JPH0732326B2 - Fan beam antenna - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circularly polarized fan beam antenna having extremely wide directivity.

[0002]

2. Description of the Related Art In order to realize a fan beam, conventionally, for example, a horn antenna in which the aspect ratio of the opening surface is greatly different is used. In this case, even if the narrower beam width can be managed, it is difficult to make the wide beam width as wide as 120 degrees, for example, and it is at most 60 to 70 degrees. It was also difficult to make it for circular polarization.

[0003]

The problem to be solved by the present invention is to realize an antenna for circularly polarized waves, which has a wide band and which can radiate or receive a fan beam having an extremely wide directivity.

[0004]

SUMMARY OF THE INVENTION The present invention is directed to rotation as a first reflector.
The parabolic concave surface (hereinafter referred to as "parabola") and the second anti
A right circular cone of the outer surface of the Ikyo, as the axis of both reflector is offset and parallel, Ru are opposed. single
Feed horn as a primary radiator for creating a beam
(Strictly speaking, the beam should be emitted from a point,
The radiation surface of the feed horn is regarded as the radiation point. ) Is provided at the focal point of the parabola.

[0005]

EFFECTS OF THE INVENTION Circularly polarized radio waves are plane waves after being reflected by a parabolic reflector, and are further bent and emitted by a conical reflector. Due to the offset of the axes, strong radiation is made in the direction in which the area of the conical surface is widely opposed to the parabolic surface, and weak radiation is made in the opposite direction.

In this case, it is necessary to select the amount to offset the axis.
The directivity can be selected by and. Directional side where the conical surface remains widely can be obtained have a wide angle (half width), therefore it is possible to have a gentle directional on this side.

The angle between the axis of the right circular cone and the generatrix is 45 degrees.
Set the axis of the parabola and the axis of the right circular cone in the vertical direction.
For example, centering on the direction of the line connecting both axes,
It is possible to obtain a wide directivity fan beam antennas wants horizontal plane.

According to the present invention, circularly polarized waves can be obtained even after the circularly polarized waves are reflected by the conical surface. This invention
Since a single beam is used, the directivity is gentle and wide.
However, to obtain a coherent wavefront over the entire area
You can This invention does not have a rotation mechanism part
Also has a gentle and wide directivity. Also, since it uses a reflecting mirror, it has essentially broadband characteristics.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the basic construction of an embodiment of the present invention.

In FIG. 1, the axis of the parabola A is shown as the Z1 axis and the axis of the right circular cone B is shown as the Z2 axis. Z1 axis and Z2
The axes are parallel and are separated by a distance L. In the following, for the parabola, the symbol "A" refers to the entire parabola and also to the reflecting mirror consisting of its paraboloid of revolution, and for the right circular cone, the symbol "B" refers to the right circular cone. The reflecting mirror composed of the conical surface is also referred to.

Since the operation of the antenna is the same for both transmission and reception, the transmission antenna will be described below.

In FIG. 1, the transmission power is radiated from the feed horn F as a circularly polarized wave. This is assumed. Parabola A whose center is the radiation phase center of the feed horn F
The radio wave W reflected at points A ₁ and A ₂ is converted from a spherical wave into a plane wave, and this plane wave has a conical shape with a cone angle of 45 degrees between the Z2 axis and the generatrix.
₁ point B, is bent 90 degrees at _two points B, if the vertical and the axis Z2 axis Z1 and cone B of the parabolic A, respectively, to radiation as a horizontal path C1, C2.

[0013] At this time, the axis Z1, Z2 bi lateral distance L are offset, the radiation pattern RA is 2
As shown in, it has directivity.

As the offset distance L between the Z1 axis and the Z2 axis is closer to zero, the radiation pattern RA is closer to an omnidirectional pattern,
As the offset distance L increases, the radiation pattern RA becomes sharper toward the front of the radiation. The offset distance L is set in accordance with the desired pattern (half-value width).

The size of the conical surface B (Z
The spread along the plane perpendicular to the two axes) does not matter as long as the opening area of the parabola A exists only in the range of the area covered when viewed parallel to the Z1 axis and the Z2 axis. Peripheral portion A of parabola A in FIG.
_0- A ₀ and the peripheral portion B ₀ -B ₀ of the conical surface B are understood to have this meaning.

On the other hand, the vertical in-plane beam width is roughly given by the height H of the conical surface in the Z2 axis direction.

[0017]

[Equation 1]

Is given by For example, H = 105
Assuming that mm and λ = 3.85 mm (78 GHz), the vertical in-plane beam width is approximately 2.6 degrees from the above equation.

(Summary of Examples) (1) The distance between the parabola A and the right circular conical surface B, such as the distance between A ₁ point and B ₁ point or the distance between A ₂ point and B ₂ point shown in FIG. The distance is set depending on the implementation.

(2) The primary radiator is of the so-called horn type.
There is no need to limit.

(3) Even when the Z2 axis goes out of the parabola A (outside the line drawn from the peripheral edge A _{0 of the} parabola A parallel to the Z1 axis), a proper radiation pattern is obtained toward the front. .

(4) The present invention is also applicable to sound waves and ultrasonic waves if only the reflection path is excluded by omitting the plane of polarization.

(5) The present invention is suitable for being implemented as a radio lighthouse for radio navigation.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an embodiment.

FIG. 2 is an explanatory diagram of an example.

[Description of symbols] A ... parabola A ₀ ... parabola A peripheral portion B ... right cone B ₀ ... axis L ... Z1 axes of Z2 ... right cone B of the peripheral portion F ... feedhorn Z1 ... parabola A straight cone B of Between Z2 and Z2 axis RA ... Radiation pattern

Claims (3)

[Claims] 1. Broadband directivity using a single beam
In a fan-beam antenna that obtains
A first reflecting mirror consisting of a surface and an outer surface of a right circular cone, and
A second reflecting mirror facing the first reflecting mirror, and
The axis of the first reflecting mirror and the axis of the second reflecting mirror are parallel and
And the primary emission point of the beam is the first
Located at the focal point of the reflector of the
A fan beam antenna that radiates toward a mirror . 2. A fan-beam antenna according to 請 Motomeko 1 and the shaft of the first reflecting mirror and the axis of the second reflecting mirror has vertically disposed. 3. A second reflecting mirror, fan-beam antenna according to claim 1 or 2 angle between the axis and generatrix is set to 45 degrees.