JP3515459B2 - Omnidirectional antenna - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an omnidirectional transmitting antenna used in a wide band.

[0002]

2. Description of the Related Art FIG. 6 shows, for example, "MICROWAVE".
PASSIVE DIRECTIONFINDING
(By STEPHEN E. LIPSKY) "is an external perspective view of the conventional biconical antenna shown in FIG. 7, and FIG. 7 is a cross-sectional view thereof. A conical conductor, and 2 is a second conical conductor connected to the jacket conductor 5 of the coaxial cable 3. The first conical conductor 1 and the second conical conductor 2 have their apexes close to each other. Are placed on opposite sides of the same axis in opposite directions, and radiate radio waves non-directionally around the cone axis when excited at a high frequency of a specific frequency range from its apex. Since the omnidirectional characteristic of a flexible antenna is disturbed if there is unnecessary radiation from the feeding line, a coaxial cable without radiation is used for the feeding line.
Excited in M mode.

Next, the operation will be described. A high-frequency signal transmitted by the coaxial cable 3 is fed between two conical conductors 1 and 2 having an appropriate opening angle and length corresponding to a certain frequency, and a non-directional pattern is radiated into space in a horizontal plane. To do.

The biconical antenna is characterized by a wide operating frequency range (band), but the presence of the coaxial cable hinders the symmetry of the shape, so that a higher-order mode does not occur near the upper limit frequency. The directivity pattern may be disturbed. In order not to disturb this, it is necessary to set the outer diameter of the outer shield of the coaxial cable to a certain value or less with respect to the upper limit frequency. On the other hand, since this omnidirectional antenna is used as a transmission antenna, when feeding high power, it is necessary to increase the outer diameter of the center conductor 4 of the coaxial cable 3 in order to reduce power loss. As a matter of course, the diameter of the outer shield 5 also becomes large.

The above relationship is shown in FIG. The horizontal axis of FIG. 8 shows the allowable excitation power, and the vertical axis shows the maximum frequency at which good characteristics (non-directionality) are obtained, in proportion to each other. Therefore, in order to satisfy the conflicting conditions under the condition that high power or high frequency is required, naturally there is a problem that either the upper limit frequency or the supplied power can be restricted. The above is the description of the case of the biconical antenna, but the same applies to the case of the discone antenna as shown in FIG. 9 in which the disc 50 is provided on the second conical conductor 2.

[0006]

The conventional omnidirectional antenna requires the shield outer diameter of the coaxial cable to be a certain value or less in order to obtain good omnidirectional antenna characteristics. To supply power, it is necessary to increase the outer diameter of the coaxial cable in order to reduce power loss. Therefore, in order to satisfy the contradictory conditions, naturally there is a problem that either the upper limit frequency or the supplied power can be restricted.

The present invention has been made to solve the above problems, and an object thereof is to obtain an omnidirectional antenna capable of increasing the power that can be fed without lowering the upper limit frequency.

[0008]

SUMMARY OF THE INVENTION An omnidirectional antenna according to the present invention is a truncated cone-shaped conductor having a first flat surface portion having a diameter of 2R at the top portion, and the top surface is opposed to the first flat surface portion so as to be coaxial and in opposite directions. arranged, the conical conductor having a second planar portion having a diameter 4R on top, the through the interior of said conical conductor
Drawn to the second planar portion, the jacket shielding the second
The flat surface portion, the center conductor of the first flat <br/> the end face portion connected away 2R together the outer diameter 2R of the frustoconical conductors to each other
It has two coaxial cables with the same specifications .

Further, a disk made of a conductor, a cone having a top facing the center of the disk and arranged coaxially with the central axis of the disk, and having a second flat portion with a diameter 4R at the top. An outer diameter 2R that penetrates through the inside of the conductor and the conical conductor and is drawn out to the second flat surface portion , and the outer shield is connected to the second flat surface portion and the center conductor is connected to the disc at a distance of 2R from each other.
The two coaxial cables having the same specifications as each other are provided.

[0010]

[0011]

[0012]

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. Hereinafter, as an omnidirectional antenna according to the first embodiment of the present invention, a biconical antenna and a feed line thereof will be described with reference to the drawings. Figure 1
2 is a perspective view of the biconical antenna of Embodiment 1, FIG.
1 is a cross-sectional view of FIG. 1, and FIG. 3 is an enlarged view of the vicinity of the feeding point from above in FIG. 1 for explaining the structure near the feeding point of FIG. FIG. 4 is also an enlarged view of the vicinity of the feeding point from the bottom of FIG. In addition ,. In each of the following drawings, the same or corresponding parts as those of the related art are designated by the same reference numerals and detailed description thereof will be omitted.

