JPH09232861A - Reflector antenna - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the lowering of the antenna gain and the degradation of a side lobe of a reflector antenna composed as a torus antenna. SOLUTION: A main reflector cross section bus-line 101 rotating by a prescribed angle range by including a z-axis in the axial periphery of a torus rotary center axis 7 and forming the curved surface of the face of the main reflector 1 and the cross section bus-line of a sub-reflector 2 receiving radiation beam of a first-order radiator 3 are composed as symmetrical types. In this case, the lowering of antenna gain and the degradation of side lobe are suppressed by suppressing the blocking effect by the sub-reflector 2 and adding a face correcting procedure so that the optimum opening surface irradiation distribution and opening surface phase distribution may be secured by the main reflector 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflector antenna, and more particularly to a torus antenna type which is equipped with a main reflector, at least one sub-reflector and one primary radiator, and which operates in the microwave band and millimeter wave band. The reflector antenna of.

[0002]

2. Description of the Related Art A torus antenna has been conventionally used as a beam scan antenna capable of scanning a beam without rotating a main reflecting mirror or as a multi-beam antenna capable of forming a plurality of beams by one main reflecting mirror. ing. This torus antenna includes a main reflecting mirror having a curved surface formed by moving a curved line along an arc orthogonal to the curved line, and a primary radiator and a sub-reflecting mirror for radiating radio waves to the main reflecting mirror. , Emits a beam of equal characteristics in any direction. As the above-mentioned certain curve, one using a parabola is often used.

As a conventional torus antenna of this type, for example, a "toroidal reflector-antenna aberration correction auxiliary reflector" (Japanese Patent Laid-Open No. 51-863) or A MU
LTIPLE-BEAM TORUS REFLECTOR ANTENNA FOR 20 / 30-GHz
SATELLITE COMMUNICATIONS SYSTEMS, (R.Kreutel, AIAA / CA
SI 6th Communication Satellite Systems Confer-enc
e, MONTREAL, CANADA / APRIL 5-8,1976) (A multiple beam torus reflector antenna fore 20/3
0-GHz Satellite Communications Systems,
Earl Kreuter, AIAA / CASI 6th Communication Satellite Systems Conference, Montreal, Canada / April 5-8, 1976).

For example, as an example of a torus antenna conventionally used as a beam scan antenna, 1
The shape of a single reflector is shown in the perspective view of FIG. 3 and the sectional view of FIG. The main reflecting mirror 1 of this conventional example has a main reflecting mirror section generating curve 101 having a main reflecting section sectional generating curve axis 6 as an axis,
The main reflecting mirror section generating curve 101 is centered on the torus rotation center axis 7 as a rotation axis of a straight line in a plane including the main reflecting mirror section generating curve 101 and the main reflecting section section generating curve axis 6 in FIG. ), A torus curved surface formed by rotating in the range of the angle γ.

The primary radiator 3 is formed by rotating the focal point P _f0 of the main reflecting mirror section generatrix 101 about the torus rotation center axis 7 within an angle β range as shown in FIG. 4 (a). Are arranged on the arc-shaped focal line 5. In the case of a beam scan antenna, when the primary radiator 3 of FIGS. 3 and 4 is moved from the points P _f1 to P _f2 at both ends of the focal line 5, the beam direction of the antenna changes from the beam direction 51 to the beam direction 52. . The position of the primary radiator in this case is expressed as 3 (a) and 3 (b). However, in the case of a multi-beam antenna, the primary radiator 3 is individually installed at a plurality of points on the focal line 5, for example, at the points P _f1 and P _f2 , so that the beam directions 51 and 52 are provided as a plurality of directions.
You can also get a beam.

The size of the torus rotation angle γ forming the above-mentioned torus curved surface depends on the size of the required beam scanning amount. That is, the required beam scanning amount (beam separation angle for a multi-beam antenna, the same applies below) is β, and the effective aperture diameter (aperture diameter of the part of the main reflecting mirror that is irradiated by one fixed primary radiator) is Assuming that d is the angle at which the effective opening diameter d is viewed from the torus rotation center axis 7 is α, the torus rotation angle γ is usually set so as to satisfy the following formula 1. Therefore, assuming that the radius of gyration of the torus is R, the lateral width D of the main reflecting mirror 1 is expressed by the following mathematical formula 2.

