JPH0728174B2 - Microwave antenna reflector - Google Patents

Description

FIELD OF THE INVENTION The present invention relates generally to antennas, and more specifically,
The present invention relates to a new hybrid RF reflection mesh and an antenna having an RF reflection surface composed of the mesh.

Prior Art The prior art is rich in a variety of antennas used both on Earth and in outer space. The antenna and hybrid antenna mesh of the present invention have features that are useful both on Earth and in outer space. However, in this specification, it is described as a parabolic antenna of a spacecraft.

Briefly, a parabolic antenna comprises a parabolic reflector and a feed at the focal point of that reflector. At the transmit antenna, the feed radiates RF energy to a reflector, which reflects the energy as a beam along its axis. At the receiving antenna, the RF energy entering the reflector parallel to the reflector axis is reflected towards the focus and collected in the feed. The parabolic antenna is designed to operate as both a receiving antenna and a transmitting antenna.

The main cases of spacecraft antennas are: That is, it is relatively lightweight; it can be folded into a compact shape on launch, and can be expanded to its working form in space; when expanded in space, its parabolic reflection surface is exactly the shape of the desired parabola. Is to match. Although terrestrial parabolic antennas do not require these requirements, it will be apparent that the present invention can be used to advantage in many terrestrial applications, particularly radio telescopes. Most but not all of the terrestrial parabolic antennas, except perhaps the larger radio telescopes, utilize rigid parabolic reflectors, but the spacecraft antenna open umbrella and weight requirements are due to the use of rigid reflectors. Will be eliminated. Therefore, various parabolic antenna reflectors were devised. Some have used rigid, but collapsible, petal-like members that can be opened into a parabolic form. The advantage of these petal-like reflectors is that they create a relatively smooth and precise parabolic surface when unfolded, but they are very heavy and complex structures. Another type of expandable parabolic reflector uses a folded metal net or mesh or metallized plastic film as the parabolic reflective surface. The reflective surface is attached to a frame that extends outwardly from the hub and can be folded to open and close the reflector. The shape of the rib is determined so that when the reflector is opened, the reflecting surface matches the parabolic surface. Patents already mentioned 396115
3; 3982248; 3987457 disclose this latter type of spread parabolic reflector. The preferred embodiment of the present invention is an improvement on these later widened antennas, allowing them to operate at much higher frequencies.

A first understanding of the parabolic antenna reflectors described in the above patents is best for understanding the invention. The reflector frame includes a plurality of generally parabolic ribs that are circumferentially spaced and pivotally mounted at their inner ends to a central hub. The rib pivots inwardly with respect to the hub to its closed state, in which state the rib is gathered on the front side of the hub. In addition, the rib is rotated outward with respect to the hub to be in a spread state, and in that state, the rib coincides with the paraboloid.

The wire mesh attached to these ribs includes first and second parallel wires, the first parallel wires extending between adjacent ribs and spaced along the ribs at their inner ends to adjacent ribs. It is fixed. The second parallel wire extends in the length direction of the rib in a cross relationship with the first wire. The first and second wires are welded together at their intersections to form a welded mesh structure, which coincides with the paraboloid when the reflector ribs are unrolled. The mesh can be folded to close the ribs.

The unique feature of this prior art welded mesh is that the wire that runs between the ribs of the reflector is shaped into a spring-like or elastic form that allows the mesh to expand and contract in response to changing temperatures experienced in space. That is. The spring wire is pulled with a predetermined tension that is preloaded to keep the spring wire tensioned, and in such a way that the welded mesh reflector can maintain a parabolic surface over the entire temperature range the reflector receives in space. The mesh is attached to the reflector.

This welded mesh is made on the welder of Patent 3,961,153. This machine feeds the mesh crossing wire through it and welds the wire at the wire crossings.

This welded mesh has certain properties that limit its use in conventional space. The present invention overcomes the disadvantages of this mesh.

To explain this point, first, in order for a wire mesh to be an effective RF reflector, its mesh size, that is, the size of its aperture or the size of the spacing between parallel mesh wires, depends on the radio frequency to be reflected. It is well known that it must be small compared to the wavelength. For the radio frequencies used to date, it is possible to make welded meshes that are small enough to create an effective reflective surface. However, conventional space communications use much higher frequencies, and therefore much shorter wavelengths, against which it is difficult to make useful welded meshes of the small meshes that are needed. And even impossible.

