JPS59193605A - Dipole antenna - Google Patents

Abstract

PURPOSE:To attain equalization of the radiation directivity characteristic at a broad band by forming symmetrically a straight line part and a folding part having a boundary near a node of current distribution to a dipole center. CONSTITUTION:In folding loosely the vicinity of an end 3 of a dipole antenna of l=2lambda (where; l is a length between dipole antenna ends and lambda is a wavelength) in the form of J, the direction of a current between folding points 5 and the direction of a current flowing between the folding point 5 and a node 4 are opposite to each other so as to weaken the radiation. Thus, this shows that only the part between the center 2 of the dipole and the node 4 becomes the antenna. In changing sequentially the frequency of a supply current of the dipole antenna from a low frequency to a high frequency, a current distribution having the symmetry of l=lambda/2 is obtained at a low frequency, a current distribution having the symmetry of l=lambda and a current distribution of l=2lambda at a high frequency are obtained respectively and electromagnetic waves are irradiated in each case. That is, electromagnetic waves having an equal directivity characteristic are irradiated over a broad band without changing the size of the dipole.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a structure of a radiating element of a dipole antenna. More specifically, the present invention relates to a dipole antenna in which the radiation directivity from the antenna is approximately the same over a wide frequency band.

As the use of radio waves increases, a wideband antenna that can be used for multiple channels is required. In particular, the UHF broadcast wave band has a wide bandwidth, and channels are often changed or shared across multiple channels. In this case, if the directivity characteristics of the antenna are not kept constant, the service area etc. will change, causing problems.

Conventionally, turn style antennas, super gain antennas, etc. were used as antennas for TV broadcasting.
Since these have a relatively narrow band, dipole antennas with a reflector, which are a combination of a dipole of approximately one wavelength and a reflector, have recently come into use. This antenna can have relatively good V, S, W, and R characteristics over a wide band by making the radiating element thicker. It is difficult.

The reason for this is that if the radiating element is shortened, the gain will decrease at low frequencies, and if the radiating element is made long, the directivity will become sharper at higher frequencies and unnecessary side lobes will occur.

Therefore, when forming an omni-directional antenna by attaching reflector-equipped antennas to the four sides of a steel tower, for example, it is difficult to achieve desired directional characteristics over a wide band.

An object of the present invention is to provide a dipole antenna which radiates electromagnetic waves over a wider band than conventional dipole antennas and whose directivity characteristics are approximately the same over a wide frequency band.

For the purpose of simplifying the explanation, only the radiating element of the dipole antenna will be explained in the present invention, but it goes without saying that the dipole antenna can be used alone or as a dipole antenna with a reflector.

The present invention will be described below with reference to the drawings.

FIG. 1, FIG. 2, and FIG. 3 are conceptual diagrams showing the current distribution when the dipole antenna is supplied with a current whose antenna length becomes 1/2 wavelength, 1 wavelength, or 2 wavelengths.

The arrows in the figure indicate the direction of current at a certain moment. When calculating the radiation from each dipole using a known formula for calculating radiation from dipole antennas, we find that the dipole antenna in Figure 3 radiates less compared to the dipole antennas in Figures 1 and 2. . The reason is shown in Figures 1 and 2.
In the case shown in the figure, the direction of the current is the same throughout the radiating element 1, whereas in the case of Fig. 3, the direction of the current near the dipole center 2 and the direction of the current near the end 3 of the dipole are opposite directions. This is because. That is, the current distribution has node 4.

In the present invention, the length a between the dipole ends 3-3 is 1/2 times ('Q = λ/2'), 1 times ('Q = λ/2') and 1 times (
It is an object of the present invention to provide a wideband dipole antenna that efficiently emits electromagnetic waves not only when Q=λ) but also when the number is doubled (u=2λ), and whose directivity characteristics are almost the same.

4 to 9 are conceptual diagrams showing various embodiments of the present invention.

The operating principle of the present invention will be explained using FIG. 4.

FIG. 4 shows the dipole antenna of FIG. 3, where 2=2λ, with the vicinity of the end 3 bent loosely into a single shape. Note that it is preferable that the radius of curvature at the bending point 5 is not too small from the viewpoint of impedance. At this time, the wavelength on the dipole radiating element changes slightly, but the current distribution is such that the terminal end 3 of the dipole antenna is one node, there is a dark spot near the bending point 5, and the direction of the current is reversed at the node 4. become.

The direction of the current at a certain moment is indicated by an arrow in FIG.

As can be seen from FIG. 4, the direction of the current flowing between the end 3 of the dipole and the bending point 50 is opposite to the direction of the current flowing between the bending point 5 and the node 4. Therefore, the radiation from this image area has opposite phases, and the radiation weakens each other. As a result, the electromagnetic waves that weaken the electromagnetic waves radiated by the current between the center 2 of the dipole and the node 40 become weaker.