[0007]

[Equation 1] γ ≈ α + β

[0008]

(2) D ≈ 2Rsin (γ / 2) ≈ 2Rsin ((α
+ Β) / 2)

[0009]

In the conventional torus antenna described above, the aberration of the main reflecting mirror 1 is large and the phase efficiency is low as an evaluation measure for increasing the beam radiation efficiency by making the phase distribution uniform on the aperture plane. There are drawbacks. The simplest solution for improving the phase efficiency is to increase the focal length f of the main reflecting mirror cross section curve 101 shown in FIGS. 3 and 4 and increase the torus radius of rotation R. However, as is clear from the mathematical formula 2 or FIGS. 3 and 4, in such a measure, the main reflecting mirror becomes large in order to secure a constant scanning amount, and the focal length becomes long. There is a problem that it becomes unavoidable to be large.

The problem of the phase efficiency of such a single reflector torus antenna is solved by the auxiliary sub-reflector, which is the antenna according to the invention of Japanese Patent Laid-Open No. 51-863 mentioned above. As shown in FIG. 5, this antenna is composed of a main reflecting mirror 1 having a torus curved surface, a sub reflecting mirror 2 for aberration correction, and a primary radiator 3. When this antenna is used as a beam scanning antenna, for example, when it is desired to scan from the beam direction 51 to the beam direction 52, the primary radiator 3 and the sub-reflecting mirror 2 are formed as an integrated structure along a focal line 3 (not shown). It may be moved from the combined position of a) · 2 (a) to the combined position of 3 (b) · 2 (b). When the present antenna is used as a multi-beam antenna, the same combination of the primary radiator 3 and the sub-reflecting mirror 2 is used for the combination position of 3 (a) and 2 (a) and 3 (b) and 2 (, respectively). It may be fixed in advance at the combination position of b).

In this antenna, the shape of the sub-reflecting mirror 2 is such that the optical path length connecting the aperture plane 4-the main reflecting mirror 1-the sub-reflecting mirror 2-the primary radiator 3 is constant over the range of the beam directions 51 and 52. Therefore, the phase error is not generated in geometrical optics except the residual phase error of the primary radiator 3. Therefore, according to the present invention, it is possible to construct an antenna having excellent phase efficiency.

There are roughly two types of configuration examples of this antenna. That is, the torus cross-section curve group to be included over the beam forming range has a symmetrical type as shown in FIG. 6B and an offset type as shown in FIG. 6A.
However, each type has its own drawbacks. The drawbacks of both are shown below.

First, the symmetrical torus antenna as shown in FIG. 6B has a problem of blocking by the sub-reflecting mirror 2. That is, in the symmetrical torus antenna,
Since the sub-reflecting mirror 2 is located at the center of the antenna aperture as shown in FIG. 6B, a so-called blocking phenomenon in which a part of the radiated power is shielded by the sub-reflecting mirror 2 occurs. Occurs. This blocking problem results in a decrease in antenna gain and deterioration in sidelobe characteristics.

On the other hand, in the offset type torus antenna shown in FIG. 6A, blocking by the sub-reflector does not occur. However, the offset type has a drawback that the antenna becomes larger than the symmetrical type. The reason
The explanation will be based on a simplified model. 6 (a) and 6 (b), the reference numerals in the drawings are the same as those in FIGS. 3 and 4 for simplification of description.

In the case of a torus antenna having an offset type cross-sectional curve group as shown in FIG. 6A, there is generally a restriction of Equation 3 between the focal length f of the main reflecting mirror and the effective aperture diameter d. .

[0016]

F / d> 0.6

This is because when the focal length f is made too small with respect to a certain moving aperture diameter d, the asymmetry peculiar to the offset type is emphasized, and it is possible to avoid the deterioration of the aperture surface irradiation efficiency, the cross polarization characteristic and the like. By planning. On the other hand, due to the nature of the torus curved surface, the relationship between the focal length f and the torus radius of gyration R is approximately as shown in Equation 4.

[0018]

(4) f / R ≈ 0.5

From Equations 3 and 4, it can be seen that the effective aperture diameter d and the torus radius of rotation R must satisfy the relationship of Equation 5.

