JP4015082B2 - Broadcast antenna apparatus and broadcast tower - Google Patents

Description

  The present invention relates to a transmission antenna device and a broadcast tower suitable for transmission of terrestrial digital broadcasting.

  Recently, preparations for the practical application of terrestrial digital broadcasting are being promoted. This terrestrial digital broadcast is intended to digitize TV broadcasts in the UHF band, and is intended to increase the amount of information transmitted such as video and audio while increasing the number of channels in a limited frequency band and to provide high-quality information. It has excellent features such as providing services.

  By the way, in the UHF band broadcast transmitting antenna apparatus, for example, as shown in FIG. 9, a plurality of, for example, four antenna units 1a, 1b, 1c, 1d are arranged in an annular shape, and each of these antenna units 1a, 1b, 1b, The radio waves are transmitted by combining the radiated power radiated from 1c and 1d. Note that this type of broadcasting transmission antenna apparatus (a plurality of antenna units 1a, 1b, 1c, 1d) is usually formed in an annular shape at the upper position of the tower (broadcast tower) 2 at a predetermined ground level. It is provided surrounded by. In addition, since each antenna unit 1a, 1b, 1c, 1d has a limited installation space for the broadcast transmitting antenna device in the upper part of the steel tower 2, the antenna unit 1a, 1b, 1c, 1d is exclusively disposed on a predetermined reflecting plate in parallel with the reflecting plate. A vertically long and compact one provided with a loop antenna is used.

  Incidentally, the double loop antenna is composed of a pair of loop antenna elements whose loop length (peripheral length) is set to be substantially equal to the transmission wavelength λ of the broadcast wave, arranged side by side on the same plane at a predetermined distance. In addition, a plurality of (for example, two) twin loop antennas are provided so that each loop antenna element is arranged in a straight line to constitute each antenna unit, thereby increasing the antenna gain.

According to the antenna unit configured using such a dual loop antenna, for example, as shown in FIGS. 10A and 10B, the loop antenna elements 3a, 3b, 3c, and 3d are arranged in a direction orthogonal to the arrangement thereof. By supplying power with the same phase, it is possible to transmit horizontally polarized radio waves orthogonal to the direction in which the loop antenna elements 3a, 3b, 3c, and 3d are arranged (see, for example, Patent Document 1). Further, as shown in FIG. 10 (c), each loop antenna element 3a, 3b, 3c, 3d is fed with the same phase in the direction of the arrangement, and the radio waves vertically polarized in the direction of the arrangement of the loop antenna elements Can be transmitted (see, for example, Patent Document 2).
JP 2002-223119 A JP 2003-152425 A

  By the way, the broadcast transmission antenna apparatus is installed so as to secure a predetermined broadcast service area. However, depending on the location, broadcast waves transmitted from a plurality of transmission antenna apparatuses may overlap and cause interference (interference). For example, on a remote island C in the service area of the broadcast tower A, there is a possibility that the broadcast wave transmitted from the broadcast tower A and the broadcast wave transmitted from the broadcast tower B on the opposite bank may interfere (interfere). In order to avoid such interference, generally, measures such as making the broadcast wave frequencies (broadcast channels) from the plurality of broadcast towers (transmitting antenna devices) A and B adjacent to the service area different from each other are taken. However, when the management of the broadcast towers A and B is different (for example, when the broadcast tower B belongs to another country), it may be impossible to avoid the interference (interference) of the broadcast wave.

  Incidentally, in the case of analog broadcasting, a certain level of video / audio quality (reception quality) can be ensured even if some interference (interference) occurs. However, in the case of digital broadcasting, the broadcast wave may not be received at all. Therefore, it is conceivable to change from a commonly used horizontal polarization to a vertical polarization for a service area including a region where interference (interference) of broadcast waves is assumed. However, in this case, it is unavoidable that the reception antenna must be changed in all the service areas including areas where there is no interference (interference), and this becomes a factor that hinders the digitization of broadcast waves.

  The present invention has been made in consideration of such circumstances, and its purpose is to avoid interference of broadcast waves without taking a major measure such as changing the polarization plane of broadcast waves from horizontal polarization to vertical polarization. Provided are a broadcasting antenna device and a broadcasting tower having a simple configuration capable of transmitting a broadcasting wave capable of ensuring a good reception state for all broadcasting service areas including an area where (interference) is assumed. There is.

