JP2001292022A - Focusing beam feeding system employing four reflecting mirrors - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a focusing beam feeding system employing 4 reflecting mirrors, that has an excellent cross polarization characteristic by canceling cross polarization caused by the asymmetry of focusing reflecting mirrors with each other. SOLUTION: A ray emitted along a center axis of a primary radiator 1 is made incident sequentially onto a 1st focusing reflecting mirror 2, a 2nd focusing reflecting mirror 3, a 3rd focusing reflecting mirror 4 and a 4th focusing reflecting mirror 5, the ray propagated through a path between the 2nd focusing reflecting mirror 3 and the 3rd focusing reflecting mirror 4 is in crossing with a horizontal plane rotary axis of an antenna sub reflecting mirror 106 and concave mirrors are employed for the 1st-3rd focusing reflecting mirrors.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises four focusing reflectors between a primary radiator and an antenna sub-reflector used for a satellite earth station, a large radio telescope and a terrestrial microwave relay line. The present invention relates to a four-reflection mirror type focused beam feeding system.

[0002]

2. Description of the Related Art An asymmetric focusing mirror is used for a four-beam reflecting mirror type focused beam feeding system, and a primary radiator, a focusing reflector, and its supporting columns are arranged so as not to be blocked, and good radiation characteristics are obtained. Some are gaining. However, in such a focused beam feeding system, there is a disadvantage that a cross polarization component is generated due to asymmetry since the focusing reflector is not rotationally symmetric.

In order to eliminate the above-mentioned disadvantages, a focused beam feeding system as shown in FIG. 5 has been conventionally used. In FIG. 5, reference numeral 101 denotes a conical horn which is a primary radiator;
Numeral 105 indicates four focusing mirrors, 106 indicates an antenna sub-reflector, and 107 indicates light rays emitted along the central axis of the primary radiator 101.

That is, four focusing reflectors 10 arranged between the primary radiator 101 and the antenna sub-reflector 106
2,103,104,105 (Reference numeral M ₁ in order from the first 5 as the fourth focusing reflector, M _2, M _3, are also shown the M ₄₎ conventional four Reflector shape converging with the In the beam feeding system, f ₁ is the focal length of the focusing reflector 102, f ₂ is the focal length of the focusing reflector 103, and f ₃ is the focusing reflector 104.
And f ₄ are the focal lengths of the focusing mirror 105, and σ ₁ is the ray 107 along the central axis of the primary radiator 101.
Angle between the incident wave and the reflected wave on the converging reflector 102, σ
₂ is the angle between the incident wave and the reflected wave of the ray 107 along the central axis of the primary radiator 101 and the reflected wave, σ ₃ is the angle of the ray 107 along the central axis of the primary radiator 101 on the focusing reflector 104. The angle between the incident wave and the reflected wave and σ ₄ are determined by focusing mirror 1 of light ray 107 along the central axis of primary radiator 101.
05 is the angle between the incident wave and the reflected wave, and d ₁ is the focusing mirror 10 for the light ray 107 along the central axis of the primary radiator 101.
The distance propagating between 2 and 103, d _2, is the primary radiator 101
Focusing mirrors 103 and 104 of light ray 107 along the central axis of
Assuming that the distance propagating between them and d ₃ is the distance that the light ray 107 along the central axis of the primary radiator 101 propagates between the focusing mirrors 104 and 105, the focusing mirrors 102, 103, 1
04 is a concave mirror, the focusing reflector 105 closest to the antenna sub-reflector 106 is a plane reflector, and the angle σ ₁ between the incident wave and the reflected wave of the ray 107 along the central axis of the primary radiator 101 on each focusing reflector. , Σ ₂ , σ ₃ and σ ₄ are 90 °,
Using the evaluation formula (1) for the amount of cross-polarization generated due to the asymmetry of the reflecting mirror given by the following equation, the design parameters are variously changed, and the cross-polarization characteristics of the entire focused beam feeding system are calculated by successive calculations. We were trying to optimize.

[0005]

(Equation 2)

Here, C is the electric field ratio between the maximum value of the cross polarization component and the maximum value of the main polarization component at the position of the antenna sub-reflector 106. However,

[0007]

(Equation 3)

Ω ₁ : beam radius on the first focusing reflector 102 ω ₂ : beam radius on the second focusing reflector 103 ω ₃ : beam radius on the third focusing reflector 104 R ₁ ′, R ₂ ′: Radius of curvature of reflected wavefronts of the first focusing mirror 102 and the second focusing mirror 103 e: base of natural logarithm (2.718 ...) θ ₁ , θ ₂ : phase of cross polarization component λ: free space wavelength It is.

