JP2001156539A - Antenna system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an offset antenna consisting of 4 reflecting mirrors that generates no cross polarized wave components over a broadband independently of the frequency. SOLUTION: Cross polarization canceling condition of through wave motion for the offset antenna consisting of 4 reflecting mirrors is obtained from an evaluation expression of a cross polarized wave generating amount of an offset antenna consisting of N reflecting mirrors taking the phase into account, it is clarified that this is a geometrical relational expression independent of frequency, and a main reflecting mirror satisfying the condition can prevent production of the cross polarized wave components for 6 kinds of downward antennas over a broadband independently of the frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a primary radiator used for microwave relay lines and satellite communications, and to a four-reflector-mirror antenna apparatus comprising three sub-reflectors and a main reflector. .

[0002]

BACKGROUND ART main reflecting mirror M _4, the sub-reflecting mirror M ₁ and the antenna device comprising a primary radiator, with asymmetrical reflector, so as not subreflector and the primary radiator and the supporting pillars and blocking In some cases to obtain good radiation characteristics. However, this antenna device has a drawback that a cross-polarization component is generated due to asymmetry since the reflecting mirror is not rotationally symmetric.

In order to eliminate the above drawbacks, conventionally, share phase center F ₀ of the conical horn 1, a conical horn 1 is a primary radiator having a phase center F ₀ as shown in FIG. 8, further focal point F ₁ sub-reflector M ₁ 2 with, there is one that is composed of the main reflector M ₄ 5 further shares the F _1. In the figure, the sub-reflecting mirror M ₁ 2 is a rotating ellipsoidal mirror or rotating hyperboloid mirror, a main reflector M ₄ 5 The parabolic mirror. Considering geometrical optics, the above-described antenna apparatus has an equivalent rotationally symmetric mirror system as shown in FIG. 9 in order to suppress cross-polarization components generated due to the asymmetry of the mirror. It is configured to be a simple parabolic antenna. In the figure, reference numeral 11 denotes a rotationally symmetric parabolic antenna. By setting the position and orientation of the primary radiator 1 so as to satisfy the condition of the following expression for further discussed when the main reflecting mirror, cross-polarization components generated sub-reflector M ₁ 2, the main reflecting mirror M ₄ 5 Can cancel each other out.

[0004]

(Equation 2)

[0005] Here, α: the angle at which the straight line connecting the focal point of the main reflector and the focal point of the sub-reflector is a straight line parallel to the Z-axis perpendicular to the aperture plane of the antenna. β: The angle between the central axis of the primary radiator and a straight line parallel to the Z axis. P: When P = + 1, the sub-reflector M ₁₂ is a rotating hyperboloid mirror, P
= Sub-reflector M ₁ 2 when -1 spheroidal mirror. K: constant

[0006]

In the conventional antenna device as described above, since the mirror system is geometrically designed, the cross polarization component is completely suppressed only when the frequency is infinite. . For this reason, in an actual operating frequency band such as a microwave band or a millimeter wave band, the cross polarization component generated due to the asymmetry of the reflector cannot be completely eliminated, and the cross polarization in the operating frequency band of the antenna device cannot be completely eliminated. There was a problem of deteriorating wave characteristics.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to obtain an antenna device having good cross-polarization characteristics regardless of frequency.

[0008]

In the antenna device according to the first aspect of the present invention, the condition for eliminating the wave-like cross polarization is satisfied in the antenna device having the primary radiator and the four reflecting mirrors, and the conditional expression is satisfied. Thus, good cross-polarization characteristics are obtained.

An antenna device according to a second aspect of the present invention is a four-reflector offset antenna comprising a primary radiator, three sub-reflectors and a downward main reflector, wherein f ₁ is the focal length of the sub-reflector M ₁ . , F ₂ the focal length of the secondary reflector M ₂ , f ₃ the focal length of the secondary reflector M ₃ and f ₄ the focal length of the main reflector M ₄ , and σ _{1 the} ray along the central axis of the primary radiator Is the angle formed by the incident wave and the reflected wave on the sub-reflector M1, and σ ₂ is the angle formed by the incident wave and reflected wave of the light ray along the central axis of the primary radiator on the sub-reflector M2, and σ ₃ is the primary radiator Angle and σ of the incident wave and the reflected wave of the ray along the central axis of
₄ primary radiator main reflecting mirror M ₄ on the incident wave of light along the center axis of the angle of the reflected wave, sub-reflector of light rays along the d ₁ to the central axis of the primary radiator M _1, M ₂ Distance to propagate between, d
₂ is the sub-reflector M ₂ , M _{3 of the} light ray along the central axis of the primary radiator
Assuming that the distance propagating between them and the distance d ₃ are the distances of light rays traveling along the central axis of the primary radiator between the sub-reflector M ₃ and the main reflector M ₄ , the sub-reflectors M ₁ , M ₂ , M ₃ Is a concave mirror, and f ₄ >
d ₃ , σ ₄ > σ ₃ .

