JP2001230719A - Broadcast wave relay system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a broadcast wave relay system capable of sufficiently securing isolation of a reception antenna and a transmission antenna and being suitable for SFN relaying ground wave digital broadcast waves. SOLUTION: Broadcast waves received through the reception antenna are relayed and retransmitted from the transmission antenna by the same broadcast frequency and especially the reception antenna 12 is provided on a position above he transmission antenna 13. Then, by providing non-directivity in a horizontal direction and setting the directivity so as to retransmit the broadcast waves to a side lower than the antenna installation height in a vertical direction in the transmission antenna, the useless radiation of radio waves in a sky direction is suppressed, the isolation between the antennas is sufficiently secured and the antennas are closely arranged.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a broadcast wave relay system for relaying a broadcast wave received via a receiving antenna and retransmitting the broadcast wave from the transmitting antenna at the same broadcast frequency.

[0002]

[Related Background Art] Terrestrial broadcasts such as television broadcasts are transmitted from a transmitting antenna 1 of a broadcasting station A, for example, as shown in FIG. The broadcast wave is received by the receiving antenna 2 of the relay station B, and is retransmitted from the transmitting antenna 3 of the relay station B to the broadcast service area covered by the relay station B.
(Broadcast). In particular, recently, in order to effectively use the broadcast frequency, a single frequency network (SFN) relay that provides the same television broadcast wave at the same broadcast frequency as the broadcast wave transmitted from the broadcast station A has been receiving attention. Furthermore, in terrestrial digital broadcasting, OFDM (Orthogonal Freq) that is resistant to interference (ghost)
Since the uency division multiplexing (orthogonal frequency division multiplexing) modulation method is used, the SFN relay can be performed effectively, and the frequency can be effectively used.

[0003]

By the way, the transmitting antenna 3 in the relay station B is generally provided above the broadcasting tower 4. In particular, the transmitting antenna 3 is exclusively used to secure a wide broadcasting service area by increasing the ground height,
It is often provided at the top of the broadcasting tower 4. Therefore, for the receiving antenna 2 installed below the transmitting antenna 3, the influence of the radio wave retransmitted by SFN relay cannot be ignored. Incidentally, when a broadcast wave (radio wave) transmitted (radiated) from the transmitting antenna 3 wraps around the receiving antenna 2 with an electric field strength of a certain level or more, oscillation occurs in the relay station B, the protection circuit is activated, and the broadcast is stopped. Fall into the waves.

Therefore, in the relay station B that performs SFN relay, it is important to ensure isolation between the receiving antenna 2 and the transmitting antenna 3. However, in order to secure the isolation between the antennas 2 and 3 by using the distance attenuation (free space attenuation) of radio waves (broadcasting waves), it is necessary to considerably increase the distance between the antennas. Receiving antenna 2 on top of 4
It is difficult to install the antenna and the transmitting antenna 3 close to each other.

The present invention has been made in view of such circumstances, and an object thereof is to dispose these antennas close to each other while ensuring sufficient isolation between a receiving antenna and a transmitting antenna. For example, an object of the present invention is to provide a broadcast wave relay system suitable for SFN relay of terrestrial digital broadcast waves.

[0006]

In order to achieve the above-mentioned object, a broadcast wave relay system according to the present invention relays a broadcast wave received via a receiving antenna and transmits the broadcast wave from the transmitting antenna at the same broadcast frequency. It is for retransmission, and is characterized in that the receiving antenna is provided at a position above the transmitting antenna.

That is, a broadcast wave service area provided by a transmitting antenna provided at a terrestrial broadcasting relay station is exclusively provided by:
The broadcast wave relay system according to the present invention is based on the fact that the broadcast wave is an area below (ground side) from the substantially same plane as the installation height of the transmitting antenna in the broadcast tower and the sky direction is not a service target of the broadcast wave. A receiving antenna for receiving a broadcast wave to be relayed in the system is provided above the broadcast wave serving area covered by the broadcast antenna.

Preferably, the transmitting antenna has a directivity for retransmitting a broadcast wave in a vertical direction below a height at which the antenna is installed, and the transmitting antenna is arranged in the sky direction. It is characterized by suppressing unnecessary radio wave radiation. Specifically, an array antenna or the like is used as a transmitting antenna, for example, by tilting its main beam downward, or by providing a reflector at the upper end of the antenna to suppress radiation in the sky direction. It is characterized in that a radio wave (broadcast wave of the same frequency) sneaking into a receiving antenna provided above is suppressed.

Further, even in the case of performing the relay (SFN relay) using the same broadcast frequency, the transmitting antenna and the receiving antenna are installed close to the same broadcasting tower. It is characterized by.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a broadcast wave relay system according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 2 is a schematic diagram of a main part of a broadcast wave relay system according to this embodiment, in which 11 is a broadcast tower provided in a relay station, 12 is a receiving antenna installed above the broadcast tower 11, and 13 is the broadcast A transmitting antenna that is provided at a position below the receiving antenna 12 in the tower 11 and that retransmits a broadcast wave received by the receiving antenna 12 at the same broadcast frequency as the broadcast wave.