[0009]

The conventional four-reflection type focused beam feeding system as described above uses the evaluation formula of the cross polarization generation amount shown in the equation (1) to sequentially calculate the cross polarization component. Therefore, there is a problem that the cross-polarization component generated due to the asymmetry of the focusing mirror cannot be completely reduced to zero.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the cross-polarization components generated by the respective focusing mirrors are canceled out in consideration of the phase, so that the focusing mirrors can be canceled. An object of the present invention is to obtain a four-reflection type focused beam feeding system in which a cross polarization component generated by asymmetry is set to 0 over a wide band.

[0011]

A four-reflection type focused beam feeding system according to the present invention includes first to fourth four focusing reflectors between a primary radiator and an antenna sub-reflector. Of these focusing reflectors, in a four-reflector-mirror focused beam feeding system in which the fourth focusing reflector closest to the antenna sub-reflector is a plane reflector, a first focusing reflector, a second focusing reflector,
The focal points of the third focusing mirror, the fourth focusing mirror and each of the mirrors are in the same plane, and the light rays emitted along the central axis of the primary radiator are sequentially focused on the first focusing mirror and the second focusing mirror. It is assumed that the light is incident on the reflecting mirror, the third focusing reflecting mirror, and the fourth focusing reflecting mirror, and a light beam propagating between the second focusing reflecting mirror and the third focusing reflecting mirror intersects the horizontal rotation axis of the antenna sub-reflecting mirror, and The first to third focusing mirrors are concave mirrors.

[0012] In addition, a first to a fourth four focusing mirrors are provided between the primary radiator and the antenna sub-reflecting mirror, and of these focusing reflectors, a fourth focusing mirror closest to the antenna sub-reflecting mirror is provided. In a four-beam reflecting mirror type focused beam feeding system using a reflecting mirror as a plane reflecting mirror, a first focusing mirror, a second focusing reflector, a third focusing mirror, and a third focusing mirror.
The focusing mirror, the fourth focusing mirror, and the focal points of the respective mirrors are in the same plane, and the light rays emitted along the central axis of the primary radiator are sequentially focused on the first focusing mirror and the second focusing mirror. , The third focusing mirror, and the fourth focusing mirror, and the relationship between the focal lengths of the first to third focusing mirrors is as follows:

[0013]

(Equation 4)

Where f _{1 is} the focal length of the focusing reflector M1 f _{2 is} the focal length of the focusing reflector M2 f _{3 is} the focal length of the focusing reflector M3 σ _{1 is} the focusing of light rays along the central axis of the primary radiator Reflector M1
The angle between the incident wave and the reflected wave above σ ₂ : Focusing mirror M2 for rays along the central axis of the primary radiator
The angle between the incident wave and the reflected wave above σ ₃ : Focusing mirror M3 for rays along the central axis of the primary radiator
The angle between the incident wave and the reflected wave above d ₁ : the distance of the ray along the central axis of the primary radiator propagating between the first and second focusing reflectors d ₂ : the ray of the ray along the central axis of the primary radiator The mirror system is characterized in that the mirror system is configured to satisfy the distance of propagation between the second and third focusing reflectors.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 shows the focal lengths of the primary radiator and the four focusing mirrors as f ₁ , f ₂ ,
FIG. 6 is a configuration diagram of a four-reflector mirror-type focused beam feeding system according to the first embodiment of the present invention, which is constituted by rotating quadric curved mirrors f ₃ and f _4, and corresponds to FIG. 5 described above. In FIG. 1, 1 is a conical horn which is a primary radiator, 2 is a first focusing mirror M1 comprising a concave mirror, 3 is a second focusing mirror M2 also comprising a concave mirror, 4 is a third focusing mirror also comprising a concave mirror M3 and M5 are fourth focusing mirrors M4, each of which is a plane reflecting mirror disposed closest to the antenna sub-reflecting mirror 106.
It is. FIG. 1 shows first to fourth focusing mirrors 2,
Symbols M ₁ , M ₂ , M ₃ , and M ₄ are sequentially described as ₃ , _4, and ₅ , respectively.

