JP3386418B2 - Re-radiated wave elimination device for television transmitting antenna. - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a re-radiated wave removing device for a television transmitting antenna, which is used for countermeasures against ghost interference in television broadcasting.

[0002]

2. Description of the Related Art Television radio transmission towers are installed at high altitudes such as at the top of mountains by broadcasting frequency (channel).
Multiple units are installed. Since these transmitting towers are installed close to each other, the radio waves radiated from the transmitting antennas of one transmitting tower are received by the transmitting antennas of other transmitting towers, propagate through the feeder line, and are reflected by the distributor. Then, it may be re-radiated from the transmission antenna of the other steel tower. This re-radiated wave causes ghost damage to general receiving households.

Therefore, in order to reduce the re-radiated wave, the transmission antenna is attached so as to tilt it upward. Thereby, the re-radiated wave can be emitted upward (in the sky).

[0004]

However, if the transmitting antenna is tilted upward, the gain for the receiving household of the radio wave of the broadcasting frequency is also reduced, so that a large tilt angle cannot be taken. Therefore, even if the above measures are taken, the effect is limited. Therefore, in order to reduce re-radiation, it is necessary to take measures to absorb the re-radiation wave itself.

An object of the present invention is to realize a re-radiated wave removing device capable of absorbing the re-radiated wave before the re-radiated wave is radiated.

[0006]

The re-radiated wave removing device of the present invention is provided between a junction box and a transmitting antenna.
A first hybrid circuit which is installed and divides a television signal supplied from the junction box into two;
Two band-pass filters that respectively pass the signals divided by the hybrid circuit, and a second hybrid circuit that combines the signals that have passed through the two band-pass filters and feeds the signal to a transmitting antenna from one terminal, connected to the other terminal of the second hybrid circuit, by Rukoto a absorbing element for absorbing the power of the signal, transmission a
The TV signal of another station that entered the
It is intended to prevent re-radiation from the tenor (Claim 1).

The pass characteristics of the band pass filters 4 and 5 need to be sufficiently sharp so that signals other than the television signal of the local station will not pass (claim 2). This will be described with reference to FIG. In FIG. 1, a television signal of its own station is shown by a white arrow and a television signal of another station is shown by a black arrow. According to the re-radiated wave removing device having this configuration, the television signal of the own station, which has entered from the power feeding line 2, is divided into two by the first hybrid circuit 3, passes through the two band pass filters 4 and 5, and It is combined in the hybrid circuit 6 and fed to the transmitting antenna 8 through the feeding line 7. At this time, the loss that the television signal of the local station receives is only the insertion loss of the two hybrid circuits 3 and 6 and the insertion loss of the band pass filters 4 and 5.

On the other hand, when the television broadcast radio wave of another station enters the transmitting antenna 8, the second line is fed through the feeder line 7.
It is divided into two by the hybrid circuit 6 and reflected by the band pass filters 4 and 5. Then, they are combined into one by the second hybrid circuit 6 and absorbed by the absorbing element 9. In this way, unnecessary incident radio waves can be reflected by the band pass filters 4 and 5 and absorbed by the absorption element 9.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 2 is a circuit configuration diagram of the re-radiated wave removing apparatus according to the embodiment of the present invention. The embodiment of the present invention is a junction box JB.
The re-radiated wave removing device of the present invention is applied to three television signals among the four television signals branched by the above method.

The four branches by the junction box JB will be referred to as the first to fourth stages, respectively. In the first stage, the branch signal of the junction box JB is directly fed to the transmitting antenna 81 via the feeding line 71.
In the second stage, the branch signal of the junction box JB is transferred to the first hybrid circuit 32 via the power supply line 22.
And is passed through the band-pass filters 42 and 52, respectively, and combined by the second hybrid circuit 62 to form the power feed line 72.
The power is supplied to the transmitting antenna 82 through.

The third and fourth stages have the same construction as the second stage. On the other hand, when the television broadcast radio wave of another station enters the transmitting antenna 82, it is divided into two by the second hybrid circuit 62 through the power feeding line 72, and the band pass filter 4
It is reflected by 2, 52. Then, they are combined into one by the second hybrid circuit 62 and absorbed by the dummy resistor 92. Reference numeral 12 represents a dummy resistor provided in the first hybrid circuit 32.

