JP3374111B2 - Transmission antenna device and broadcast tower - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an omnidirectional transmission antenna device and a broadcasting tower suitable for transmitting a plurality of broadcast waves having different radio frequencies.

[0002]

Related Background Art Broadcast waves such as radio and television are radiated from, for example, an omnidirectional transmission antenna installed at the upper part of a broadcasting tower. It is desirable to install this type of transmitting antenna at a position where the ground height is as high as possible in order to secure the radio wave reach. Further, since it is desirable for the side that receives a plurality of broadcast waves that the arrival directions of the broadcast waves be the same, generally, the transmission antennas for the broadcast waves are attached to the same broadcasting tower.

[0003]

In the broadcasting tower, for example, as shown in FIG. 6, a skeleton frame body 1 in the form of a steel frame is assembled, and a pole portion 2 vertically provided at the upper end thereof.
Consists of. An omnidirectional transmitting antenna such as the turnstile antenna 3 is attached to the pole portion 2 exclusively. However, the number of transmitting antennas that can be attached to the pole portion 2 is naturally limited because it is limited by the length of the pole portion 2.

Therefore, it has been attempted to attach a transmitting antenna composed of the multi-faceted synthetic antenna 4 to the peripheral surface of the upper end portion of the frame body 1 having a relatively small cross section. The multi-sided synthesis antenna 4 has a plurality of antenna elements (antenna units) such as twin loop antennas arranged at equal angular intervals around the skeleton frame body 1 and synthesizes radio waves emitted from the respective antenna elements in the air. By doing so, an omnidirectional radiation pattern of the radio wave is obtained, which is called a four-sided synthetic antenna, an eight-sided synthetic antenna or the like depending on the number of faces on which the antenna elements (antenna units) are arranged. However, if such a multi-sided composite antenna 4 is used in combination, the number of transmitting antennas that can be attached to the broadcasting tower is also limited, so that a problem remains in dealing with a large number of broadcasting waves that are expected to increase in the future.

The present invention has been made in view of the above circumstances, and its object is to install the equipment in a limited equipment space, for example, in the outer peripheral portion of the steel frame where the diameter of the antenna mounting surface is relatively large in the upper part of the broadcasting tower. It is an object of the present invention to provide an omnidirectional transmission antenna device that is suitable for transmitting a plurality of broadcast waves having different radio frequency. Another object of the present invention is to provide a broadcasting tower in which a plurality of transmitting antenna devices for transmitting a plurality of broadcasting waves having different broadcasting radio frequencies are compactly mounted in a limited equipment space.

[0006]

In order to achieve the above-mentioned object, a transmitting antenna device according to the present invention comprises a plurality of multi-sided composite antennas each having a different transmission radio frequency.
Antenna units with the same number of planes or more are arranged circularly in a predetermined order in a horizontal plane to form an antenna group for multi-frequency multi-plane synthesis, and a plurality of antenna groups with different transmission radio frequencies. Is characterized in that they are coaxially arranged in multiple stages in the vertical direction.

In a preferred aspect of the present invention, a plurality of antenna units respectively constituting the respective multi-sided composite antennas are arranged at equal intervals on a predetermined circumferential surface to form the plurality of antenna groups, respectively. Item 2), in particular, the radio frequency assigned to each multi-sided composite antenna of the upper antenna group is set higher than the radio frequency assigned to each multi-sided composite antenna of the lower antenna group. 3). At this time, the diameter of the antenna array surface for arranging the plurality of antenna elements forming the lower antenna group in an annular shape is defined as the antenna array surface for arranging the plurality of antenna elements forming the upper antenna group in an annular shape. It is characterized in that the diameter is set larger than the diameter (claim 4).

Further, the present invention realizes a broadcasting tower in which the transmitting antenna device having the above-mentioned structure is compactly installed in a limited equipment space at a predetermined ground clearance (claim 5).