In the antenna device according to a third aspect of the present invention, the sub-reflecting mirrors M ₁ , M ₂ , and M ₃ are concave mirrors and satisfy f ₄ <d ₃ , σ ₄ > σ ₃ .

In the antenna device according to a fourth aspect of the invention, the sub-reflecting mirrors M ₁ , M ₂ , and M ₃ are concave mirrors, and satisfy f ₄ <d ₃ and σ ₄ <σ ₃ .

In the antenna device according to a fifth aspect of the invention, the sub-reflecting mirrors M ₁ and M ₂ are concave mirrors, the sub-reflecting mirror M ₃ is a convex mirror, and f ₄ >
d ₃ , σ ₄ > σ ₃ .

In the antenna device according to a sixth aspect of the invention, the sub-reflecting mirrors M ₁ and M ₂ are concave mirrors, the sub-reflecting mirror M ₃ is a convex mirror, and f ₄ >
d ₃ , σ ₄ <σ ₃ .

In the antenna device according to a seventh aspect of the invention, the sub-reflecting mirrors M ₁ and M ₂ are concave mirrors, the sub-reflecting mirror M ₃ is a convex mirror, and f ₄ <
d ₃ , σ ₄ <σ ₃ .

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Figure 1 shows primary radiation
The focal lengths of the reflector, three sub-reflectors and the main reflector
Re f ₁, F_Two, F_Three, F_FourComposed of four rotating quadric mirrors
FIG. 3 is a configuration diagram of a four-reflector mirror offset antenna formed.
FIG. 8 corresponds to FIG. In FIG. 1, 1, 2, and 5 are
They have the same name. In the figure, 3 is a sub-reflector M_Two4 is a sub-reflection
Mirror M_Three, F_FourIs the main reflector M_Four5 focus. here,
M₁, M_Two, M_Three, M_Four, F_FiveAre in the same plane
You.

Here, a description will be given of the conditions for canceling the wave cross-polarization of radio waves. Consider the mirror system as configured Figure 7 in N pieces of rotational quadric surface mirror, turn to the focal length f _1, f _2, · · ·, and f _N from the reflecting mirror closest to the primary radiator 1,
It is defined by the following equation. In the figure, 1 is the same name as in FIGS. 1 and 8, 6 is a reflecting mirror # 1, 7 is a reflecting mirror # 2, 8 is a reflecting mirror #
Reference numerals 3 and 9 are reflecting mirrors # N-1, and 10 is a reflecting mirror #N. Here, N is an arbitrary natural number of 2 or more.

[0017]

(Equation 3)

Here, n = 1, 2,..., N,
N is a natural number of 2 or more.

Further, R _n and R _n ′ are the focal point F on the incident side of the reflecting mirror.
_n , and the distance between the reflection-side focal point _{Fn + 1} and the intersection of the central ray and the reflecting mirror #n, and takes a value (-) when the focal point is in the traveling direction of the ray. In equation (2), when f _n is positive, the mirror is a concave mirror, and when f _n is negative, the mirror is a convex mirror. Further, the beam radii of the reflecting mirror near the primary radiator 1 are changed to ω ₁ , ω ₂ ,
, Ω _N and angles σ ₁ , σ ₂ ,..., Σ _N are defined as shown in FIG.
Vol. As shown on page J-66B No. 3'310, the cross-polarization component generated by each reflecting mirror is expressed by the following formula, where C _N is the sum of the results for the _N reflecting mirrors in consideration of the phase. Is done.

[0020]

(Equation 4)

[0021] Here, lambda is the free space wavelength, the d _n is the distance between the reflector as measured along the central ray. Expression (3) is expanded using the relational expression of Expressions (4) and (5),

[0022]

(Equation 5)

An evaluation expression of the cross polarization generation amount of the N-piece reflecting mirror offset antenna expressed by the expression (6) is obtained.

[0024]

(Equation 6)

In equation (6), 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 antenna is C _N =
Given as 0, the following equation is obtained.

