JPS62137902A - Antenna system - Google Patents

Abstract

PURPOSE:To make the aperture efficiency of an antenna constant over a wide range by forming a mirror surface system so as to satisfy a prescribed relation between a distance between reflection mirrors and a focus in replacing each sub reflection mirror into a lens. CONSTITUTION:A confocal point of two sub reflection mirrors exists at an aperture of a main reflection mirror, and the mirror surface system is constituted so as to have a relation of 0m<l2<0.7m,(1/f1-1/l1-1/l2)(1/f2-1/tau2-1/l3)approx.=1/l2<2>, where M1, M2 are points at which a ray irradiated along the center axis of a primary radiator 1 contacts two sub reflection mirrors 2, 3 sequentially, M is a point at which a ray via the point M2 contacts a main reflection mirror 4, l1, l2, l3 are distances between the aperture of the radiator 1 and the point M1, between the points M1 and M2, between the points M2 and M respectively, F0 is one focus of the mirror 2 coincident with the phase center of the radiator 1, F1 is other focus of the mirror 2 being a confocal point with the mirror 3, F2 is a confocal point of the mirror 3 to the mirror 4, f1, f2 are focus in replacing the mirrors 2, 3 into lenses, and the points F0-F2, M1, M2, M are on the same plane. Thus, the antenna aperture efficiency is made constant over a wide band, different from the mirror system requiring a prolonged distance l2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement of an antenna device used for microwave terrestrial relay operation, etc.

[Conventional technology]

The conventional antenna device is K as shown in FIG.

A primary radiator (l) having a phase center FQ, a second sub-reflector (2) sharing the phase center F of the primary radiator and also having a focal point F1, a third sub-reflector (2) sharing the focal point itself and further having a focal point F2; Some reflectors are composed of two sub-reflecting mirrors (3) and a main reflecting mirror (4) consisting of a paraboloid of rotation φ that shares a focal point 2.

In the figure, M1, M1, M2, and M are points along the central axis of the primary radiator +11 where the emitted light beam (5) hits the valley mirror surface in order.

Further, 11 is the distance from the aperture of the primary radiator (1) to point L11, and 12 is the distance from point M1 to point +42. Further, 13 is the distance from point M2 to point M3.

This antenna is shown in the fi4 diagram in Figure 5.

By making 12 longer, the cross-polarization peak value can be lowered, as shown in the measured value π of the cross-polarization radiation pattern in Figure 6, so the cross-polarization discrimination of the antenna can be customized. Becomes good. In Figure 6, the solid line is l! 2=12m
The two-dot line is the case when lh=1 m.

[Problems to be solved by the invention] However, when using the antenna for multiple frequencies,
Because the distance j2 between the sub-reflectors is increased, the aperture efficiency of the antenna cannot be kept constant, which results in a decrease in antenna gain and increases the depth of the antenna, making it difficult to mount it on a steel tower. There were many shortcomings.

This invention has been made to overcome the above-mentioned problems, and aims to provide an antenna device in which the aperture efficiency of the antenna is constant over a wide band.

[Means for solving problems]

The antenna device according to this invention has a distance of 12 between the sub-reflectors.
fQm<l! 2≦0.7m, and the first sub-reflection 9 (21
And the focal lengths when the second sub-reflector (3) is replaced with a lens are f1 and f2.

The mirror system is constructed in such a way that

[Effect]

As described above, the antenna device according to the present invention can keep the aperture efficiency of the antenna constant over a wide band, unlike the mirror system construction method in which the distance 12 between the sub-reflectors is set to Om and 12≦0,7. .

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, (1), f21. t3), t
41. f5) has the same name as in FIG. Also, F
Q, F1, M1, M2゜) A, lh, 12.
ls is the same as that shown in FIG. When the mirror system shown in Fig. 1 is replaced with 5 equivalent lens arrays as shown in Fig. 2, the first sub-reflector (2) and the second sub-reflector (3) have focal lengths of f, , f2. Then, f1,
f2 and 11. Between 12.13 and 12.13.

The lens array shown in Fig. 2, that is, the mirror surface system shown in Fig. 1, is constructed so as to satisfy Qm(l+≦0.7 m (i). It is determined.

The lens array shown in Fig. 2 is based on the power close to the primary radiator (1), so if lens [61, lens 2 (71), and lens 3 (8)] are the first sub-reflector + 21.i second reflector, respectively (3) and the main reflecting mirror (4).

Therefore, the field distribution on the main reflecting mirror (4) is given by the following equation from the complex beam parameter q3VC on the lens 3 (8).