There are two reasons why it is difficult to fabricate a small mesh welded mesh for such high frequencies. First, the number of welds in making the welded mesh of a typical spacecraft parabolic reflector is very large, making it impractical or impossible, at least in an economic sense. Even. Second, the resulting welded mesh welds are too close together to be too stiff for a retractable parabolic reflector. With this,
There is a need for improvements in RF reflective meshes that can be used at these higher frequencies in the future.

SUMMARY OF THE INVENTION The present invention is sized for very high frequency operation that would be used in conventional space communications; is easy to fabricate; and a retractable spacecraft such as a dish-shaped parabolic reflector. Provided is an improved high frequency reflective mesh suitable for use in an antenna reflector.

The improved mesh is a hybrid mesh that includes a support mesh and a conductive mesh overlying the support mesh and secured to the support mesh. The conductive mesh forms the RF-reflecting surface of the hybrid mesh and has a relatively small mesh suitable for the high frequency electromagnetic wave wavelength to be reflected. In this regard, the conductive mesh of the best mode of the present invention is a very small mesh knit wire fabric or woven mesh that can be used at frequencies on the order of 24 GHz and has 16 wires per inch. Is.

The embodiment described below of the present invention is a reflector of a retractable parabolic antenna for a spacecraft that utilizes a hybrid mesh as the reflective paraboloid of the reflector. The support mesh in this example is the elastic, welded wire mesh described in the above-referenced patents, where the mesh may be any convenient size. This hybrid mesh is relatively supple and can be easily opened and closed to squeeze or unfold the reflector. The elasticity of the support mesh and the woven mesh allows the hybrid mesh to retain its parabolic contour over the temperature range encountered in the spacecraft.

Embodiments The spread parabolic antenna 10 of FIGS. 1 and 2 is the same as the conventional one except for the RF reflecting surface 12 of its parabolic reflector or dish 14. Therefore, detailed description of the antenna is unnecessary. The frame 15 of the antenna reflector 14
Suffice it to say that it includes a central hub 16 mounted to a support, which is part of a spacecraft, to which the inner ends of the ribs 20 of the parabola are mounted by hinges 22.

These ribs are capable of rotating between the folded or contracted condition shown in dashed lines in FIG. 2 and the open or expanded condition shown in solid lines in FIG. In its contracted state, the ribs extend generally toward the front of the hub and fit within an enclosed space of approximately the same diameter as the hub. In the expanded state, the ribs align with the parabola or paraboloid including the front surface 24 of the hub. The spring 26 has the rib expanded. An opening means (not shown) is provided for keeping the ribs in a contracted state.

As I will explain in detail, the RF of the parabolic reflector 14
The reflective surface 12 comprises the hybrid mesh 28 of the present invention. This mesh is attached to reflector ribs 20 and opens and closes with the ribs. Expanding the ribs coincides with the reflective mesh 28, the hub front 24, and the parabolic surface having the focal point f.

The antenna feed 30 extends forward from the hub 16 along the central axis. The radiator of the feed at the focus f and /
Or there is a receiver 32.

The gist of the present invention resides in the structure of the hybrid mesh 28 forming the RF reflection surface 12 of the parabolic reflector 14. This mesh will be described with reference to FIGS. 3-7.

The hybrid mesh 28 comprises a support mesh 34 and a conductive mesh 36 overlying and secured to the support mesh 34. The mesh of the support mesh 34 may be of a size that can be easily made. The conductive mesh 36 is a wire mesh or a metallized synthetic fiber mesh. The mesh is appropriately sized for the wavelength of the radio frequency to be reflected. The main advantage of the present invention is that it suits the very high frequencies intended for future space engineering. This means that very small meshes can be made using standard knitting techniques and machines. For example, as will be readily appreciated, the mesh is a mesh-like, knitted fabric of the order of 0.10 inches suitable for frequencies in the 5-6 GHz range.

For further details, please refer to the accompanying drawings. Preferred support mesh 34
Is the same welded wire mesh as described in the previously mentioned prior patents. Strands or wires 38 of this preferred support mesh extend between adjacent ribs 20 of reflector 14 generally along the circumferential direction of the reflector, and strands or wires 40 are orthogonal to wires 38 and generally the radius of the reflector. It extends in the direction. The wires 38, 40 intersect each other and are welded at their intersection 42. The circumferential wires 38 are undulating as shown in FIG. 5 and as described in the previously mentioned prior patents, these wires being elastic so as to be elastically pulled towards their ends. It is supposed to have.
Thus, the support mesh 34 becomes elastically pulled in the direction toward the end parallel to the wire 38. Spring wire 38 is tensioned as described in the prior patent.

