JP2003152425A - Antenna unit, antenna device, and broadcasting tower - Google Patents

Abstract

PROBLEM TO BE SOLVED: To exhibit the wide band properties of a stacked loop antenna element itself sufficiently while sustaining the directivity of a stacked loop antenna commonly used presently. SOLUTION: The antenna unit comprises two 2L antenna elements 1 and 2 forming two loop antenna elements, a feeder line 4 for transmitting power to each 2L antenna element 1, 2, and a coaxial tube 3 interposed between each 2L antenna element 1, 2, and the feeder line 4 while dividing the feeder line 4 into two branches being connected directly with the feeding point of each 2L antenna element 1, 2 and having a characteristic impedance equal to two times that of the feeder line 4 and substantially equal to the impedance of each 2L antenna element 1, 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antenna unit, an antenna device, and a broadcast that can exhibit the wideband characteristics of a 2L antenna element itself that forms 2N (N is a natural number) loops having wideband characteristics in the UHF band. It is about the tower.

[0002]

2. Description of the Related Art In the near future, digital terrestrial broadcasting will reach UH
It starts in the F band. A twin loop antenna is often used as a UHF band transmission antenna in the current analog broadcasting, and is designed according to each frequency. It is considered that the digitization of the UHF band, unlike analog broadcasting, is progressing with network development on the same time axis. For this reason, satellite stations tend to construct antenna systems jointly with other companies. Therefore, in order to reduce the antenna cost, a wideband antenna that can cover a plurality of channels is effective. On the other hand, considering analog / analog conversion in the transition period before the start of digital broadcasting,
A broadband antenna is considered essential.

FIG. 16 is a plan view of a conventional twin loop antenna, and FIG. 17 is a right side view of the conventional loop antenna. The loop antenna 100 is an arc-shaped loop whose peripheral length is approximately the wavelength λ of the transmission frequency on a flat plate-shaped reflector 106 that is bent at both edges along the longitudinal direction at approximately 45 ° and forms a main surface. The loop antenna having the antenna elements 101 to 104 is unidirectionally transmitted in a direction perpendicular to the main surface. The loop antenna 10
Reference numeral 0 is a 4L loop antenna in which the four loop antenna elements 101 to 104 are fed from one feed line 108.

[0004]

By the way, although the loop antenna has wide band characteristics, the loop antenna element 1
01 to 104 are parallel lines, and a coaxial line having a characteristic impedance of 50Ω or 75Ω is used on the feeder line side. Therefore, as shown in FIG. 18A, the loop antenna elements 101 to 104 and the feeder line are connected. Between baluns (balance-
An unbalance conversion circuit: balun) circuit 202 is provided.
Although the balun circuit 202 is not provided between the normal antenna element and the feeder line, the loop antenna 100 is a coaxial line because the loop antenna elements 101 to 104 form a substantially parallel line. It has the peculiarity that the balun circuit 202 must be provided between the power supply line and the power supply line.

The balun circuit 202 is a matching circuit for converting and connecting an unbalanced line (coaxial line) and a balanced line (parallel line) as shown in FIG. 18 (b). This is because if the unbalanced line formed by the loop antenna elements 101 to 104 and the parallel line formed by the feed line are directly connected, an unbalanced amount of current will always occur at the connection point.

FIG. 19 is a sectional view of the loop antenna shown in FIG. 16 taken along the line CC, showing the inner conductor 30 of the feeder line 108.
1 is connected to the outer conductor 303 arranged in parallel with the outer conductor 302 via the connection portion 304. Outer conductor 30
2, 303 are connected by the connecting portion 304 and short-circuited by the short-circuiting portion 305 at about 1 / 4λ. The outer conductors 302 and 303, the connection portion 304, and the short-circuit portion 305 are balun circuits. There are various types of balun circuits, such as a U balun and a Spertov (blocking tube).

However, by providing the balun circuit 202, the frequency characteristic of the impedance of the twin loop antenna including the feeding portion includes the frequency characteristic of the balun circuit 202 itself, resulting in a narrow band. There was a problem that it would end up.

