large, and the desired antenna performance may not be obtained.
However, each of the folded dipole antennas 31 and 32 includes the first parallel conductor 12a, the second parallel conductor 12b, and the short-circuit conductor 12c as described above, and thus has the same function as the balance-unbalance conversion circuit unit. Therefore, it is possible to reduce cross polarization and obtain desired antenna performance.

Therefore, in FIG. 3, a balance-unbalance conversion circuit section as shown in FIG. 8, that is, a coaxial feed line, is provided between the feed unit 34 (feed line connection section 35) and the folded dipole antennas 31 and 32, respectively. There is no need to provide the branch conductor 81 nearby. For example, it is not necessary to provide the branch conductor 81 between one folded dipole antenna 31 and the feeding unit 34 (feeding line connecting portion 35), and the other folded dipole antenna 32 and the feeding unit 34 (feeding line connection). It is not necessary to provide the branch conductor 81 with the portion 35).
As a result, according to the present embodiment, the two folded dipole antennas 31 and 32 can be installed close to each other, and the antenna unit 3 can be downsized.

  In order to reduce the cross-polarized wave component, if a balanced / unbalanced conversion circuit unit as shown in FIG. 8 is installed between the dipole antennas, depending on the configuration of the circuit unit, the direction of the main polarized wave May have a significant effect on sex. However, in the present embodiment, the first parallel conductor 12a (11a) and the second parallel conductor 12b (11b) are disposed between the antenna element 32a-1 (31a-1) and the folded portion 32b (31b). The first parallel conductor 12a (11a) and the second parallel conductor 12b (11b) extend in the longitudinal direction of the antenna element 32a-1 (31a-1), that is, in the direction orthogonal to the polarization direction of the antenna. Therefore, the influence on the directivity of the main polarization can be suppressed.

  The simulation result about the said function of the dipole antennas 31 and 32 by this embodiment is demonstrated. FIG. 10 shows the horizontal plane directivity of the antennas 31 and 32 of the present embodiment of FIG. On the other hand, FIG. 11 shows horizontal plane directivity by the configuration of the comparative example in which the first parallel conductor 12a, the second parallel conductor 12b, and the short-circuit conductor 12c are removed from the antenna unit 3 shown in FIG. 10 and 11, the solid line indicates the main polarization (vertical polarization), and the broken line indicates the cross polarization (horizontal polarization).

In the comparative example of FIG. 11, there is a direction (angle) in which the component difference between the main polarization and the cross polarization is less than 20 dB. In a general antenna, the cross polarization needs to be about 20 dB lower than the main polarization. This is because, for example, when an area that receives radio waves with horizontal polarization and an area that receives radio waves with vertical polarization are provided adjacent to each other, the receiving side can sufficiently discriminate between horizontal polarization and vertical polarization. This is because inconvenience occurs if it cannot be done. That is, the antenna unit 3 of the present embodiment can be used as vertical polarization, but if the component of horizontal polarization that is cross-polarization is large, it will interfere with radio waves in the region that is transmitting with horizontal polarization. This is because there is a fear.
On the other hand, in the present embodiment of FIG. 10, the difference in components between the main polarization and the cross polarization is ensured to be 20 dB or more in all directions (angles). Thus, according to the present embodiment, cross polarization can be reduced and desired antenna performance can be obtained.

  In the folded dipole antennas 31 and 32, it is possible to change the impedance of the antenna and adjust the VSWR by adjusting the length and diameter of the antenna element, the ratio of the diameter between the antenna element and the folded portion, and the distance between them. It is. However, it is also important to give good antenna characteristics to the frequency band to be used. For this reason, in the present embodiment, as described above, the first parallel conductor 12a (11a) and the first parallel conductor 12a (11a) are connected to the first short conductor 12c (11c). The short-circuit position with the two parallel conductors 12b (11b) can be changed. Thereby, the impedance of the folded dipole antenna 32 (31) can be further adjusted. Note that if the length of the antenna element is greatly changed in order to adjust the impedance, the directivity may be greatly affected. In the present embodiment, the short-circuit member 12c is not changed without changing the length of the antenna element. It is only necessary to adjust the position of (11c), and it is possible to prevent the directivity from being greatly affected.