[0026]

(Equation 7)

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

[0028]

(Equation 8)

From equation (9), the four-mirror offset offset
The tena wave dynamic cross polarization cancellation condition is C _4R= 0, C_4I= 0
Given by:

[0030]

(Equation 9)

Equations (11), (12) and (13)
Is the condition for canceling the wave-like cross polarization of the four-reflector offset antenna, and is a geometrical relational expression not related to the frequency. Therefore, a mirror system that satisfies this relationship does not satisfy the cross-polarization component regardless of the frequency.

Equations (11), (12) and (13)
From Equations (14) and (15) are obtained, and the form of the mirror system can be discussed.

[0033]

(Equation 10)

Table 1 shows a list of mirror systems satisfying the conditions of the equations (14) and (15).

[0035]

[Table 1]

FIG. 1 shows f in Table 1._Three> 0, f_Four> D_Three, Σ_Four>
σ_ThreeFIG. 2 shows f in the table._Three> 0, f_Four<D_Three, Σ_Four>
σ_ThreeFIG. 3 shows f_Three> 0, f_Four<D_Three, Σ_Four<Σ_ThreePhase
FIG. 4 shows f_Three<0, f_Four> D_Three, Σ_Four> Σ_ThreeIs equivalent to
FIG._Three<0, f_Four<D_Three, Σ _Four<Σ_ThreeAnd FIG._Three<0,
f_Four> D_Three, Σ_Four<Σ_ThreeIs equivalent to

In the conventional antenna device which satisfies the condition of geometrical optical cross-polarization cancellation, the respective reflecting mirrors are arranged so that their focal positions are confocal with each other. However, in the antenna device according to the present invention, Since the arrangement of the reflecting mirror is determined by the beam radius, it is not necessary to use a confocal point, and the degree of freedom in design is greatly increased. In addition, the four-reflector offset antenna can have a primary radiator attached to the back of the main reflector in the same manner as the two-reflector offset antenna, and has the same performance in terms of structure.

Although the case where a 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 quadratic curved mirror has been described. However, the present invention is not limited to this, and may be used for an antenna device or the like in which the reflecting mirror has a modified mirror surface. Also, the case where the antenna device is used for a terrestrial relay line has been described, but the present invention is not limited to this, and may be used for a satellite communication base station antenna, a satellite-mounted antenna, and the like.

[0039]

According to the present invention, in the four-reflector offset antenna, the cross-polarization component generated by the asymmetry of the reflector can be obtained regardless of the frequency by satisfying the wave-like cross-polarization cancellation condition. Can be set to 0.

[Brief description of the drawings]

FIG. 1 is a diagram showing a mirror system of a four-reflector mirror offset antenna according to the present invention.

FIG. 2 is a view showing another mirror system of the four-reflector offset antenna of the present invention.

FIG. 3 is a diagram showing another mirror system of the four-reflector offset antenna of the present invention.

FIG. 4 is a diagram showing another mirror system of the four-reflector offset antenna of the present invention.

FIG. 5 is a view showing another mirror system of the four-reflector offset antenna of the present invention.

FIG. 6 is a diagram showing another mirror system of the four-reflector offset antenna of the present invention.

FIG. 7 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. 8 is a diagram showing a conventional two-reflector mirror offset antenna.

FIG. 9 is a diagram showing an equivalent parabola.

[Description of Signs] 1 primary radiator, 2 sub-reflector M ₁ , 3 sub-reflector M ₂ ,
4 Sub-reflector M ₃ , 5 main reflector M ₄ , 6 Reflector # 1, 7
Reflector # 2, 8 Reflector # 3, 9 Reflector # N-1,
10 Reflector #N, 11 equivalent parabola.

Claims (7)