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a transmitting antenna device according to an embodiment of the present invention and a broadcasting tower including the transmitting antenna device will be described with reference to the drawings. Figure 1 (a)
(C) shows a schematic configuration of the broadcasting tower 50 according to this embodiment and the transmitting antenna device 60 incorporated in the upper steel structure portion 51 of the broadcasting tower 50. In the figure, 61, 62,
Reference numeral 63 denotes a plurality of existing transmission antenna devices incorporated in the upper steel structure portion 51 of the broadcasting tower 50 and the pole portion 52 above it.

In the transmitting antenna device 60 according to this embodiment, for example, a plurality of antenna units 10 configured as shown in FIGS. 2 (a) and 2 (b) are annularly formed around the upper steel structure 51. By arranging and spatially synthesizing the radio waves radiated from the respective antenna units 10, it is realized as a multi-sided synthesis antenna configured to obtain an omnidirectional radio wave radiation pattern in the horizontal direction.

In particular, the transmitting antenna device 60 shown in this embodiment has two different broadcast radio wave frequencies fa and fb.
By alternately arranging each of the 15 antenna units 10 to which is allocated on a predetermined circumferential surface at equal intervals as shown in FIG. The antenna group 20 which is provided as an antenna and substantially forms two multi-sided composite antennas is realized with a basic configuration. More specifically, the antenna group 20 includes two multi-sided synthetic antennas by alternately arranging 15 antenna units 10 to which the broadcast radio frequencies fa and fb are allocated on a predetermined circumferential surface at equal intervals. 2 sets of ring-shaped antenna devices formed on the same horizontal plane are prepared, and these antenna devices are arranged coaxially in two stages in the vertical direction, whereby the directivity in the vertical direction is enhanced. .

The transmitting antenna device 60 prepares five kinds of the antenna group 20 having the above-mentioned structure by making the broadcasting radio wave frequencies different from each other, and coaxially vertically around the upper steel structure portion 51 in the broadcasting tower 50. It is realized as including the arrayed first to fifth antenna groups 21, 22, and 25. By the way, each of these antenna groups 21, 22, ~
The broadcast radio frequency assigned to each of the 25 is set so that the frequency of the antenna group on the upper side is higher than the frequency of the antenna group on the lower side. Specifically, for example, the lowest first antenna group 21 has a UHF band of 21
Radio frequencies of ch and 22ch are assigned, and radio frequencies of 23ch and 24ch in the UHF band are assigned to the second antenna group 22 in the upper stage. Similarly, the third antenna group 23 has 25ch and 26ch of UHF band.
Of the UHF band for the fourth antenna group 24
Radio frequencies of 7ch and 28ch are assigned to the fifth antenna group 25, and radio frequencies of 29ch and 30ch in the UHF band are assigned to the fifth antenna group 25, respectively.

However, it is said that the broadcast radio waves transmitted from the respective antenna groups 21, 22 to 25 have shorter radio wave reaching distances as the frequency becomes higher depending on the radio wave frequency when the transmission powers are equal. It has the property. In this regard, in the transmitting antenna device having the above-described configuration, the antenna group having a higher radio frequency is arranged on the upper stage side and is provided at a position with a high ground height in the broadcasting tower 50, and the radio wave reaching distance depends on the radio frequency. The reduction is compensated. As a result, the radio wave arrival distances (service areas) of a plurality of broadcast waves having different radio wave frequencies respectively transmitted from a plurality of antenna groups 21, 22, to 25 provided in coaxial multiple stages are equalized.

The diameter of the antenna array surface formed by annularly arranging the antenna units 10 constituting each of the antenna groups 21, 22 to 25 is larger than that of the antenna group on the upper side where the broadcast radio frequency is high. Then, the diameter of the antenna group on the lower side is set to be large. That is, since each antenna unit 10 is realized as a size (horizontal width) according to the wavelength λ of the broadcast radio frequency, for example, as will be described later, each antenna group 21, 22 ,.
5 is formed by forming an antenna array surface having a perimeter corresponding to the lateral width of each antenna unit 10, and by setting the diameter of the antenna array surface. In this way, by setting the diameter of the antenna array surface of each antenna group 21, 22, to 25, in a limited equipment space around the upper steel structure part, which generally tapers as the ground height increases, A transmission antenna device 60 is realized in which the antenna groups 21, 22 to 25 for respectively transmitting a plurality of broadcast waves having different radio frequencies are efficiently and compactly arranged in a multi-stage coaxially.