The function of this short-circuit conductor 12c will be described. FIG. 12 is a graph showing the relationship between the frequency (horizontal axis) and the VSWR (vertical axis), showing the actual measurement result by the antenna unit 3 of the present embodiment, (a) (b) (c ) The short-circuit member 12c is moved away from the power feeding part 32d in the order of (d) (see FIG. 5). Specifically, FIG. 12A shows a case where the length L (see FIG. 5) is 70 mm, FIG. 12B shows a case where the length L is 80 mm, and FIG. 12C shows a case where the length L is 90 mm. Yes, FIG. 12D shows the case of 110 mm.
As shown in the respective graphs of FIG. 12, the lowest frequency of VSWR is 216 MHz for (a), 227 MHz for (b), 232 MHz for (c), and 236 MHz for (d). In each of (a), (b), (c), and (d), the band in which VSWR is preferable (the band in which VSWR is 1.5 or less) does not change greatly and does not narrow.
Thus, by changing the position of the short-circuit member 12c, the impedance of the folded dipole antenna 32 can be easily adjusted, and the VSWR can be improved in the frequency band to be used.

  In addition, according to the present embodiment, as described above, it can have the same function as the balance-unbalance conversion circuit unit, and unnecessary radiation from the antenna unit 3 can be suppressed. Since unnecessary radiation can be suppressed in this way, a wide band in which the VSWR of the antenna unit 3 is good can be obtained.

  Further, in the present embodiment, in FIG. 5, a balanced transmission line is configured by the first and second parallel conductors 12a and 12b which are considered to be effective because it has substantially the same function as the balanced / unbalanced conversion circuit unit. The length L from the portion, that is, the end of the balanced transmission line on the power feeding unit side to the short-circuit positions 12a-1 and 12b-1 is, as a particularly preferable case, λ / 35 (40 mm) or more as described above. Although set, this is to facilitate adjustment of impedance. That is, when the length L is less than λ / 35 (40 mm), that is, when the short-circuit positions 12a-1 and 12b-1 are close to the power feeding unit 32d, the short-circuit positions 12a-1 and 12b-1 are adjusted and changed. Then, the change in impedance becomes large, and there is a possibility that delicate adjustment (matching) of impedance becomes difficult.

A specific example of this short-circuit position will be described. FIG. 13 is a polar chart showing the relationship between the short-circuit position and the change in impedance. In FIG. 13, reference numerals 71 to 78 of arrows respectively indicate short-circuit positions 12a-1 and 12b-1 (X2 in FIG. 5) from the end (position X1 in FIG. 5) of the first parallel conductor 12a (second parallel conductor 12b). ), The distance (length L) is 0 mm, 10 mm, 20 mm, 30 mm, 40 mm, 60 mm, 80 mm, and 100 mm.
In FIG. 13, from 71 (0 mm) to 75 (40 mm), the moving pitch of the short-circuit position 12a-1 is 10 mm, but the change in impedance is large for each moving pitch. On the other hand, from reference numeral 76 (60 mm) to reference numeral 78 (100 mm), although the movement pitch of the short-circuit position 12a-1 is 20 mm, the change in impedance for each movement pitch is 10 mm. It is smaller than the case.
In other words, this means that when the distance (length L) is less than λ / 35 (40 mm), the impedance changes sensitively with respect to the change in the position of the short-circuit conductor 12c. Adjustment may be difficult.
Therefore, the distance, that is, the length L is preferably λ / 35 (40 mm) or more.

[2.3 Details of the dipole body and folded part]
FIG. 14 shows the dipole main body portions 31a and 32a, the folded portions 32a and 3b, the connecting portions 31c and 32c, and the mounting column 2 extracted from the cross-sectional view of FIG.
As shown in FIG. 14, a horizontal XY orthogonal coordinate system with the cross-sectional center O of the mounting column 2 as the coordinate center is considered. When the four quadrants of the XY rectangular coordinate system are A1, A2, A3, and A4, respectively, the dipole main body portions 31a and 32a or the folded portions 31b, 32b is present.