On the other hand, the loop antenna elements 101 to 104
And impedance matching between the power supply line 108 and
The impedance matching circuit 201 shown in FIG.
It must be formed between the loop antenna elements 101 to 104 and the feeding side. In the loop antennas shown in FIGS. 16 and 17, impedance matching is performed by changing the diameter of the inner conductor to convert the length to 1 / 4λ. In addition, as the impedance matching circuit 201, a stub such as a trap is often inserted.

However, this impedance matching circuit 20
In No. 1, there was a problem that the return loss was large because the center frequency was perfectly matched, but the other frequencies were not matched.

In this case, if a plurality of impedance matching circuits 201 are used, for example, three impedance matching circuits are used to gradually convert the impedance, the frequency characteristic becomes small and the band can be widened, but the power feeding section is considerably long. Will cause the problem of becoming.

Therefore, in the conventional loop antenna,
Since the balun circuit 202 and the impedance matching circuit 201 described above are connected to the connection points of the loop antenna elements 101 to 104, the frequency characteristics thereof are deteriorated and the wide band property of the twin loop antenna element itself cannot be fully utilized.

On the other hand, if the directivity of the loop antenna is destroyed, a new reception dead zone is generated. To eliminate this reception dead zone, a suitable place such as a new broadcasting tower is searched for,
Because of the need for construction, it is a strong demand for the development of antennas that use the wide band characteristics of the loop antennas that are currently in widespread use in order to realize terrestrial digital broadcasting. Is.

The present invention has been made in view of the above,
An object of the present invention is to provide an antenna unit, an antenna device, and a broadcasting tower, which can sufficiently exhibit the wide band property of the loop antenna element itself while maintaining the directivity of the loop antenna which is widely used at present.

[0014]

In order to achieve the above object, each of the antenna units according to claim 1 has two antenna units.
2 m (where m is a natural number) loop antennas that form N (N is a natural number) loops and is fed from the center of each loop to form a plane of polarization in the longitudinal direction formed by 2N loops. An element, a first feeder line for transmitting electric power to the loop antenna element, and a first feeder line disposed between each loop antenna element and the first feeder line,
2 of the power feeding line is repeated m times, and the characteristic impedance of the first feeding line is 2 m times, and the characteristic impedance is substantially equal to the impedance of each loop antenna element. The m-th power antenna side end point is formed, and each antenna side end point is 2 m.
And a second feed line directly connected to the feed point of each of the loop antenna elements.

According to the invention of claim 1, the electric power transmitted from the first power supply line is repeatedly branched into two by the second power supply line and supplied to the power supply point of each loop antenna element. At this time, the characteristic impedance at the final stage of the second power supply line is set to be substantially equal to the impedance of each loop antenna element so that impedance matching adjustment is eliminated and there is no change in characteristics even without providing a balun circuit. There is.
In addition, since the polarization plane is formed in the longitudinal direction formed by the 2N loops, the installation form is not changed at the time of replacement with the antenna unit forming the polarization plane orthogonal to this polarization plane, and the horizontal and vertical antenna directivities are maintained. It can be replaced without changing.

According to a second aspect of the present invention, in the above invention, the antenna unit is provided in the vicinity of the junction between the loop antenna element and the second feed line, and has an impedance substantially equal to that of the loop antenna element. It is characterized by further including a balun having impedance.

According to the invention of claim 2, the electric power transmitted from the first power supply line is repeatedly branched into two by the second power supply line and supplied to the power supply point of each loop antenna element. At this time, the characteristic impedance of the final stage of the second power supply line is made substantially equal to the impedance of each loop antenna element to facilitate impedance matching adjustment, and
The balun is provided near the junction between each loop antenna element and the second feed line, and near the junction between each loop antenna element and the second dielectric wire, and the balun By making the impedance substantially equal to the impedance, the power feeding corresponding to the impedance of each loop antenna element is easily realized.

According to a third aspect of the present invention, in the above invention, the antenna unit further comprises a reflector, and the loop antenna element is arranged on the reflector at a predetermined distance from the second antenna. The electric wire is arranged on the back surface or the front surface of the reflection plate.

According to the invention of claim 3, a more efficient antenna directivity can be obtained by using the reflector.
It is possible to easily install the second power supply line or the antenna unit.