[0020]

[Equation 5] R> 1.2d

Further considering the equation 2, the lateral width D of the main reflecting mirror 1 shown in FIG. 4 is accompanied by the condition represented by the equation 6 in the case of FIG. 6 (a).

[0022]

[Equation 6] D ≈ 2Rsin (γ / 2)> 2.4 × dsi
n ((α + β) / 2)

Here, the ratio d / D of the effective aperture diameter d to the lateral width D of the main reflecting mirror is referred to as "aperture utilization ratio". In the above-described offset type antenna, for example, when the beam scanning amount β = 60 °, the aperture utilization rate is about 50%. In other words, when focusing on a beam in only one direction, about half of the main reflecting mirror is unused.

On the other hand, in the case of a torus antenna having a symmetrical sectional curve group as shown in FIG. 6B, the antenna aperture can be located on both sides of the central axis of the generatrix, so the limit on f / d is half of that of the mathematical expression 3. And is expressed by the following Equation 7.

[0025]

[Formula 7] f / d> 0.3

Also, the relationship between the focal length f and the torus radius of gyration R is expressed by the following formula 8 even in the case of the symmetric type, and the relationship between the effective aperture diameter d and the torus radius of gyration R is a group of symmetrical section curves. From the shape of the above, it is expressed as in Expression 9.

[0027]

[Formula 8] f / R ≈ 0.5

[0028]

[Equation 9] R> 0.6d

From the comparison between Expression 9 and Expression 5, it can be seen that the torus antenna having the symmetrical section curve group requires a smaller radius of torus than the torus antenna having the offset section curve group, and the antenna can be miniaturized. I understand. However, if the size of R is selected to be small with respect to a constant effective aperture diameter d, the aberration of the torus curved surface becomes large, and the sub-reflecting mirror for correcting this becomes too large. , D are set as in Expression 10.

[0030]

[Equation 10] R> d

Therefore, from the expressions 2 and 9, the relationship between the effective aperture diameter d and the lateral width D of the main reflecting mirror is expressed by the following expression 11.

[0032]

[Equation 11] D ≈ 2Rsin (γ / 2)> 2.0 × d
sin ((α + β) / 2)

When the aperture utilization factor in the case of the beam scanning amount β = 60 ° is calculated in the same manner as in the case of the offset type, it becomes 60% in the symmetrical type. That is, in the case of the symmetrical torus antenna as shown in FIG.
For a constant effective aperture diameter and a constant beam scanning amount, the radius of rotation R of the torus and the lateral width D of the main reflecting mirror can be made smaller than those of the offset type, and the antenna can be made compact.

The above calculation is a simplified model calculation example for explaining the limit of antenna miniaturization. In the actually designed antenna, both the offset type and the symmetric type have aperture utilization ratios. It's a little different.
As described above, the symmetric type allows the antenna to be downsized, but has a problem of suppressing or blocking the radiated radio wave by the sub-reflecting mirror. On the other hand, in the offset type,
Although the blocking by the sub-reflector does not occur, there is a drawback that the antenna becomes large.

An object of the present invention is to eliminate the above-mentioned drawbacks and to make it possible to reduce the size of the entire antenna while ensuring a predetermined antenna gain and a predetermined beam scanning amount (beam separation angle in a multi-beam antenna). It is to provide a reflector antenna of a torus antenna type.

[0036]

The present invention has the following means in order to achieve the above object. That is, the first configuration of the present invention relating to the reflector antenna is the main reflector,
In a torus antenna-type reflector antenna including at least one sub-reflector and at least one primary radiator, a main-reflector cross-section generatrix and a sub-reflector cross-section generatrix are substantially along the same axis. It is determined by a condition that is line-symmetrical and gives a desired irradiation distribution and a substantially uniform phase distribution within the cross section of the opening surface, and the curved surface of the main reflecting mirror is a rotation axis of a certain rotation axis in the main reflecting mirror cross-section generating curve. It is configured as a part of a curved surface rotated around, and the curved surface of the sub-reflecting mirror is combined with the curved surface shape of the main reflecting mirror that determines the curved surface to provide a substantially uniform phase distribution in the aperture plane. It has a configuration determined based on the above.