Here, WQ&1 is the beam radius on the aperture of the primary radiator (1), and lh is the length of the primary radiator (1).

Also, the beam radius W3 on the lens 3 (8) and the wavefront radius R
3 has the following relational expression.

Eri of the third and fourth equations, W3 and R5 are obtained. What is the size of the edge level of the main reflecting mirror (4)?

It is related to the size of the beam radius W3. Also, the frequency of the aperture efficiency @Note is the beam waist half ff of the radiation wave at the aperture.
The y value can be changed with a change of 1Wr. Frequency of w5+wr! vf
Note: Obtained by finding the differential coefficient with respect to the wavelength. Namely.

becomes. In order to easily customize the frequency of the aperture distribution, that is, the aperture efficiency, the values of the fifth and sixth expressions may be made smaller. If the structural dimensions are determined so that KBj:O, the frequency dependence of the aperture efficiency disappears, and the aperture efficiency becomes constant over a wide band.

From the third equation, Bt is given as follows.

Therefore, by setting Bt20, the second equation can finally be obtained from the cuff equation.

As is clear from the above, Bi=O and Dingi Lba.

Although the frequency dependence of the aperture η and the ratio V is completely eliminated, due to the structural limitations of the antenna, it is often impossible to completely reduce the value to +40. :The solution is to bring Bt closer to 0nζ in two directions.

Therefore, as shown in the third example, we found the 5 l'Ji field 1 that is equal to the aperture efficiency of the antenna from the direct and other calculations VC, and set the range of 12 as shown in the first equation.

By configuring the mirror system of the antenna as a VC so that the first and second equations are added by 1, the length 12 between 1li14 reflection theory is made longer. J: 5 can be used as a conventional competition (company) system Mizosari and can be used for an antenna aperture efficiency of 8 wide EF matches.

In addition, in the above example of Fig. 1, the &il1 reflection intermediate axis axis hQ nod angle is the king reflex acute (・1) ■ 1 inversion angle of 1 counterclockwise force with respect to the rotation axis is ↑ Ding I and One'J
L" ML is flowing, but as shown in Figure 4, it is okay to be stubborn.

〔Effect of the invention〕

As described above, according to the present invention, the distance between the sub-reflecting arms/
! 2 is Om (12≦0.7m, and further.

U VcT! ! ! By configuring a self-system, the aperture efficiency of the antenna can be made constant over a wide band, and the depth of the antenna can be shortened, so that the antenna can be made smaller.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an antenna device according to an embodiment of the present invention, Fig. 2 is a diagram showing a lens array equivalent to the antenna device shown in Fig. 1, and Fig. 3 is a diagram showing an example of calculating 10 efficiency. Figure, 4th
The figure shows an embodiment of the antenna device of the present invention, FIG. 5 shows the configuration of a conventional Q antenna device, and FIG. 6 shows a custom-made custom-made antenna device for the conventional antenna device shown in FIG. FIG. In the figure, (1) is the -Kyu-shaki, and (2) is the -Ashitan! 4. J
Arm, (3) is the second sub-reflector, (5) is the optical chamber, (6N)
Lens 1. +71 is lens 2. (81&'! Lens 3. The same reference numerals in the two figures indicate the same or corresponding parts.

Claims (1)

[Claims] Two sub-reflectors are arranged between the primary radiator and the main reflector, and the main reflector is above the primary radiator and the sub-reflector,
Moreover, in an antenna device configured such that the confocal points of the two sub-reflectors are on the aperture side of the main reflector, the sub-reflector near the primary radiator is S_1, the other sub-reflector is S_2,
One focus of sub-reflector S_1 that coincides with the phase center of the primary radiator is F_0, the other focus of sub-reflector S_1 that is confocal with sub-reflector S_2 is F_1, and the main reflector of sub-reflector S_2 is When considered from a geometrical optics perspective with the confocal point of F_2 as
2, furthermore, let M be the point where the ray that passed through point M_2 hits the main reflecting mirror R, then let the distance from the aperture of the primary radiator to point M_1 be l_1, and the distance from point M_1 to point M_2 be l_1.
_2, M_The distance from point M_2 to point M is l_3, and the focal lengths when sub-reflector S_1 and sub-reflector S_2 are replaced with lenses are f_1 and f_2, respectively, and F_
0, F_1, F_2, M_1, M_2, M_ are in the same plane, 0m<l_2≦0.7m, [(1/f_1)
-(1/l_1)-(1/l_2)] [(1/f_2)
-(1/l_2)-(1/l_3)]≒1/l^2_2
An antenna device characterized in that a mirror system is configured so that