In order to achieve the above-described object, a broadcasting antenna apparatus according to the present invention has a plurality of antenna units arranged in an annular shape, and transmits radio waves by combining the power radiated from each of these antenna units. There,
In particular, among the plurality of antenna units, a specific antenna unit is set so as to radiate a radio wave including a polarization component and another polarization component respectively radiated from another antenna unit.

  Preferably, each of the other antenna units radiates one of a horizontally polarized wave and a vertically polarized wave, and the specific antenna unit includes a horizontally polarized wave component and a vertically polarized wave component. It is configured to emit radio waves, specifically radio waves obliquely polarized with respect to the ground surface (obliquely polarized waves) or circularly polarized radio waves.

  In addition, it is desirable that the antenna units have the same shape in which a double loop antenna is provided on the reflecting plate in parallel with the reflecting plate. For the specific antenna unit, the feeding point and / or the phase of the feeding power to the loop antenna element constituting the dual loop antenna is set to the loop antenna element constituting the twin loop antenna in the other antenna unit. What is necessary is just to comprise so that the electromagnetic wave which has a polarization plane different from another antenna unit may be radiated | emitted by making it differ from a feed form.

  The broadcasting tower according to the present invention is realized by installing the broadcasting antenna device having the above-described configuration at a position (for example, an upper portion of a steel tower) where the specific antenna unit is directed to a radio wave interference area and has a predetermined ground height. The

  According to the broadcasting antenna device and the broadcasting tower having such a configuration, if the specific antenna unit described above is installed toward a radio wave interference area, a polarization different from the interference wave (for example, horizontal polarization) is directed toward this area. A radio wave having a wavefront (for example, oblique polarization or circular polarization) is transmitted. Therefore, in a radio wave interference area, it is possible to receive a broadcast wave without radio wave interference (interference) by receiving the polarization component (for example, vertical polarization component). In areas other than the radio interference area, it is only necessary to receive radio waves of a predetermined polarization plane (for example, horizontal polarization) obtained by combining the power radiated from the plurality of antenna units. It is possible to satisfactorily receive the broadcast wave using the receiving antenna. Accordingly, it is possible to transmit a broadcast wave that can ensure a good reception state for all the broadcast service areas including the radio wave interference area.

  In addition, only for a specific antenna unit among a plurality of antenna units, the polarization component radiated from each of the other antenna units is simply changed to the loop antenna element that constitutes the dual loop antenna. Since radio waves including different polarization components can be radiated, it can be realized as a broadcasting antenna apparatus having a simple structure without significantly changing the overall configuration of the plurality of antenna units. By the way, the specific antenna unit radiates radio waves including polarization components (horizontal polarization components) and other polarization components (vertical polarization components) emitted from other antenna units. Thus, there is no problem in synthesizing the power radiated from the plurality of antenna units in order to transmit the horizontally polarized broadcast wave over all directions. Therefore, it is possible to efficiently transmit broadcast waves to all of the broadcast service areas with a broadcast antenna apparatus having a simple configuration in which the power supply forms for the plurality of antenna units are different.

Hereinafter, a broadcast antenna device and a broadcast tower according to embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a planar configuration of a broadcast tower 10 and a broadcast antenna apparatus incorporated in the upper part of the broadcast tower 10. A plurality of broadcast antenna apparatuses are arranged in a ring around the upper steel tower of the broadcast tower 10. It is configured by (for example, four) antenna units 11 (11a, 11b, 11c, 11d). Each of these antenna units 11 comprises a reflection plate 12 provided with a dual loop antenna 13 as a radiating element in parallel with the reflection plate 12, as will be described in detail later with reference to FIG. . As shown in FIG. 2, the broadcast antenna apparatus constituted by these antenna units 11 combines the electric power (radio wave energy) radiated from each antenna unit 11 to omnidirectionally. A radio wave having a substantially uniform electric field strength is transmitted over the entire area.

