JP3043768B2 - Mirror modified antenna - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a mirror-surface modified antenna for modifying a mirror surface of a reflector antenna.

(Prior Art) Mirror-modified antennas have been widely used for higher efficiency and lower sidelobes of ground station antennas and satellite-mounted antennas.

A conventional mirror-modified antenna uses two reflective antennas, such as a Cassegrain antenna and a Gregorian antenna, and a method of adjusting the amplitude distribution of the aperture surface to a desired distribution by modifying the main reflector and the sub-reflector. Was. For example, if the focus is on high efficiency, the mirror system is modified so that the amplitude distribution is constant at the aperture, and if the side lobes are reduced, the mirror surface is adjusted so that the edge level of the amplitude distribution on the aperture surface is low. A method of modifying the system was employed.

In recent years, there has been an increasing trend to use this mirror surface modification technology for beam shaping of satellite-mounted antennas. Beam shaping refers to shaping a beam into a shape of a region to be irradiated by an antenna, for example, a long and narrow shape suitable for a country in the case of Japan, and efficiently transmitting and receiving radio waves. The advantage of beam shaping by mirror surface modification is that there is no need to convert the primary radiator into an array, and a shaped beam can be created with only one primary radiator, so it is important that there is no power loss in the feed system. .

Various methods have been proposed for designing such a mirror-modified antenna. The most general idea is a method that focuses on a conventional aperture plane distribution, and adjusts the amplitude and phase distribution of the aperture plane so as to form a desired far-field pattern. In this case, the modified mirror surface system requires an antenna having two reflecting mirrors, such as a Cassegrain antenna or a Gregorian antenna, and the design method is complicated, and fabrication is not easy.

On the other hand, there has been proposed an idea of forming a shaped beam by modifying a single reflector antenna such as a parabolic antenna. In this case, beam shaping is performed by modifying the mirror surface so as to adjust the phase distribution of the aperture surface. However, it is still possible to form a beam having a sufficiently high degree of shaping. And since only one reflector needs to be modified,
There is an advantage that manufacturing is easy. However, there is a drawback that the procedure is somewhat complicated because attention is paid to the opening surface.

By the way, the shaped beam antenna obtained by the above-mentioned mirror surface modification method can only be an optimal design using only a single frequency and a single polarization component. However, when considered as an actual satellite-borne antenna, it is important to determine whether the shaped beam is effective in a wide band and whether it is effective in two separate frequency bands such as transmission and reception. Come. In addition, suppression of the reverse polarization component is also important in the actual operation of satellite broadcasting and satellite communication. With respect to such a problem, the conventional modified mirror surface antenna has no solution.

(Problems to be Solved by the Invention) As described above, the conventional mirror-modified antenna is generally difficult to design and manufacture, and an effective shaped beam cannot be obtained in a wide frequency band or two separate frequency bands. Polarization and reverse polarization could not be formed simultaneously.

The present invention solves the above problems, can be designed and manufactured by a simple procedure, can obtain an effective shaped beam even in a wide frequency band or two frequency bands separated from each other, and has two polarizations of a forward polarization and a reverse polarization. An object of the present invention is to provide a mirror-modified antenna that can obtain an effective shaped beam for waves.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the above problems, the present invention provides a primary radiator that emits a predetermined beam, and a modified mirror surface constituted by a plurality of minute plane mirrors, the primary radiation A reflector which reflects a beam emitted from the reflector and forms a beam having a desired shape by reflecting the power of an electric field radiated by the beam reflected by the reflector. Are determined for a plurality of directions to be performed, and each error between the power value of the radiated electric field in each of the obtained directions and the power value of the desired radiated electric field in each of these directions is obtained. The difference between the correction amount from one of the micro flat mirrors along the micro flat mirror adjacent to the micro flat mirror does not exceed a predetermined set value, and the integrated value of the absolute value of the error is calculated. To reduce the size, the at least one micro flat mirror constituting the reflecting mirror is translated in a predetermined fixed direction by an amount corresponding to the modification amount, and each of the micro flat mirrors is inclined, and the translation and the inclination are adjusted. The provided micro flat mirror is a surface continuous with the adjacent micro flat mirror, and the vertices of a polygon forming the plane of the micro flat mirror constituting the reflecting mirror are inclined in a direction in which the adjacent micro flat mirrors coincide with each other. The surface to be formed and modified has a smooth mirror surface as a whole.