A second structure of the present invention is the torus antenna type reflection mirror according to the first structure, which comprises a main reflection mirror, at least one sub-reflection mirror, and at least one primary radiator. In the antenna, the main reflecting mirror section generating curve and the sub-reflecting section are determined by the conditions that give the desired irradiation distribution in the section of the aperture plane, the constant optical path length, and the conditions based on the law of reflection on the reflecting mirror section. Has a generating curve,
The curved surface of the main reflecting mirror is configured as a part of a curved surface obtained by rotating the main reflecting mirror cross-section generating curve about a certain rotation axis in space, and the curved surface of the sub-reflecting mirror is determined to be a curved surface. It has a configuration formed by a curved surface of the reflecting mirror, a curved surface that is determined based on a condition of a constant optical path length and a condition based on the law of reflection on the reflecting mirror surface.

A third structure of the present invention has a structure applied to the beam scanning antenna which can scan a beam without rotating the main reflecting mirror in the first or second structure.

A fourth structure of the present invention is the same as the first or second structure, in which the main reflecting mirror is rotated without rotating.
It has a configuration applied to a multi-beam antenna capable of forming a plurality of beams by a single main reflecting mirror.

[0040]

BEST MODE FOR CARRYING OUT THE INVENTION Without rotating the main reflecting mirror,
A beam scan antenna capable of beam scanning when used in combination with a sub-reflecting mirror, or a torus antenna used as a multi-beam antenna capable of forming a plurality of beams with one main reflecting mirror has a large beam scanning amount (beam scanning antenna). ) Or a large beam separation angle (multi-beam antenna) is attempted, the main reflector becomes very large. In order to avoid this problem, the antenna can be miniaturized by arranging the sub-reflecting mirrors constituting the antenna in a symmetrical type instead of the offset type, but in the conventional technique, the sub-reflecting mirror causes blocking to suppress the radiated power, and the antenna gain Cause deterioration of the side lobe characteristics.

In the present invention, the main reflecting mirror cross-section generatrix is determined not based on the offset type but based on the symmetric type, and blocking by the sub-reflecting mirror is suppressed to obtain the optimum aperture plane irradiation distribution. The torus antenna that secures the antenna gain and side lobe characteristics is secured by the modification.

In order to specifically realize such a torus antenna, the method of determining the curved surface of the antenna of the reflecting mirror of the present invention shown in FIG. 1 has the following embodiments. When determining the main reflecting mirror cross-section generating curve and the sub-reflecting cross-section generating curve, blocking by the sub-reflecting mirror is avoided and mirror surface modification is performed so as to obtain the optimum aperture surface irradiation distribution and aperture surface phase distribution. The main reflector curved surface is determined by rotating the main reflector cross-section generating curve obtained in (1). The sub-reflector curved surface is determined on the basis of the main-reflecting mirror curved surface obtained in step 1 and the conditions for obtaining the optimum aperture plane phase distribution.

[0043]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a perspective view of a torus antenna-type reflector antenna according to an embodiment of the present invention, and FIG. 2 is a sectional view of a torus-type reflector antenna according to an embodiment of the present invention. The reflecting mirror antenna of this embodiment includes a main reflecting mirror 1, a sub-reflecting mirror 2 for correcting aberration of the main reflecting mirror 1, and a primary radiator 3.
In addition, the sub-reflecting mirrors 2 (a) and 2 (b) showing the state at the moving position of the sub-reflecting mirror 2 or the independent arrangement state, and the primary radiation showing the state at the moving position of the primary radiator 3 or the independent arrangement state. In addition to the devices 3 (a) and 3 (b), the torus rotation center axis 7, the beam directions 51 and 52, and the main reflection mirror cross section generatrix 101 are shown together. The reference numerals in the drawings of FIGS. 1 and 2 are given the same reference numerals as those of the corresponding constituent elements in FIGS. 3 to 6 for the sake of simplification of description.

Next, the operation of this embodiment will be described.
The sectional curve group formed in the reflector antenna of the present embodiment has the following characteristics (a) and (b). (B) The cross-section curve group is "symmetrical type" rather than "offset type". (B) The mirror surface shaping method is adopted to prevent the occurrence of blocking phenomenon by the sub-reflecting mirror and to secure the optimum aperture surface irradiation distribution and aperture surface phase distribution.

