JP3777458B2 - Antenna optimized for reflecting mirror surface and method for determining its focal position - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an antenna system including, for example, an antenna main reflecting mirror, a sub reflecting mirror, various power feeding devices, and a beam directing direction control device mounted on a communication satellite. The present invention also relates to a relatively large reflecting mirror structure generally used on the ground.
[0002]
[Prior art]
FIG. 5 shows the setting of the virtual parabolic surface by the conventional method. 1 is a measurement point for discrete shape measurement distributed on the actual main reflector, 2 is a virtual parabolic mirror surface by a conventional method which is not truly electrically equivalent , 3 is a parabolic axis of 2, 4 is each of 1 This is an error in the parabolic axis direction between the measurement point and the two virtual parabolas. When there is one measurement point group, the second virtual parabola is calculated so that the sum of squares of all measurement points of the error in the parabolic axis direction (boresight direction) is minimized. The conventional antenna system is constructed assuming two virtual parabolas.
[0003]
FIG. 6 shows an example of an antenna system including a parabolic main reflector designed according to the conventional method. Reference numeral 5 denotes a focal position of the second virtual parabola, 6 denotes a feeding system for the second parabola, 7 denotes an irradiation direction of the beam reflected by the second virtual parabola, and 8 denotes an actual beam radiation direction. In other words, the designer assumed that the antenna system designer is actually radiating the radio wave 8 because the power feeding system is arranged with respect to two parabolas rather than a truly electrically equivalent one. Radiation direction 7 does not match.
[0004]
On the other hand, the electrically equivalent virtual parabolic surface of the actual main reflecting mirror in which one measurement point is distributed is 9, and 10 represents the focal position.
[0005]
[Problems to be solved by the invention]
In the antenna system including the above parabolic curved surface structure, the feeding position is determined assuming a virtual parabolic curved surface that minimizes the sum of squares of errors focusing only on the boresight direction from each measurement point. Since directivity direction control and the like are performed, the radio wave propagation path is not accurately optimized, and there is a possibility that desired electrical characteristics may not be obtained. In particular mirror focal length of the parabolic having a target using the shortened yet offset position away from the parabola axis, to the difference between the error of the error and the radio propagation in the boresight direction increases, electrical equivalent There is a possibility that the reflection surface and the virtual parabolic surface which is not electrically equivalent as assumed in the prior art are completely different.
[0006]
An object of the present invention is to configure an antenna system that is electrically and optically optimal for a parabolic curved surface, a hyperbolic surface, or an elliptic curved surface structure.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is an antenna having a truly electrically equivalent virtual parabolic curved surface and a wave source element attached to a focal position of the virtual parabolic curved surface,
A line segment from the actual measurement point to the first point where the line connecting the measurement point and the wave source element intersects the virtual parabolic curved surface, and a line parallel to the parabolic axis passing through the measurement point from the actual measurement point For the path difference that is the sum of the line segment from the first point to the second point that is the intersection when the perpendicular is drawn, the sum of the squares of the path differences at all measurement points is minimized. The virtual parabolic curved surface is determined .
The present invention also includes an antenna having a first step of determining a truly electrically equivalent virtual parabolic curved surface and a second step of determining a mounting position of the wave source element with reference to a focal position of the virtual parabolic curved surface. The focal position determination method of
In the first step, the line from the actual measurement point to the first point where the line connecting the measurement point and the wave source element intersects the virtual parabolic curved surface and the actual measurement point pass through the measurement point. For the path difference that is the sum of the line segment to the second point that is the intersection when the perpendicular is drawn from the first point to the line parallel to the parabolic axis, the sum of the squares of the path differences at all measurement points The virtual parabolic curved surface is determined so that is minimized .
[0008]
The antenna system is different from the conventional antenna system in that the antenna system is arranged assuming a virtual curved surface (parabola, hyperboloid, elliptical surface) that minimizes the path difference of the radio wave propagation path.
[0009]
Since the present invention is configured as described above, there is an effect that an optimal antenna system can be assembled electro-optically with respect to the reflecting mirror surface.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows the setting of a virtual parabolic surface according to the present invention. 11 is the virtual parabolic mirror surface according to the present invention, 12 is the 11 parabolic axes, and 13 is the focal point of the 11 parabolic mirror surfaces. The sum of line segment A and line segment B in the figure is the propagation path difference or optical path difference of radio waves between one measurement point and the virtual parabolic mirror surface.
[0011]
Eleven virtual parabolic mirror surfaces are calculated such that when there is one measurement point group, the sum of squares of all the measurement points of the propagation path difference or optical path difference of the radio wave is minimized. The antenna system according to the present invention is constructed assuming 11 virtual parabolas.
