JP3513828B2 - Antenna reflector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reflector antenna structure mounted on an artificial satellite, comprising a reflecting surface structure and a supporting structure, and a connecting structure for connecting both of them. Regarding what is being done. For example, an antenna structure in which a reflection surface structure is formed by a lightweight and flexible structure such as a metal film surface, and the reflection surface structure is supported by a deployable skeleton structure corresponds to this. [0003] A reflector antenna structure mounted on an artificial satellite has a method in which a reflection surface 1 is formed using a CFRP honeycomb plate, and the back surface thereof is reinforced using a frame structure 2 or a rib structure. It has been widely used (FIG. 1). When an attempt is made to make a large reflector antenna structure with such a structure, it is possible to store the antenna in a small area to some extent by moving a portion fixed to the satellite body (FIG. 2). , Diameter 10
It is practically difficult to accommodate a reflector antenna structure having a size exceeding m in a rocket fairing having a diameter of about 5 m including the satellite body. [0005] Therefore, in a mobile communication satellite using a relatively low communication frequency, a concept has been proposed in which a reflecting surface structure is formed using a metal film surface and is supported using a deployable structure. (FIG. 3). In many cases, the reflector antenna structure mounted on a satellite has a paraboloid of revolution, but approximating the paraboloid of revolution with both the reflective surface structure and the support structure takes into account that the support structure expands Then it is difficult. Therefore, in many cases, the support structure constitutes a spherical surface approximating a paraboloid of revolution, and by adjusting the length of the connection structure 6 (FIG. 4) connecting the support structure 7 and the reflective surface structure 5, the support structure is formed. Absorbs the error of the paraboloid of revolution. Therefore, it is necessary to derive a spherical surface that approximates the shape of the reflecting surface structure formed by a given paraboloid of revolution with as little error as possible. An approximation sphere was derived such that the sum of the portions having a reflection surface structure of the square of the difference between the sphere and the paraboloid of revolution was minimized. When an approximate spherical surface is obtained by a method that minimizes the sum of a portion having a reflective surface structure of the square of the difference between the approximate spherical surface in the direction in which radio waves are reflected and the paraboloid of revolution, The difference between the approximate spherical surface and the paraboloid of revolution, that is, the length of the connection structure connecting the reflection surface structure and the support structure does not become shorter than a certain value. If the connection structure is not shortened, a force is applied to the connection structure by the tension of the reflection surface structure attached to the tip of the connection structure, and if the connection structure is bent, the accuracy of the reflection surface structure cannot be maintained. An object of the present invention is to provide a method for further shortening the length of a connection structure for deriving the length of the connection structure by the above-described method, and preventing a force from being applied to the connection structure. A spherical surface is determined so as to minimize the sum of even powers of the difference between the approximate spherical surface in the direction of radio wave reflection and the paraboloid of revolution in the portion forming the reflecting surface structure. By doing so, the overall length of the connection structure is shortened and the connection structure is prevented from being applied with force. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As described in the prior art, a sphere formed by a supporting structure of an onboard antenna of an artificial satellite using a metal film surface as a reflecting surface structure, a connecting structure, and a deployable supporting structure. The shell was designed in the following way. At that time, the point where the difference in the Z-axis direction between the paraboloid of revolution having the reflecting surface structure and the spherical shell approximating the paraboloid of revolution was largest was minimized. First, the formula of the paraboloid of revolution shown by the flow chart element 8 in FIG. 8 is derived. As shown in Fig. 5, the origin is the vertex of the paraboloid of revolution, the Z-axis is the direction in which the paraboloid of revolution is spreading, and the direction coincides with the direction in which the earth is viewed from the antenna. Let it be the Y axis.
Next, a portion used for the reflection surface structure is determined as follows. The distance from the origin of the paraboloid of revolution to the portion where the reflecting surface structure starts is Y-axis offset, YD, and the size of the reflecting surface structure portion in the Y-axis direction is D. And from the electrical characteristics, the formula Z _p of the paraboloid is expressed focal length of the paraboloid of revolution is at fm, as shown in the following equation. ## EQU1 ## The position on the Z axis is O _z , and the position on the Y axis is O
_y, wherein Z _s spherical shell shown in the flow chart element 9 is represented by the radius r is as follows. At this time, since both the paraboloid of revolution and the spherical shell are axisymmetric with respect to the Z axis, no offset on the X axis is considered. ## EQU2 ## The Z expressed by these equations (1) and (2)
The difference in the Z direction wherein _p and Z _s in order to minimize, firstly,
An equation was created such that the part where the difference in the Z direction was the largest became larger and the part where the difference was smaller became smaller. Therefore, the value obtained by subtracting Z _p from Z _s is 2
The value was raised to the m-th power, and the portion forming the reflection surface structure was integrated. m to 10.
When a large number of such 0, large place is greater for Z _s and Z _p, you can place small smaller. As shown in FIG. 5, the portion of the paraboloid of revolution which is the integration range, which becomes the reflecting surface structure, is YD to YD in the Y-axis direction.
Up to + D, the diameter D in the X-axis direction when viewed from the Z-axis
This is the part of the circle. The equation shown in flowchart element 10 that integrates Z _s -Z _{p to} the power of 2m is as follows. [Equation 3] When r, O _y , and O _{z in} equation (3) are once differentiated, the value becomes 0 when the difference between Z _s and Z _{p in} the Z-axis direction is minimized. The equations are shown below. [Equation 4] (Equation 5) [Equation 6] The values of r, O _y , and O _z when these equations (4), (5), and (6) are satisfied are represented by the flowchart element 11.