Further, in the antenna unit according to a fourth aspect of the present invention, in the above invention, the balun is formed by a flat plate arranged in parallel with a second feed line between the joint point and the reflection plate. The flat plate connects the joining point and the reflection plate.

According to the invention of claim 4, a balun is formed by a flat plate arranged in parallel to the second feed line between the junction point and the reflection plate, whereby a 2N loop antenna is formed. A balun having an impedance substantially equal to the impedance of the element or each loop antenna element can be easily formed.

Further, the antenna device according to claim 5 is
A plurality of antenna units according to any one of claims 1 to 4 are evenly arranged in an annular shape, and radio waves radiated from each antenna unit are combined to obtain a substantially omnidirectional horizontal radiation pattern. And

According to the invention of claim 5, claims 1 to
The plurality of antenna units described in any one of 4 are evenly arranged in a ring shape, and radio waves emitted from the respective antenna units are combined to obtain a substantially omnidirectional horizontal radiation pattern.

A broadcasting tower according to claim 6 is characterized in that the antenna device according to claim 5 is installed at a predetermined ground clearance.

According to the sixth aspect of the present invention, the antenna device according to the fifth aspect is installed at a predetermined height above the ground, whereby the vertical combined directivity can be changed and set to any desired value, and the antenna device is substantially omnidirectional. A broadcasting tower with horizontal directivity can be realized.

[0026]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of an antenna unit, an antenna device and a broadcasting tower according to the present invention will be described in detail below with reference to the accompanying drawings.

(Embodiment 1) FIG. 1 is a schematic diagram showing a schematic configuration of an antenna unit according to Embodiment 1 of the present invention. In FIG. 1, this antenna unit 10
Has two 2L antenna elements 1 and 2 composed of two loop antenna elements. That is, four loop antenna elements are provided. The 2L antenna elements 1 and 2 are arranged in series in the longitudinal direction of the 2L antenna elements 1 and 2. The impedance of each 2L antenna element 1 and 2 itself is about 100Ω. The circumference of each loop antenna element is set to the wavelength λ of the transmission frequency.

Power is fed from the feeding points of the 2L antenna elements 1 and 2 toward the circle centers of the two loop antenna elements of the 2L antenna elements 1 and 2, and further from the circle centers of the two loop antenna elements in the longitudinal direction (Fig. It extends in the upper and lower directions and is connected to each loop antenna element. It can be considered that a dipole in the longitudinal direction is formed at the center of the circle of each loop antenna element, and the plane of polarization resonates along the longitudinal direction.

At the feeding points of the 2L antenna elements 1 and 2,
A coaxial tube 3 having a characteristic impedance of 100Ω is connected to each other, and a coaxial cable 4 having a characteristic impedance of 50Ω is connected to the center (middle point) of the coaxial tube 3 and a coaxial cable 4 is connected.
Also, power is supplied to each of the 2L antenna elements 1 and 2 via the coaxial tube 3. The coaxial tube 3a branched at the midpoint of the coaxial tube 3 extends toward the 2L antenna element 1 side, and the coaxial tube 3a
The inner conductor 11a is directly connected to one of the feeding elements 1a and 1b of the 2L antenna element 1, and the outer conductor of the coaxial tube 3a is directly connected to the other feeding element 1b. The coaxial tube 3b branched at the midpoint of the coaxial tube 3 extends toward the 2L antenna element 2 side, and the inner conductor 11b of the coaxial tube 3b is directly connected to one of the feeding elements of the 2L antenna element 2.
The outer conductor of is directly connected to the other feeding element.

The coaxial cable 4 includes a coaxial tube 3a,
3b is branched into two and connected in parallel to form a parallel pipe 3a,
Considering the combined impedance of 3b, the coaxial cables 3a and 3b having a characteristic impedance of 100Ω and the coaxial cable 4 are simply impedance-matched. Also, each 2
The impedance of the L antenna elements 1 and 2 is approximately 100Ω.
Therefore, impedance matching is easily achieved with the coaxial tubes 3a and 3b having a characteristic impedance of 100Ω. Therefore, it is not necessary to provide an impedance matching circuit.
Moreover, complicated impedance adjustment is not necessary.

