JP2883497B2 - Transmission line radio interference reduction method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reducing radio interference in transmission lines, which can greatly reduce radio interference such as television reception interference caused by the transmission line itself.

[0002]

2. Description of the Related Art In television reception, as is well known, so-called ghosts appearing in such a manner that video images slightly shifted from direct signal images by broadcast radio waves appear to overlap each other.

[0003] The cause of this is that the reflection of radio waves caused by obstacles such as high-rise buildings in the middle of propagation of radio waves is input with a slight time lag, and the ghost interference in the above-mentioned television reception is caused. In addition to the above, countermeasures such as causing false images in radar are desired. However, in reality, there are difficult problems such as finding out the distribution of the reflection source of the radio wave, and it is a fact that it is difficult to take countermeasures. As specific ghost countermeasures, adoption of an antenna with strong directivity, selection of the installation location of the antenna, installation of a ghost canceling device on the receiver, CA
There is a joint reception by the TV system and the like, and a countermeasure on the transmission side includes installation of a satellite station in the UHF band.

[0004] On the other hand, while the above description has shown an example in which the reflection of radio waves mainly by building obstacles is the main cause, an overhead transmission line may cause radio waves in some areas.

That is, the overhead power transmission line is constructed by continuously erection of towers having a considerable height, and recently a multi-conductor transmission line of two or more conductors is connected between the towers, and reflected waves from these lines are generated. There is also the idea that it can cause ghosting.

[0006] However, the tower is high enough, but the constituent members are a combination of steel pipes, steel bars and the like, most of which are spaces, and the area involved in the reflection of radio waves is surprisingly small. .

[0007] Therefore, it is considered that the mechanism of the radio wave obstruction due to the transmission line is based on a mechanism different from the above-described mechanism by the physical reflection of the radio wave.

[0008]

When considering the radio interference caused by the transmission line, the influence of the direct reflected wave is not negligible, but it is considerably small in view of the reflection area.

[0009] Most of the television transmission waves from a broadcasting station are horizontally polarized waves, and the influence of retransmission from electric wires is much greater than the occurrence of interference waves due to towers, and the range of influence is considered to be wide. .

[0010] That is, the electric wire is at a height capable of receiving the terrestrial wave of the broadcast radio wave, and functions as a so-called terrestrial wave receiving antenna. There is no problem if the signal is simply received, but the electromagnetic wave is induced in the electric wire by the received wave, and the energy of this electromagnetic induction causes the electric wire to act as a transmitting antenna in reverse and re-radiate the received radio wave to the surroundings. It is considered that this re-radiated radio wave causes a ghost.

In order to reduce such a ghost caused by the electric wire, a radio wave absorbing material may be provided on the outer periphery of the electric wire to attenuate the received radio wave so as not to generate re-radiated energy.

However, for this purpose, the thickness of the radio wave absorbing material must be considerably increased, and as a result, there arises a problem that the wind pressure load increases with an increase in the cross-sectional area of the electric wire, and further, the weight of the electric wire increases. There are many problems such as the necessity of rebuilding the tower, and it has not yet reached the stage of practical use.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and cancel out re-radiated radio waves from an electric wire with an extremely simple structure without using a material such as a radio wave absorbing material. An object of the present invention is to provide a new method for reducing radio wave interference of a transmission line, which can surely solve the risk of a failure.

[0014]

SUMMARY OF THE INVENTION According to the present invention, another conductor is attached in parallel to a conductor of an overhead power transmission line at a predetermined interval on a side from which television broadcast radio waves arrive with inclination. And the optical
The re-radiated radio waves from the conductor of the transmission line in the reflection direction are canceled by the phase difference of the re-radiated radio waves from the auxiliary conductor.

[0015]

In the transmission line, another conductor which is parallel to the conductor of the conductor of the transmission line is attached to the side of the conductor, and the distance between the conductor and the additional conductor is set to 180.
If the interval is set to ゜, the radio waves re-emitted from both act so as to cancel each other, and the re-radiated radio waves become zero.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below with reference to embodiments.

FIG. 1 is an explanatory view showing the principle of the method according to the present invention. In FIG.
It is assumed that the radio wave arrives at an angle θ toward.

Another conductor 2 is laid in parallel with the conductor 1 on the side of the conductor 1 from which radio waves come, with an interval d.

Now, the radio wave received and re-emitted by the conductor 1 is Ea, the radio wave received and re-emitted by the auxiliary conductor 2 is Eb, and the incident angle of each radio wave in this case is θ.

In the above, the re-radiated radio wave (scattered wave) Ea
Alternatively, the direction in which Eb becomes the maximum is the optical reflection direction, that is, the angle θ direction that is opposite to the incident angle θ.

Assuming that the path difference between the re-radiated radio waves Ea and Eb is l, the sum of l ₁ and l _{2 in} FIG.

[0022]

(Equation 1)

## EQU1 ##

If the scattering coefficients (the ratio of the intensity of the incident wave radio wave and the intensity of the re-radiated radio wave) are assumed to be equal for the sake of simplicity, the re-radiated radio waves Ea and Eb are expressed as follows.