According to a second aspect of the present invention, a primary radiator that emits beams of a plurality of frequencies and a modified mirror surface constituted by a plurality of minute plane mirrors reflect the beam radiated from the primary radiator to form a beam having a desired shape. And a reflecting mirror comprising: a reflector that performs beam shaping, for each of the frequencies, the power value of the radiated electric field due to the beam reflected by the reflecting mirror is determined for a plurality of directions in which the beam shaping of the desired shape is to be performed. The error between the power value of the radiated electric field in each direction for each frequency and the power value of the desired radiated electric field in each direction for each frequency is calculated, and the error is calculated on a predetermined surface set as an initial value. The difference between the modification amount from one of the small plane mirrors and the modification amount of the minute plane mirror adjacent to the small plane mirror does not exceed a predetermined set value, and the integrated value of the absolute value of the error In order to minimize the distance, at least one micro flat mirror constituting the reflecting mirror is translated in a predetermined fixed direction by an amount of modification, and each of the micro flat mirrors is tilted, and the translation and tilting is performed. The micro flat mirror is formed as a continuous surface between the adjacent micro flat mirrors, and the vertices of a polygon forming the plane of the micro flat mirror constituting the reflecting mirror are formed to be inclined in a direction coincident between the adjacent micro flat mirrors. The surface to be retouched has a smooth mirror surface as a whole.

According to a third aspect of the present invention, a primary radiator that emits two polarized beams and a modified mirror surface constituted by a plurality of small plane mirrors reflect a beam emitted from the primary radiator to form a beam having a desired shape. In a mirror-modified antenna comprising a reflecting mirror that performs shaping, the power value of the radiated electric field due to the beam reflected by the reflecting mirror for each of the polarizations in a plurality of directions in which the beam shaping of the desired shape is to be performed. On the other hand, each error between the obtained power value of the radiated electric field in each direction for each polarization and the power value of the desired radiated electric field in each direction for each polarization was obtained and set as an initial value. The difference between the correction amount from one micro flat mirror along a predetermined plane and the correction amount of the micro flat mirror adjacent to the micro flat mirror does not exceed a predetermined set value, and minimizes the integrated value of the absolute value of the error. You As described above, at least one of the minute plane mirrors constituting the reflecting mirror is translated in a predetermined fixed direction by the amount of the modification, and each minute plane mirror is tilted, so that the parallel movement and inclination are increased. The plane mirror is formed as a continuous surface between the adjacent plane mirrors, and the vertices of a polygon forming the plane of the plane mirror constituting the reflecting mirror are formed in such a manner that the vertices of the polygons are inclined in a direction coinciding between the plane mirrors adjacent to each other. The surface to be formed has a smooth mirror surface as a whole.

(Operation) In the present invention, the power value of the radiated electric field due to the beam reflected by the reflecting mirror is obtained for a plurality of directions in which the beam shaping into a desired shape is performed, and the power value of the radiated electric field in each direction is obtained. Each error with each desired power value of the radiated electric field is obtained, and the plane mirror constituting the reflecting mirror is moved in parallel so that the integrated value of the absolute value of each error is minimized. Can design and manufacture.

By taking the above procedure in consideration of a plurality of frequencies, an effective shaped beam can be obtained even in a wide frequency band or two separated frequency bands.

Further, by taking the above procedure in consideration of two polarizations, an effective shaped beam can be obtained for two polarizations, that is, a normal polarization and a reverse polarization.

(Example) Hereinafter, an example of the present invention is described based on a drawing.

FIG. 1 is a view showing the appearance of a mirror-modified antenna according to one embodiment of the present invention.

As shown in the figure, the reflecting mirror is constituted by minute plane mirrors 1 to 52. Further, 100 is a primary radiator, and 90 is a pedestal supporting the reflector and the primary radiator.

Each of the small plane mirrors _{1 to 52} has an individual modification amount W _{1 to} W _{52 respectively.}
Is given. This modification amount will be described with reference to FIG.

FIG. 2 is a cross-sectional view of the antenna shown in FIG. 1 in the xz plane.