  With such an arrangement, the antenna unit 3 as a whole can ensure omnidirectionality even with the antenna unit 3 including only the antennas 31 and 32 arranged at the same height of the mounting column 2. That is, as in the present embodiment, when the dipole main body portions 31a and 32a and the folded portions 31b and 32b are arranged so that the longitudinal directions thereof are substantially perpendicular, the folded dipole antennas 31 and 32 are omnidirectional in the horizontal plane. A vertically polarized omnidirectional antenna.

In this arrangement, the surface 40 surrounded by the dipole main body portions 31a and 32a and the folded portions 31b and 32b (and the connection portions 31c and 32c) is a surface that is substantially perpendicular to the ground. In the present embodiment, the two folded dipole antennas 31 and 32 are disposed opposite to each other with the mounting support 2 interposed therebetween, and the substantially vertical surfaces 40 of the two folded dipole antennas 31 and 32 are respectively mounted. It faces the outer peripheral surface of the column 2.
Therefore, even if the individual antennas 31 and 32 are omnidirectional, when the mounting column 2 is metallic, the mounting column 2 functions as a reflector, and the antennas 31 and 32 are connected to the mounting column 2. Radio wave emission in the direction to go is obstructed.

However, as described above, each of the four quadrants A1, A2, A3, and A4 of the orthogonal coordinate system having the mounting column 2 as the coordinate center has at least one of the dipole main body portions 31a and 32a and the folded portions 31b and 32b. By arranging to exist, the radio wave radiation that is hindered by the mounting column 2 is complemented by another antenna. Therefore, the antenna unit 3 as a whole can secure a directivity in all directions and be an omnidirectional antenna.
That is, for example, the first radio wave radiated from the dipole main body portion 31 a of one antenna 31 toward the folded portion 32 b of the other antenna 32 is reflected by the mounting support 2 and the folded portion of the other antenna 32. Although it does not travel in the direction of 32b, instead, the second radio wave radiated from the folded portion 32b of the other antenna substitutes for the first radio wave, so that omnidirectionality can be ensured.

In order to obtain the arrangement shown in FIG. 6, the distance between the dipole main body portions 31 a and 32 a and the folded portions 31 b and 32 b (the distance in the X direction; the length of the connection portions 31 c and 32 c) The distance between the two dipole antennas 31 and 32 (the distance in the Y direction) may be made larger than the distance W1 in the Y direction of the mounting column 2.
Note that the distance between the dipole body portions 31a and 32a and the folded portions 31b and 32b may be substantially the same as the lateral width W2 of the mounting column 2 in the X direction, or the distance between the two dipole antennas 31 and 32 ( The interval in the Y direction may be substantially the same as the interval W1 in the Y direction of the mounting column 2.

[2.4 Configuration of feeding unit of antenna unit (second embodiment)]
FIG. 15 is a perspective view showing another embodiment of the antenna unit 3. The antenna unit 3 includes two folded dipole antennas 31 and 32 and a feeding unit 134 for feeding power to the antennas 31 and 32, respectively, as in the embodiment (FIG. 3). Note that the difference between the antenna unit 3 in FIG. 15 and the antenna unit 3 in FIG. 3 is the configuration of the power supply unit 134 and the power supply unit 34. In FIG. 15, the holding member 33 has left and right arm portions 33a attached to the insulating members 31e and 32e, and a plate-like portion 33b interposed between the left and right arm portions 33a. The antenna unit 3 is fixed to the mounting column 2 by the plate-like portion 33b.

The power supply unit 134 in FIG. 15 will be described.
The power supply unit 134 is provided between the antennas 31 and 32, and a power supply line connection portion 135 to which an end of a main power supply line (coaxial cable) 5 extending from the wireless device 4 (see FIG. 2) is connected, A feed relay unit 138 is provided which is provided in electrical parallel from the feed line connection unit 135 to the feed units 31 d and 32 d of the plurality of dipole antennas 31 and 32.