The above-mentioned antenna unit 10 is provided with a loop-shaped radiating element as shown in, for example, a plane structure shown by cutting out a part thereof in FIGS. 2A and 2B and a side structure thereof. 4-element twin loop antenna (antenna element)
11, a flat-plate-shaped main reflector 12 provided on the back surface side of the 4-element twin-loop antenna 11 in parallel with the antenna surface formed by the 4-element twin-loop antenna 11, and further, in the antenna horizontal plane direction of the main reflector 12. And sub-reflecting plates 13 respectively provided at both ends of the. This sub-reflector 1
3 is substantially perpendicular to the main reflection plate 12 (for example, 90 ± 10
°) provided respectively. Also, the height h of the sub-reflector 13
Is set to about 0.01λ to 0.14λ, for example, as will be described later, with respect to the wavelength λ of the broadcast radio frequency.

Here, as an antenna element,
Three 4-element twin loop antennas 11 (11a, 11b, 1
An antenna unit 10 having a structure in which 1c) are provided side by side and in parallel at a predetermined interval is shown. These four-element twin loop antennas 11 (11a, 11b, 11c) have an arc-shaped loop antenna element section (radiating element) 15 whose perimeter L is approximately one wavelength (λ) of the radio frequency, approximately 1 / 4 via the parallel feed section 16 having a length of 2 wavelengths (λ / 2).
It has a structure in which each element is formed. The three four-element twin loop antennas 11 (11a, 11b, 11c) are arranged side by side in parallel with an interval of about 1 wavelength (0.95λ), for example, at a power ratio of 1: 2: 1. It is supplied with power and emits broadcast waves of the above radio frequency.

Therefore, the 4-element twin loop antenna 11 (1
1a, 11b, 11c) main reflector 1 provided on the back side
Reference numeral 2 reflects the radio wave radiated from the loop antenna element section 15 to play a role of giving unidirectionality in a direction perpendicular to the reflection surface of the main reflection plate 12. The main reflector 12
The sub-reflecting plates 13 provided on both sides of the sub-reflecting plate 13 serve to suppress the electric waves that come around via both side parts of the main reflecting plate 12 to suppress the side lobes and the back lobes and enhance the directional characteristics thereof.

The antenna unit 10 is also provided with a protective cover (a radome) 14 which is provided on the radio wave radiation surface of the four-element twin loop antenna 11 (11a, 11b, 11c). The protective cover 14 is made of a synthetic resin material or the like having good radio wave transparency, and is attached so as to cover the entire antenna surface via the sub-reflecting plate 13. With such a protective cover 14, the four-element twin loop antenna 11 (11a, 1a, 1a, 1
1b, 11c) are protected, and the structural strength of the antenna unit 10 against a wind load which is easily received when the antenna unit 10 is attached to the upper steel frame structure portion 51 of the broadcasting tower 50 is secured. At the same time, when the plurality of antenna units 10 are arranged in an annular shape around the upper steel structure portion 51, the protective cover 14 forms a cylindrical surface having less unevenness as a whole, so that the protective cover 14 is not easily affected by wind pressure. It also realizes the function of protecting the broadcasting tower 50 itself from wind pressure load and reducing the strength of the broadcasting tower 50.

