JPH07240627A - Paraboloidal antenna - Google Patents

Abstract

PURPOSE:To simplify a structure, to provide the characteristics of low side lobe over a wide angle and to enable a wide-band operation by constituting a primary antenna provided on the focus of a rotation parabolodial reflector by metallic conductors wound in a helical form. CONSTITUTION:In this paraboloidal antenna composed of the rotated parabolic reflector and the primary antenna provided on the focus, the metallic conductors 3 and 4 wound in the helical form are used for the primary antenna. That is, the metallic conductor 3 is wound in the helical form counterclockwise at the outer periphery of a cylinder 2; the metallic conductor 4 is wound in the helical form clockwisely at the outer peripheral of the cylinder 2; and the length of one round is turned to be approximately coincident to the center wavelength of radio waves to be used. Then, a balanced current balance-to-unbalance transformed in a slit balun 5 provided in the tip part of a coaxial power feeding line 1 reaches to the power feeding part of the tip part. In this case, the balanced current lead to the metallic conductors 3 and 4 radiates an electric field to a current along a helical rotation direction; circularly polarized waves in mutually reverse rotation directions are superimposed; and linear polized waves are generated.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a parabolic antenna, and more particularly to its primary antenna.

[0002]

2. Description of the Related Art Conventionally, a parabolic antenna for wireless communication used for a wireless telephone line or the like has a wide band characteristic so as to cope with a large amount of wireless communication lines with different frequencies used, and the interference between the adjacent antennas is reduced. Side lobes to prevent
An antenna that can suppress (side radiation lobe) low is desirable. Conventionally, a dipole antenna having a cavity structure has been widely used as a primary antenna for this type of parabolic antenna.

FIG. 2 is a diagram showing an example of a dipole antenna used as a primary antenna of a conventional parabolic antenna, in which 101 is a coaxial feed line.
102 is a reflector, 103 is a dipole, 104 is an adjusting terminal, 105 is a slit balun, 106
Is a metal cylinder. The dipole antenna shown in FIG.
In order to suppress the interference with the adjacent antenna, the dipole antenna having the reflector 102 having strong radiation in the wide-angle direction is covered with the metal cylinder 106, and the cavity structure has a structure that suppresses the radiation level in the wide-angle direction.

[0004]

As described above, the conventional parabolic antenna uses the antenna having the cavity structure of the dipole antenna as the primary antenna, and the characteristics thereof are loosened to widen the band. There is a problem that it becomes complicated and it is difficult to design and adjust the antenna.

A normal dipole antenna has a frequency ratio band of about 10%, and since it has a cavity structure, the frequency characteristic is further narrowed. Therefore, in the dipole antenna shown in FIG. 2, the dipole 103 is thicker than usual and has a very short shape. In addition, the slit / balun normally has a structure in which the width of the slit is narrowed to suppress the radiation from the slit portion and perform smooth balanced / unbalanced conversion. On the other hand, in the dipole antenna shown in FIG. The band is widened by making the antenna thick and radiating radio waves from this part as well, and making it a structure with loose characteristics as much as possible, so there are many empirical and experimental factors in antenna design and adjustment. This is necessary, and since it is difficult to obtain sufficient characteristics, the adjustment terminal 104 is provided.

The present invention has been made to solve the above problems, and it is easy to design and manufacture, requires almost no adjustment, has a simple structure, can operate in a wide band, and has a low side lobe over a wide angle. The object is to provide a parabolic antenna having various characteristics.

[0007]

A parabolic antenna according to the present invention is characterized in that a metal conductor wound in a helical shape is used for its primary antenna. Further, the primary antenna is characterized by using two sets of metal conductors that are helically wound on the same cylinder with the feeding portion at the same position.
Further, the two sets of metal conductors are characterized in that they are helically wound in directions opposite to each other.

