Technical Field The invention relates to antenna reflectors which simulate the response of a three dimensional reflector. In one embodiment, the antenna reflector is flat and simulates a response of a normal parabolic reflector. The flat antenna reflector in accordance with this embodiment can also simulate other shaped reflectors. In another embodiment, the reflector is parabolic in that an array of dipoles are suspended over a parabolic ground plane to assume a parabolic shape.

The flat collapsible antenna reflector in accordance with the first embodiment of the invention is especially adaptable for use on space capsules.

Background Art

Collapsible antennas are known in art as illustrated in, for example, U.S. Patent 3,699,581, Hall et al, October 17, 1972, U.S. Patent 3,969,731, Jenkins et al, July 13, 1976 and U.S. Patent 5,132,699, Rupp et al, July 21, 1992.

The ' 581 Patent teaches a collapsible antenna arrangement for use in space. Foldable antennas are stowed in a cylindrical shroud during launch, and they are unfolded when the spacecraft body has been launched into space. As seen in Figure 6, antenna elements 42 are arranged on one side of the panels. As disclosed at column 3, lines 31 and 32, these elements are arranged in a manner of a phased array.

The '731 Patent teaches a mesh article useful as a reflector in space. The strands 2 of the mesh, as illustrated in Figure 1, are covered by a conductive material 4 along their entire length.

The '699 Patent was selected as of interest in its teachings of a collapsible antenna comprising a plurality of panels each of which panel is inflatable. As seen in Figure

4, the panels comprise tubular elements 20 having disposed within them dipole elements 26.

Summary of Invention It is an object of the invention to provide a novel flat collapsible antenna reflector.

It is a further object of the invention to provide such an antenna reflector which includes a ground plane and a spaced phasing plane. It is a still further object of the invention to provide such an antenna reflector wherein the ground plane and the phasing plane are made of flexible materials whereby both planes are foldable so that the entire antenna reflector is collapsible. It is a further object of the invention to provide an antenna reflector in which an array of dipoles over a parabolic ground plane such that the dipole array assumes a parabolic shape.

It is another object of the invention to provide such an antenna reflector whereby the dipoles are of the correct length and spacing so as to convert a received electromagnetic wave into a shaped beam.

In accordance with a particular embodiment of the invention there is provided a flat, collapsible, antenna reflector, for use in a predetermined bandwidth, and for reflecting an E-M wave, comprising: a ground plane enclosed in a ground plane frame; a phasing plane enclosed in a phasing plane frame; spacer means for maintaining said planes in connected, spaced relationship; said phasing plane including a plurality of reactive elements sensitive to different frequencies in said bandwidth; whereby, to cause said E-M wave to be reflected at a predetermined angle to the angle of reception thereof.

In accordance with an other embodiment of the invention there is provided a passive parabolic shaped antenna reflector, for use in a predetermined bandwidth, said

antenna being configured to reflect a received E-M wave, said antenna comprising: a parabolic shaped ground plane; a parabolic shaped phasing plane; spacer means for maintaining said planes; said phasing plane including a plurality of reactive elements for causing a received E-M wave to be reflected from said reflector at a predetermined angle to the angle of reception thereof.

Brief Description of the Drawings

The invention will be better understood by an examination of the following description, together with the accompanying drawings, in which: FIGURE 1 illustrates generally the principles for forming a flat, collapsible, reflector antenna in accordance with one embodiment of the invention;

FIGURE 2 illustrates a particular embodi-ment of a phasing plane in accordance with the invention; FIGURE 3 illustrates a second embodiment of the phasing plane in accordance with the invention;

FIGURE 4 illustrates a still further embodiment of a phasing plane in accordance with the invention;

FIGURE 5 shows in greater detail a cylinder used in the Figure 4 embodiment;

FIGURE 6 illustrates a further embodiment of a ground plane using the cylinders of Figure 5;

FIGURE 7 illustrates a still further embodiment of a ground plane; FIGURE 8 illustrates a still further embodiment of a phasing plane;

FIGURE 9a illustrates a top view of another embodiment of the invention; and

FIGURE 9b is a cross-section of the embodiment of Figure 9a.

Brief Description For Carrying Out The Invention

Referring to Figure 1, it can be seen that the antenna reflector in accordance with a first embodiment of the invention comprises a ground plane, illustrated generally at 1 _> and a phasing plane illustrated at 3. The planes are connected by spacers 5 which maintain the two planes in connected, but spaced, relationship.