The sub-reflecting plates 13 provided substantially vertically on both sides of the main reflecting plate 12 have three horizontal widths of the main reflecting plate 12 which are arranged in parallel at a predetermined interval. The 4-element twin loop antenna 11 (11a, 11b, 11c) is set narrow enough to secure the equipment space, and accordingly, the antenna unit 10 is designed to be compact. Is provided to compensate for the deterioration. That is, the main reflector 12 is
In order to secure an antenna installation area that is determined by the arrangement width of the three 4-element twin loop antennas 11 and the lateral width of the 4-element twin loop antennas 11, for example, it is set compactly as a lateral width of about 2.5λ, It is hard to say that a sufficiently wide radio wave reflection surface is formed when viewed from the 4-element twin loop antenna 11 (11a, 11b, 11c) side. Sub-reflecting plates 13 are provided on both sides of the main reflecting plate 12 in order to supplement the reflection characteristic of the main reflecting plate 12 and secure the directional characteristics of the antenna unit 10 itself.

FIG. 3 shows the size of the side lobe and the back lobe with respect to the main lobe when the height h of the sub-reflecting plate 13 is variously changed for the antenna unit 10 having such a main reflecting plate 12. The result of the experiment is shown. Note that this experiment was performed using the antenna unit 10 for 545 MHz, which is a substantially central radio frequency of the broadcast wave in the UHF band described above.

However, as shown in the experimental results,
When the height h of the sub-reflecting plate 13 is set to [0], that is, when the sub-reflecting plate 13 is not provided, the size of the side lobe is about −17 dB, and the size of the back lobe is substantially −.
It was 22 dB. It was also found that the size of the side lobe gradually increases as the height h of the sub-reflecting plate 13 increases, while the size of the back lobe gradually decreases.

On the other hand, the present inventors have conducted various experiments, and as described above, the three 4-element twin loop antennas 11 (11
a), 11b, 11c), when implementing a multi-sided composite antenna using 15 antenna units 10, it is desirable to practically suppress the side lobe to -15 dB or less and the back lobe to -25 dB or less. I found that. Under such conditions, from the experimental results shown in FIG. 3 described above, the height h of the sub-reflector 13 with respect to the side lobe is set to about 0.14λ (about 70 mm) or less, and the above-mentioned sub-reflection with respect to the back lobe. It has been clarified that the height h of the plate 13 needs to be about 0.018λ (about 5 mm) or more.

Based on such knowledge, in the transmitting antenna device according to the present invention, the height h of the sub-reflecting plate 13 constituting the antenna unit 10 is set to 0.01λ to 0.14λ, preferably 0.08λ ( By setting the width to about 30 mm), the directional characteristics of the antenna unit 10 itself are sufficiently ensured even when the width of the main reflector 12 is set narrow as described above.

The inventors of the present invention made a trial product by bending both sides of the main reflection plate 12 to the front side of the main reflection plate 12 at an angle of about 45 °, and provided the function as a sub reflection plate. When the directivity characteristics were compared, it was confirmed that there was almost no difference in antenna characteristics. On the contrary, the lateral width of the antenna unit 10 can be narrowed by the amount of the sub-reflecting plate 13 provided substantially vertically, and the structural effect that the size can be reduced can be achieved.

Thus, according to the transmitting antenna apparatus of the present invention constructed by using the antenna unit 10 having the structure as described above, the antenna unit 10 itself has a sufficiently good directivity with its side ropes and back lobes suppressed. Since the antenna group 20 has characteristics and has a compact shape with its width suppressed, it is possible to construct the antenna group 20 in which the diameter of the antenna array surface is reduced to the necessary minimum and the overall shape is made compact. . Then, as the diameter of the antenna array surface is reduced, a combining lobe spatially combined between adjacent antenna units 10 and each antenna unit 10
Since it is possible to reduce the fall of the radio wave intensity between the main lobe and the main lobe, it is possible to form an omnidirectional pattern having excellent radio wave radiation characteristics.

Even when the transmitting antenna device is constructed by disposing the antenna unit 10 between the antenna elements of the existing transmitting antenna device 61 as shown in FIG. 1, the width of each antenna unit 10 is Since it is kept narrow, the antenna unit 10 is prevented while avoiding contact with each antenna element of the transmitting antenna device 61.
Can be attached, and the effect that the transmitting antenna device can be installed by effectively utilizing the limited antenna installation space of the upper steel frame structure portion 51 is exhibited.