By adopting such a group of sectional curves, it is possible to downsize the antenna, reduce performance deterioration due to blocking, and optimize antenna gain and side lobe characteristics. When the present antenna is used as a beam scan antenna, for example, when it is desired to scan a beam from the beam direction 51 to the beam direction 52, the primary radiator 3 and the sub-reflecting mirror 2 are integrated into one unit, and 3 (a), 2
3 (b), 2 from the position expressed by the combination of (a)
It may be moved to the position represented by the combination of (b). When using as a multi-beam antenna,
Each combination of the primary radiator 3 and the sub-reflecting mirror 2 is 3
(A), 2 (a) combination position and 3 (b), 2
It may be arranged independently in advance at the combined position of (b).

Next, the basic design procedure of the reflector antenna of this embodiment will be described. The reflector antenna according to the present embodiment is designed by the following procedure, for example. (1) Determination of the main reflecting mirror section generatrix 101 and the subreflecting section cross section curve 201. These sectional curves are determined by the following three conditions. Aperture plane amplitude distribution condition This is a condition for generating an optimum aperture plane irradiation distribution that can secure a desired antenna gain and side lobe characteristics. That is, when the desired aperture plane irradiation electric field distribution is E _a (x) and the radiation pattern of the primary radiator is E _p (θ), the following formula 12 is satisfied.

[0047]

(Equation 12)

The meaning of the above-mentioned expression 12 is as follows. Formula 12 is a formula that should be established based on the energy conservation law, and the denominator on the left side is the aperture length x = 0, and in the case of FIG. 2, the desired aperture surface from the minimum aperture length x _min to the maximum aperture length x _max. It represents the total power energy by the irradiation electric field distribution E (a), and the molecule is the electric power energy of the irradiation electric field at an arbitrary opening position x. The denominator on the right side is θ in FIG. 2 due to the radiation pattern electric field distribution E _p (θ) of the primary radiator.
Represents the total power energy from 0 to θ _{m of} θ _max , and the numerator shows the power energy at any θ. Here, θ is a line including the reflection point and the point P _F when the primary radiator arranged at the focal position P _F in FIG. 2 radiates the sub-reflector of the sub-reflector cross section generating curve 201, and the z-axis. It is an angle.

Thus, the relational expression based on the energy conservation law between the radiant energy and the irradiation energy is established. In order to avoid blocking due to the sub-reflecting mirror, the following Expression 13 may be set when determining the aperture plane distribution.

[0050]

E _a (x) = 0 for x ≦ x _min , where x _min ≧ x _sm (x _sm is the radius of the sub-reflecting mirror)

In this way, the central ray from the primary radiator 3 is geometrically and optically reflected by the sub-reflector section generatrix 201 and the main-reflector section generatrix 101, and then the sub-reflector section generatrix 201. It reaches the opening surface cross section 401 without being shielded by.

The portion of the main reflecting mirror section generatrix 101 shown by the broken line in FIG. 2 is a broken line for the sake of convenience of description for the section which does not contribute to reflection geometrically.
However, this portion is necessary for ensuring efficient reflection in three-dimensional scanning over the torus rotation angle γ, and is present in an actual configuration in consideration of diffraction due to wave nature of radio waves.

Condition of constant optical path length In FIG. 2, a point P _Ac on the cross section 401 of the aperture plane-a point P _Mc on the cross-section curve 101 of the main reflecting mirror-a cross-section curve of the sub-reflecting mirror 20
That is, the optical path length connecting the point P _Sc on 1 to the phase center P _F of the primary radiator 3 is constant, that is, the following formula 14 is established.

[0054]

[Equation 14]

Conditions based on the law of reflection: The incident angle and the reflection angle of the light ray should be equal on the reflecting mirror. That is, the following formulas 15 and 16 are established on the main reflecting mirror section generating curve 101 and the sub-reflecting section generating curve 201, respectively.

[0056]

(Equation 15)

[0057]

(Equation 16)

If the incident angle and the reflection angle are equal to each other, the expression 15 means that the inclination dz with respect to the x-axis represented by the cross section 401 of the main reflecting mirror cross section generatrix 101 at the point P _Mc in FIG. / dx is the normal to the point P _Mc, the angle [psi / 2 and a line connecting the point P _Mc and P _Ac Tangen
Indicates the relation that can be expressed by t. The incident angle and the reflection angle are equal to ψ / 2.