The knit wire mesh 36 is essentially a knit wire chain 44 that extends toward one end of the mesh and a knit wire fabric or fabric that extends orthogonally to these chains 44 and that are joined together at the intersections of the chains. Be correct. The knit mesh has various open knit patterns. The preferred pattern shown in FIG. 4 is the tricot 2 bar knit pattern. This knit pattern is well known and needless to say. The knit mesh 36 can extend to some extent in-plane towards all edges, but can extend predominantly in the diagonal direction of the mesh 48 of the mesh.

Conductive mesh fabric or fabric supporting mesh 36 Mesh 3
It is placed on top of 8, 40 and extends diagonally of the mesh 48 of knit mesh on the support meshes 38, 40. The knit mesh is welded to the support mesh at the appropriate intersections of the support mesh wires 38, 40 and the knit wire chains 44, 46. It will be appreciated from the above description that the vibrit mesh 28 elastically extends in a direction toward the end of the elastic spring wire 38 of the support mesh 34.

In the parabolic reflector 14 shown, the hybrid mesh reflecting surface 12 includes a plurality of panels 50. Each panel is fixedly arranged between two adjacent reflector ribs 20. Figures 6 and 7 show one of these panels on an enlarged scale. Each reflector panel 50 has a pair of metal mounting pieces 52.
Support mesh elastic wire 38 on these mounting pieces
The ends of are fixed. These mounting pieces are fixed to the ribs 20 of the reflector frame. .

When the reflector 14 is spread evenly, the support mesh 34 conforms to the parabolic surface, as described in the prior patent. The support mesh 34 supports a conductive mesh fabric 36, and the conductive mesh fabric 36 conforms to the parabolic surface defined by the support mesh 34. This support mesh has a mesh size that is easy to make. The conductive mesh fabric 36 is sized to be suitable for the RF wavelength to be reflected. As an example, for frequencies in the range 5-6 GHz, a 10 gauge mesh, or 10
2 conductors (10 wire chains per inch 44/4
6).

As noted above, the preferred knit pattern for conductive mesh fabric 36 is a 2-bar tricot knit.
Other knit patterns, such as Rashichel knit, can also be used. Further, the conductive mesh fabric 36 may be a woven fabric rather than a knit fabric.

The conductive mesh fabric 36 described herein is a knit wire fabric. However, the conductive mesh fabric may be metallized synthetic fibers.

The support mesh 34 may be a wire mesh or a synthetic fiber mesh. The advantage of placing the wire support mesh over the support mesh of non-conductive fibers is that the wire support mesh can be short circuited if there is a break in the conductive mesh fabric. This drawback is overcome by metallizing the synthetic fiber support mesh.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a parabolic antenna using the hybrid and mesh reflectors of the present invention. FIG. 2 is an enlarged view of a reflector fragment. FIG. 3 is an enlarged view of the hybrid mesh of the antennas of FIGS. FIG. 4 is another enlarged view of the hybrid mesh. FIG. 5 is an enlarged view of the elastic wire used for the support mesh of the hybrid mesh. FIG. 6 shows a hybrid mesh panel of the reflector of FIG. FIG. 7 is an enlarged perspective view of the panel. In the figure: 10: Parabolic antenna 12: RF reflecting surface 14: Reflector 15: Frame 16: Hub 20: Rib 22: Hinge 24: Front surface 26: Spring 28: Hybrid mesh 30: Feed 32: Radiator and / or reflector 34 : Support mesh 36: Conductive mesh fabric 38: Strand or wire 40: Strand or wire 42: Intersection 44; 46: Knit wire chain 48: Mesh 50: Panel 52: Mounting piece

Claims (1)

[Claims] 1. A collapsible support frame comprising a central hub and a plurality of radial ribs attached to the central hub so as to rotate about one end as a rotation axis and rotating between a folded state and an open state. A support wire mesh fixed to the radial ribs, which is formed by connecting shrinking and elastic peripheral wires and radial wires intersecting these wires at intersections, Microwave antenna reflector comprising a woven wire of suitable mesh size or a cloth mesh of metallized synthetic fibers, with a fixed and supported microwave reflecting mesh on said supporting wire mesh. .