  The feed line connecting portion 135 includes an external conductor connecting portion 135b into which the main feed line 5 composed of a coaxial feed line (coaxial cable) is inserted and electrically connected to the external conductor 5o of the main feed line 5; And an inner conductor connecting portion 135a to which the inner conductor 5i of the electric wire 5 is electrically connected. By connecting the main power supply line (coaxial cable) 5 to the power supply line connecting part 135, it is possible to supply power to the folded dipole antennas 31 and 32 in cooperation with the power supply relay part 138.

  The power feeding relay unit 138 includes a pair of relay members 138a and 138b. Each of the relay members 138a and 138b is made of a conductive member. In the present embodiment, the relay members 138a and 138b are flat plate members extending linearly in the horizontal direction, and both are arranged in parallel.

  One end portion of the first relay member 138a is electrically connected to the first terminal portion 31d-1 of the first folded dipole antenna 31, and the other end portion of the first relay member 138a is the second end portion. Are electrically connected to the first terminal portion 32d-1 of the folded dipole antenna 32. The inner conductor connecting portion 135a, to which the inner conductor 5i of the main feeder 5 is electrically connected, is provided at the center of the first relay member 138a. In the present embodiment, the inner conductor connecting portion 135a is formed at the center portion of the first relay member 138a, and includes a hole for inserting the inner conductor 5i of the main feeder 5 and fixing it with solder or the like.

  One end portion of the second relay member 138b is electrically connected to the second terminal portion 31d-2 of the first folded dipole antenna 31, and the other end portion of the second relay member 138b is the second end portion. Are electrically connected to the second terminal portion 32d-2 of the folded dipole antenna 32. The second relay member 138b is connected to the outer conductor connecting portion 135b at the center thereof, and is electrically connected to the outer conductor 5o of the main feeder 5 via the outer conductor connecting portion 35b. Has been.

Of the first relay member 138a and the second relay member 138b, the first folded dipole antenna 31 side is closer to the first relay feed than the feed line connecting portion 135 (inner conductor connecting portion 135a, outer conductor connecting portion 135b). Part 141, and the second folded dipole antenna 32 side of the feeder line connecting part 135 (inner conductor connecting part 135a, outer conductor connecting part 135b) is the second relay feeding part 142.
Thus, the first relay power supply unit 141 and the second relay power supply unit 142 are connected from the power supply line connection unit 135 (the internal conductor connection unit 135a and the external conductor connection unit 135b) to the power supply units 31d and 32d of the antennas 31 and 32. It becomes the structure provided in parallel electrically.
The impedances of the first relay power supply unit 141 and the second relay power supply unit 142 are set to approximately twice the impedance of the main power supply line 5. For example, if the impedance of the main feeder 5 is 50Ω, the impedance of each of the first relay feeder 141 and the second relay feeder 142 is 100Ω.

  Here, as viewed from the main power supply line 5, the first relay power supply unit 141 and the second relay power supply unit 142 are connected in parallel. Therefore, the combined impedance of the first relay power supply unit 141 and the second relay power supply unit 142 viewed from the main power supply line 5 is 50Ω. Therefore, impedance matching is established between the main feeder 5 and the relay feeder 138, and no matching transformer is required between them.

Further, the first relay power supply unit 141 includes two parallel lines by a part of the first relay member 138a (left half in FIG. 15) and a part of the second relay member 138b (left half in FIG. 15). In addition, the second relay power feeding part 142 is parallel by the other part of the first relay member 138a (right half in FIG. 15) and the other part of the second relay member 138b (right half in FIG. 15). Two lines are configured. In other words, the relay power supply unit composed of the first relay power supply unit 141 and the second relay power supply unit 142 is composed of two parallel lines that are linearly provided between the power supply units 31d and 32d of the antennas 31 and 32. One (first relay member 138a) is connected to the internal conductor 5i, and the other of the two parallel wires (second relay member 138b) is connected to the internal conductor 5i.
Note that the two parallel wires on the left side (first relay power supply portion 141) are not short-circuited at their ends, and the two parallel wires on the right side (second relay power supply portion 142) are at the end portions thereof. They are not short-circuited with each other, and have different properties from the parallel two lines (balanced transmission lines) of the balanced / unbalanced circuit section.