Even when the television broadcast radio waves of other stations enter the transmitting antennas 83 and 84, the same configuration is used.
It is absorbed by the dummy resistors 93 and 94. In addition, since the re-radiated wave removing device of the present invention is not used in the first stage, the incident radio wave is reflected and re-radiated by the junction box JB.
1 is at a relatively high position, and the tilt (4
This is because it was decided that only () could be used.

FIG. 3 is a perspective view showing a specific structure of the hybrid circuit. This hybrid circuit is a 3 dB directional coupler, and has two opposing metal parallel plates 11,
Connect terminals 13 and 14 to one end of 12 and terminal 1 to the other end
5 and 16 are connected. Then, the whole is shielded by the metal cylinder 17, and the coaxial cable C1-is connected from each terminal 13-16.
C4 is pulled out. The signal input from the coaxial cable C1 has a phase of 90 ° from the coaxial cables C2 and C4.
The output is shifted. A signal input from the coaxial cables C2 and C4 with a phase difference of 90 ° is output from one of the coaxial cables C1 and C3. Coaxial cable C1 or C
Which of the three is output depends on the phase lead / lag of the signals input from the coaxial cables C2 and C4.

In FIG. 3 above, the hybrid circuit is 3d.
Although the example in which the hybrid circuit is configured by the B-directional coupler is shown, the hybrid circuit may be configured by a bridge diplexer, a rat race circuit, a hybrid ring, a short slot, or the like, in addition to this. Although not shown, the band pass filter may be, for example, an LC filter including a coil and a capacitor. In the circuit of FIG. 2, the band pass filters are continuously connected in two stages.

FIG. 4 is a graph showing the pass loss (solid line) and the reflection loss (broken line) of a typical bandpass filter. The horizontal axis shows the frequency, from 204MHz to 210
Up to MHz (VHF10 channel) is the frequency of the television signal of the own station, and from 216 MHz to 222 MHz (VHF12 channel) is the frequency of the television signal of the other station. According to this graph, the television signal of the own station passes with almost no loss, and the television signal of the other station reflects with almost no loss. Therefore, even if the re-radiated wave removing device of the present invention is used, the television signal of the own station can be passed with almost no loss, and the television signal of the other station can be reflected and absorbed by the dummy resistors 93 and 94. .

[0016]

As described above, according to the re-radiated wave removing apparatus of the present invention, unnecessary incident radio waves from other stations can be absorbed, so that re-radiation from the transmitting antenna can be prevented. . Therefore, it is possible to prevent the occurrence of the ghost failure.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram for explaining a function of a re-radiated wave removing device of the present invention.

FIG. 2 is a circuit configuration diagram of a re-radiated wave removing device according to an embodiment of the present invention.

FIG. 3 is a perspective view showing the internal structure of a 3 dB directional coupler.

FIG. 4 is a graph showing frequency characteristics of a pass loss (solid line) and a reflection loss (broken line) of a bandpass filter.

[Explanation of symbols]

1 Re-radiation wave removal device 2,22,23,24 feeder line 3,32,33,34 First hybrid circuit 4,42,43,44 bandpass filter 5,52,53,54 Bandpass filter 6,62,63,64 Second hybrid circuit 7,71,72,73,74 Feed line 8, 81, 82, 83, 84 transmitting antenna 9,92,93,94 Absorption element JB junction box

Front page continuation (72) Inventor Hiroshi Iida 1-3-3 Shimaya, Konohana-ku, Osaka City Sumitomo Electric Industries, Ltd. (56) References JP-A-1-319303 (JP, A) JP-A-11 -251929 (JP, A) JP 2000-236270 (JP, A) JP 61-35022 (JP, A) JP 8-254556 (JP, A) Actual flat 4-36303 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04B 1/04 H01P 1/213 H04N 5/38

Claims (2)

(57) [Claims] 1. A junction box and a transmission antenna
Which is a re-radiated wave removing device installed between the first hybrid circuit and the first hybrid circuit for dividing the television signal supplied from the junction box into two. A band-pass filter, a second hybrid circuit that synthesizes the signals that have passed through the two band-pass filters and feeds the signal to a transmitting antenna from one terminal, and a signal that is connected to the other terminal of the second hybrid circuit the Rukoto comprising an absorbent element for absorbing power,
The television signal of another station that entered the transmitting antenna is transmitted.
A re-radiated wave removing device for a television transmitting antenna, which prevents re-radiation from a receiving antenna. 2. The re-radiated wave removing device according to claim 1, wherein the band-pass filter has a pass characteristic that does not pass signals other than a television signal of the local station.