JPH10126145A - Four-wire conical helix antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize the antenna suitable for a mobile body, utilizing a geostationary satellite or a simple earth station for emergency disasters, in which a rotary V-shaped elevating angle directivity is provided for a circularly polarized wave and its direction elevating angle is variable. SOLUTION: The shape of the conical helix antenna consisting of four antenna elements 11 -14 is formed to be a thin and long frustum of a circular cone. That is, an apex angle of the cone (twice the frustum slope angle) is selected to be 1.8 deg. or 2.4 deg., pitch angles β1 -β4 of the antenna elements 11 -14 are selected to be 45 deg. or 60 deg., and upper ends adjacent to each other among upper ends of the antenna elements 11 -14 are fed with opposite polarity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to an antenna suitable for an on-board antenna mounted on a mobile object (car or the like) that performs communication using a geostationary satellite such as R or a simple earth station antenna for satellite communication in an emergency disaster.

[0002]

2. Description of the Related Art An antenna mounted on a terrestrial mobile body that communicates using a geostationary satellite, for example, a mobile body that does not have a very large swing such as a car, has directivity only in an elevation angle direction. An antenna that is omnidirectional in a horizontal plane is desirable. As an antenna having such directivity, for example, (1) “Two-wire helical linear array antenna for mobile satellite communication” (The Institute of Electronics, Information and Communication Engineers, 19)
1994 Fall Conference Paper, B-85), (2) "Directional Variable Helical Antenna" (IEICE Technical Report, A
P92-32, April 1994) and (3) an antenna proposed in "Consideration on Conical Spiral Antenna" (IEICE Autumn Meeting 1994, B-81).

[0003]

Among the antennas proposed in the prior art, the antennas (1) and (2) have disadvantages in that the height of the antenna is considerably high and the antenna is slightly unstable. The antenna (3) has a disadvantage that the gain is slightly low.

[0004]

According to the present invention, a common envelope surface formed by four conical helical antenna elements has a truncated cone shape close to a cylindrical shape and a cone apex angle (twice the tilt angle of the truncated cone). ) Is formed to be 1.8 ° to 2.4 °, and the antenna elements are wound at equal intervals from each other, and each pitch angle of the antenna elements is selected from 45 ° to 60 °,
Position each upper end of the antenna element at a position that divides the upper edge of the frusto-conical envelope close to a common cylinder into four equal parts in the circumferential direction. The object of the present invention is to eliminate the conventional disadvantages by realizing an antenna whose adjacent upper ends are fed with opposite polarities.

[0005]

PREFERRED EMBODIMENTS FIG. 1 (a) is a plan view showing an essential part of an embodiment of the present invention, and FIG. 1 (b) is a side view, 1 ₁ to 1 ₄ is equal in length to each other in conical helix antenna elements, a common envelope surface formed by the to 1 ₄ antenna elements 1 ₁ is an elongated truncated cone close to the cylindrical, conical apex angle (twice the truncated cone tilt angle) 1.8 ° to 2.4 formed to have a °, wound spaced equidistant from each other with and 1 ₄ antenna elements 1 _1, the antenna element 1 ₁
To 1 to select ₄ each to the pitch angle beta no ₁ beta ₄ of the 45 ° to 60 °, the respective upper end portions of the antenna elements 1 ₁ to 1 _4, the common upper edge of the frusto-conical envelope surface in the circumferential direction It is located at the place where it is divided into four. In FIG. 1, 2
Shows a common frustoconical envelope surface which is formed by to 1 ₄ antenna elements 1 _1.

[0006] Although not shown in FIG. 1, the feeding line in the present invention antenna, which, for example, coax - to no antenna element 1 ₁ forms in Bull common frustoconical formed by 1 ₄ inserted into the envelope, Inpi - to no antenna element 1 ₁ through dancing matcher and distributor (both not shown) is connected to each upper end of the 1 _4, FIG. 1
(A), the respective upper end portions of the antenna elements 1 ₁ and 1 ₃ are, for example, is powered by a positive polarity, the antenna element 1
Each upper end of the ₂ and 1 ₄ is, as powered by the negative polarity, of the upper end portions of the antenna elements 1 ₁ to 1 _4, so that the upper portion adjacent to each other in the circumferential direction is fed with opposite polarities Formed. The antenna of the present invention configured as described above has a simple and compact configuration, a high gain, good circular polarization characteristics, and a rotating V-shaped directivity.

FIG. 2 shows the height of the antenna of the present invention and the rotation V
FIGS. 2A and 2B are diagrams for explaining the relationship between the shape of the antenna and the elevation directing direction. FIG. 2A shows a case where the height of the antenna of the present invention is relatively high, and FIG. shows a case of forming relatively low, in any case of FIGS. 2 (a) and 2 (b), to the antenna element 1 ₁ maintaining the respective length of 1 ₄ constant, in FIG. 2 (a) to increase the height of the antenna by the small while maintaining mutually equal beta ₄ to 1 each pitch angle beta from ₁ to ₄ antenna elements 1 _1, each of the antenna elements 1 ₁ to 1 ₄ in FIG. 2 (b) The height of the antenna is reduced by increasing the pitch angles β ₁ to β ₄ while keeping them equal to each other. In FIGS. 2 (a) and 2 (b) represents antenna elements 1 ₁ to 1 collectively 1 _4, are expressed in beta together to beta ₄ pitch angle beta ₁ to. FIG.
(C) is in the plane including the central axis of the present invention antenna, i.e., a diagram showing the directivity in the vertical plane, theta ₁ is FIGS. 2 (a)
Oriented elevation, theta ₂ of the antenna shown in is a directional elevation angle of the antenna shown in FIG. 2 (b). FIG. 2 (a) and FIG.
In any of the antennas shown in (b), the directivity in the horizontal plane is non-directional. When the pitch angle of the conical helical antenna element is represented by β and the directional elevation angle is represented by θ, a relationship of θ = αβ generally holds between the two. Here, α is a constant determined by the shape of the antenna.