  The broadcast antenna apparatus according to this embodiment is characterized by a transmission wave (radio wave) radiated from a specific antenna unit, for example, the antenna unit 11a, facing the radio wave interference area among the plurality of antenna units 11. The polarization component is set so as to include the polarization component of the transmission wave (radio wave) radiated from each of the other antenna units 11b, 11c, and 11d and the other polarization component. Then, with respect to the direction in which the specific antenna unit 11a faces, the other polarization component is simultaneously transmitted together with the electric field intensity component transmitted substantially uniformly over the above-mentioned all directions.

  Specifically, when the other antenna units 11b, 11c, and 11d radiate horizontally polarized broadcast waves (radio waves), the specific antenna unit 11a receives a horizontal polarization component H and the horizontal polarization component. A broadcast wave (radio wave) including a vertical polarization component V different from H, for example, a broadcast wave (radio wave) having a polarization plane (oblique polarization) oblique to the ground surface, or its polarization plane in terms of time. It emits a circularly polarized broadcast wave (radio wave) that changes.

  Here, of the four antenna units 11a, 11b, 11c, and 11d, only one specific antenna unit 11a installed toward the radio wave interference area radiates the above-described obliquely or circularly polarized radio waves. In the case where there is a radio wave interference area in the middle of the direction in which two adjacent antenna units face each other, the two adjacent antenna units (for example, the antenna units 11a and 11b) are described. ) May be configured to radiate the above-described obliquely polarized wave or circularly polarized radio wave.

  In this way, a horizontally polarized radio wave H is transmitted from the other antenna units 11b, 11c, and 11d, and an obliquely polarized radio wave S is transmitted from the specific antenna unit 11a. According to FIG. 2, the horizontal polarization component Hs of the obliquely polarized radio wave C and the horizontal polarization component H radiated from the other antenna units 11b, 11c, and 11d as shown in FIG. Thus, a horizontally polarized radio wave having a substantially uniform electric field intensity α is transmitted in all directions. Further, the vertical polarization component Hs of the obliquely polarized radio wave S is also emitted in the direction in which the specific antenna unit 11a faces. Therefore, in an area in which the specific antenna unit 11a is installed, not only horizontally polarized radio waves (broadcast waves) α but also vertically polarized radio waves (broadcast waves) β can be received. . Therefore, in an area where radio wave interference occurs like the above-mentioned remote island C, the receiving antenna (not shown) is simply installed so as to receive the vertical polarization component V instead of the horizontal polarization component H where radio wave interference occurs. Thus, the broadcast wave can be received satisfactorily (without causing radio wave interference). In other areas where there is no problem of radio wave interference, the horizontal polarization component H can be received as before, so that a good broadcast service can be provided to all of the broadcast service areas.

  Here, the specific configuration of the antenna unit 11 described above will be described. Each antenna unit 11 is, for example, vertically long as shown in FIGS. 3A to 3C in its plan view, side view, and bottom view. The two double-loop antennas 13a and 13b as radiating elements are arranged side by side on the main reflector 12a having a rectangular shape in parallel with the main reflector 12a. As is well known, the dual loop antenna 13 (13a, 13b) includes a loop element 14 having a loop length (peripheral length) substantially equal to the transmission wavelength λ, which is separated by approximately one wavelength, and is provided with two dual loop antennas. The loop elements 13a and 13b are arranged so that these loop elements 14 are arranged in a straight line at a distance of approximately one wavelength.

  The main reflector 12a described above is disposed behind these double loop antennas 13a and 13b, and reflects one side of the radio wave radiated in the direction of the central axis of each loop element 14 to reduce the back lobe. To play a role. Further, auxiliary reflectors 12b are provided on the side edges of the main reflector 12a at an angle of approximately 45 ° with respect to the main reflector 12a. These auxiliary reflecting plates 12b play a role of narrowing the width of the main reflecting plate 12a necessary for reducing the above-mentioned back lobes, and reduce side lobes of radio waves radiated from the double loop antennas 13a and 13b. Take a role to reduce. Since the reflector 12 composed of the main reflector 12a and the auxiliary reflector 12b has been proposed in the past, the detailed description thereof will be omitted. Further, a technique for transmitting horizontally polarized radio waves from the antenna unit 11 having such an antenna shape is disclosed in Patent Document 1 described above, and a technique for transmitting vertically polarized radio waves is disclosed in Patent Document 2 described above. The description thereof will be omitted here.

