JP2515148Y2 - Monopole antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a monopole antenna used in a rocket, an aircraft, or the like.

[Conventional technology]

FIG. 3 is a cross-sectional view of a conventional rocket monopole antenna viewed from the side.

In the figure, (1) is a radiation conductor, and a thin strip conductor is used to reduce air resistance.
(2) is a dielectric that supports the radiation conductor, (3) is a ground conductor,
(4) is a connector. FIG. 4 is a sectional view of the monopole antenna of FIG. 3 as seen from the front.

Next, the operation will be described. The radiating conductor (1) is fed by the connector (4), and high frequency radio waves flow. This current is a standing wave in which the current becomes maximum at the connection between the radiation conductor (1) and the ground plane (3) and becomes zero at the tip of the radiation conductor (1). The dielectric (2) is a member that supports the radiation conductor (1), and a material that withstands vibration of the rocket and aerodynamic heating and that transmits radio waves is selected.

Therefore, the high frequency radio wave fed by the connector (4) is radiated to the air by the radiation conductor (1) in almost 100%.

[Problems to be solved by the invention]

The conventional monopole antenna must be mounted vertically on the ground plane, and the length of the radiation conductor must be about 1/4 wavelength.
However, the total length of the antenna is very long.

In addition, the input impedance of the conventional monopole antenna is about 35Ω, so it has a drawback that it is not perfectly matched with the 50 series coaxial connector.

The present invention was made in order to solve the above problems, and an object thereof is to obtain a monopole antenna capable of reducing the total length of the antenna and achieving impedance matching with a power feeding connector. is there.

[Means for solving problems]

The monopole antenna according to the present invention is formed by bending the monopole antenna in a zigzag shape and using it as a folded antenna, and short-circuiting the electrical line length of 1/4 wavelength from the feeding point.

[Action]

The monopole antenna in this invention has a zigzag radiating conductor, which shortens the overall length, and achieves perfect impedance matching between the antenna and the connector due to the effects of bending and short-circuiting.

〔Example〕

 An embodiment of this invention will be described below with reference to the drawings.

In FIG. 1, (1) is a radiating conductor having a folded structure,
(2) is a dielectric material that supports the radiation conductor (1), and (3) is a ground conductor. (4) is a connector for feeding the radiation conductor (1), and (5) is a short-circuit plate for short-circuiting the folded structure.

In the figure, since the radiation conductor (1) is a strip conductor and is bent in a zigzag shape, the total length (L) of the antenna is shorter than the total length (L ') of the antenna in FIG. The input impedance when the antenna resonates in this state is calculated to be 12.5Ω. In order to match this impedance with the 50Ω coaxial connector (4), the radiation conductor (1) has a folded structure composed of two parallel lines of equal width. One line of this folded structure is grounded to the ground plane (3) and the other line is connected to the connector (4).
Connect to the center conductor of. Here, according to the principle of the folded antenna, the input impedance seen from the connector (4) side is quadrupled, so 12.5Ω × 4 = 50Ω, and the radiation conductor (1) and the connector (4) are matched. However, as it is, the total length of the radiation conductor (1), that is, the length between the feeding point and the conductor tip, is longer than 1/4 wavelength due to the effect of the zigzag structure. Therefore, the impedance at the feeding point is not 50 Ω because the reactance due to the stub with a total length longer than 1/4 wavelength is added in parallel to the radiation resistance of the antenna.

Therefore, the electrical line length of 1/4 wavelength is short-circuited from the feeding point, the reactance is set to infinity, and the feeding point impedance is set to 50Ω to match the connector. The dielectric (2) supports the strip-shaped radiation conductor (1) and protects the radiation conductor (1) from vibration and aerodynamic heating at the time of rocket launch. The presence of this derivative (2) causes a slight change in the resonance frequency of the monopole, but by slightly changing the length of the radiation conductor, there is no problem in matching.

 Here is a summary of this idea.

(1) The linear antenna has a zigzag shape for downsizing.

(2) The zigzag shape reduced the impedance at the feeding point, so a folded antenna was used to match the feeding cable.

(3) When a folded antenna is used, the reactance of the stub line is loaded in parallel to the feeding point, and this value is a finite value because the electrical length of the zigzag antenna is 1/4 wavelength or more, and VSWR at the feeding point Will increase.

(4) In order to eliminate this drawback, the adverse effect of the stub line was eliminated by short-circuiting the electrical length of 1/4 wavelength from the feeding point and making the reactance loaded in parallel at the feeding point infinite.

(5) However, the portion beyond the short-circuit plate operates as one antenna, and it is not always necessary to have a folded structure, but if this is removed, the radiation resistance of the antenna itself decreases and the power supply cable Will not be consistent with. Therefore, the part ahead of the short-circuit plate is always necessary.

Although the radiating conductor (1) is entirely folded in the above embodiment, the strip plate may be left as it is from the feeding point to the portion beyond the short-circuit plate (5). Furthermore, the radiation conductor (1)
Has the same effect even with a folded wire or pipe.

[Effect of device]

As described above, the invention of this application uses a folded antenna to shorten the total length of a 1/4 wavelength monopole antenna, and further folds it in zigzag to short-circuit the line length of 1/4 wavelength from the feeding point. This is to improve the addition of parallel reactance due to the decrease in radiation resistance and the increase in antenna line length due to the zigzag shape of the antenna. That is, the reduction of the radiation resistance is improved by using the folded antenna, and the parallel reactance is added to the feeding point due to the increase of the antenna line length due to the zigzag shape. By short-circuiting, however, the reactance added in parallel is made infinite, and the effect is eliminated.

[Brief description of drawings]

FIG. 1 is a sectional view of the monopole antenna according to the present invention seen from the side, FIG. 2 is a sectional view of the monopole antenna of FIG. 1 seen from the front, and FIG. 3 is a sectional view of the conventional monopole antenna seen from the side. FIG. 4 and FIG. 4 are sectional views of the monopole antenna of FIG. 3 seen from the front. In the figure, (1) is a radiation conductor, (2) is a dielectric, (3) is a ground plane,
(4) is a connector and (5) is a short-circuit plate. In the drawings, the same or corresponding parts are designated by the same reference numerals.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) Bibliographic data Sho 57-152805 (JP, U) Real development Sho 57-98010 (JP, U) Real development Sho 57-82709 (JP, U) Real public sho-37- 27324 (JP, Y1)

Claims (1)

(57) [Scope of utility model registration request] 1. A folded monopole antenna formed on a ground plane, wherein the monopole is bent in a zigzag shape to form a folded antenna, and the line length is 1 / the total length electrically from the feeding point.
A monopole antenna characterized by shorting four wavelengths.