In the figure, 11 is a first plane portion 31 on the top.
A truncated cone-shaped conductor, 12 is the first of the truncated cone-shaped conductor 11
It is a conical conductor that is arranged coaxially in the opposite direction with its top facing the flat portion 31. The conical conductor 12 also has a second flat surface portion 3 formed by cutting the apex portion of the conical conductor at a right angle to the axis of the conical body.
Equipped with 2. Both the first flat surface portion 31 and the second flat surface portion 32 are conductive surfaces.

The first flat surface portion 31 and the second flat surface portion 32 are arranged so as to face each other at a narrow interval. 13 is a first coaxial cable having an impedance of 50Ω, and its central conductor 14
Is pierced through the second plane portion 32 and connected to the end of the first plane portion 31. Reference numeral 23 is a second coaxial cable of the same standard as the first coaxial cable 13, and its center conductor 24 penetrates through the second flat surface portion 32 and ends of the first flat surface portion 31 (the first flat surface portion 3).
1) is connected to the first surface of the first coaxial cable 13 at a position opposite to the position where the central conductor 14 of the first coaxial cable 13 is connected. The diameter of the first plane portion 31 is almost the same as the diameter (2R) of the first coaxial cable 13 or the second coaxial cable 23, and the outer diameters of the first and second coaxial cables 13 and 23 are 2R, respectively. If so, the central conductors 14 and 24 on the first flat surface portion 31 are arranged at a distance of exactly 2R. In addition, the diameter of the second flat portion 32 is 4R (coaxial cable 2
Diameter of the main line) is almost equal.

The outer shields 15 and 25 of the first and second coaxial cables 13 and 23 are both connected to the second plane portion 32.

In the biconical antenna of the first embodiment,
If the same first and second coaxial cables 13 and 23 as the conventional coaxial cable 3 are used, the permissible power that can be supplied to one cable does not change. The permissible power performance can be improved accordingly. Further, since the outer diameter of each coaxial cable has not changed, the upper limit frequency that can be used does not change and only the allowable power can be increased.

When power of the same frequency is fed to two coaxial cables, consideration should be given to the design of the transmitter system including the length of the coaxial cables so that the power is fed in phase at the feeding point. is necessary.

With the dimensions and shapes shown in FIGS. 1 to 4, impedance matching with the antenna can be achieved for each of the two coaxial cables 13 and 23. By the way,
When the distance 2R between the two center conductors 14 and 24 is increased (decreased), the impedance seen from the coaxial cable side to the antenna side can be increased (decreased). Further, the distance between the first plane portion 31 and the second plane portion 32 is
It may be adjusted so that the directional characteristics of the biconical antenna are good, and the lengths of the center conductors 14 and 24 may be determined accordingly. The biconical antenna of FIG. 1 is called an omnidirectional antenna in the present invention. The 1st plane part 31 and the 2nd plane part 32 are only called plane parts. If the central conductors 14 and 24 are directly connected to the inclined surface of the first truncated cone without providing the first plane portion 31, the apex of the cone enters between the two central conductors, and a higher-order mode occurs. The desired characteristics cannot be obtained.

Embodiment 2. FIG. 5 shows an enlarged view of the vicinity of the feeding point of the biconical antenna of the second embodiment. The parts not shown are the same as those in FIG. 3 of the first embodiment. The frustoconical conductor 11 and the center conductors 14 and 24 in the figure have the same structure as that of the first embodiment shown in FIG. 3, and a top portion is provided with a first plane portion 31. 52 is a conical conductor, but is not a truncated cone type. While the second conical conductor 12 of FIG. 3 has the second flat surface portion 32 formed of a flat surface orthogonal to the axis of the conical conductor, it does not have the flat surface portion and is directly attached to the conical surface (slope). The end faces of the outer shields of the first and second coaxial cables 13 and 23 are arranged. That is, the end faces of the first and second coaxial cables 13 and 23 form a part of the conical slope. Although not clearly shown in the figure, the outer shields 15 and 25 of the first and second coaxial cables 13 and 23 are both connected to the conical surface of the conical conductor 52.