[Claims] 1. A four-reflector offset antenna comprising a primary radiator and three sub-reflectors and a main reflector, wherein: F ₁ : focal length of sub-reflector M ₁ f ₂ : focal length of sub-reflector M ₂ f ₃ : focal length of sub-reflector M ₃ f ₄ : focal length of main reflector M ₄ σ ₁ : primary The angle between the incident wave and the reflected wave of the ray along the central axis of the radiator on the sub-reflector M ₁ σ ₂ : the angle of the incident wave and the reflected wave of the ray along the central axis of the primary radiator on the sub-reflector M ₂ Angle σ ₃ : The angle between the incident wave and the reflected wave of the ray along the central axis of the primary radiator on the sub-reflector M ₃ σ ₄ : The angle on the main reflector M _{4 of the} ray along the central axis of the primary radiator Angle d ₁ between incident wave and reflected wave: sub-reflector M 1 for light rays along the central axis of the primary radiator
Distance propagates between M2 d _2: a primary radiator sub-reflector of light M2 along the central axis of,
Distance to propagate between M3 d _3: primary radiator sub-reflector M3 of light rays along the central axis of,
An antenna device, wherein a mirror system is configured so as to satisfy a distance that propagates between the main reflecting mirrors M4. 2. A four-reflector offset antenna comprising a primary radiator, three sub-reflectors and a main reflector,
The f ₁ the focal length of the sub-reflecting mirror M _1, the focal length of the f ₂ sub-reflector M _2, the f ₃ is the focal length and f ₄ of the sub-reflecting mirror M ₃ and the main reflector focal length of M _4, sigma ₁ is the angle between the incident wave and the reflected wave of the light ray along the central axis of the primary radiator on the sub-reflector M1, σ
₂ is the angle between the incident wave and the reflected wave of the ray along the central axis of the primary radiator on the sub-reflector M2, and σ ₃ is the incident wave and the reflection of the ray along the central axis of the primary radiator on the sub-reflector M3. The angle between the waves and σ ₄ are the angles between the incident wave and the reflected wave on the main reflector M4 of the ray along the central axis of the primary radiator, and d ₁ is the sub-reflector of the ray along the central axis of the primary radiator. The distance propagating between M ₁ and M ₂ , d ₂ is the distance along the central axis of the primary radiator, and the distance propagating between the sub-reflectors M ₂ and M ₃ and d ₃ is the ray along the central axis of the primary radiator subreflector M ₃ of, when the distance to propagate between the main reflector M _4, the sub-reflecting mirror M _1, M _2, M ₃ and the concave mirror, f _4> d _3, it has a σ _4> σ ₃ An antenna device characterized by the above-mentioned. 3. A four-reflector offset antenna comprising a primary radiator, three sub-reflectors and a main reflector,
The f ₁ the focal length of the sub-reflecting mirror M _1, the focal length of the f ₂ sub-reflector M _2, the f ₃ is the focal length and f ₄ of the sub-reflecting mirror M ₃ and the main reflector focal length of M _4, sigma ₁ is the angle between the incident wave and the reflected wave of the light ray along the central axis of the primary radiator on the sub-reflector M1, σ
₂ is the angle between the incident wave and the reflected wave of the ray along the central axis of the primary radiator on the sub-reflector M2, and σ ₃ is the incident wave and the reflection of the ray along the central axis of the primary radiator on the sub-reflector M3. The angle between the waves and σ ₄ are the angles between the incident wave and the reflected wave of the light ray along the central axis of the primary radiator on the main reflector M4, and d ₁ is the sub-reflector of the light ray along the central axis of the primary radiator. The distance propagating between M ₁ and M ₂ , d ₂ is the distance along the central axis of the primary radiator, and the distance propagating between the sub-reflectors M ₂ and M ₃ and d ₃ is the ray along the central axis of the primary radiator The sub-reflecting mirrors M ₁ , M ₂ , and M ₃ are concave mirrors, and f ₄ <d ₃ , σ ₄ > σ ₃ , assuming that the distance between the sub-reflecting mirror M ₃ and the main reflecting mirror M ₄ propagates. An antenna device characterized by the above-mentioned. 4. A four-reflector offset antenna comprising a primary radiator, three sub-reflectors and a main reflector,
The f ₁ the focal length of the sub-reflecting mirror M _1, the focal length of the f ₂ sub-reflector M _2, the f ₃ is the focal length and f ₄ of the sub-reflecting mirror M ₃ and the main reflector focal length of M _4, sigma ₁ is the angle between the incident wave and the reflected wave of the light ray along the central axis of the primary radiator on the sub-reflector M1, σ