Here, the configuration of the antenna unit 10 will be described with reference to FIGS. 2 is a front view showing the configuration of the antenna unit 10, FIG. 3 is a right side view showing the configuration of the antenna unit 10, and FIG.
FIG. 3 is a cross-sectional view of the antenna unit 10 taken along the line AA.

In FIGS. 2 and 3, the 2L antenna elements 1 and 2 are bent on both edges along the longitudinal direction at an angle of about 45 °, and a wavelength of about λ is provided on a flat plate-like reflector 5 having a main surface.
It is a twin loop antenna having an arc-shaped loop antenna element. The 2L antenna elements 1 and 2 are installed parallel to the surface of the reflection plate 5 at a height L3. The distance between the loops is "L1", and each of the 2L antenna elements 1 and 2 is
The distance is “L2”.

The coaxial waveguide 3 has a rectangular cross section, and the inner conductors 11a and 11b at each end are directly connected to one feeding element at the center of the 2L antenna elements 1 and 2. The coaxial tube 3 passes through the back surface of the reflection plate 5 and is connected to the coaxial cable 4 at the central portion. As described above, the coaxial tube 3 has a characteristic impedance of 100Ω. The coaxial tube 3 may be arranged on the surface of the reflection plate 5. In this case, no convex portion is formed on the back surface of the reflection plate 5, and the antenna unit can be easily and firmly attached.

In FIG. 4, the inner conductor 11a passes between the parallel lines in the central portion of the 2L antenna element 1, and the leading end of the inner conductor 11a and the feeding element 1a are bridged in an L-shape by the conducting member 1c so as to be electrically connected. It On the other hand, the outer conductor is connected to the other feeding element 1b. A ring member 11c is mounted on the inner conductor 11a to adjust the impedance between the 2L antenna element 1 and the coaxial tube 3.

Further, the above-mentioned inter-loop distance "L1",
The distance "L2" between the 2L antenna elements 1 and 2 and the height "L3" of the 2L antenna elements 1 and 2 with respect to the reflector 5 can be further adjusted to further improve the radiation pattern, the gain, and the like. it can. Further, although the characteristic impedance of the coaxial cable 4 described above is 50Ω, if the characteristic impedance of the coaxial cable as the power supply line is 75Ω, 75Ω → 50Ω conversion may be performed.

Further, the above-mentioned 2L antenna elements 1 and 2 are used.
Although the impedance of itself is about 100Ω, for example, when the impedance of the 2L antenna elements 1 and 2 itself is about 150Ω, the characteristic impedance of the coaxial cable 4 is 75Ω and the characteristic impedance of the coaxial tube 3 is 150Ω. And it is sufficient. Similarly, 2L
The impedance of the antenna elements 1 and 2 itself is, for example, 2
If it is 00Ω, the coaxial tubes 3 may be connected in multiple stages. For example, as shown in FIG. 5, when the impedance of each 2L antenna element 21, 22, 26, 27 is 200Ω, the coaxial cable 4 having a characteristic impedance of 50Ω.
Connect a 100Ω coaxial tube 23 to the
A coaxial tube having a characteristic impedance of 200Ω may be connected to the coaxial tube 23, and the inner conductor of the 200Ω coaxial tube may be directly connected to each of the four 2L antenna elements 21, 22, 26 and 27.

It is preferable that each antenna unit is provided with a radome to have strength against wind and rain.

In the first embodiment, the impedance is substantially equal to the impedances of the 2L antenna elements 1 and 2 and is connected between the 2L antenna elements 1 and 2 and the coaxial cable 4 as a feeder line, and the characteristic impedance of the coaxial cable 4 is It has twice the characteristic impedance of
Since the coaxial tube 3 in which the inner conductor of the coaxial tube 3 is directly connected to the 2L antenna elements 1 and 2 is provided, a balun circuit or an impedance matching circuit is not required. It is possible to obtain the wide band property of the 2L antenna elements 1 and 2 itself which is limited by the circuit. Further, even when the balun circuit or the impedance circuit is not provided, the antenna directivity does not change, so that the antenna directivity of the conventional antenna unit can be maintained as it is.
Furthermore, since the 2L antenna elements 1 and 2 can radiate the polarization plane (vertical polarization plane) along the longitudinal direction in which the loop antenna elements are arranged, the antenna unit 10 that radiates the conventional horizontal polarization plane is arranged. It is possible to change only the plane of polarization without changing the antenna directivity.