Here, an antenna device (antenna group 20) formed by forming the above-described two multifaceted composite antennas having different radio frequencies on the same antenna surface will be briefly described. This antenna device is typically composed of a plurality of, for example, four antenna units A (A1, A2, A3,
A4) and B (B1, B2, B3, B4) are alternately arranged in an annular shape at equal intervals. Therefore, one of the antenna units A (A1, A2, A3, A4) has phase shifters φa1, φa2, φa3, φa4.
Are fed with phase difference via the respective antennas, and the other antenna unit B (B1, B2, B3, B4) has phase shifters φb1, φb2, φb.
Phase-difference feeding is performed via 3, and φb4, respectively, and broadcast waves having different radio wave frequencies fa and fb are emitted.

Specifically, for example, one antenna unit A1, A2, A3, A4 supplies a power by giving a phase difference of [2π / 4], and the other antenna unit B1, B2, B3, B
Each 4 supplies a power by giving a phase difference of [0]. Then, the antenna units A (A1, A2, A3, A4), B (B1,
(B2, B3, B4) are evenly arranged in an arc shape at equal angular intervals, so that the coupling phase in the radio wave radiation space is the same between the antenna units A and B. Further, the components of the radio frequency fa radiated from the antenna units A1, A2, A3, and A4, sneak into the antenna units B1, B2, B3, and B4 to be received and synthesized and output are
It is zero [0] because it is combined by the phase difference of feeding 1, A2, A3, A4. Similarly, antenna units B1, B2,
Radiation from B3 and B4 respectively, antenna unit A1,
The components of the radio frequency fb, which are received by the A2, A3, and A4 and are combined and output, are antenna units B1, B2, B3,
It is zero [0] because it is combined by the phase difference of feeding B4.

That is, by giving a predetermined phase difference [2π / 4] to the radiated radio waves that wrap around each other through the adjacent antenna units A and B, the antenna units A1 and A
2, A3, A4 The phase of each of the components fa1, fa2, fa3, fa4 of the broadcast wave of the radiated radio frequency fa received and received by the antenna units B1, B2, B3, B4 is [0], [ π / 2], [π], [3π / 2], and the combined output component becomes zero [0]. In addition, each phase of the components fb1, fb2, fb3, fb4 of the broadcast wave of the radio frequency fb radiated from the antenna units B1, B2, B3, B4 that are received by the antenna units A1, A2, A3, A4. Also becomes [0], [π / 2], [π], [3π / 2], and their combined output component becomes zero [0].

As a result, the antenna units A1, A2, A3,
Interference between A4 and antenna units B1, B2, B3, B4 is prevented, and each antenna unit A, B emits broadcast waves of different radio frequencies fa, fb as shown in the exploded view of FIG. The two multi-sided composite antennas will be configured respectively. Here, the case where a multi-sided composite antenna is configured by using four antenna units A1, A2, A3, A4 (B1, B2, B3, B4) has been described as an example. In the case of forming a multi-sided composite antenna using the antenna unit 10, for example, it is sufficient to give a phase difference of [2π / 15] to the radiated radio waves that wrap around each other to feed the radiated radio waves.

The present invention is not limited to the above embodiment. For example, the number of antenna units forming the multi-sided synthesis antenna may be determined according to the specifications, and it is also possible to configure a multi-sided synthesis antenna in which three or more radio wave frequencies are assigned in the same horizontal plane. Is. Although an example of an antenna unit including a loop-shaped radiating element is shown here, the same can be applied to the case of configuring an antenna unit including a dipole-shaped radiating element.

Also, the number of antenna elements is not particularly limited. In addition, the number of the plurality of antenna groups arranged in the coaxial multi-stage is not particularly limited, and it is of course possible to set the diameters of the antenna array planes forming the antenna groups in each stage to be equal. Regarding the diameter of the antenna array surface, considering the size of the supporting column of the broadcasting tower 50, for example, the size (the length W of one side) of the upper steel frame structure part 51 having a square cross section, the upper steel frame structure part is considered. It may be determined so that the size including 51 includes the dimensions necessary for mounting each antenna unit 10 and that each antenna unit 10 can be arranged as close as possible. Needless to say, the same can be realized when an antenna unit having a sub-reflecting plate provided at an angle of about 45 ° is used. In addition, the present invention can be variously modified and implemented without departing from the scope of the invention.

