JPS6351402B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the structure of an antenna, and more particularly to a short-backfire antenna with a high aperture efficiency and having a main reflecting mirror with a diameter of two or more wavelengths.

The conventional short backfire antenna is the first
Shown in Figures A and B. 1 is the main reflecting mirror, 2, 2 ₁ , 2
₂ , 2 ₃ , 2 ₄ are feeding elements, 3, 3 ₁ , 3 ₂ , 3 ₃ , 3 ₄
is a planar reflector, and 4 is a side edge. Generally, the main reflecting mirror 1 is formed of a plane or a paraboloid, and the feeding elements 2, _{2 1} , 2 ₂ , 2 ₃ , 2 ₄ are formed of a single dipole, a crossed dipole, or the like. In FIG. 1A, part of the electromagnetic waves radiated from the feed element 2 is reflected by the planar reflector and reaches the main reflecting mirror, and the rest directly reaches the main reflecting mirror. At this time, in the case of a small main reflecting mirror of about one wavelength, the main reflecting mirror 1 and the side edges 4 can be irradiated with sufficient intensity to cause strong resonance with a single feeding element and a single planar reflector, The reflection mirror 1, the flat reflector 3, and the side edges 4 can provide a sufficiently strong confinement. A short backfire antenna is characterized by obtaining a high aperture efficiency due to the resonance phenomenon caused by the confinement of this electromagnetic field. However, in the case of a short backfire antenna in which the diameter of the main reflector 1 is about 2 wavelengths or about 3 wavelengths, which utilizes higher-order resonance, the diameter of the main reflector 1 is more than 2 wavelengths, the feeding element 2 Since the mirror surface and side edges 4 of the main reflecting mirror 1 could not be sufficiently irradiated with the electromagnetic waves radiated from the main reflecting mirror 1, the resonance phenomenon did not occur and the aperture efficiency could not be increased. In order to solve this problem, conventionally, a plurality of feeding elements are provided as shown in FIG. 1B, and the main reflecting mirror 1 and the side edges 4 are irradiated with sufficient intensity to solve this problem.
However, in this method, the reflectors 3 ₁ , 3 ₂ , 3 ₃ ,
3 ₄ and feed elements 2 ₁ , 2 ₂ , 2 ₃ , 2 ₄ are required, and a power divider is required to feed multiple feed elements, making the antenna configuration complex and expensive. It had the disadvantage of becoming.

The present invention aims to improve the above-mentioned drawbacks of the conventional technology, and its purpose is to provide an antenna that achieves high aperture efficiency with a single radiating element even when using a main reflector with a diameter of two wavelengths or more. By changing the shape of the reflector, the main reflecting mirror and the side edges are irradiated with sufficient intensity to achieve a good resonance condition.

The features of the present invention for achieving the above object include: a substantially circular main reflecting mirror having a diameter of two wavelengths or more; and a main reflecting mirror for radiating radio waves from a feeding element to the main reflecting mirror.
In a short backfire antenna having a reflector provided almost in the center of a main reflector,
the reflector is only one, its shape is axially symmetrical, and the shape is a combination of an a-plane and a conical surface;
The short backfire antenna has a shape selected from a combination of a b-plane and a spherical surface, and a combination of two types of conical surfaces having different apex angles. Examples will be described below with reference to the drawings.

FIGS. 2A to 2C show the shapes of the feed element and the reflector in one embodiment of the present invention, and they are 5 ₁ , 5 ₂ , 5
₃ is a flat portion of the reflector, and 6 ₁ , 6 ₂ , and 6 ₃ are conical portions of the reflector. The electromagnetic waves emitted from the feeding element 2 are reflected by the flat portion 5 ₁ and the conical portion 6 ₁ of the reflector shown in FIG. 2A. On this occasion,
Electromagnetic waves are diffusely reflected by the conical portion 6 ₁ over a wide angle (the angle between the antenna axis and the edge of the main reflector with the apex near the position of the feeding element), and reflected waves by the planar portion 5 ₁ and the feeding element. It is combined with the direct wave from 2. As a result, Figure 3 shows part 1.
As shown in the example, a radiation characteristic 7 with sufficient intensity over a wide angle (the angle between the antenna axis and the edge of the main reflector with the apex near the position of the feed element) is obtained, and the conventional feed element As in the case where a plurality of mirrors are used, the main reflecting mirror and the side edges can be irradiated with sufficient intensity, and a good resonance state can be achieved. The short backfire antenna of the present invention using a reflector having the above shape is similar to an antenna using a plurality of feed elements as shown in the conventional example, in which diffuse reflection from the reflector and direct waves from the feed element occur. A wider main reflecting mirror can be irradiated with sufficient intensity, a good resonance state can be achieved, and a high aperture efficiency can be obtained. Similar radiation characteristics can be obtained from the planar portions 5 ₂ and 5 ₃ as shown in Fig. 2B and C.
Realization is also possible with a reflector having conical surface portions 6 ₂ , 6 ₃ . Further, the same effect can be obtained by replacing the conical surface portions 6 ₁ , 6 ₂ , and 6 ₃ in FIGS. 2A, B, and C with spherical surfaces. Furthermore, the same effect can be obtained even if the reflector is configured by a combination of two types of conical surfaces having different apex angles.