In the figure, the small plane mirrors 2, 7, 14, 22, 30, 38,
45, 50 are micro flat mirrors 2a, 7a, 14a, 22a, 30a, 38a, 45a, 50a along the parabolic surface P set as initial values, respectively.
, The translation amounts W ₂ , W ₇ , W ₁₄ , W ₂₂ , W ₃₀ , W ₃₈ , W ₄₅ , and W ₅₀ are translated in the z direction.

 Next, a method of setting the modification amount will be described.

In the modified mirror surface shown in FIG. 3 (a), the modification (parallel movement in the z direction) from the initially set parabolic surface of the minute plane mirror is only approximately the excitation phase of the antenna if the minute plane mirror is considered to be a minute antenna. Is equivalent to a change in That is, the modified mirror surface in FIG.
Can be said to be equivalent to the array antenna shown in FIG. here,
The element antenna 400 of the array antenna shown in FIG. 3B is arranged along the initially set parabolic surface P, and the phase shifter 600 gives a phase amount corresponding to the amount of modification to the output of the power distributor 500. . The radiation field of the element antenna can be easily obtained by obtaining a current induced by the primary radiator on a micro flat mirror arranged on the initially set parabolic surface P, and integrating the contribution of the current to the radiation field with respect to the micro plane. Required. The radiation field of the array antenna obtained by giving an excitation phase shift by a phase shifter to the radiation field of this element antenna and combining the contributions from each element antenna matches the radiation field of the modified mirror antenna.

From the above, the problem of producing a desired shaped beam by the modified mirror surface antenna results in a problem of producing a desired shaped beam by adjusting the excitation phase of the array antenna.

Hereinafter, a specific procedure of a method of setting the amount of modification using a mathematical expression will be described.

When there are a total of N small plane mirrors, and the I-th small plane mirror is on the initial parabolic surface, Radiation field And the excitation phase is θ _I , the combined radiation field of the array antenna Becomes as follows.

Here, the frequency f _X.

At this time Directional radiation field power Is Becomes Here, * indicates a complex conjugate.

this Is the desired radiated power The required shaped beam is constructed by choosing the excitation phase {θ _I } to be equal to

In order to find the optimal excitation phase, the following evaluation function Φ
Is defined.

Differentiating this Φ with θ _D gives And therefore Becomes

 Here, the phase vector Ω is defined as follows.

Then, by performing the following repeated calculations,
It is possible to approach Ω which makes Φ the minimum or the minimum.

Ω _{n + 1} = Ω _n −μ∂ {Φ / ∂Ω _n (7) By the above method, the excitation phase {θ _I } that minimizes or minimizes the evaluation function Ф is obtained. When the excitation phase θ _I corresponding to each of the small plane mirrors is converted into an optical path length R _I , R _I = −θ _I · λ _X / (2π) (8), and with reference to FIG. _The following relationship exists between _I , the amount of modification (the amount of plane movement in the z direction), and WI.

R _I + V _I = W _I + U _I (9) where V _I is the distance between the center and the primary radiator when the I-th micro flat mirror is on the default parabolic surface, and U _I is I th minute plane mirror is the distance between the center and the primary radiator in the case of retouching than parabolic surfaces only W _I.

The modification amount (W _I ) of the minute plane mirror is obtained by the above procedure, and by setting this value, a reflector antenna that radiates a desired shaped beam is configured.

By the way, since the element pattern for each micro flat mirror slightly changes before and after the modification, the mirror surface after the modification is close to the optimal mirror surface and is not always optimal. Therefore, the mirror surface after modification is considered as a new initial mirror surface, the element pattern is recalculated, the amount of modification of the micromirror surface is calculated again by the method described above, and this is set again, thereby bringing the mirror surface closer to the truly optimal mirror surface. be able to. Similar calculations can be repeated. Further, by reducing the size of the small plane mirror, it is possible to provide a mirror-modified antenna that emits a beam with a higher degree of shaping.

The design method of the present invention is simple in concept and procedure,
Beam forming is also effective because it can be performed directly by focusing on the far field. Therefore, the design and manufacture of the mirror-modified antenna can be performed in a short time and easily. In addition, since an effective shaped beam can be obtained by modifying the single reflecting mirror, the effect is large in terms of the weight and cost of the antenna.

 Next, another embodiment of the present invention will be described.