The receiving antenna 12 is composed of, for example, a grid parabolic antenna of 3 mφ. The main beam direction is directed to a transmitting antenna (not shown) of a broadcasting station, and a broadcasting wave from the broadcasting station (for example, a terrestrial digital antenna) is transmitted. (A television broadcast wave). Note that a planar array antenna having unidirectionality as described later can be used as the receiving antenna 12.

On the other hand, the transmitting antenna 13 basically comprises an array antenna or a dual loop array antenna. In particular, the transmitting antenna 13 controls its directivity in the vertical direction by tilting its antenna surface toward the ground side by a predetermined angle or adjusting the phases and power distribution of a plurality of antenna elements. Beam is transmitting antenna 1
3 has a directivity from substantially horizontal to the lower side (ground side) with respect to the transmission center plane, and is set so as to suppress radiation toward the sky at the same time.

In order to suppress unnecessary radiation of radio waves from the transmitting antenna 13 to the sky side, and to efficiently radiate broadcast waves from a substantially horizontal plane at the antenna installation height to an area on the ground side, for example, A reflector (not shown) may be provided at the upper end of the antenna reflector of the transmitting antenna 13. In short, the directivity in the vertical direction is set so that many radio waves are radiated downward (on the ground side) from the transmitting antenna 13 with a depression angle.

Thus, according to the above-described broadcast wave relay system, the transmitting antenna 13 transmits a radio wave (broadcast wave) from the ground height where the antenna 13 is installed to a lower side (ground side), Since the receiving antenna 12 for receiving the radio wave from the station is located above the transmitting antenna 13 and is installed at the uppermost end of the broadcast tower 11, the radio wave (broadcast wave) radiated from the transmitting antenna 13 is It is possible to effectively suppress the wraparound to the receiving antenna 12, and it is possible to sufficiently secure the isolation between the antennas.

That is, since the receiving antenna 12 only receives a broadcast wave from a broadcasting station, its main beam direction is sharply directed toward the broadcasting station, whereas the transmitting antenna 13 is Located below the antenna 12,
Broadcast waves (radio waves) are mainly radiated downward (ground side) from the transmission center plane, so that the radio wave directivity area of the receiving antenna 12 and the radio wave directivity of the transmitting antenna 13 are schematically shown in FIG. It is possible to avoid overlapping with the area. As a result, the isolation between the receiving antenna 12 and the transmitting antenna 13 is made sufficiently large, and the radio wave (broadcast wave) radiated from the transmitting antenna 13 is effectively suppressed from entering the receiving antenna 12. It becomes possible.

Therefore, although the broadcast wave received by the receiving antenna 12 is relayed and retransmitted (SFN relay) from the transmitting antenna 13 at the same broadcast frequency, the broadcast wave (radio wave) is It is possible to effectively prevent undesired oscillation at the relay station by preventing looping. Furthermore, as described above, the reception antenna 12 and the transmission antenna 13 can be provided close to the same broadcast tower 11 while securing the isolation between the antennas 12 and 13, so that the equipment space can be reduced. Thus, the system configuration can be simplified. Specifically, for example, the distance attenuation (free space attenuation) of a radio wave (broadcast wave) is increased by separating the reception antenna 12 and the transmission antenna 13 by 1000 m or more, thereby securing isolation between the antennas. There is an advantage that there is no need to take systematic measures.

In order to reduce the size of the receiving antenna 12, a rectangular planar array antenna as shown in FIG. 3, for example, may be used instead of the above-mentioned 3 mφ grid parabolic antenna. This planar array antenna has a microstrip antenna on a rectangular antenna reflector 21 made of a metal flat plate, as schematically shown in FIGS. A plurality of antenna elements (radiating elements) 22 are arranged, and an interference preventing body 23 having a substantially cylindrical conductor surface is provided at an end (upper and lower ends) of the antenna reflector 21. It has a structure provided in parallel. In the figure, reference numeral 24 denotes a radome made of, for example, FRP resin and provided on the upper surface of the antenna reflector 21 so as to cover the antenna element (radiating element) 22.
Reference numeral 25 in the figure denotes a stay for attaching the interference preventing body 23 to the end of the antenna reflector 21.

More specifically, this planar array antenna (receiving antenna 12) has, for example, a size of 1200 mm on one side.
Reflector 21 made of a rectangular conductor (metal plate)
A configuration in which four antenna elements (microstrip antennas) 22 are arranged in a square at a predetermined height above, that is, at an installation interval of 0.5λ in the vertical direction and 0.8λ in the horizontal direction via the air layer Is done. In addition, these antenna elements (microstrip antennas) 22 are
It may be formed on a dielectric substrate (not shown) of about 25 mm, and the antenna reflector 21 may be formed on the back side of the dielectric substrate.