Also, 20 is emitted along the central axis of the primary radiator 1, and is sequentially transmitted to the first focusing reflector 2, the second focusing reflector 3, the third focusing reflector 4, and the fourth focusing reflector 5. It is an incident light beam. Reference numeral 30 denotes a horizontal axis of rotation of the antenna sub-reflector 106, and a light beam propagating between the second focusing mirror M2 and the third focusing mirror M3 intersects with a horizontal axis of rotation of the antenna auxiliary reflector 106. . Here, it is assumed that the first focusing reflector 2, the second focusing reflector 3, the third focusing reflector 4, the fourth focusing reflector 5, and the focal point of each reflector are in the same plane.

First, a description will be given of the conditions for canceling the wave-like cross polarization of radio waves. Consider the mirror system such as FIG. 2 configured in N pieces of rotational quadric surface mirror, the order the focal distance from the reflector closer to the primary radiator 1 f _1, f _2, · · ·, When f _N , Equation (3). In FIG. 2,
1 is the same primary radiator as in FIG. 1, 6 is a reflector # 1,
7 is a reflecting mirror # 2, 8 is a reflecting mirror # 3, 9 is a reflecting mirror # N-
Reference numerals 1 and 10 are reflecting mirrors #N.

[0018]

(Equation 5)

Here, n = 1, 2,..., N,
N is one or more natural numbers.

R _n and R _n ′ are the radius of curvature of the wavefront incident on the reflecting mirror #N and the radius of curvature of the reflected wavefront, respectively, and take a value (−) when the focal point is in the traveling direction of the light beam. In Equation (3), when f _n is positive, the mirror is a concave mirror, and when f _n is negative, the mirror is a convex mirror. Furthermore, from the reflector closer to the primary radiator 1 and the beam radius omega _1, omega _2, · · ·, and omega _N,
If the angles σ ₁ , σ ₂ ,..., Σ _N are defined as shown in FIG. 2, the IEICE Transactions '83 / 3 Vol.J-66B No. 3
As shown on page 310, “Analysis and Design Method by Beam Mode Expansion of Focused Beam Feeding System”, cross-polarization components generated by each reflecting mirror were summed up for N reflecting mirrors in consideration of phase. Assuming that the result is C _N , it is expressed by equation (4).

[0021]

(Equation 6)

Here,

[0023]

(Equation 7)

Here, θ _n : the phase of the cross polarization component k _n : the traveling direction vector of the radio wave j1: a vector perpendicular to the paper surface.

[0025] Here, lambda is the free space wavelength, the d _n is the distance between the reflector as measured along the central ray. Expression (4) is expanded by using a relational expression between the two expressions of expression (5) and the beam mode parameter expressed by the following expression (6).

[0026]

(Equation 8)

An expression for evaluating the amount of cross-polarization generated by the N reflector offset antennas, which is expressed by the following equation (7), is obtained.

[0028]

(Equation 9)

In equation (7), the first term is the cross-polarization component generated by the first reflector, the second term is the cross-polarization component generated by the second reflector, and the third and subsequent terms are The cross polarization component generated by the third and subsequent reflecting mirrors is shown. The wave cross-polarization cancellation condition of the _N reflector offset antennas is C _N
= 0, and the following equation is obtained.

[0030]

(Equation 10)

[0031] In this _{case, q n = sign (j1 ·} k n × k n + 1) n = 1,2,3, ···, a N, N: 1 or more is a natural number.

The cross polarization component generated by the four rotating quadric mirrors is given by the following equation by substituting N = 4 into equation (7).

[0033]

[Equation 11]

Here,

[0035]

(Equation 12)

Is as follows.

The wave-like cross-polarization canceling condition of the four-reflecting mirror-type focused beam feeding system is as follows. Since the fourth focusing mirror is a plane mirror, f ₄ = ∞ is substituted into Expression (10), and C _4R = 0, C _4I =
Assuming 0, the following equation is obtained.

[0038]

(Equation 13)

[0039]

[Equation 14]

Here, from the mirror system of FIG. 1, q _n = sign
_{(J1 · k n × k n} + 1) using _{a, q 1 = -1, q 2} = + 1, q 3
= -1. Equations (11) and (12) are wave-like cross-polarization canceling conditions of the four-reflection mirror focused beam feeding system, and are geometrical relational equations not related to frequency. Therefore, in a mirror system satisfying this relationship, no cross-polarized component is generated regardless of the frequency.

If Equation (13) is defined from Equations (11) and (12), since σ ₁ and σ ₂ are in the range of 0 and π, ta
_{n (σ 1/2)>} 0, tan (σ 1/2)> 0, also d
Since _1> is 0, d _2> 0, equation (14) is obtained. From Equations (13) and (14), the form of the mirror system can be discussed.