In the antenna of the present invention, for example, NS
Various types of antennas having different heights are mounted on a mobile object such as TAR which performs communication using a geostationary satellite, and antennas having different heights are provided for each area having a different elevation angle for viewing the N-STAR, that is, a required directivity. to use by selecting an antenna in accordance with the elevation angle, or a to 1 ₄ antenna elements 1 _1, equal in length, have a suitable elasticity, respectively, mechanical such as to hold the required shape on its own by forming in strip or linear conductor having an intensity, changing the height of the antenna without changing the respective length of the conductor forming the to 1 ₄ antenna elements 1 _1, the pitch angle of the antenna elements 1 ₁ to 1 ₄ The antenna configured to change the directional elevation angle by changing the angle may be mounted on the moving body.

[0009] Figure 3 is a common radius r ₀ and 0.15λ (λ is the wavelength used for the upper base of the frustoconical envelope surface of the antenna elements 1 ₁ to 1 ₄ are formed in the present invention antenna shown in FIG. 1 ), 0.22Ramuda the radius r ₁ of the common lower base of the frustoconical envelope surface, the length of the antenna elements 1 ₁ to 1 ₄ L _e
Is 0.636λ, and the height h of the antenna is 4λ, 3.8
7A and 7B are diagrams showing the directional characteristics when formed at λ and 3.6λ, where the horizontal axis is the directional elevation angle θ (deg.), and the vertical axis is the gain G.
ain (dBi), the dashed line with a small interval indicates the height h of the antenna.
= 4.0λ, the broken line with a large interval is h = 3.8λ, and the solid line is h
= 3.6λ. As is clear from the figure, the directional elevation angle of the antenna of the present invention is a V-shaped rotation, and the elevation angle changes from approximately 30 ° to 45 ° according to the height of the antenna.

FIG. 4 is a diagram showing the frequency characteristics of the gain of the antenna of the present invention constituted by the specifications shown in paragraph 0009. The horizontal axis represents the frequency f (MHz), and the vertical axis represents the gain Gai.
n (dBi), as is apparent from the figure, N-STAR
Frequency band 2505M in communication system using
Hz to 2535 MHz, and transmission frequency band 26
7dB gain at 60MHz to 2690MHz
i and above indicate that the antenna of the present invention is suitable as a transmission / reception antenna in a communication system using N-STAR.

FIG. 5 shows that the length of the four antenna elements is kept constant, and the specifications other than the height of the antenna are described in paragraph 0009.
In the antenna of the present invention selected in the same manner as shown in the above, changes in the directional elevation angle and the gain when the height h of the antenna is changed from 3.4λ to 4.4λ are shown, and the horizontal axis is Height h of the antenna expressed by the used wavelength λ
(Λ), the vertical axis is the directional elevation angle Elevation (de
g. ) Or gain (dBi), the dashed line indicates a change in the directivity elevation angle, and the solid line indicates a change in the gain. As is apparent from the figure, the directional elevation angle changes almost linearly in accordance with the change in the height of the antenna, and the gains in the elevation angle range of 20 ° to 50 ° are all 8 dBi or more. In this case, the elliptical polarization rate and the impedance
It was confirmed that the dance characteristics were all good.

[0012]

The antenna according to the present invention has a relatively simple and compact structure, a high gain, and has a rotating V-shaped elevation directivity. In addition, the antenna of the present invention can freely select the directional elevation angle by changing the pitch angle of the antenna element. Therefore, for example, a mobile antenna in a communication system using a geostationary satellite such as N-STAR, or It is suitable for a simple earth station antenna for satellite communication at the time of an emergency disaster.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of the present invention.

FIG. 2 is a diagram illustrating the relationship between the height of the antenna of the present invention and the elevation directivity.

FIG. 3 is a diagram showing a change in gain when the directional elevation angle of the antenna of the present invention and the height of the antenna are changed.

FIG. 4 is a diagram illustrating frequency characteristics of gain in the antenna of the present invention.

FIG. 5 is a diagram showing the relationship between the height of the antenna of the present invention, the directional elevation angle, and the gain.

[Explanation of symbols]

1,1 ₁ to 1 ₄ conical helix antenna element 2 envelope surface of the conical helix antenna element forms β, β ₁ ~β ₄ pitch angle theta ₁ of conical helical antenna element, theta ₂ directed elevation

Claims (1)

[Claims] 1. A conical helix antenna comprising four antenna elements, wherein the shape of the antenna is an elongated truncated cone, that is, the apex angle of the cone (twice the tilt angle of the truncated cone) is 1.8 ° to 2 °. .4 °, and the pitch angle of the antenna element is 45 ° to 60 °. A four-wire conical helix antenna.