In the embodiments of the present invention described above, by setting the sizes of all the small plane mirrors to be substantially equal, it is possible to provide a mirror modified antenna that radiates an effective shaped beam with a small number of small plane mirrors. This is because the contribution of the radiation from each of the small plane mirrors becomes substantially equal. For example, there is a method of selecting the small plane mirror so that the projection area of each small plane mirror on the aperture surface is equal as shown in FIG. Can be Here, (a) is an example in which the minute plane mirror is a square,
(B) shows an example in which the minute plane mirror is a triangle, and (c) shows an example in which a circular opening reflecting mirror is cut in the circumferential direction and the radial direction to have the same area.

Another embodiment shown below is a reflecting mirror in which the plane of the micro flat mirror in the embodiment of FIG. 1 is taken as a plane perpendicular to the z-axis.
As shown in FIG. 6, each micro flat mirror has an independent inclination. By doing this,
A step between adjacent minute plane mirrors in the modified reflecting mirror can be removed, and deterioration of side-rope characteristics at a wide angle and deterioration of cross-polarization characteristics due to scattering caused by the step can be prevented.

By further developing this idea, the optimal function for minimizing or maximizing the evaluation function Ф under the constraint that the vertices of the polygon that creates the plane of the micro-planar mirror from the beginning match between the adjacent micro-planar mirrors The amount of retouching can be set. In this case, the optimum phase amount {θ _I } is obtained, the modification is performed with a limitation on the modification amount {W _I } of the micro flat mirror, and after the modification, the inclination of the plane of the micro flat mirror matches the vertex of the plane. By repeating the calculation process of re-determining as described above several times, a modified mirror surface is created. An embodiment in this case is shown in FIG. Here, an example using triangular minute plane mirrors 101 to 212 is shown. With such a modified mirror antenna,
It is possible to prevent deterioration of wide-angle side lobe characteristics and emit a desired shaped beam.

In addition to the step between the small plane mirrors, a large difference in inclination between adjacent small plane mirrors also causes scattering, causing the side lobe characteristic to fire. Therefore, a limiting condition that the difference in the amount of modification between adjacent minute plane mirrors does not exceed a certain set value is imposed, and a modified mirror surface antenna in which the optimal amount of modification that minimizes or maximizes the evaluation function Ф can be achieved. With such an antenna, it is possible to prevent deterioration of wide-angle side lobe characteristics and to emit a desired shaped beam.

In the above description, the example of the mirror-surface modified antenna in which one reflecting mirror is constituted by a number of minute planes has been described. However, as shown in FIG. Smooth mirror surface 300 to be equal
Thus, a similar effect can be obtained even if a modified mirror surface antenna is formed. In this case, if the size of the micro flat mirror is smaller than the wavelength, the difference in electrical characteristics between the reflector antenna using the micro flat mirror and the reflector antenna using the smooth mirror surface can be ignored.

The same effect can be obtained by using a mirror surface using a mesh as the micro flat mirror. By using a mesh, the weight of the entire antenna can be reduced, and it is very effective for modifying the mirror surface of a deployable reflector antenna having a truss structure.

Further, the same effect can be expected by indirectly supplying power to the sub-reflector 700 as shown in FIG. 9 instead of directly supplying power to the modified mirror surface from the primary radiator. In this case, the weight and cost increase due to the increase in the number of reflecting mirrors, but since the sub-reflecting mirror can be set completely freely, the degree of freedom of design is higher than the conventional method of modifying both reflecting mirrors together. Is increased. In addition, since the position of the primary radiator can be freely set by using the sub-reflector, it is convenient in configuring the antenna and is suitable for miniaturization.

The above describes the mirror-shaped modified antenna for beam shaping at single frequency and single polarization, but provides a mirror-shaped modified antenna that emits an effective shaped beam at two frequencies and two polarizations by biasing the evaluation function. can do.
Hereinafter, an embodiment in this case will be described.

First, an embodiment in the case of dual frequency sharing will be described. In this case, the following evaluation function _ＡA is defined instead of the above-mentioned evaluation function Ф.

here, Are vectors at frequencies f _X and f _Y , respectively. Is the power of the radiated electric field from the entire reflecting mirror radiated in the direction of Are vectors at frequencies f _X and f _Y , respectively. Is the desired value of the power of the electric field radiated from the entire reflecting mirror radiated in the direction of.

Is as shown in equation (2). Is Becomes

Radio wave radiated from the primary radiator at a frequency f _Y is I,
Through the second small plane mirror The radiated electric field in the direction, q = f _Y / f _X.