Is derived using the equation (7) of the Newton method shown in FIG. i
Is the number of iterations of the Newton method. [Equation 7] When an approximate spherical surface is obtained by the conventional method of least squares, m in equations (3) to (6) becomes 1. When the Newton method converges as shown in flowchart elements 12 and 13, r, O _y , and O _z are obtained. FIG. 6 shows the error in the Z-axis direction between the paraboloid of revolution and the spherical shell obtained by the least square method. D of the paraboloid of revolution is 1
5000mm, YD is 3000mm, fm is 10,000
mm. The solid lines and various dotted lines in FIG. 6 are differences (approximation errors) between the paraboloid of revolution in the Z-axis direction and the spherical shell, and indicate the position of a cross section parallel to the X-axis as a parameter. The positive maximum value at this time, the position of the paraboloid of revolution in the Z-axis direction is the Z of the spherical surface.
The maximum value when larger than the axial position is 241.51 mm
And the minimum value when the position of the paraboloid of revolution in the Z-axis direction is smaller than the position of the spherical surface in the Z-axis direction is -192.8.
6 mm. Since the spherical surface supports the paraboloid of revolution from below in the Z-axis direction, the fact that there is a portion where the Z-axis value of the spherical surface is larger than that of the paraboloid of revolution means that the spherical surface has a negative maximum value. Must be lowered from the paraboloid of revolution in the Z-axis direction. Then, the value in the Z-axis direction of the approximate spherical surface and the paraboloid of revolution becomes a value obtained by adding the positive maximum value and the negative maximum value, and the height difference of the connection structure is 438.37 m.
m. In order to further reduce the height difference of the connection structure, it is more effective to use a method of reducing the maximum error in the Z-axis direction between the approximate spherical surface and the paraboloid of revolution than using the least square method. FIG. 7 shows the result of calculating the value of m proposed in the present invention with a larger value, and compares the result with the result of calculation using the above-mentioned least square method. When m is 10, D is 15000 mm, YD is 3000 mm, and fm is 10
000 mm, and the positive maximum value of the difference in the Z-axis direction at that time is 186.33 mm, and the negative maximum value is -176.1.
6 mm. That is, the height difference of the connection structure is 364.49.
mm. Compared to the difference in height of the connection structure of 438.37 mm when the least squares method is used, it can be shortened by 73.88 mm. When the connection structure becomes longer, a force is applied to the tip of the connection structure due to the tension of the reflection surface structure, and the connection position between the connection structure and the reflection surface structure is shifted from the specified position toward the reflection surface structure. For example, when the deviation is 5 mm, the position of the node point 14 attached to the reflecting surface structure is 1 at the maximum.
If the connection position is shifted by 10 mm, the position of the node point is shifted by 21.43 mm. As described above, even when the difference between the connection positions of the connection structure and the reflection surface structure is small, the node position is largely shifted. If the deviation is large, it becomes impossible even to adjust the tension of the reflecting surface structure to a desired tension. For this reason, it is necessary to prevent the deformation of the connection structure by making the connection structure as short as possible. When the paraboloid of revolution is approximated by a spherical shell, the method of minimizing the largest error in the Z-axis direction between the paraboloid of revolution and the spherical shell is smaller than the method of least squares. The error can be reduced, and the connection structure connecting the reflector structure and the support structure can be made shorter. To minimize the largest part of the error,
What is necessary is just to minimize the sum of the even powers of the error. The even value is preferably 4 or more. Even powers are smaller, smaller errors are larger, and large errors are larger, so the sum of even powers is represented by the largest part of the error. By shortening the connection structure, the accuracy of the cable network forming the metal film surface can be increased, the load on the support structure can be reduced, and the weight of the whole antenna mounted on the satellite can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a conventional reflector antenna structure. FIG. 2 shows a deployed and stored state of a reflector antenna structure of a conventional artificial satellite mounted antenna. FIG. 3 shows an image diagram of a conventional satellite. FIG. 4 is a connection diagram of a reflection surface structure, a support structure, and a connection structure. FIG. 5 is an explanatory view of a portion having a paraboloidal reflection surface structure. FIG. 6 is a graph of the error of the paraboloid of revolution and the spherical shell in the Z-axis direction by the least square method. FIG. 7 is a graph of the Z-axis error of the paraboloid of revolution and the spherical shell due to a larger even power. FIG. 8 is a flowchart for implementing the method of the present invention. [Description of Signs] 1 Conventional reflector antenna structure 2 Frame structure 3 Deployment state of antenna mounted on conventional satellite 4 Storage state of conventional satellite in rocket fairing 5 Reflective surface structure 6 Connection structure 7 Support structure 8 Flowchart element 9 Flowchart element 10 Flowchart element 11 Flowchart element 12 Flowchart element 13 Flowchart element 14 Node point

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01Q 15/00-15/24 H01Q 17/00 H01Q 19/00-19/32

Claims (1)

(57) [Claims] [Claim 1] A rotary discharger comprising a metal film surface that reflects radio waves
Object-shaped reflective surface structure, and support structure having a spherical shape approximating the paraboloid of revolution
When a connection structure for connecting the support structure and the reflective surface structure,
In the antenna reflecting mirror comprising: a portion of the paraboloid of revolution that becomes the reflecting surface structure.
Te, the paraboloid between the spherical and the paraboloid
The sum of powers of even numbers greater than 4 of the difference in the direction of the symmetric axis is determined, and the spherical surface is determined so that the sum is minimized.
The length of the connection structure is determined based on the
Antenna reflector, characterized in that that.