₂ is the angle between the incident wave and the reflected wave of the ray along the central axis of the primary radiator on the sub-reflector M2, and σ ₃ is the incident wave and the reflection of the ray along the central axis of the primary radiator on the sub-reflector M3. The angle between the waves and σ ₄ are the angles between the incident wave and the reflected wave on the main reflector M _{4 of the} ray along the central axis of the primary radiator, and d ₁ is the sub-reflection of the ray along the central axis of the primary radiator. The distance propagating between the mirrors M ₁ and M ₂ , d ₂ along the central axis of the primary radiator, and the distance of light rays traveling between the sub-reflectors M ₂ and M ₃ and d ₃ along the central axis of the primary radiator Assuming that the light propagates between the sub-reflecting mirror M ₃ and the main reflecting mirror M ₄ , the sub-reflecting mirrors M ₁ , M ₂ and M ₃ are concave mirrors, and f ₄ <d ₃ and σ ₄ <σ ₃ . An antenna device, comprising: 5. A four-reflector offset antenna comprising a primary radiator, three sub-reflectors and a main reflector,
The f ₁ the focal length of the sub-reflecting mirror M _1, the focal length of the f ₂ sub-reflector M _2, the f ₃ is the focal length and f ₄ of the sub-reflecting mirror M ₃ and the main reflector focal length of M _4, sigma ₁ is the angle between the incident wave and the reflected wave of the ray along the central axis of the primary radiator on the sub-reflector M ₁ , σ ₂
Is the angle between the incident wave and the reflected wave of the ray along the central axis of the primary radiator on the sub-reflector M ₂ , and σ ₃ is the incident wave and the reflection of the ray along the central axis of the primary radiator on the sub-reflector M 3 The angle between the waves and σ ₄ are the angles between the incident wave and the reflected wave of the light ray along the central axis of the primary radiator on the main reflector M4, and d ₁ is the sub-reflector of the light ray along the central axis of the primary radiator. The distance propagating between M ₁ and M ₂ , d ₂ is the distance along the central axis of the primary radiator, and the distance propagating between the sub-reflectors M ₂ and M ₃ and d ₃ is the ray along the central axis of the primary radiator subreflector M ₃ of, when the distance to propagate between the main reflector M _4, the sub-reflecting mirror M _1, M ₂ a concave mirror, the secondary reflecting mirror M ₃ and convex _{mirror, f 4> d 3, σ} 4> An antenna device characterized by σ ₃ . 6. A four-reflector offset antenna comprising a primary radiator, three sub-reflectors and a main reflector,
The f ₁ the focal length of the sub-reflecting mirror M _1, the focal length of the f ₂ sub-reflector M _2, the f ₃ is the focal length and f ₄ of the sub-reflecting mirror M ₃ and the main reflector focal length of M _4, sigma ₁ is the angle between the incident wave and the reflected wave of the light ray along the central axis of the primary radiator on the sub-reflector M1, σ
₂ is the angle between the incident wave and the reflected wave of the ray along the central axis of the primary radiator on the sub-reflector M2, and σ ₃ is the incident wave and the reflection of the ray along the central axis of the primary radiator on the sub-reflector M3. The angle between the waves and σ ₄ are the angles between the incident wave and the reflected wave on the main reflector M _{4 of the} ray along the central axis of the primary radiator, and d ₁ is the sub-reflection of the ray along the central axis of the primary radiator. The distance propagating between the mirrors M ₁ and M ₂ , d ₂ along the central axis of the primary radiator, and the distance of light rays traveling between the sub-reflectors M ₂ and M ₃ and d ₃ along the central axis of the primary radiator Assuming that the light beam travels between the sub-reflecting mirror M ₃ and the main reflecting mirror M ₄ , the sub-reflecting mirrors M ₁ and M ₂ are concave mirrors, the sub-reflecting mirror M ₃ is a convex mirror, and f ₄ > d ₃ , σ ₄ <antenna apparatus characterized by having a sigma _3. 7. A four-reflector offset antenna comprising a primary radiator, three sub-reflectors and a main reflector,
The f ₁ the focal length of the sub-reflecting mirror M _1, the focal length of the f ₂ sub-reflector M _2, the f ₃ is the focal length and f ₄ of the sub-reflecting mirror M ₃ and the main reflector focal length of M _4, sigma ₁ is the angle between the incident wave and the reflected wave of the light ray along the central axis of the primary radiator on the sub-reflector M1, σ
₂ is the angle between the incident wave and the reflected wave of the ray along the central axis of the primary radiator on the sub-reflector M2, and σ ₃ is the incident wave and the reflection of the ray along the central axis of the primary radiator on the sub-reflector M3. The angle between the waves and σ ₄ are the angles between the incident wave and the reflected wave on the main reflector M4 of the ray along the central axis of the primary radiator, and d ₁ is the sub-reflector of the ray along the central axis of the primary radiator. The distance propagating between M ₁ and M ₂ , d ₂ is the distance along the central axis of the primary radiator, and the distance propagating between the sub-reflectors M ₂ and M ₃ and d ₃ is the ray along the central axis of the primary radiator subreflector M ₃ of, when the distance to propagate between the main reflector M _4, the sub-reflecting mirror M _1, M ₂ a concave mirror, the secondary reflecting mirror M ₃ and convex _{mirror, f 4 <d 3, σ} 4 < An antenna device characterized by σ ₃ .