  Now, the transmitting antenna device according to the present invention has an obliquely polarized radio wave (broadcast wave) or circular polarization as described above from a specific antenna unit 11a in the antenna unit 11 having the antenna shape as shown in FIG. A radio wave (broadcast wave) is transmitted, and the specific method will be described below.

  When the antenna unit 11 is composed of one twin loop antenna 13, as shown in FIGS. 4 (a) and 4 (b), radio waves horizontally polarized from one of the two loop antenna elements 14 constituting the dual loop antenna 13 are obtained. Each loop antenna element 14 may be driven in the same phase so as to radiate and radiate vertically polarized radio waves from the other loop antenna element 14. Specifically, as shown in FIG. 4A, one loop antenna element 14a is balancedly fed from a direction perpendicular to the direction in which the two loop antenna elements 14a and 14b are arranged, and the other loop antenna element 14b is supplied. May be balanced and fed from the same direction as the arrangement direction. In this way, as shown in FIG. 4 (b), horizontally polarized radio waves are radiated from one loop antenna element 14a, and vertically polarized radio waves are radiated from the other loop antenna element 14b. Therefore, these radio waves are combined in space (antenna radiation surface) and the obliquely polarized radio waves are radiated from the double loop antenna 13 (antenna unit 11).

  Alternatively, as shown in FIG. 4 (c), if balanced power is supplied to the loop antenna elements 14a, 14 from a direction inclined by 45 ° with respect to the direction of the arrangement, the loop antenna elements 14a, 14b are respectively inclined ( A radio wave polarized at 45 ° is emitted.

  In the case where the antenna unit 11 is configured with two dual loop antennas 13a and 13b, as shown in FIGS. 5 (a) and 5 (b), the horizontally polarized radio wave from one of the dual loop antennas 13a is generated. It is only necessary to radiate and radiate vertically polarized radio waves from the other dual-loop antenna 13a. Specifically, as shown in FIG. 5A, unbalanced power is supplied to one of the twin loop antennas 13a, and horizontally polarized radio waves having a plane of polarization in a direction perpendicular to the direction of the arrangement of the loop antenna elements. The other dual-loop antenna 13a is configured to radiate, and a feed point is set in each of the loop antenna elements 14 in the arrangement direction thereof, and balanced feeding is performed to radiate vertically polarized radio waves. .

  Alternatively, as shown in FIG. 5 (b), with respect to one twin-loop antenna 13a, each loop antenna element 14 is set to a feed point in a direction perpendicular to the arrangement direction of the loop antenna elements 14, and is balancedly fed to be horizontally polarized. The other dual-loop antenna 13b is radiated with a balanced feed by setting a feeding point in each of the loop antenna elements 14 in the arrangement direction in the same manner as shown in FIG. 5 (a). Radiate vertically polarized radio waves. In these cases, it goes without saying that the dual loop antennas 13a and 13b are driven in the same phase.

  In this way, the form of power feeding to the two dual-loop antennas 13a and 13b is made different so that the radio waves horizontally polarized from one dual-loop antenna 13a and vertically polarized from the other dual-loop antenna 13b. 5 (c), the horizontal polarization component and the vertical polarization component are combined on the space (antenna radiation plane), so that From the antenna unit 11 including the two dual loop antennas 13a and 13b, radio waves polarized in an oblique direction are radiated.

  When circularly polarized radio waves are radiated from the dual loop antenna 13, for example, as shown in FIGS. 6A to 6C, the two loop antenna elements 14a and 14b constituting the dual loop antenna 13 are provided. As described above, the feeding points of the two loop antenna elements 14a and 14b may be driven with a phase difference of [π / 2]. Specifically, as shown in FIG. 6 (a), the phase of the feeding power to each loop antenna element 14a, 14b is changed to [π / 2] by changing the line length of the feeding line to the two loop antenna elements 14a, 14b. A phase shifter 15 that gives a phase difference of [π / 2] is inserted in the middle of the feed line to one loop antenna element 14a as shown in FIG. 6B. It ’s fine.