(Second Embodiment) Next, a second embodiment of the present invention will be described. In the first embodiment described above, the antenna unit has two 2L antenna elements 1 and 2, but in the second embodiment, the antenna unit has two 4L antenna elements 31 and 32.

FIG. 6 is a schematic diagram showing a schematic configuration of an antenna unit according to the second embodiment of the present invention. In FIG. 6, two 4L antenna elements 31 and 32 are provided instead of the two 2L antenna elements 1 and 2. The 4L antenna elements 31 and 32 each have four loop antenna elements, and four loops are formed in the longitudinal direction.
Further, a coaxial tube 33 is provided instead of the coaxial tube 3. Like the coaxial tube 3, the coaxial tube 33 has a characteristic impedance of 100Ω. However, 4L antenna elements 31, 3
Since 2 has more loop antenna elements than the 2L antenna elements 1 and 2, the coaxial tube 33 is longer than the coaxial tube 3. The coaxial tube 33 is connected to the coaxial cable 4 having a characteristic impedance of 50Ω as in the first embodiment, and the inner conductors of the coaxial tube 33 are directly connected to the 4L antenna elements 31 and 32, respectively. Here, the impedance of each of the 4L antenna elements 31 and 32 is approximately 10
Since it is 0Ω, the impedance matching circuit and the balun circuit are not required as in the first embodiment.

In the second embodiment described above, the 4L antenna elements 31 and 32 have been described. However, the present invention is not limited to this, and can be applied to a 6L antenna element having six loop antenna elements. That is, it can be applied to a device having a loop antenna element that is a multiple of 2.

According to the second embodiment, the first embodiment
Similarly, since the balun circuit and the impedance matching circuit are not necessary and the balun circuit and the impedance matching circuit are not present, it is possible to obtain the wide band property of the 4L antenna elements 31 and 32 themselves limited by the balun circuit and the impedance matching circuit. Further, even when the balun circuit or the impedance circuit is not provided, the antenna directivity does not change, so that the antenna directivity of the conventional antenna unit can be maintained as it is.

(Third Embodiment) Next, a third embodiment of the present invention will be described. Although the 2L antenna elements 1 and 2 are arranged in series in the longitudinal direction in the above-described first embodiment, the third embodiment is described.
Then, the antenna units are arranged in parallel along the longitudinal direction of the 2L antenna elements 41 and 42 corresponding to the 2L antenna elements 1 and 2.

FIG. 7 is a schematic diagram showing a schematic configuration of an antenna unit according to the third embodiment of the present invention. In FIG. 7, the two 2L antenna elements 41 and 42 are arranged in parallel along the longitudinal direction. The other structure is the same as that of the first embodiment. That is, the characteristic impedance 5
Characteristic impedance 10 bifurcated from 0Ω feeder line 4
The coaxial tubes 43 of 0Ω each have an impedance of 100Ω and two of each.
It is directly connected to one of the feeding elements of the L antenna elements 41 and 42.

FIG. 8 is a schematic diagram showing a schematic configuration of an antenna unit which is an application example of the third embodiment of the present invention. In FIG. 8, two 4L antenna elements 51 and 52 are provided.
Are arranged in parallel along the longitudinal direction. The other structure is the same as that of the first embodiment. That is, the coaxial tube 53 having a characteristic impedance of 100Ω, which is branched into two from the feeder line 4 having a characteristic impedance of 50Ω, has an impedance of 10
It is directly connected to one of the feeding elements of the 0L 4L antenna elements 51 and 52.

According to the third embodiment, the first embodiment
Similarly, the balun circuit and the impedance matching circuit are not required, and the absence of the balun circuit or the impedance matching circuit makes it possible to obtain the wide band property of the 2L antenna elements 41 and 42 themselves limited by the balun circuit and the impedance matching circuit.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described. Embodiments 1 to 3 described above
Then, neither had a balun circuit,
In the fourth embodiment, a balun circuit is provided.