As explained above, the antenna of the present invention has any of the following shapes: a combination of an a-plane and a conical surface, a combination of a b-plane and a spherical surface, and a combination of two types of conical surfaces with different c apex angles. By using a feeding element with a reflector of this configuration, it is possible to irradiate the main reflector and side edges of two wavelengths or more with sufficient intensity with only one element, and achieve a good resonance state, which is better than the conventional one. The power supply element can be saved compared to
Moreover, there is an advantage that a comparable high aperture efficiency can be achieved.

[Brief explanation of the drawing]

FIGS. 1A and 1B are conventional short-backfire antennas. FIGS. 2A, B, and C are examples of feed elements and reflectors used in the short-backfire antenna of the present invention. Figure 3 shows part 1 of the present invention.
It is a radiation pattern obtained by a feeding element and a reflector which are examples. 1... Main reflecting mirror, 2, _{2 1} , 2 ₂ , 2 ₃ , 2 ₄ ...
Feeding element, 3, _{3 1} , 3 ₂ , 3 ₃ , 3 ₄ ... Planar reflector, 4 ... Side edge, 5 ₁ , 5 ₂ , 5 ₃ ... Plane portion of reflector, 6 ₁ , 6 ₂ , 6 ₃ ... Conical surface portion of reflector, 7 ... Radiation pattern of feed element with reflector plate.

Claims (1)

[Scope of Claims] 1. A substantially circular main reflecting mirror with a side edge and a diameter of about N (an integer of N>2) that resonates at a desired frequency, and a main reflecting mirror in front of the main reflecting mirror. a feeding element that is provided in parallel with the feeding element and emits radio waves in both front and rear directions; and a feeding element that is provided further in front of the feeding element and directs the radio waves radiated forward from the feeding element toward the main reflector and back. In a short backfire antenna having a reflector arranged to reflect toward the main reflector so as to be approximately in phase with the radiated radio waves, each of the feeding element and the reflector is unique. The reflector is axially symmetrical with respect to the central axis of the antenna and is composed of a central part and a peripheral part so that the radio waves from the feeding element are diffused and radiated to the entire main reflector, and the reflector has a central part and a peripheral part. A short backfire antenna characterized in that one of its shapes is a flat surface and the other is a conical surface. 2. A substantially circular main reflecting mirror with a side edge and a diameter of approximately N (an integer of N>2) wavelengths that resonates at a desired frequency, and a main reflecting mirror provided in front of the main reflecting mirror in parallel with the main reflecting mirror, A feeding element that emits radio waves in both front and rear directions, and a radio wave that is provided further in front of the feeding element and is radiated forward from the feeding element and directed from the feeding element to the main reflector and then emitted backward. In the short-backfire antenna having a reflector arranged to reflect the light toward the main reflector so as to be in the same phase, the feed element and the reflector are each unique, and the reflector is unique. The antenna is composed of a central part and a peripheral part that are axially symmetrical with respect to the central axis so that the radio waves from the feeding element are diffused and radiated throughout the main reflecting mirror, and the shape of either the central part or the peripheral part is A short backfire antenna characterized in that one side is flat and the other side is spherical. 3. A substantially circular main reflecting mirror with a side edge and a diameter of approximately N (an integer of N>2) wavelengths that resonates at a desired frequency, and a main reflecting mirror provided in front of the main reflecting mirror in parallel with the main reflecting mirror, A feeding element that emits radio waves in both front and rear directions, and a radio wave that is provided further in front of the feeding element and is radiated forward from the feeding element and directed from the feeding element to the main reflector and then emitted backward. In the short-backfire antenna having a reflector arranged to reflect the light toward the main reflector so as to be in the same phase, the feed element and the reflector are each unique, and the reflector is unique. The antenna is axially symmetrical with respect to the central axis and is composed of a central part and a peripheral part so that the radio waves from the feeding element are diffused and radiated throughout the main reflecting mirror, and the central part and the peripheral part have different apex angles. A short backfire antenna characterized by a conical surface.