Expression 16 is a relational expression when the same idea as Expression 15 is applied to the point P _Sc on the subreflector cross section generatrix 201, and in this case, the point P _Sc is the phase center of the primary radiator. It is expressed in polar coordinates (γ.θ) with P _F as the origin. Here, r is the distance between the points P _F and P _Sc, and θ is the angle between the point P _Sc and the z axis. Also in this case, the point P on the sub-reflecting mirror
_{In Sc} , the equation 16 is derived according to the equation 15 under the condition that the incident angle and the reflection angle are (θ + ψ) / 2 and are equal.

The main reflecting mirror section generatrix 101 is determined based on the above three conditions. A desired torus curved surface is determined by rotating the main reflecting mirror cross-section generatrix 101 thus determined within the range of a constant angle γ about the torus rotation center axis 7 of FIG. 1 included in the same plane. You can It should be noted that the magnitude of γ is determined by the above-mentioned formula 1.

(2) Determination of sub-reflecting mirror curved surface. Based on the curved surface of the main reflecting mirror determined by (1), the following 2
The sub-reflector curved surface is determined according to the conditions. Conditions for a constant optical path length Point _A on the aperture plane 4-Point P _M on the main reflecting mirror 1-Point P _S on the sub-reflecting mirror 2-Primary radiator 3 The optical path length connecting the phase centers P _F is constant thing. When it is shown in the following formula 17, point P
_A , point P _M, and point P _S are points P _Ac and P _{Mc in} FIG. 2, respectively.
And the point P _Sc , and the aperture surface, the main reflecting mirror, and the sub-reflecting mirror are all considered to be three-dimensional, and therefore they are denoted by reference numerals without the subscript c.

[0062]

[Equation 17]

Conditions based on the law of reflection: The incident angle and the reflection angle of the light ray should be equal on the reflecting mirror. That is, at an arbitrary point P _M on the main reflecting mirror,
8 and Formula 19 should be established. If the condition of constant optical path length with the law of reflection on the main reflecting mirror 1 is satisfied, the law of reflection on the sub-reflecting mirror 2 is automatically satisfied.

[0064]

(Equation 18)

[0065]

[Equation 19]

The meanings of the above equations 18 and 19 are as follows. That is, Equation 18 and Equation 19
Is a unit vector connecting the points P _A and P _M existing on the same plane and a unit vector connecting the points P _S and P _M under the condition that the incident angle and the reflection angle are equal, Equation 18 shows that the inner product with the normal vector at the point P _M on the curved surface of the main reflecting mirror 1 is equal, and Equation 19 shows the symmetry of the two unit vectors with respect to the normal vector.

In the embodiment described above, the condition based on the law of reflection in determining the curved surface of the main reflecting mirror is to pay attention to the inclination with respect to the reflecting points on the main and sub-reflecting mirrors with respect to the opening cross section,
In addition, the conditions based on the law of reflection in determining the curved surface of the sub-reflecting mirror are set by focusing on the symmetry of the unit vector regarding the reflection points on the main and sub-reflecting mirrors. The points are not limited to the contents of this embodiment, and can be changed as appropriate in consideration of the design.
For example, the procedure of paying attention to the inclination with respect to the aperture cross section to the sub-reflecting mirror and the procedure of paying attention to the symmetry of the unit vector to the main reflecting mirror can be applied according to the above-described embodiments.

The mirror surface system thus determined is an antenna having excellent phase efficiency because the condition of equal optical path length is strictly met geometrically and optically. Further, if the shielding by the sub-reflecting mirror does not occur geometrically when the cross-sectional curve is determined, the antenna will be less blocked by the sub-reflecting mirror even in the final antenna mirror surface system.