FIG. 9 is a diagram showing the structure of an antenna unit according to the fourth embodiment of the present invention. In FIG.
In this antenna unit, a conductor flat plate 12a parallel to the coaxial tube 3a is provided between the 2L antenna element 1 and the reflection plate 5, and functions as a balun. Similarly, a conductor flat plate 12b parallel to the coaxial tube 3b is provided between the 2L antenna element 2 and the reflector 5 and functions as a balun. Other configurations are the same as those of the first embodiment, and the same components are designated by the same reference numerals.

By inserting these baluns, the horizontal directivity becomes symmetrical. That is, the horizontal directivity of the antenna unit of the 2L antenna elements 1 and 2 is as shown in FIG. Here, as compared with the horizontal directivity of the conventional antenna unit shown in FIG. 11, there is no inclination of the main lobe and the back lobe is also symmetrical. As a result, even if a plurality of antenna devices each including an antenna unit are arranged in an annular shape in a broadcasting tower or the like, the combined horizontal directivity can easily be omnidirectional.

(Fifth Embodiment) Next, a fifth embodiment of the present invention will be described. In the fifth embodiment, an antenna device and a broadcasting tower using the antenna unit described in the first to fourth embodiments are realized.

FIG. 12 is a diagram showing a schematic configuration of a broadcasting tower including an antenna device according to a fifth embodiment of the present invention.
In FIG. 12, the broadcasting tower has a tower-shaped skeleton frame body 71 in which iron frame members are assembled, and a pole portion 72 provided vertically at the upper end thereof. The antenna unit 7 corresponding to the antenna unit 10 described above is provided in the pole portion 72 and the cylindrical portion 75 of the skeleton frame body 71 having a relatively small cross section.
3,74 are attached.

The attachment of the antenna units 73 and 74 is realized by arranging them horizontally and evenly around the pole portion 72 or the cylindrical portion 75. However, the number of the antenna units 73 and 74 to be attached is determined by the size of the cross section of the pole portion 72 or the cylindrical portion 75, that is, the length of the circumference, so as not to form a portion where the transmission gain drops in the horizontal direction. Place them closely. Therefore, the pole portion 72 requires a small number of antenna units 73, and the cylindrical portion 75 requires a relatively large number of antenna units 74.

Here, with reference to FIG. 13, an example of the antenna device installed in the broadcasting tower will be described. FIG.
FIG. 13 is a diagram showing a configuration of an antenna device installed on the pole portion 72, FIG. 13 (a) is a front view of the antenna device, and FIG. 13 (b) is a sectional view taken along line BB. FIG.
In, four antenna units 73-1 to 73-4
Is provided on the same circumference as the periphery of the pole portion 72,
The antenna units 73-1 to 73-4 are evenly arranged by 90 °. In addition, each antenna unit 73-1
73-4 are the antenna units shown in FIG.
That is, it is an antenna unit that radiates in the plane of vertical polarization.

FIG. 14 is a diagram showing the horizontal directivity of the antenna device shown in FIG. The antenna unit 7
The direction in which 3-4 is arranged is 0 °, and the direction in which the antenna unit 73-3 is arranged is 90 °. A portion having high antenna directivity is formed between the antenna units 73-1 to 73-4. For example, a peak P71 is formed between the antenna units 73-3 and 73-4. This peak P71 is the antenna unit 73-
At the hem of the main lobe of 3,73-4, peaks are formed by strengthening each other in the 45 ° left and right directions. Since each antenna unit 73-1 to 73-4 has a gain obtained by combining two 2L antenna elements and has a relatively sharp antenna directivity, it is not possible to extremely increase the peak P71 as shown in FIG. Absent. Thereby, it is possible to obtain relatively non-directional horizontal directivity even with the four antenna units 73-1 to 73-4 arranged every 90 ° on the entire circumference.

Incidentally, each antenna unit 73-1 to 73
-4 is collectively fed by the feeding device 76 arranged at the inner edge of the pole portion. The other antenna devices provided with the pole portion 72 and the antenna device provided in the cylindrical portion 75 may be collectively fed by the power feeding device 76.