The anti-interference member 23 provided at the end of the antenna reflector 21 has a length substantially equal to the width of the end of the antenna reflector 21, and is a substantially cylindrical conductor having an outer diameter of 80 mmφ. It consists of a rod having a surface. The anti-interference body 23 may be made of a material having conductivity such as metal, but may be formed by forming a conductive metal film on the surface of an insulating material or by plating. Is also good.
As shown in FIGS. 4A to 4C, examples of the structure of the interference preventing body 23 include a columnar body, a cylindrical body (pipe), and a substantially columnar surface. It may be an octagon that can be regarded as being formed, or a polygonal prism having a larger number of faces. Further, as shown in FIG. 4D, a semi-circular (semi-cylindrical) shape having a substantially cylindrical surface only on the antenna reflector 21 side may be used.

The interference preventing body 23 has its longitudinal direction parallel to the end of the antenna reflector 21 and is separated from the end of the antenna reflector 21 directly or via a stay 25 by a predetermined distance L. It is attached and is electrically coupled to the antenna reflector 21. The mounting height position of the interference preventing body 23 is determined by the height of the interference preventing body 23 specified by the diameter D of the interference preventing body 23 such that the surface formed by the antenna reflection plate 21 and the antenna surface formed by the antenna element 22 are determined. Is set to fall within the range.

According to the planar antenna provided with such an interference preventive body 23, as shown in FIG. 5, the antenna characteristics when the diameter D of the interference preventive body 23 is changed. As a result, it has been found that the antenna characteristics are improved particularly by about 10 dB in the side lobe level in the ± 90 ° direction. In addition, it was confirmed that when the diameter D of the interference preventing body 23 is a certain size, and in this example, when the diameter D is 80 mmφ, the best improvement effect of the antenna characteristics can be expected.

FIG. 6 shows the antenna characteristics when the space L (separation distance) between the interference preventing member 23 and the antenna reflecting plate 21 is changed. When mounted (the mounting interval L is 0 mm), the side lobe level in the substantially 90 ° direction can be reduced as a whole,
It was confirmed that the side lobe level in the 90 ° direction could be significantly reduced locally when mounted at a distance of about 80 mm.

The side lobe in the 90 ° direction can be reduced by providing the interference prevention member 23 at the end of the antenna reflector 21 because the diffraction of the radio wave generated at the end of the antenna reflector 21 is substantially cylindrical. This is considered to be caused by interference components of the radio wave in various directions by the interference preventing body 23 having the conductor surface of the above. This is because even if a quadrangular pole-shaped rod-shaped conductor is provided at the end of the antenna reflector 21 in the same manner as the interference preventing body 23, the effect of reducing the side lobe level in the 90 ° direction cannot be expected so much. Considering that, when this quadrangular prism-shaped conductor is used, it is considered that the reflection components of the radio waves generated at the end of the antenna reflector 21 are aligned in a certain direction, and as a result, the diffraction is hardly disturbed. Because.

Thus, according to the planar antenna having the above-described configuration, the side lobe in the 90 ° direction on the side where the interference preventing member 23 is mounted can be reduced by about 10 dB. Moreover, without increasing the size of the antenna reflector 21,
Unnecessary reflection components can be suppressed by reducing side lobes in the 90 ° direction. As a result, the planar antenna (receiving antenna 12) is connected to the transmitting antenna 13 as described above.
Even in the case where they are provided side by side, sufficient isolation from the transmitting antenna 13 can be ensured, and the size can be reduced. Therefore, it is easy to suppress interference with an antenna of the same frequency band installed adjacently, and it is extremely useful, for example, to use the antenna as an SFN relay antenna described above.

The transmitting antenna 13 can be realized as a multi-plane composite antenna in which a plurality of antenna units are arranged in a ring. Incidentally, each of the above-mentioned antenna units is a two-element double-loop antenna having a loop-shaped radiating element, for example, as shown in FIG. (Antenna element) 31 and a flat main reflector 32 provided on the back side of the two-element dual loop antenna 31 in parallel with the antenna surface, and both ends of the main reflector 32 in the antenna horizontal plane direction And a sub-reflection plate 33 provided in each section. The sub reflector 33 is substantially perpendicular to the main reflector 32 (for example, 90 ± 10
°), and the height h is set to about 0.01λ to 0.14λ with respect to the wavelength λ of the broadcast frequency.