[0025]

(Equation 2)

Here, a: amplitude representing the strength of the radio wave (the value on the re-emission side is different from that on the incident side a 'in FIG. 1) ω: frequency angular velocity t: time γ: phase difference of the radio wave Is a re-radiated wave E

[0027]

(Equation 3)

## EQU2 ##

Here, γ is the phase difference of the radio wave as described above, and is determined by the path difference l.

[0030]

(Equation 4)

## EQU1 ##

In Equation 3 , if the interval d is determined so that cos ( γ / 2) becomes 0, the combined re-radiated radio wave E is always 0, which is equivalent to apparently no re-radiated radio wave being generated. become. That is, in the number 4 γ = (2n +
1) When an interval d that becomes π (n = 0, 1, 2,...) Is obtained,

(Equation 5)

If the additional conductors 2 are arranged at an interval d that satisfies Equation 5, the electric field intensity due to re-radiation becomes zero, and radio interference can be prevented.

FIG. 2 is an explanatory view showing an embodiment of an actual overhead wire according to the present invention, in which a conductor 2 is attached to a conductor 1 of a transmission line at a position of an interval d shown by Formula 5. And conductor 1
In addition, spacers 3 are arranged at predetermined intervals in order to keep a constant interval between the conductors 2 attached.

The conductor 2 attached is not necessarily the same as the conductor 1 of the transmission line, and may be a conductor having a smaller size than the conductor 1. That is, by arranging such a conductor 2 on the transmitting antenna side, a radio wave incident on the conductor 1 behind the conductor 2 is shielded by the conductor 2,
Because they can be weakened.

By arranging the spacers 3 at appropriate intervals, scattered waves can be reduced. That is, when the incident angle of radio waves on the transmission line is θ, the spacer interval L is

[0037]

(Equation 6)

It suffices to arrange them at intervals such that

FIG. 3 is an explanatory diagram showing an example in which the method according to the present invention is applied to a two-conductor power transmission line. Elementary conductors 1a and 1
With respect to the two conductors b, an additional conductor 2 is installed in parallel with a gap d 'on the transmitting antenna side.

Assuming that the distance between the elementary conductors of the two conductors is d ₀ , the distance d ′ between the elementary conductor 1 b and the subducted conductor 2 is given by the above _{equation (} 5).
alike

[0041]

(Equation 7)

By setting to, the re-radiation intensity can be reduced most.

The spacer interval L is also preferably set to the value shown in Expression 6.

In the case of two conductors, the spacing between the two conductors is set to d which satisfies Equation 5 and the spacer interval L is arranged so as to satisfy Equation 6 without adding an additional line. Needless to say, a similar effect can be obtained.

[0045]

As described above, according to the method for reducing radio wave interference of a transmission line according to the present invention, measures are taken for the transmission line itself, which is the source of the trouble, and the conventional method of receiving the signal As compared with the countermeasure on the transmitting side or the countermeasure on the transmitting side, the present invention can exhibit excellent advantages unique to the present invention, such as that the cost of the countermeasure is lower and maintenance after the countermeasure is unnecessary.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for explaining the principle of the present invention.

FIG. 2 is an explanatory diagram showing an embodiment in which the present invention is applied to a single conductor transmission line.

FIG. 3 is an explanatory view showing an embodiment applied to a two-conductor power transmission line.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Conductor 1a, 1b Element conductor 2 Substrate conductor 3 Spacer

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takashi Aizawa 3-7-1, Ichibancho, Aoba-ku, Sendai City, Miyagi Prefecture Tohoku Electric Power Co., Inc. 84 Banmachi Tohoku Electric Power Co., Inc. Niigata Branch (72) Inventor Masanobu 2-1-2 Marunouchi, Chiyoda-ku, Tokyo Inside Hitachi Cable Co., Ltd. (72) Inventor Masahiko Toshima 5 Hidaka-cho, Hitachi City, Ibaraki Prefecture JP-A-59-154710 (JP, A) JP-A-60-207411 (JP, A) JP-A-57-154910 (JP, A) A) JP-A-3-84997 (JP, A) JP-A-56-86032 (JP, A) JP-A-56-162916 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) ) H01Q 17/00 H02G 7/00 H05K 9/00

Claims (2)

(57) [Claims] 1. A telescopic cable which is inclined toward a conductor of an overhead power transmission line.
On the side coming arrives bicycloalkyl airwaves, and添架another conductor in parallel with a predetermined interval with respect to the conductor, TV airwaves
A method for reducing electric wave interference of a transmission line, in which re-radiated electric waves from the conductor of the transmission line in the optical reflection direction opposite to the incident direction of the transmission line are canceled by the phase difference of the re-radiated electric waves from the auxiliary conductor. 2. The method according to claim 1, wherein a spacer made of a conductive material is provided at a predetermined interval between the conductor of the transmission line and the additional conductor.