The antenna device described above can be applied not only to the broadcast tower of the master station shown in FIG. 12, but also to the broadcast tower of the slave station having the relay function shown in FIG. Figure 15
In the broadcasting tower shown in Fig. 15, the receiving antenna device 81 for receiving radio waves from the broadcasting tower of the master station or the broadcasting tower which is a higher-order slave station shown in Fig. 15 and the transmitting antenna device 82 which is the above-mentioned antenna device are provided. The receiving antenna device 81 is installed in the lower part of the broadcasting tower, and the transmitting antenna device 82 is installed in the upper part of the broadcasting tower so as not to interfere with each other.

It is preferable that each antenna unit be provided with a radome so as to have strength against wind and rain.

According to the fifth embodiment, at least the antenna directivity of the current dual-loop antenna can be maintained, and further improved antenna directivity can be obtained, and as described in the first to fourth embodiments. It is possible to realize an antenna device and a broadcasting tower having a wide band characteristic.

[0059]

As described above, according to the first aspect of the present invention, the electric power transmitted from the first power feed line is repeatedly branched into two by the second power feed line, and the power of each loop antenna element is increased. It is supplied to the feeding point. At this time, the characteristic impedance at the final stage of the second power supply line is set to be substantially equal to the impedance of each loop antenna element so that impedance matching adjustment is eliminated and there is no change in characteristics even without providing a balun circuit. There is. In addition, since the polarization plane is formed in the longitudinal direction formed by the 2N loops, the installation form is not changed at the time of replacement with the antenna unit forming the polarization plane orthogonal to this polarization plane, and the horizontal and vertical antenna directivities are maintained. It can be replaced without changing. As a result, the balun circuit and the impedance matching circuit can be removed, and the wide band property limited by the balun circuit and the impedance matching circuit can be secured, which is covered by the currently diversified twin loop antenna. It is possible to realize an antenna unit having a wide band without changing the reception area, and it is possible to easily switch between horizontal polarization and vertical polarization.

According to the second aspect of the invention, the electric power transmitted from the first feed line is repeatedly branched into two by the second feed line and is supplied to the feed point of each loop antenna element. At this time, the characteristic impedance at the final stage of the second feed line is made substantially equal to the impedance of each loop antenna element to facilitate impedance matching adjustment, and the balun is provided for each loop antenna element and the second feed element. Each loop antenna is provided near a junction with an electric wire, is provided near a junction between each loop antenna element and the second dielectric wire, and has an impedance substantially equal to the impedance of each loop antenna element. The power supply corresponding to the element impedance is easily realized. As a result, there is an effect that it is possible to obtain antenna directivity that is bilateral and symmetrical.

According to the third aspect of the present invention, by using the reflection plate, more efficient antenna directivity can be obtained, and the second feeding line or the antenna unit can be easily installed. It has the effect of being able to.

Further, according to the invention of claim 4, the balun is formed by the flat plate arranged in parallel to the second feed line between the joining point and the reflection plate, whereby the 2N loop is formed. The balun having an impedance substantially equal to the impedance of the antenna element or each loop antenna element can be easily formed.

According to the invention of claim 5, claim 1
Since the plurality of antenna units according to any one of to 4 are evenly arranged in an annular shape and the radio waves emitted from the respective antenna units are combined to obtain a substantially omnidirectional horizontal radiation pattern, The present invention has an effect that it is possible to realize an antenna device which can be changed and set to an arbitrary vertical combined directivity and can obtain substantially omnidirectional horizontal directivity.

According to the invention of claim 6, claim 5
The antenna device described in (1) is installed at a predetermined height above the ground, and by doing so, it is possible to change and set to any vertical composition directivity, and it is possible to realize a broadcasting tower that can obtain substantially omnidirectional horizontal directivity, so a simple configuration Thus, it is possible to eliminate the dead zone corresponding to the installation location.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a schematic configuration of an antenna unit according to a first embodiment of the present invention.

FIG. 2 is a front view of the antenna unit shown in FIG.

FIG. 3 is a right side view of the antenna unit shown in FIG.

4 is a cross-sectional view of the antenna unit shown in FIG. 1 taken along the line AA.

FIG. 5 is a schematic diagram showing a schematic configuration of an antenna unit that is an application example of the first embodiment of the present invention.