Embodiment 3. The number of the coaxial cables of the first and second embodiments may be three or more.
In the case of a plurality of conductors, the central conductors are connected to the periphery of the first flat surface portion 31 at equal angular intervals. That is, 180 for two
In the case of three lines, the intervals are 120 °. The specifications of the plurality of coaxial cables need not be the same, but if, for example, cables with different impedances are used, the position to be connected to the first plane portion 31 must be adjusted for each one. Since it is very troublesome to do so, it is preferable to use the coaxial cable having the same specifications in practice.

The magnitude of the electric power supplied to each of the plurality of coaxial cables does not have to be the same, but may be different. Of course, the power supply to one or more coaxial cables may be zero.

Fourth Embodiment In the configuration shown in the third embodiment, for each of the plurality of coaxial cables,
It is also possible to supply high-frequency power of different frequencies. Since the impedance of the antenna seen from the feeding point does not change even if the frequency is changed, it is not necessary to adjust the position of the feeding point when changing the frequency. The omnidirectionality at each frequency is maintained, and they do not affect each other except when the connection position of the coaxial cable is improper (position is not accurate).

Embodiment 5. In the case of the conventional discone antenna shown in FIG. 9, the circular plate 50 replaces the truncated cone-shaped conductor 11 of FIG. Generally, a conductive plate such as a metal plate or a wire mesh is used as the disc 50, but in any case, the disc 50 can be regarded as having the first flat surface portion 31 as it is, and therefore, the first to fourth embodiments. The description of can be applied as it is.

[0025]

As described above, the omnidirectional antenna of the present invention has a truncated cone-shaped conductor having a flat portion at the top thereof, and a conical conductor having a vertex opposed to the flat portion and arranged coaxially in the opposite direction,
Pulled out to the top thereof through the interior of the conical conductor, two outer on top of the shield is conical conductor, the center conductor is the outer diameter 2R connected apart 2R one another in the plane of the frusto-conical conductor
Since the coaxial cable is provided, the effect that the performance of the omnidirectional characteristic due to the higher-order mode is less than that of the maximum power that can be supplied is obtained.

Further, the disc of the conductor, the conical conductor arranged on the axis orthogonal to the disc, and penetrating through the inside of the conical conductor to the top thereof, the outer shield is provided on the top of the conical conductor. , The center conductors were connected to the disc 2R apart from each other
Since with the two coaxial cables having an outer diameter 2R, effect that distortion of the omnidirectional high order mode is less relative feedable maximum power.

[0027]

[0028]

[Brief description of drawings]

FIG. 1 is a perspective view of an omnidirectional antenna (biconical antenna) according to a first embodiment of the present invention.

FIG. 2 is a sectional view of FIG.

FIG. 3 is a partially enlarged view of FIG.

FIG. 4 is a partially enlarged view of FIG.

FIG. 5 is a perspective view of a biconical antenna according to a second embodiment of the present invention.

FIG. 6 is a perspective view of a conventional biconical antenna.

7 is a cross-sectional view of the antenna of FIG.

8 is a characteristic explanatory view of the biconical antenna of FIG.

FIG. 9 is an external view of a conventional discone antenna.

[Explanation of symbols]

1 1st conical conductor, 2 2nd conical conductor, 3
Coaxial cable, 4 center conductor, 5 outer shield, 11 truncated cone conductor, 12, 52 conical conductor, 13 first coaxial cable, 14 first center conductor, 15 first outer shield, 23 second coaxial Cable, 24 2nd center conductor, 25 2nd outer shield, 31 1st plane part, 32 2nd plane part.

Claims (2)

(57) [Claims] 1. A frusto-conical conductor having a first flat portion having a diameter of 2R at the top, coaxially and oppositely arranged with the top facing the first flat portion, and a second flat surface having a diameter of 4R at the top. conical conductor having a section, wherein through the interior of said conical conductor
Drawn to the second planar portion, the jacket shielding the second
The flat surface portion, the center conductor of the first flat <br/> the end face portion connected away 2R together the outer diameter 2R of the frustoconical conductors to each other
An omnidirectional antenna characterized in that it is equipped with two coaxial cables having the same specifications . 2. A disc made of a conductor, a cone having a top facing the center of the disc, coaxial with the center axis of the disc, and having a second flat surface with a diameter of 4R at the top. conductor,
An outer diameter 2R having an outer diameter of 2R that is penetrated through the conical conductor and drawn out to the second flat surface portion , and a jacket shield is connected to the second flat surface portion and a center conductor is connected to the circular plate 2R apart from each other.
An omnidirectional antenna characterized by having two coaxial cables with the same specifications .