Next, the sizes of the conventional offset antenna with a correction reflector and the antenna of the present invention will be compared under certain identical design conditions (λ is the wavelength of radio wave). [Design conditions] Antenna effective aperture diameter d: 500λ Beam scanning amount β: 70 ° [Conventional antenna design example] Antenna width D: 1500λ Torus radius of gyration R: 1000λ Generating focal length f: 500λ [Antenna design example of the present invention] Antenna width D: 1070λ Torus radius of rotation R: 620λ Generating curve focal length f: 310λ

As is clear from the above comparison, the design example according to the present invention has a higher aperture utilization ratio than the conventional one, and the antenna can be miniaturized. It should be noted that the application to the beam scan antenna has been described above, but it goes without saying that the application to the multi-beam antenna is also possible.

[0071]

As described above, according to the present invention, the cross-section generatrix is mirror-shaped so that the cross-section generatrix is symmetrical and the blocking by the sub-reflecting mirror is reduced to obtain an optimum aperture surface irradiation distribution. By adopting a mirror surface shaping method that applies modification, while reducing performance deterioration due to blocking,
The effect of being able to significantly reduce the size of the entire antenna while ensuring optimization of the antenna gain and side lobe characteristics and maintaining a predetermined antenna gain and a predetermined beam scanning amount (beam separation angle in a multi-beam antenna) Have.

[Brief description of drawings]

FIG. 1 is a perspective view of a torus type reflector antenna according to an embodiment of the present invention.

FIG. 2 is a sectional view of a torus type reflector antenna according to an embodiment of the present invention.

FIG. 3 is a perspective view of a torus antenna configured as a conventional single reflector antenna.

FIG. 4 is a sectional view (a) of a torus antenna configured as a conventional single reflector antenna and a partial sectional view (b) showing a portion related to the primary radiator 3 (a) extracted from the sectional view (a).
It is.

FIG. 5 is a perspective view of a torus antenna configured as a conventional two-reflection mirror antenna.

6A and 6B are a cross-sectional view (a) of a torus antenna having an offset type cross-section curve group and a cross-sectional view (b) of a symmetric type cross-section curve group that are configured as a conventional two-reflection mirror antenna.

[Explanation of symbols]

 1 Main Reflector 2 Sub Reflector 2 (a) Sub Reflector 2 (b) Sub Reflector 3 Primary Radiator 3 (a) Primary Radiator 3 (b) Primary Radiator 4 Aperture 5 Focus Line 6 Main Reflector Cross-section generating curve axis 7 Torus rotation center axis 101 Main reflecting mirror section generating curve 201 Sub-reflecting section generating curve 202 Sub-reflecting section generating curve 401 Opening surface section

Claims (4)

[Claims] 1. A torus antenna-type reflector antenna comprising a main reflector, at least one sub-reflector, and at least one primary radiator, wherein a main reflector cross-section generatrix and a sub-reflector cross-section mother curve are provided. The curves are substantially line symmetric with respect to the same axis, and are determined by the conditions that give a desired irradiation distribution and a substantially uniform phase distribution in the cross section of the opening surface, and the curved surface of the main reflecting mirror is the cross section of the main reflecting mirror. The generating curve is configured as a part of a curved surface rotated about a certain rotation axis in space, and the curved surface of the sub-reflecting mirror is combined with the curved surface shape of the main reflecting mirror to determine a curved surface and is substantially uniform. A reflector antenna characterized by being determined based on a condition that gives a phase distribution in the aperture plane. 2. A torus antenna-type reflector antenna including a main reflector, at least one sub-reflector, and at least one primary radiator, and conditions for providing a desired irradiation distribution within the cross section of an aperture surface. , Having a constant optical path length and a main reflecting mirror section generating curve and a sub-reflecting section section generating curve determined by a condition based on the law of reflection on the reflecting section.
The curved surface of the main reflecting mirror is configured as a part of a curved surface obtained by rotating the main reflecting mirror cross-section generating curve about a certain rotation axis in space, and the curved surface of the sub-reflecting mirror is determined to be a curved surface. The reflector antenna according to claim 1, wherein the reflector antenna is formed by a curved surface of the reflecting mirror, a constant optical path length condition, and a curved surface determined based on a condition based on the law of reflection on the reflecting mirror surface. 3. The reflector antenna according to claim 1, wherein the reflector mirror antenna is applied to a beam scan antenna capable of scanning a beam without rotating the main reflector. 4. The reflector antenna according to claim 1, which is applied to a multi-beam antenna capable of forming a plurality of beams by one main reflector without rotating the main reflector.