FIG. 6 is a schematic diagram showing a schematic configuration of an antenna unit that is Embodiment 2 of the present invention.

FIG. 7 is a schematic diagram showing a schematic configuration of an antenna unit that is Embodiment 3 of the present invention.

FIG. 8 is a schematic diagram showing a schematic configuration of an antenna unit that is an application example of a third embodiment of the present invention.

FIG. 9 is a schematic diagram showing a schematic configuration of an antenna unit that is Embodiment 4 of the present invention.

10 is a diagram showing horizontal directivity of the antenna unit shown in FIG.

FIG. 11 is a diagram showing horizontal directivity of a conventional antenna unit.

FIG. 12 is a diagram showing a schematic configuration of a broadcasting tower including an antenna device according to a fifth embodiment of the present invention.

13 is a diagram showing an example of the antenna device shown in FIG.

14 is a diagram showing horizontal directivity of the antenna device shown in FIG.

FIG. 15 is a diagram showing an example of an antenna device applied to a broadcasting tower of a slave station.

FIG. 16 is a front view showing the configuration of a conventional antenna unit.

17 is a right side view showing the configuration of the antenna unit shown in FIG.

18 is a diagram showing a schematic circuit configuration of the antenna unit shown in FIG.

FIG. 19 is a cross-sectional view taken along the line CC of the antenna unit shown in FIG.

[Explanation of Codes] 1, 21, 21, 22, 26, 27, 41, 42, 66-
69 2L antenna elements 1a, 1b Feeding elements 3, 3a, 3b, 23, 24, 33, 33a, 33b,
43, 43a, 43b, 53, 63a, 63b Coaxial tube 4 Coaxial cable (feed line) 5 Reflector 10, 73, 73-1 to 73-4, 74 Antenna unit 11a, 11b Internal conductor 12a Conductor flat plate 31, 32, 51, 52 4L antenna element 71 skeleton frame body 72 pole portion 75 cylindrical portion 76 power feeding device 81 receiving antenna device 82 transmitting antenna device

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yukitoshi Kudo             2-6-1, Marunouchi, Chiyoda-ku, Tokyo             Kawa Electric Industry Co., Ltd. (72) Inventor Reiji Fukuhara             2-6-1, Marunouchi, Chiyoda-ku, Tokyo             Kawa Electric Industry Co., Ltd. F-term (reference) 5J021 AA02 AA08 AA11 AB04 BA01                       FA32 GA07 GA08 HA05 JA02                       JA03                 5J047 AA03 AB01 AB11 BG05

Claims (6)

[Claims] 1. Each of 2N (N is a natural number) loops is formed and is fed from the center of each loop.
Form a plane of polarization in the longitudinal direction formed by N loops 2
M power antennas (m is a natural number), first feed lines for transmitting electric power to the loop antenna elements, and arranged between the loop antenna elements and the first feed line, Two branches of the first power supply line are repeated m times to obtain a characteristic impedance of 2 m of the first power supply line.
2 m antenna-side end points having characteristic impedances that are powers of multiples and that are substantially equal to the impedances of the loop antenna elements are formed, and each antenna-side end point is 2 m power of the loop antennas. An antenna unit, comprising: a second power supply line that is directly connected to a power supply point of the element. 2. A balun, which is provided in the vicinity of a junction point between each of the loop antenna elements and the second feed line and has an impedance substantially equal to an impedance of each of the loop antenna elements. The antenna unit according to Item 1. 3. A reflection plate is further provided, the loop antenna element is arranged on the reflection plate at a predetermined distance, and the second feed line is arranged on a back surface or a front surface of the reflection plate. The antenna unit according to claim 1 or 2, wherein: 4. The balun is formed by a flat plate arranged in parallel with a second power supply line between the junction and the reflector, and the flat plate connects the junction and the reflector. The antenna unit according to claim 3, wherein the antenna units are connected to each other. 5. A substantially omnidirectional horizontal radiation pattern by arranging a plurality of antenna units according to any one of claims 1 to 4 evenly in an annular shape and combining radio waves radiated from each antenna unit. An antenna device characterized by obtaining. 6. A broadcasting tower in which the antenna device according to claim 5 is installed at a predetermined ground clearance.