In addition, the length (electric length) of the first relay power supply unit 141 (the two parallel lines on the left side) and the length (electric length) of the second relay power supply unit 142 (the two parallel lines on the right side) are substantially matched. Is set to Thus, by making the lengths substantially coincide, both antennas 31 and 32 have the same phase.
In addition, since the impedance of the first relay feeding unit 141 (first folded dipole antenna 31) and the impedance of the second relay feeding unit 142 (second folded dipole antenna 32) are equal, the first relay feeding unit 141 and the second The power is evenly distributed to the two relay power supply units 142.

  The impedances of the first folded dipole antenna 31 connected to the first relay feed unit 141 and the second folded dipole antenna 32 connected to the second relay feed unit 142 are the first relay feed unit 141 to the second relay feed. It is set so as to substantially match the portion 142. For example, as described above, when the impedance of each of the first and second relay power feeding units 141 and 142 is 100Ω, the impedance of each of the first and second folded dipole antennas 31 and 32 is also 100Ω. Accordingly, the folded dipole antennas 31 and 32 and the relay power feeding units 141 and 142 are impedance matched, and no matching transformer is required between them.

  Further, when the folded dipole antennas 31 and 32 are viewed from the main feed line 5 side, the impedance (100Ω) of the folded dipole antennas 31 and 32 is substantially twice the impedance (50Ω) of the main feed line. . Therefore, the combined impedance of the two folded dipole antennas 31 and 32 connected in parallel is 50Ω, and substantially matches the impedance (50Ω) of the main feeder 5. For this reason, no matching transformer is required between the main feeder 5 and the folded dipole antennas 31 and 32.

  The folded dipole antennas 31 and 32 of the embodiment of FIG. 15 are the same as the folded dipole antennas 31 and 32 of the embodiment (FIG. 3), and the folded dipole antennas 31 and 32 of FIG. Similarly to the embodiment (FIG. 3), the first parallel conductors 11a and 12a extending from the first terminal portions 31d-1 and 32d-1 and the second parallel to the first parallel conductors 11a and 12a. Second parallel conductors 11b and 12b extending from the terminal portions 31d-2 and 32d-2, and short-circuit conductors 11c and 12c short-circuiting the first parallel conductors 11a and 12a and the second parallel conductors 11b and 12b, have.

  For this reason, the embodiment of FIG. 15 can also have the same function as the balanced / unbalanced conversion circuit unit, and can reduce cross polarization and obtain desired antenna performance. Moreover, it is not necessary to provide a conventionally known balanced / unbalanced conversion circuit (λ / 4 branching conductor) between the feed line connecting portion 135 and each of the dipole antennas 31 and 32. Since they can be installed close to each other, the antenna performance can be improved and the antenna unit 3 can be downsized.

[2.5 First and second forms of power supply unit of antenna unit]
The power supply unit 34 of the first embodiment shown in FIG. 7 functions as a relay power supply unit that electrically connects the main power supply line (coaxial power supply line) 5 and the power supply units 31d and 32d of the antennas 31 and 32 in parallel. The branch power supply lines 36a and 36b are configured by a coaxial tube as described above (note that the power supply connection portion 35 is also configured by a coaxial tube), whereas the power supply of the second embodiment shown in FIG. In the unit 135, the relay power supply units 141 and 142 are configured by two parallel lines as described above.

  FIG. 16 is a diagram illustrating a simulation result of the horizontal directivity of the antenna unit 3. FIG. 16A illustrates a case where power is distributed and supplied by a coaxial tube (corresponding to the first embodiment), and FIG. This is a case where power is distributed and distributed by two parallel wires (corresponding to the second embodiment). According to FIG. 16, there is a slight difference in horizontal plane directivity between (a) the case where power is supplied by a coaxial tube and (b) the case where power is supplied by parallel two lines, but both realize omnidirectionality. It can be said that the performance is equivalent.