[0012]
FIG. 2 shows an example of an antenna system including a parabolic main reflector designed according to the present invention. Reference numeral 11 denotes a virtual parabolic mirror surface that minimizes the sum of squares of the propagation path difference or optical path difference of the radio wave with respect to the measurement point as described above, and substantially coincides with the truly electrically equivalent parabolic mirror surface of 9. Reference numeral 14 denotes a power feeding device set for 11 parabolic mirror surfaces.
[0013]
As an example of measurement data, it is assumed that the test data of FIGS. 3A to 3D is obtained. The number of the measurement point and the coordinate values in the X, Y, and Z directions are shown from the left side. FIG. 4 shows a comparison between the virtual parabola based on the present invention and the virtual parabola according to the prior art for a total of 197 measurement points. There is a difference of about 5 mm in the focal length, and there is a slight difference in the translation position. As a result, the mirror surface error from the parabola considered to be electrically equivalent is 0.286 mm RMS for the virtual parabola according to the present invention, whereas the mirror surface error of the virtual parabola according to the conventional method is 1.35 mm RMS.
[0014]
By the way, as a shape condition required for the mirror surface of the antenna, it is assumed that the error of the mirror surface is 1/50 or less of the wavelength of the radio wave handled. Accordingly, the required accuracy for the C band (wavelength 50 mm) is 1 mm RMS or less, and the required accuracy for the Ku band (wavelength 21.4 mm) is 0.4 mm RMS or less. Therefore, when an antenna system is constructed assuming an equivalent parabola according to the conventional method using a mirror surface corresponding to the above measurement data, desired electrical characteristics cannot be expected for the C band and Ku band. it is conceivable that.
[0015]
【The invention's effect】
As described above, the present invention is a virtual parabolic curved surface that minimizes the sum of the squares of the optical path difference and the radio wave propagation path difference between each position-measurable measurement point data for a parabolic curved surface, hyperbolic surface, or elliptical curved surface. Alternatively, the wave source position is determined on the assumption of a hyperboloid or an elliptical curved surface, and the beam directing direction control is performed, so that there is an effect that an optimal electro-optical antenna system can be built on the reflecting mirror surface. .
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a setting of a virtual parabola according to the present invention.
FIG. 2 shows an antenna system according to an embodiment of the present invention.
FIG. 3A is test data for illustrating the effect of the present invention.
FIG. 3B is test data for illustrating the effect of the present invention.
FIG. 3C is test data for illustrating the effect of the present invention.
FIG. 3D is test data for illustrating the effect of the present invention.
4 is a diagram illustrating a comparison between a virtual parabola according to the present invention and a virtual parabola according to a conventional method with respect to the test data of FIGS. 3A to 3D. FIG.
FIG. 5 is a diagram illustrating setting of a virtual parabolic surface by a conventional method.
FIG. 6 shows an antenna system designed by a conventional method.
[Explanation of symbols]
To minimize the parabola axis error with respect to 1 the actual main reflector on the measurement point 2 1 measuring point group, truly each measurement point electrically not equivalent virtual parabola 3 2 parabolic shaft 4 1 and 2 virtual parabolic parabolic axis error 5 2 parabolic focus 6 2 of the placed power feeding apparatus 7 2 virtual radio wave radiation direction 8 actual radio wave radiation direction 9 true for parabolic to focus electrically equal the The parabolic mirror surface 10 9 The focal point 11 of the parabolic mirror surface 11 The virtual parabola 12 that is truly electrically equivalent to minimize the radio wave propagation path difference or optical path difference with respect to the measurement point group 1 1 The parabola axis 13 of the virtual parabola 11 Power feeding device placed at the focal point 14 11 of the virtual parabola 11

Claims (2)

An antenna having a truly electrically equivalent virtual parabolic curved surface and a wave source element attached to the focal position of the virtual parabolic curved surface,
A line segment from an actual measurement point to a first point where a line connecting the measurement point and the wave source element intersects the virtual parabolic curved surface, and the parabolic axis passing through the measurement point from the actual measurement point The sum of the squares of the path differences at all measurement points with respect to the path difference that is the sum of the line segment to the second point that is the intersection when the perpendicular is drawn from the first point to the line parallel to The antenna is characterized in that the virtual parabolic curved surface is determined so that is minimized . A method of determining a focal position of an antenna, comprising: a first step of determining a virtual parabolic curved surface that is truly electrically equivalent; and a second step of determining a mounting position of a wave source element with reference to a focal position of the virtual parabolic curved surface. Because
The first step includes a line segment from an actual measurement point to a first point where a line connecting the measurement point and the wave source element intersects the virtual parabolic curved surface, and the actual measurement point. About the path difference that is the sum of the line segment to the second point that is the intersection when the perpendicular line is drawn from the first point to the line parallel to the parabolic axis passing through the measurement point, at all measurement points The method of determining a focal position of an antenna , wherein the virtual parabolic curved surface is determined so that a sum of squares of the path differences is minimized .

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