Here, as the antenna element,
An antenna unit 30 having a structure in which six two-element dual loop antennas 31 are arranged in three rows and two stages is shown. Further, the two-element dual loop antenna 31 has an arc-shaped loop antenna element portion (radiating element) 35 whose circumference L is approximately one wavelength (λ) of the broadcast wave frequency, and is reduced to approximately 波長 wavelength (λ / 2). , And two elements are formed via the parallel feeder 36 having a length of.

When a multi-plane composite antenna composed of a plurality of such antenna units arranged in an annular shape is used as the above-described transmitting antenna 13, for example, the antenna surface of each antenna unit is set to the ground side. The antenna is tilted so as to be depressed, and the feeding phase and the feeding power to the plurality of two-element dual loop antennas 31 are adjusted to radiate radio waves from the horizontal plane to the lower side (ground side), and the sky side (upper side) ) May be suppressed.

Using the receiving antenna 12 and the transmitting antenna 13 configured as described above, the receiving antenna 12 positioned above the transmitting antenna 13
According to the broadcast wave relay system that relays the broadcast wave received at the same time and retransmits it from the transmitting antenna at the same broadcast frequency, it is possible to ensure a sufficiently high isolation between the antennas. The relay of the broadcast wave (SFN relay) can be performed stably without inviting troubles such as interference and oscillation. In addition, since the receiving antenna 12 and the transmitting antenna 13 can be provided vertically close to each other, the broadcast tower 11 having a limited height can be effectively used and S
There are many practical effects such as FN relay.

The present invention is not limited to the above embodiment. For example, the broadcast wave to be relayed is FM
It goes without saying that any broadcast wave of the band, the VHF band, and the UHF band may be used, and the broadcast wave is not limited to the television broadcast. The receiving antenna 12 and the transmitting antenna 13
Is only required to conform to the specifications, and the antenna type is not particularly limited. In controlling the directivity of the transmitting antenna 13 in the vertical direction, not only the above-described electrical control such as the phase control and the power distribution control, but also mechanical adjustments such as adjusting each antenna mounting and devising a reflector. Control may be performed. In addition, the present invention can be variously modified and implemented without departing from the gist thereof.

[0030]

As described above, according to the present invention, in a broadcasting relay system for retransmitting a broadcast wave received via a receiving antenna at the same frequency via a transmitting antenna, a receiving antenna is provided. Provided above the transmitting antenna, the transmitting antenna has omnidirectionality in the horizontal direction, and its directivity in the vertical direction so as to retransmit broadcast waves below the antenna installation height. , So that the isolation between the receiving antenna and the transmitting antenna can be simplified and effectively secured,
In addition, a great effect in practical use such as the fact that these antennas can be arranged close to each other can be obtained.

Therefore, the receiving antenna and the transmitting antenna are installed in the same broadcasting tower, so that the broadcast wave at the same frequency can be effectively relayed, and the overall structure of the broadcast wave relay system can be simplified. And the like.

[Brief description of the drawings]

FIG. 1 is a diagram showing the concept of a conventional general broadcast wave relay.

FIG. 2 is a diagram showing a schematic configuration of a broadcast wave relay system according to an embodiment of the present invention.

FIG. 3 is a diagram showing an example of a receiving antenna used in the broadcast wave relay system of the embodiment shown in FIG. 2;

FIG. 4 is a view showing an example of the shape of an interference preventing body incorporated in the receiving antenna (flat antenna) shown in FIG. 3;

FIG. 5 is a view showing a change in antenna characteristics when the size (diameter D) of the interference preventing body is changed in the planar antenna shown in FIG. 4;

FIG. 6 is a diagram showing a change in antenna characteristics when the distance L between the end of the antenna reflector and the interference preventing body is changed in the planar antenna shown in FIG. 4;

FIG. 7 is a diagram showing a configuration example of an antenna unit forming a multi-plane combined antenna used as a transmission antenna in the broadcast wave relay system of the embodiment shown in FIG. 2;

[Explanation of symbols]

 11 Broadcast Tower 12 Receiving Antenna 13 Transmitting Antenna

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Reiji Fukuhara 2-6-1 Marunouchi, Chiyoda-ku, Tokyo Inside Furukawa Electric Co., Ltd. (72) Kazuo Kogure 2-6-1 Marunouchi, Chiyoda-ku, Tokyo No. Furukawa Electric Co., Ltd. 5K072 AA04 BB14 BB27 CC05 CC33 GG02 GG14

Claims (3)

[Claims] 1. A broadcast wave relay system for relaying a broadcast wave received via a receiving antenna and retransmitting the same at the same broadcast frequency from a transmitting antenna, wherein the receiving antenna is A broadcast wave relay system provided at an upper position. 2. The broadcast wave relay system according to claim 1, wherein the transmission antenna has a directivity for retransmitting a broadcast wave vertically below the antenna installation height. 3. The broadcast wave relay system according to claim 1, wherein the transmitting antenna and the receiving antenna are installed in the same broadcasting tower.