  If the radio waves horizontally polarized from one loop antenna element 14a and the radio waves vertically polarized from the other loop antenna element 14a are radiated in this way, the radiation is radiated from each loop antenna element 14a. The phase of the radio wave synthesized in space (antenna radiation surface) rotates in time because the generated radio wave has a [π / 2] phase shift, so that circularly polarized radio waves are radiated here. It becomes possible. As shown in FIG. 6C, obliquely polarized radio waves are emitted from one loop antenna element 14a, and obliquely polarized radio waves are emitted from the other loop antenna element 14b. Even when the phase of the power supplied to the loop antenna elements 14a and 14b is shifted by [π / 2], similarly circularly polarized radio waves can be obtained.

  In the case of the antenna unit 11 configured with two dual loop antennas 13a and 13b, circularly polarized radio waves are radiated from the dual loop antennas 13a and 13b as shown in FIG. These radio waves may be synthesized in space to increase the radio wave intensity. Even in this case, it is sufficient to supply power to the dual loop antennas 13a and 13b as shown in FIGS. Further, as shown in FIG. 7 (b), a vertically polarized radio wave is radiated from the double loop antenna 13a, and a horizontally polarized radio wave is radiated from the double loop antenna 13b to each of the double loop antennas 13a and 13b. Even when the phase of the power supply is shifted by [π / 2], similarly, a circularly polarized radio wave can be obtained.

  Thus, as described above, a radio wave including a horizontally polarized wave component and a vertically polarized wave component (an obliquely polarized wave or a circularly polarized wave) is radiated from a specific antenna unit 11a, and another antenna unit 11b, According to the transmitting antenna device configured to radiate horizontally polarized radio waves from 11c and 11d, the radio waves (broadcast waves) horizontally polarized in all directions are efficiently transmitted, and The vertically polarized radio wave (broadcast wave) can be transmitted simultaneously in the direction in which the antenna unit 11a is installed. Therefore, the problem of radio wave interference can be effectively solved simply by installing the specific antenna unit 11a described above toward an area where radio wave interference (interference) occurs. In particular, in most broadcasting service areas where there is no problem of radio wave interference, broadcast waves are transmitted by general horizontal polarization, so digital broadcast waves can be transmitted using existing analog broadcast reception antennas as they are. Reception is possible, and the transition to digitalization can proceed smoothly.

  Considering the intensity (electric field intensity pattern) of the broadcast wave (radio wave) transmitted from the transmitting antenna device, the horizontal polarization of the same intensity from the four antenna units 11 (11a, 11b, 11c, 11d). When the generated electric power (radio wave) is radiated, the electric field strength with respect to all directions becomes substantially uniform as shown in FIG. However, the electric field intensity in the direction perpendicular to the antenna surface of each antenna unit 11 (direction of 0 °, 90 °, 180 °, 270 °) and the intermediate direction between adjacent antenna units 11 (45 °, 135 °, 225) The combined electric field strength (degrees of 315 °) is slightly higher than other directions, but it can be said that the radiation characteristics are generally omnidirectional.

  On the other hand, when the polarization plane of the radio wave radiated from one specific antenna unit 11a is an oblique polarization, the electric field with respect to the installation direction (0 ° direction) of the antenna unit 11a as shown in FIG. Although the strength is slightly reduced, it can be omnidirectional as a whole. However, in this case, as indicated by a dotted line in FIG. 8B, although the electric field strength of the horizontal polarization component is slightly lower, the vertical polarization component is also radiated. Accordingly, in the installation direction (0 ° direction) of this specific antenna unit 11a, it is possible to receive both the horizontal polarization component and the vertical polarization line segment of the broadcast wave without hindrance. Therefore, if there is a problem of radio wave interference in the horizontal polarization component, the problem can be solved if radio waves of the vertical polarization component are received.

  On the other hand, there is a case where a specific antenna unit 11a cannot be installed in an area where there is a problem of radio wave interference. In this case, if radio waves polarized obliquely are radiated from the two adjacent antenna units 11a and 11b, the vertical deviation between the two antenna units 11a and 11b is obtained as shown in FIG. Since wave components can also be combined, a vertically polarized broadcast wave can be transmitted together with a horizontally polarized broadcast wave over a wider range. Therefore, even in a case where areas with problems of radio wave interference (interference) are widely dispersed, this can be effectively dealt with.