Turning to Figure 2, in one embodiment, the phasing plane 3 comprises a metallic sheet having cut out slots 9.

The slots form single or crossed dipoles. In accordance with the invention, the slots are of unequal size and may be unequally spaced from each other.

With a phasing plane as illustrated in Figure 2, the ground plane can comprise a metallic sheet which would be of the same size as the metallic sheet 7 of Figure 2. Turning now to Figure 3, in another embodiment, the phasing plane comprises a dielectric sheet 11. Metallic patterns 13 are printed onto the dielectric sheet to form the dipoles. Once again, the painted on metallic patterns are of different size and of different spacing therebetween. In the embodiment of Figure 3, the ground plane may also comprise a metallic sheet of the size as the dielectric sheet 11.

In a further embodiment, illustrated in Figure 4, the phasing plane comprise frame elements 15, 17, 19 and 21.

The frame elements may be rigid members of, for example, a plastic material. Alternatively, they can be flexible members of, for example, a rope like material or the like.

The embodiments of Figures 2 and 3 are also enclosed by frame elements.

The frame elements enclose a plurality of different sized and differently spaced cylinders 23. The cylinders are made of a metallic material.

As can be seen, the cylinders are strung along vertical strands 25 and horizontal strands 27. As seen in Figure 5, each metallic cylinder 23 comprises a horizontal opening 29 extending along the axis of the cylinder, and a vertical opening 31 which extends transversely to the axis of the cylinder. As can be seen, the vertical strands 25 extend

through the opening 31 and the horizontal strands 27 extend through the opening 29.

Figure 6 illustrates an embodiment of the ground plane using metallic cylinders. In Figure 6, the metallic cylinders 230 are all of equal size and there is equal spacing between the cylinders. Once again, the ground plane is enclosed by frame elements 15, 17, 19 and 21. The cylinders are strung by vertical strands 25 and horizontal strands 27. A further embodiment of a ground plane is illustrated in Figure 7. In Figure 7, the ground plane is also enclosed by frame elements 15, 17, 19 and 21. The ground plane is then made of vertical strands 250 and horizontal strands 270. The strands are made of a dielectric material, for example, Kevlar. Cylinders 231 are painted onto the Kevlar strands with a metallic paint. In the Figure 7 embodiment, each of these cylinders is of equal size and is equally spaced from every other cylinder.

A phasing plane which uses the same approach as Figure 7 is illustrated in Figure 8. In Figure 8, once again, the frame elements 15, 17, 19 and 21 enclose the plane. The plane includes vertical strands 250 and horizontal strands 270. The strands are also of a dielectric material, for example, Kevlar. Cylinders 233 are painted onto the strands with a metallic material. In the Figure 8 embodiment, the cylinders are of an unequal size and are unequally spaced from each other.

On the phasing plane, the different approaches provide dipoles which, because of their unequal size and spacing, will have different reactions to an E-M wave of a given frequency. Thus, when an E-M wave of a given frequency is directed at the phasing plane, each dipole will cause it to reflect at a different angle, and the array of dipoles on the phasing plane of the reflector are adjusted to provide the proper phase relationships between the incident and reflected waves. The total reflected wave will constitute the sum of all of the reflected waves.

The dipoles on the ground plane are made to be resonant at the center frequency of the bandwidth of the antenna reflector.

Both the ground planes and the phasing planes, especially as shown in Figures 4-8, can be folded up in the manner of a window blind with horizontal slats.

Referring now to Figure 9a, we have shown a top view of the parabolic dipole array according to another embodiment of the present invention. The array 90 consists of an array of dipoles or microstrip patches 91 suspended over a parabolic ground plane 92. The distance A and B between the dipole elements or patches is constant everywhere thus the dipole array assumes a parabolic shape as well.

The ground plane 92 can be made of any electrical conductor such as aluminum or copper. The dipole elements or patches 91 are etched onto a Kapton sheet of about .001 inch thickness using standard etching techniques. The Kapton sheet is supported and separated from the parabolic ground plane 92 using a foam or Kevlar honeycomb structure 93. The feed horn 94 is used to launch an electromagnetic wave at the antenna array. The feed horn is placed some distance in front of the antenna array. The exact location is determined by the length of the dipoles or patches. The dipole elements are of a predetermined length so as to convert the received electromagnetic wave into a shaped beam.

Although several embodiments have been described, this was for the purpose of illustrating, but not limiting, the invention. Various modifications, which will come readily to the mind of one skilled in the art, are within the scope of the invention as defined in the appended claims.