[0033]

As described above, according to the present invention, there is provided an antenna group for transmitting a plurality of broadcast waves from the same plane, which is formed by circularly arranging antenna units having different transmission radio frequencies in a circular arrangement. Since the transmitting antenna device is configured by providing radio waves with different radio frequencies and coaxially arranged in multiple stages in the vertical direction, the antenna array surface such as the steel structure part can effectively utilize the limited equipment space with a relatively large diameter, and It is possible to install an antenna capable of transmitting the broadcast wave.

Moreover, since the radio frequency of the broadcast wave assigned to the antenna provided on the upper side is made higher than the radio frequency of the broadcast wave assigned to the antenna on the lower side,
It is possible to effectively compensate for the reduction of the radio wave reach depending on the radio frequency by the height of the antenna, and thus it is possible to equalize the service areas of a plurality of broadcast waves regardless of the difference in radio frequency. The effect such as is achieved. Further, even when the antenna installation space is tapered toward the upper part like the steel frame structure, each antenna group can be effectively mounted while minimizing the diameter of the antenna mounting surface. Also, it becomes possible to construct a broadcasting tower in which the transmitting antenna device is compactly attached.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a transmission antenna device according to an embodiment of the present invention and a broadcasting tower in which the transmission antenna device is installed.

FIG. 2 is a diagram showing a configuration example of an antenna unit that constitutes the transmitting antenna device shown in FIG.

FIG. 3 is a diagram showing the sizes of side lobes and back lobes that change depending on the height h of the sub-reflector and the optimum range of the height h of the sub-reflector.

FIG. 4 is a diagram for explaining a feeding system of a multi-sided composite antenna including a plurality of antenna units and its operation.

FIG. 5 is a view for explaining the action of two multi-sided composite antennas formed in the same plane by a plurality of antenna units.

FIG. 6 is a diagram showing an example of a broadcasting tower in which a transmitting antenna for broadcasting is installed.

[Explanation of Codes] 10 Antenna Unit 11 4 Element Twin Loop Antenna (Antenna Element) 12 Main Reflector 13 Sub-Reflector 14 Protective Cover 20, 21, 22, ~ 25 Antenna Group (Multi-faceted Synthetic Antenna) 50 Broadcast Tower 60 Transmission Antenna apparatus

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01Q 21/20 H01Q 21/28 H01Q 21/30

Claims (5)

(57) [Claims] 1. A multi-frequency multi-sided synthesis by arranging three or more antenna units having the same number of planes, each constituting a plurality of multi-sided synthesis antennas having different transmission radio frequencies, in a circular arrangement in a predetermined order in an annular shape. And a plurality of antenna groups having different transmission radio frequencies, which are coaxially arranged in a vertical direction in multiple stages. 2. The plurality of antenna groups is characterized in that a plurality of antenna units respectively constituting the respective multi-faceted composite antennas are arranged at equal intervals on a predetermined circumferential surface. Transmitting antenna device. 3. The radio frequency assigned to each multi-sided composite antenna of the upper antenna group is set higher than the radio frequency assigned to each multi-sided composite antenna of the lower antenna group. Item 2. The transmitting antenna device according to Item 1. 4. A diameter of an antenna array surface on which a plurality of antenna units forming the lower-side antenna group are arranged in a ring shape, the diameter of an antenna array surface is such that a plurality of antenna units forming the upper-side antenna group are arranged in a ring shape. The transmitting antenna device according to claim 1, wherein the transmitting antenna device is set to have a diameter larger than a diameter of the array surface. 5. A broadcasting tower comprising the transmitting antenna device according to claim 1 at a predetermined ground clearance.