JPS606126B2 - reflector antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reflector antenna that is powered by an array antenna and has a sufficiently low side rope level.

Hereinafter, an offset type parabolic reflector antenna will be explained as an example. Conventionally, the side rope of the antenna (Side
In order to keep lo low), an appropriate distribution is given to the excitation amplitude on the antenna entrance.

The optimal amplitude distribution for this purpose is Taylor (Tayl).
or) distribution, and these optimal distributions are usually symmetrical about the center of the aperture.

Now, FIG. 1 is an explanatory diagram of an antenna related to the present invention. That is, in FIG. 1, 1 is a parabolic reflector whose mirror surface is a part of a rotating parabolic surface, and 2 is a power feeding array antenna as a primary radiator that irradiates the parabolic reflector 1 with radiated power. The array antenna 2 generally consists of a plurality of element antennas.

The focal point of the parabolic reflector 1 is at point F in Fig. 1, so clearly the parabolic reflector 1 is offset by the feeding array antenna
) is powered. Note that FIG. 1 shows a vertical sectional view. The reflector antenna related to this invention is thus composed of the parabolic reflector 1 and the power feeding array antenna 2.

Further, in FIG. 1, numeral 3 is a virtual open face of the reflector antenna, 4 is the center line of the closed face 3, and 5 is the center line of the power feeding array antenna 2. Also, 61, 62
, 71, 72 are geometrical optical rays emitted from the power feeding array antenna 2, which are necessary to explain the operation of the antenna. Now, based on the conventional concept, in order to keep the side lobes of the reflector antenna low, it is assumed that the excitation amplitude distribution of the array antenna 2 is given as a symmetrical distribution with respect to the center line 5 as shown in a.

After this symmetrical amplitude distribution a passes through the parabolic reflector 1,
The fact that the amplitude distribution on the Sekiguchi surface 3 is converted into an asymmetrical distribution with respect to the center line 4 as shown in FIG. 1b can be easily explained as follows. That is, in FIG. 1, two light rays 61 and 62 exit from the power feeding array antenna 2 with a certain angular width of 0 and are reflected at the upper part of the parabolic reflector 1, and two light rays 71 and 72 are reflected at the lower part. As is clear from the comparison, the distance between the two reflected rays is wider for the one that hits the upper part.

That is, the density of the reflected light beam becomes higher as it goes lower, and therefore the power density on the Sekiguchi surface 3 becomes higher as it goes lower. That is, when the excitation distribution of the feeding array antenna 2 is given as shown in a, the maximum amplitude on the closed surface 2 clearly moves below the center line 4, resulting in an asymmetric amplitude distribution b.
Become. The side lobes of a reflector antenna having such an amplitude distribution b naturally have a high level. As is clear from the above explanation, if the amplitude distribution of the power feeding array antenna 1 is given so as to correct the deviation of the amplitude distribution caused by the properties of the parabolic reflector 1, the distribution can be made symmetrical on the aperture surface 3. I can do it.

This is the gist of the present invention, and an embodiment will be described below with reference to FIG. In FIG. 2, 1, 2, 3, 4, and 5 are all the same as in FIG. The excitation amplitude distribution of the feeding array antenna 2 in the present invention is given as an asymmetrical distribution with respect to the center line 5, as shown in FIG. That is, the maximum point of the amplitude distribution on the paper of FIG. 2 deviates from the center line 5 and has moved upwards of the stone compared to the case of FIG. 1. As a result, the amplitude distribution on the Sekiguchi surface 3 realized through the parabolic reflector 1 is a symmetrical amplitude distribution d with respect to the center line 4.
This is clear from the explanation using the light rays 61, 62, 71, and 72 in FIG. This distribution is, for example, a Taylor distribution that can suppress side lobes to a low level. In other words, by using the feeding array antenna 2 having the asymmetric amplitude distribution c shown in FIG. 2, the side ropes of the reflector antenna in FIG. 2 can be suppressed to a sufficiently low level for practical purposes. Although we have explained the case, it can of course also be used for reception.Also, the reflecting mirror surface is not limited to a parabolic surface as in the example.
It may be a spherical surface, a polygonal surface, an ellipsoidal surface, etc. In addition, as the power feeding array antenna, it is possible to use not only an array antenna that emits a fixed beam, but also a so-called phased array antenna that performs beam scanning electronically by phase scanning, frequency scanning, etc. I can do it.

As described above, in this invention, by making the amplitude distribution of the feeding array antenna asymmetrical, it is possible to realize a reflector antenna with sufficiently low side lobes, so if this is used for radar or communication purposes, it will be very effective. It is clear that it can be used effectively.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a reflector antenna based on a conventional concept, and FIG. 2 is an explanatory diagram of an embodiment of the present invention. In the figure, 1 is a parabolic reflector, 2 is a feeding array antenna, 3 is an aperture surface, and a to d are amplitude distributions. In addition, in the figure,
Identical or equivalent parts are designated by the same reference numerals. 1 Zuta ZI Juku

Claims (1)

[Claims] 1. In an offset reflector antenna that uses an array antenna consisting of a plurality of element antennas as a primary radiator for power feeding, the excitation amplitude of the array antenna is adjusted so that the amplitude distribution on the aperture surface of the reflector antenna is symmetrical. A reflector antenna characterized by having an asymmetric distribution, thereby lowering side lobes.