[0042]

(Equation 15)

[0043]

(Equation 16)

Therefore, from the first expression of Expression (13), the first focusing reflector 2 is a concave mirror when the third focusing mirror 4 is a concave mirror, and a convex mirror when the third focusing reflector 4 is a convex mirror. When the third focusing reflector 4 is a convex mirror, the second focusing reflector 3 is always a concave mirror according to the second expression of Expression (13). When the third focusing mirror 4 is a concave mirror, the second focusing mirror 3 is a convex mirror.
When δ ₂ = −1 in the second expression of the expression (14), that is, from the second expression of the expression (13),

[0045]

[Equation 17]

This is the case.

The second focusing reflector 3 becomes a concave mirror when δ ₂ = + 1 in the second equation of the equation (14), that is, from the second equation of the equation (13).

[0048]

(Equation 18)

This is the case.

Table 1 shows a list of mirror systems satisfying the conditions of the equations (13) and (14).

[0051]

[Table 1]

The example shown in FIG. 1 corresponds to f1> 0, f2 in Table 1.
> 0, f3> 0, and the example shown in FIG.
1> 0, f2 <0, f3> 0, and the example shown in FIG. 4 corresponds to f1 <0, f2> 0, f3 <0 in Table 1.

The conventional four-reflector mirror-type focused beam power supply system includes:
In order to minimize the cross-polarization component generated by the asymmetrical reflecting mirror, the shape of the mirror system was obtained by sequential calculation, but the present invention also considers the phase of the cross-polarization component generated by the reflecting mirror, Since the reflection mirrors cancel each other out so that there is no frequency characteristic, the cross polarization can be made completely zero regardless of the frequency and the frequency can be used effectively, so that the transmission capacity increases. There is an effect that can be achieved.

When the wave-like cross-polarization canceling condition in which the cross-polarization components generated by the reflecting mirrors are canceled out by the respective reflecting mirrors is applied to the design of the focused beam feeding system, a comparison is made with the successive calculation method. Thus, an optimum mirror system can be obtained in a short time.

Although the case where the conical horn is used as the primary radiator has been described above, the present invention is not limited to this, and any horn having a central axis may be attached as the primary radiator. In the above description, the case where the reflecting mirror is a rotating quadric curved mirror has been described. However, the present invention is not limited to this, and the present invention is also applicable to a four-reflecting mirror-type focused beam feeding system in which the reflecting mirror is mirror-modified. Is also good. Also, a case has been described in which the four-reflection mirror type focused beam power supply system is used in a satellite communication earth station, but the present invention is not limited to this, and may be used in a radio telescope or a terrestrial microwave relay line.

[0056]

As described above, according to the present invention, the first to fourth four focusing mirrors are provided between the primary radiator and the antenna sub-reflector. A four-reflecting mirror-type focused beam feeding system in which a focusing reflector closest to an antenna sub-reflector is a plane reflector, comprising a first focusing reflector, a second focusing reflector, a third focusing reflector, and a fourth focusing mirror. The reflectors and the focal point of each reflector are assumed to be in the same plane, and the rays emitted along the central axis of the primary radiator are sequentially focused on a first focusing reflector, a second focusing reflector, a third focusing reflector, It is assumed that the light is incident on the fourth focusing mirror, and the light beam propagating between the second focusing mirror and the third focusing mirror intersects with the horizontal rotation axis of the antenna sub-reflecting mirror, and the first to third focusing mirrors. Since this is a four-reflector mirror-type focused beam feed system with a concave mirror as the reflecting mirror, it is generated at each reflecting mirror. Differential polarizations can be canceled by taking phase into consideration, and among the four focusing mirrors, concave mirrors are used for the first to third focusing mirrors. This has the effect of being able to be reduced as compared with.

The first to fourth four focusing mirrors are provided between the primary radiator and the antenna sub-reflector, and the fourth focusing reflector closest to the antenna sub-reflector among the focusing reflectors is provided. A four-beam reflecting mirror type focused beam feeding system using a mirror as a plane reflecting mirror, wherein a first focusing reflector, a second focusing reflector, a third focusing reflector, a fourth focusing reflector, and a focal point of each reflector are It is assumed that the focal lengths of the first to third focusing mirrors are in the same plane.