  The present invention is not limited to the embodiment described above. Here, a broadcasting antenna apparatus using four antenna units has been described, but the number of antenna units arranged in an annular shape may be determined according to the facility specifications. Incidentally, as the number of antenna units increases, the difference in electric field strength with respect to all directions can be reduced. However, since the diameter for arranging a plurality of antenna units in an annular shape increases, the size of the steel tower is actually increased. It is sufficient to determine the number in consideration of. Also, the form of power supply for each antenna unit may be set according to the specifications, and various power supply methods conventionally proposed can be appropriately employed. Also, here, radio waves with horizontally polarized waves are transmitted from other antenna units, and radio waves with a polarization plane that prevents interference with horizontally polarized radio waves are transmitted from specific antenna units. The present invention can be applied in the same manner when transmitting a radio wave. In addition, the present invention can be variously modified and implemented without departing from the scope of the invention.

The figure which shows schematic structure of the broadcast tower and the antenna apparatus for transmission attached to this broadcast tower. The figure which shows the electric field strength pattern of the antenna apparatus for transmission which concerns on this invention. The figure which shows the structural example of the antenna unit which comprises the transmitting antenna apparatus which concerns on this invention. The figure which shows the example of the electric power feeding form with respect to the double loop antenna which radiates | emits the radio wave polarized diagonally. The figure which shows the example of the electric power feeding form with respect to each said double loop antenna at the time of radiating | emitted the radio wave polarized diagonally from the antenna unit provided with two double loop antennas. The figure which shows the example of the electric power feeding form with respect to the double loop antenna which radiates | emits the circularly polarized electric wave. The figure which shows the example of the electric power feeding form with respect to each said double loop antenna at the time of radiating | emitted the circularly polarized electromagnetic wave from the antenna unit provided with two double loop antennas. The figure which shows an electric field strength pattern when changing the polarization plane of the electromagnetic wave radiated | emitted from a specific antenna unit. The figure which shows schematic structure of the antenna apparatus for transmission. The figure which shows the electric power feeding form in radiating | emitting the horizontally polarized broadcasting wave from the antenna unit comprised using a twin loop antenna, and the electric power feeding form in radiating | emitting a vertically polarized broadcasting wave, respectively.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Broadcasting tower 11,11a, 11b, 11c, 11d Antenna unit 12 Reflector 13,13a, 13b Double loop antenna 14,14a, 14b Loop antenna element 15 Phase shifter

Claims (5)

A plurality of antenna units arranged in an annular shape, a broadcasting antenna device that transmits radio waves by combining the power radiated from each of these antenna units,
A broadcast in which a specific antenna unit among the plurality of antenna units is set to radiate a radio wave including a polarization component and another polarization component respectively radiated from another antenna unit. Antenna device. Each of the other antenna units radiates one of a horizontally polarized wave and a vertically polarized wave, and the specific antenna unit emits a radio wave including a horizontally polarized wave component and a vertically polarized wave component. The broadcasting antenna apparatus according to claim 1, wherein the broadcasting antenna apparatus is configured to radiate. Each antenna unit is composed of a double loop antenna provided on the reflecting plate in parallel with the reflecting plate,
The specific antenna unit makes a feeding point to a loop antenna element constituting a dual loop antenna of the specific antenna unit different from a feeding point to a loop antenna element constituting a dual loop antenna in the other antenna unit. Thus, the broadcasting antenna apparatus according to claim 1 or 2, which radiates a radio wave having a polarization plane different from that of the other antenna unit. Each antenna unit is composed of a double loop antenna provided on the reflecting plate in parallel with the reflecting plate,
The specific antenna unit makes a feeding point to a loop antenna element constituting a dual loop antenna of the specific antenna unit different from a feeding point to a loop antenna element constituting a dual loop antenna in the other antenna unit. In addition, a polarization plane different from that of the other antenna units is obtained by giving a shift of [π / 2] to the phase of the power supplied to the two loop antenna elements constituting the dual loop antenna in the specific antenna unit. The broadcasting antenna device according to claim 1, wherein the broadcasting antenna device emits radio waves having 5. A broadcasting tower according to claim 1, wherein the broadcasting antenna device according to any one of claims 1 to 4 is installed at a position where the specific antenna unit is at a predetermined height above the radio interference area.

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