  FIG. 17 is a diagram showing a simulation result of VSWR. FIG. 17A shows a case where power is distributed by a coaxial tube (corresponding to the first embodiment), and FIG. 17B is distributed by two parallel lines. Is supplied (corresponding to the second embodiment). Even when (a) power is supplied by a coaxial tube or (b) power is supplied by two parallel wires, the VSWR is good in a wide frequency band. That is, a wide band in which VSWR is 1.5 or less is secured. In particular, when (a) power is supplied through a coaxial tube, the VSWR is improved in a wider frequency band than in the case of (b) parallel two lines. That is, the performance of the antenna is higher when power is supplied through the coaxial tube.

However, when the structure is compared between FIG. 7 and FIG. 15, the structure of the feeding unit can be simplified in the case of the parallel two lines (FIG. 15) than in the case of the coaxial tube (FIG. 7). Further, the use of two parallel wires can reduce the weight.
In particular, in FIG. 7, a large block material is used for the branch portion 37. In other words, the block material is processed by cutting to form the branch portion 37 that connects the branch feed lines 36a and 36b and the main feed line 35b made of a coaxial tube, and the structure is relatively complicated.
For example, brazing is performed in order to connect the branch power supply lines 36 a and 36 b and the main power supply line 35 b to the branch portion 37. In order to reduce the weight of the branch part 37 (and the power supply lines 36a, 36b, and 35b), it can be made of aluminum. However, in this case, the brazing operation is difficult and requires manufacturing time, so that the manufacturing cost May increase. For this reason, in order to make brazing comparatively easy, the branch part 37 can be made into brass, However In this case, a weight will become large.
However, when the parallel two lines are employed, the structure is simple and the manufacture is facilitated.

  As described above, when the coaxial tube (FIG. 7) is used, the performance of the antenna can be improved, but it is inferior to the case of using two parallel wires (FIG. 15) in terms of manufacturing or weight reduction. That is, in the case of using two parallel lines (FIG. 15), brazing can be eliminated, and as a result, aluminum can be adopted for the power supply unit 135, which is excellent in terms of manufacturing and weight reduction. ing. However, it is somewhat inferior in terms of antenna performance as compared with the case using a coaxial tube (FIG. 7).

[3. Antenna system including the antenna unit of each embodiment]
As described above, according to the antenna unit 3 of each of the above embodiments, the antenna unit 3 can be reduced in size and weight. For this reason, the diameter of the mounting column 2 can be reduced.
Therefore, as shown in FIG. 1, the antenna system 1 of the present embodiment has a configuration in which a plurality of the antenna units 3 are arranged in the height direction of the mounting support 2 in addition to the mounting support 2. The system 1 can also be reduced in size and weight. Furthermore, omnidirectionality can be ensured with a small number of antennas 31 and 32, and a plurality of antenna units 3 are arranged in the height direction of the mounting column 2 to be multistaged, so that the gain can be increased.

[4 Other antenna units]
Moreover, according to the invention described below, the problem of downsizing the antenna system can be solved. That is, referring to FIG. 3 (FIG. 15), the invention is an antenna unit 3 attached to the attachment column 2, and is connected to a plurality of dipole antennas 31 and 32 and a coaxial feeder 5 extending from the radio unit 4. A plurality of feed line connecting portions 35 (135) and a plurality of dipole antennas 31 and 32 that are electrically connected in parallel to the feed line connecting portions 35 (135). A combined power supply unit, and a combined impedance of the plurality of dipole antennas 31 and 32 substantially matches an impedance of the coaxial power supply line 5.

  In the embodiment of FIG. 3, the relay power supply unit is a branch power supply line 36 (first branch power supply line 36 a and second branch power supply line 36 b). In the embodiment of FIG. 15, the relay power supply unit is These are the first relay power supply unit 141 and the second relay power supply unit 142.

According to the present invention, since the feed line connecting portion 35 (135) to which the coaxial feed line 5 from the wireless device 4 is connected is provided, the antenna unit 3 has a plurality of dipole antennas 31 and 32. It is not necessary to connect the coaxial feed line 5 to each dipole antenna, and it is sufficient to connect the coaxial feed line 5 to the feed line connecting portion 35 (135). Therefore, the number of coaxial feeders 5 extending to the antenna unit 3 can be reduced.
In addition, since the combined impedance of the plurality of dipole antennas 31 and 32 substantially matches the impedance of the coaxial feeder 5, no matching transformer is required for impedance matching even if the plurality of dipole antennas 31 and 32 are provided. Therefore, downsizing is achieved.
In the present invention, the other configurations are the same as those in the above-described embodiments.