[0058]

[Equation 19]

Where f _{1 is} the focal length of the first focusing reflector, f _{2 is} the focal length of the second focusing reflector, f _{3 is} the focal length of the third focusing reflector, and σ ₁ is the center of the primary radiator. The angle between the incident wave and the reflected wave on the first focusing mirror of the ray along the axis,
σ ₂ : angle between the incident wave of the ray along the central axis of the primary radiator and the reflected wave on the second focusing reflector, σ ₃ : incidence of the ray along the central axis of the primary radiator on the third focusing reflector The angle between the wave and the reflected wave, d ₁ : the first of the rays along the central axis of the primary radiator
And a distance between the second and third focusing mirrors, d ₂ : four mirrors having a mirror system configured so as to satisfy a distance of a ray along the central axis of the primary radiator between the second and third focusing mirrors. Since it is a reflecting mirror type focused beam feeding system, the cross-polarization component generated by the asymmetry of the reflecting mirror should be zero regardless of the frequency by satisfying the wave dynamic cross-polarization canceling condition shown in the above equation. Since the frequency can be effectively used, the transmission capacity can be increased.

[Brief description of the drawings]

FIG. 1 is a diagram showing a mirror system of a four-reflection mirror focused beam feeding system according to the present invention.

FIG. 2 is a diagram showing a mirror surface system of an N-piece reflecting mirror offset antenna for explaining the operation of the present invention.

FIG. 3 is a diagram illustrating an example of a mirror system of a four-reflection mirror type focused beam feeding system.

FIG. 4 is a diagram showing another example of another mirror system of the four-reflection mirror type focused beam feeding system.

FIG. 5 is a diagram showing a conventional four-reflection mirror focused beam system.

[Explanation of symbols]

1 primary radiator (conical horn), 2 first focusing reflector,
3 Second focusing reflector, 4 Third focusing reflector, 5 Fourth focusing reflector, 6 Reflector # 1, 7 Reflector # 2, 8 Reflector # 3, 9 Reflector # N-1, 11 Reflector #N, 10
6 Antenna secondary reflector.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Takamasa Furuno 2-12-5 Iwamotocho, Chiyoda-ku, Tokyo F-term (reference) 5J020 AA03 BA08 BC06 DA03 DA05

Claims (2)

[Claims] The present invention further comprises first to fourth four focusing mirrors between a primary radiator and an antenna sub-reflector, and a fourth focusing mirror closest to the antenna sub-reflector among the focusing mirrors. In the four-reflecting mirror-type focused beam feeding system in which the reflecting mirror is a plane reflecting mirror, the first focusing mirror, the second focusing reflector, the third focusing reflector, the fourth focusing reflector, and the focal point of each reflector are the same. The rays radiated along the central axis of the primary radiator shall be incident on the first focusing reflector, the second focusing reflector, the third focusing reflector, and the fourth focusing reflector in this order. A beam propagating between the second focusing mirror and the third focusing mirror intersects a horizontal axis of rotation of the antenna sub-reflecting mirror, and the first to third focusing mirrors are concave mirrors. Reflective mirror-type focused beam power supply system. 2. A first to a fourth four focusing mirrors are provided between a primary radiator and an antenna sub-reflecting mirror, and a fourth focusing mirror closest to the antenna sub-reflecting mirror among the focusing mirrors is provided. In the four-reflecting mirror-type focused beam feeding system in which the reflecting mirror is a plane reflecting mirror, the first focusing mirror, the second focusing reflector, the third focusing reflector, the fourth focusing reflector, and the focal point of each reflector are the same. The rays radiated along the central axis of the primary radiator shall be incident on the first focusing reflector, the second focusing reflector, the third focusing reflector, and the fourth focusing reflector in this order. , First to third
The relation of the focal length of the focusing reflector is given by Here, f ₁ : focal length of the focusing mirror M1 f ₂ : focal length of the focusing mirror M2 f ₃ : focal length of the focusing mirror M3 σ ₁ : focusing mirror M1 of light rays along the central axis of the primary radiator
The angle between the incident wave and the reflected wave above σ ₂ : Focusing mirror M2 for rays along the central axis of the primary radiator
The angle between the incident wave and the reflected wave above σ ₃ : Focusing mirror M3 for rays along the central axis of the primary radiator
The angle between the incident wave and the reflected wave above d ₁ : the distance of the ray along the central axis of the primary radiator propagating between the first and second focusing reflectors d ₂ : the ray of the ray along the central axis of the primary radiator A four-reflector mirror-type focused beam feeding system, wherein a mirror system is configured to satisfy a distance that propagates between the second and third focusing mirrors.