By obtaining the phase {θ _I } that minimizes or minimizes Ф _A in the same procedure as in the equation (7), the amount of modification {W _I } of the micro flat mirror can be obtained. The modified mirror-surface antenna in which the amount of modification is set can emit a desired shaped beam at two frequencies f _X and f _Y. Such a modified mirror antenna is effective when a good shaped beam is required over a wide band, and is also effective for beam shaping when the transmission and reception are shared by one reflector and the frequencies are distant. is there. In consideration of the above, there is a great effect as a satellite-mounted antenna for satellite broadcasting and satellite communication requiring a wide band and shared transmission and reception. In this embodiment, it is possible to set an optimum mirror surface in consideration of not only two frequencies but also higher frequencies.

Next, an embodiment in the case of dual polarization is described. In this case, instead of the above-mentioned evaluation function .PHI defining an evaluation function .PHI _B as follows.

here, Is a vector at frequency f _X Power of the reverse polarization component of the radiated electric field from the entire reflecting mirror radiated in the direction of Is a vector at frequency f _X Is a desired value of the power of the reverse polarization component of the electric field radiated from the entire reflecting mirror radiated in the direction.

Is as described above. In this case, the component is related to the positive polarization.

Is It is.

Means that the radio wave radiated from the primary radiator at the frequency f _X is I
From the I-th micro-plane mirror through the I-th micro-plane mirror It is the reverse polarization component of the electric field emitted in the direction.

By obtaining the phase {θ _I } that minimizes or minimizes this _{Ｂ B} by the same procedure as in the equation (7), both the corrections {W _I } of the micro flat mirror can be obtained. The modified mirror-surface antenna in which the amount of the modification is set can emit a desired shaped beam in two polarizations, and is effective as a mirror-surface modification antenna for dual polarization. Also, it is possible to suppress the reverse polarization component, which is effective for an antenna requiring low cross polarization.

Although several embodiments have been described above, it is also possible to configure a modified mirror surface antenna having the conditions of a plurality of embodiments among them.

As an example, a mirror modified antenna for dual frequency dual polarization will be described. In this case, the following evaluation function の
Define _C.

here, Is a vector at the frequency f _X shown in the equation (3). Indicates the power component of the positive polarization of the radiated electric field of the entire reflector radiated in the direction, Is the vector at the frequency f _X shown in equation (13). Shows the power component of the reverse polarization of the radiated electric field from the entire reflector that radiates in the direction, Is a vector at the frequency f _Y shown in equation (11). Shows the power component of the positive polarization of the radiated electric field from the entire reflecting mirror radiated in the direction, Is a vector at frequency f _Y 5 shows the power component of the reverse polarization of the radiated electric field from the entire reflector radiated in the direction. Also, Are each Is the desired value of the power corresponding to

Is expressed as follows.

At the frequency f _Y , the radio wave radiated from the primary radiator passes through the I-th small plane mirror It is the reverse polarization component of the electric field radiated in the direction.

The phase {θ _I } that minimizes or minimizes Ф _C in equation (14)
Is obtained by the same procedure as in the equation (7), thereby obtaining a modification amount {W _I } of the micro flat mirror. The modified mirror-surface antenna in which the amount of modification is set can shape the radiation pattern into a desired shape in each of the two polarized waves in the two frequency bands. Practical advantage is great, and when the dual-polarization is required for transmission and reception, one modified reflector can perform dual-frequency dual-polarization, and the effect of the reflector is extremely large because the pivot of the reflector can be reduced. .

[Effects of the Invention] As described above, the mirror-modified antenna of the present invention is effective because the design method and procedure are simple, and beam shaping can be performed directly and appropriately by focusing on the far field. Therefore, the design and manufacture of the mirror-modified antenna can be performed in a short time and easily.
In addition, since an effective shaped beam can be obtained by modifying the single reflecting mirror, the effect is large in terms of the weight and cost of the antenna.