In addition, with respect to the present invention, the embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is not meant to be described above, but is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.
For example, the antenna system of the present invention is not limited to the one installed on the roof of a building, and can be installed in any place. Further, the number of antenna units attached to the attachment column is not particularly limited.

  1: Antenna system 2: Mounting column 3: Antenna unit 5a to 5c: Main feed line (coaxial feed line) 5i: Inner conductor 5o: Outer conductor 11a: First parallel conductor 11b: Second parallel conductor 11c: Short-circuit conductor 12a: 1st parallel conductor 12b: 2nd parallel conductor 12c: Short circuit conductor 31: Dipole antenna 31a-1: 1st antenna element 31a-2: 2nd antenna element 31d: Feed part 31d-1: 1st terminal part 31d- 2: 2nd terminal part 32: Dipole antenna 32a-1: 1st antenna element 32a-2: 2nd antenna element 32d: Feed part 32d-1: 1st terminal part 32d-2: 2nd terminal part 33: Holding member 35: Feed line connecting portion 35a: Coaxial terminal 36: Branch feeding Wire (relay feeding portion) 36ai: Internal conductor 36ao: External conductor 36bi: Internal conductor 36bo: External conductor 135: Feed line connecting portion 138a: Relay member (conductive member) 138b: Relay member (conductive member) 141: First relay power supply Unit 142: Second relay power feeding unit

Claims (5)

An antenna unit that can be attached to a mounting column,
Multiple dipole antennas,
A feed line connecting portion to which a coaxial feed line extending from the radio is connected;
A plurality of relay power feeding units provided in parallel from the feeding line connection unit to each power feeding unit of the plurality of dipole antennas,
With
Each of the relay feeding parts has an inner conductor and an outer conductor that are electrically connected to an inner conductor and an outer conductor of the coaxial feeding line, respectively, and consists of a coaxial pipe branched from the feeding line connection part,
The antenna unit, wherein a combined impedance of the plurality of dipole antennas substantially matches an impedance of the coaxial feeder. An antenna unit that can be attached to a mounting column,
Multiple dipole antennas,
A feed line connecting portion to which a coaxial feed line extending from the radio is connected;
A plurality of relay power feeding units provided in parallel from the feeding line connection unit to each power feeding unit of the plurality of dipole antennas,
With
Each of the relay power supply units is composed of two parallel lines of a conductive member electrically connected to the inner conductor of the coaxial power supply line and a conductive member electrically connected to the outer conductor of the coaxial power supply line,
The antenna unit, wherein a combined impedance of the plurality of dipole antennas substantially matches an impedance of the coaxial feeder.   A holding member that holds the plurality of dipole antennas is further provided so that the plurality of dipole antennas are positioned around the mounting column at substantially the same height as the mounting column when the plurality of dipole antennas are mounted on the mounting column. The antenna unit according to claim 1 or 2. A holding member for attaching the plurality of dipole antennas to the periphery of the mounting column, further comprising:
Each of the plurality of dipole antennas is electrically connected to the first antenna element, the second antenna element, the inner conductor of the coaxial feed line connected to the feed line connecting portion and the relay feed portion, and A first terminal that feeds power to the first antenna element, and an external conductor of the coaxial feed line connected to the feed line connecting part and the relay feed part are electrically connected to the second antenna element. A second parallel portion extending from the first terminal portion, a first parallel conductor extending from the first terminal portion, a second parallel conductor extending in parallel with the first parallel conductor, and the first parallel conductor The antenna unit according to any one of claims 1 to 3, further comprising a short-circuit conductor that short-circuits the second parallel conductor. 2. An antenna system in which a plurality of antenna units are provided side by side in the height direction of a mounting column, wherein the antenna unit is the antenna unit according to claim 1.

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