[0008]

[Function] So-called helical antenna
Is a circularly polarized wave antenna, but it can operate in a wide band of 1 octave or more. Its directivity becomes a pencil beam, and the directivity of the electric field surface and the magnetic field surface are almost the same. Known to be weak. Therefore, if a helically wound metal conductor having the same shape is used as the primary antenna of the parabolic antenna, a parabolic antenna in which side lobes are suppressed in a wide angle direction and which can operate in a wide band can be obtained. Also, if two sets of metal conductors are helically wound in opposite rotation directions, for example, if one set of metal conductors generates a right-handed circularly polarized wave, the other set of metal conductors will rotate left. Circularly polarized waves can be generated twice, and both circularly polarized waves can be overlapped to generate a linearly polarized wave.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1A is a perspective view showing a primary antenna for a parabolic antenna which is an embodiment of the present invention, and FIG.
It is a front view seen from the arrow M direction of (A), in the figure, 1 is a coaxial feed line, 2 is a cylinder, 3 is a set of metal conductors, 4 is another set of metal conductors, and 5 is a slit. It is a balun. The primary antenna of the present embodiment is configured as shown in FIG. 1 and has a slit provided at the tip of the coaxial feed line 1.
The balanced current, which has been balanced / unbalanced converted by the balun 5, reaches the power feeding portion at the tip.

As shown in FIG. 1B, an outer conductor of the coaxial feed line and a set of metal conductors 3 are connected to the power feeding portion, and an inner conductor and another set of metal conductors 4 are connected to the outside. It is connected via a conductor, and a slit balun 5 is provided between them. Further, as shown in FIGS. 1A and 1B, the metal conductor 3 is helically wound in the counterclockwise direction (or clockwise direction) on the outer circumference of the cylinder 2, and the metal conductor 4 is wound around the cylinder 2. The outer periphery has a structure in which the direction of rotation is helically wound clockwise (or counterclockwise). In addition, 1 for each
The length of the winding is configured to substantially match the center wavelength of the radio wave used. And these two sets of metal conductors 3, 4
The equilibrium current guided to the electric current flows through the helically wound metal conductors 3 and 4, and radiates an electric field corresponding to the electric current in the rotation direction into the space. Therefore, the electric field generated by this antenna has a rotation direction that coincides with the winding direction of the helical metal conductor, and circular polarizations in mutually opposite rotation directions are generated from the two sets of metal conductors. Therefore, the circularly polarized waves can be overlapped to generate a linearly polarized wave.

As described above, in the parabolic antenna of the present embodiment, since the metallic conductors 3 and 4 wound in a helical shape are used for the primary antenna, the electric field surface and the magnetic field surface are substantially equal and the pencil is used. It has directivity close to that of a beam. Further, since this antenna operates by a traveling wave current, the frequency characteristic can be operated in an extremely wide band, and the operation in a specific band of about one octave can be easily performed. Therefore, if the parabolic antenna is configured by using the antenna of this embodiment as the primary antenna, a parabolic antenna that operates in a wide band and has a low side lobe in the wide angle direction can be obtained. In the primary antenna of this embodiment, needless to say, the cylinder 2 is made of an insulating material.
It is only for holding the metal conductors 3 and 4, and can be omitted.

[0012]

As described above, in the parabolic antenna of the present invention, since the helically wound metal conductor is used for the primary antenna, it is easy to design and manufacture with a simple structure, and almost no adjustment is required. It is possible to obtain an antenna that is capable of operating a required wide band and has a low side lobe in a wide angle direction.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a conventional primary antenna for a parabolic antenna.

[Explanation of symbols]

 1 coaxial feed line 2 cylinder 3 metal conductor 4 metal conductor 5 slit balun

Claims (3)

[Claims] 1. A parabolic antenna comprising a rotating parabolic reflector and a primary antenna provided at the focal point of the parabolic reflector, wherein the primary antenna is configured by using a helically wound metal conductor. antenna. 2. A parabolic antenna comprising a rotating parabolic reflector and a primary antenna provided at the focal point of the parabolic antenna, wherein two sets of metal conductors are helically wound on the same cylinder with the feeding portion at the same position. A parabolic antenna comprising the above primary antenna. 3. The parabolic antenna according to claim 2, wherein the two sets of metal conductors are helically wound in directions opposite to each other.