[Brief description of the drawings]

FIG. 1 is a perspective view of a mirror modified antenna showing an embodiment of the present invention, FIG. 2 is a diagram showing a modification amount of a micro flat mirror, FIG. 3 is a diagram showing a principle of mirror modification, FIG. FIG. 5 is a diagram showing the relationship between the amounts of modification, FIG. 5 is a diagram showing division of the mirror surface of a mirror-modified antenna according to another embodiment of the present invention, and FIG. 6 is a cross-section of the mirror modified antenna according to another embodiment of the present invention. FIGS. 7, 7 and 8 are perspective views of a mirror-modified antenna according to another embodiment of the present invention, and FIG. 9 is a cross-sectional view of the mirror-modified antenna according to another embodiment of the present invention. 1 to 52, 101 to 212: Small flat mirror 100: Primary radiator 300: Modified mirror surface

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01Q 15/16 H01Q 19/12

Claims (3)

(57) [Claims] 1. A primary radiator for emitting a predetermined beam, and a reflecting mirror in which a modified mirror surface constituted by a plurality of small plane mirrors reflects a beam radiated from the primary radiator to form a beam having a desired shape. In a mirror-corrected antenna comprising, the power value of the radiated electric field due to the beam reflected by the reflecting mirror is determined for a plurality of directions in which the beam shaping of the desired shape is to be performed, The error between the power value and the power value of the desired radiated electric field in each of these directions is determined, the amount of modification from one of the small plane mirrors along a predetermined plane set as an initial value, and the small plane mirror adjacent to the small plane mirror. At least one of the minute planes constituting the reflecting mirror so that the difference from the retouch amount does not exceed a predetermined set value, and the integrated value of the absolute value of the error is minimized. Are translated in the predetermined direction by the amount of the modification, and each of the micro flat mirrors is inclined, and the parallel and inclined micro flat mirror is connected to the adjacent micro flat mirror. The surface to be modified by forming the vertices of the polygon forming the plane of the micro flat mirror constituting the reflecting mirror in a direction in which the micro flat mirrors adjacent to each other are inclined has a smooth mirror surface as a whole. Mirror modified antenna. 2. A primary radiator for radiating beams of a plurality of frequencies, and a reflecting mirror formed by a plurality of small plane mirrors for reflecting the beam radiated from the primary radiator to form a beam having a desired shape. In a mirror-modified antenna including a mirror, for each of the frequencies, the power value of the radiated electric field due to the beam reflected by the reflecting mirror is obtained for a plurality of directions in which the beam shaping of the desired shape is to be performed. The error between the obtained power value of the radiated electric field in each direction at each frequency and the power value of the desired radiated electric field in each direction at each frequency is obtained, and the error along the predetermined plane set as the initial value is obtained. The difference between the retouch amount from the two micro flat mirrors and the retouch amount of the micro flat mirror adjacent to the micro flat mirror does not exceed a predetermined set value, and minimizes the integrated value of the absolute value of the error. In such a manner, at least one micro flat mirror constituting the reflecting mirror is translated in a predetermined fixed direction by an amount corresponding to a modification amount, and the micro flat mirror is inclined with respect to each other. The plane mirror is formed as a continuous surface between the adjacent plane mirrors, and the vertices of a polygon forming the plane of the plane mirror constituting the reflecting mirror are formed in such a manner that the vertices of the polygons are inclined in a direction coinciding between the plane mirrors adjacent to each other. A mirror-modified antenna, characterized in that the surface to be etched has a smooth mirror surface as a whole. 3. A primary radiator that emits two polarized beams and a modified mirror surface composed of a plurality of small plane mirrors reflect the beam radiated from the primary radiator to form a beam having a desired shape. In a mirror-modified antenna comprising a reflector, for each of the polarization, the power value of the radiated electric field due to the beam reflected by the reflector, for a plurality of directions to perform the beam shaping of the desired shape, The error between the obtained power value of the radiated electric field in each direction for each polarization and the power value of the desired radiated electric field in each direction for each polarization is obtained, and the error is calculated on the predetermined surface set as the initial value. The difference between the modification amount from one of the small plane mirrors and the modification amount of the small plane mirror adjacent to the small plane mirror does not exceed a predetermined set value, and minimizes the integrated value of the absolute value of the error, At least one of the micro flat mirrors constituting the reflecting mirror is translated in a predetermined fixed direction in parallel by an amount of modification, and each micro flat mirror is tilted. The surface is continuous with the adjacent small plane mirror, and the vertices of the polygons forming the plane of the small plane mirror forming the reflecting mirror are formed and modified by being inclined in the same direction between the adjacent small plane mirrors. A mirror-modified antenna characterized by having a smooth mirror surface as a whole.