In other words, the dipole antenna in FIG.
This is equivalent to an antenna covering only the portion between the center 2 of one ball and the above-mentioned node 4. In other words, it is equivalent to the dipole antenna shown in Figure 2. Therefore, their radiation directivity characteristics are also approximately the same.

If the frequency of the current supplied to the divolor antenna in Figure 4 is changed sequentially from low frequency to high frequency, the current distribution at low frequencies will have the symmetry shown in Figure 1, emitting electromagnetic waves, and then the current distribution as shown in Figure 2. It radiates electromagnetic waves with a symmetrical current distribution, and at high frequencies, the current distribution becomes the one shown in FIG. 4, which radiates electromagnetic waves with the same symmetry as the dipole antenna shown in FIG. 2. That is, it is possible to radiate electromagnetic waves over a wide band without changing the dimensions of the dipole, and to make the directivity characteristics almost equal.

Figures 5 and 7 show another embodiment of the present invention.

The dipole antenna shown in FIG. 5 is an antenna in which the vicinity of the end 3 of the dipole is bent into a chevron shape, and the vicinity of the center 2 of the dipole is formed into a straight line. When this antenna is supplied with a high frequency current (a current with a frequency equivalent to that shown in FIG. 3), the current flow at a certain moment is as shown by the arrow in FIG. 5. Although the currents shown by arrows a and 2 are not completely antiparallel, they contain antiparallel components as vectors, so the electromagnetic waves emitted from each of them weaken each other to some extent. Therefore, the electromagnetic waves radiated from the current shown by the arrow C near the anti+ center are effectively radiated without being weakened by the electromagnetic waves radiated from the currents shown by the arrows a and arrows A. As a result, the dipole antenna of FIG. 5 has substantially the same effect as the dipole antenna of FIG. 4.

The bent portion 6 in FIG. 5 is bent so that the current flowing through the bent portion has an antiparallel component vectorwise. Therefore, there are various variations in its implementation.

FIG. 6 is a conceptual perspective view of an embodiment in which a bent portion 6a is provided in the direction of the electromagnetic wave main lobe of a flat dipole antenna.

FIG. 7 is a conceptual example of an embodiment in which a bent portion 6b is provided in a direction perpendicular to the main lobe.

Figures 4 to 7 show antennas that suppress radiation due to the current from node 4 of the current distribution in Figure 3 to end 3 of the dipole.
h'-1 which is the antenna in the figure Node 4 of the current distribution in Figure 3
A similar effect can be obtained by suppressing radiation due to the current between the dipole center 2 and the dipole center 2.

FIG. 8 is a conceptual diagram of a dipole antenna in which a bent portion 6C is provided near the center of the dipole.

The dipole antenna shown in Figure 8 also radiates electromagnetic waves in a wide band. In other words, the distance Q between the dipole ends 3-3
For K, even if the wavelength 1λ is changed to C=λ/2°2−λ, −3λ=2λ, electromagnetic waves are effectively radiated.

In FIGS. 5 to 8, the bent portion 6°6a,
6b, 6c are formed by a single chevron curve, but based on the principle of operation of the antenna of the present invention, the same effect can be obtained by forming the reed zero by a small chevron curve, that is, a waveform curve.

FIG. 9 shows another embodiment of the present invention in which the bent portion 6 of the antenna shown in FIG. 5 is realized by a wave-shaped bent portion 6dK.

[Brief explanation of the drawing]

Figures 1 to 3 are diagrams showing current distributions when currents of e = λ/2, Q = λ, and Q = 2λ are supplied to dipole antennas according to the prior art, respectively, and Figures 4 and 5
The figure shows the current distribution and direction of the current when a current equivalent to the current distribution in FIG. 3 is supplied to the dipole antenna of the present invention, and FIGS. 6 to 9 show examples of the present invention. 2...Dipole center, 3...Dipole end, 4...Node, 5...Bending point, 76, 6
a, 6b l 6c, 6d, ,,,,, bending part. Figure 1 Figure 2 Figure 3 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 21

Claims (6)

[Claims] (1) Let α be the distance between both ends of the dipole 3-3, and α
It is formed of a radiating element that has a straight part with a boundary near node 4 and a bent part symmetrically with respect to the dipole center 2 in the current distribution when supplying a current with a wavelength λ that satisfies the relationship 2λ. A dipole antenna featuring (2) The above bent part is the dipole center 2 and the above node 4
2. The dipole antenna according to claim 1, wherein the dipole antenna is provided between 0 and 0. (3) The bent portion is formed by bending the dipole radiating element in the direction of the electromagnetic wave main rope of the flat dipole antenna.
Dipole antenna described in section. (4) The bent portion is formed by bending the dipole radiating element in a direction perpendicular to the main lobe of the flat dipole antenna.
Dipole antenna described in section. (5) The dipole antenna according to claim 1, wherein the bent portion is provided between the dipole center 2 and the node 4. (6) The dipole antenna according to claim 1, wherein the bent portion is a small wave-shaped bent portion.