Communications: radio wave antennas – Antennas – Antenna components
Reexamination Certificate
1999-11-18
2001-08-21
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
Antenna components
C343S840000, C343S881000, C343S882000
Reexamination Certificate
active
06278416
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to support structures, such as but not limited to those for deploying energy-directing surfaces (e.g., radio wave or solar reflectors), in either terrestrial or space applications, and is particularly directed to a new and improved antenna mesh deployment architecture, that is compactly stowable, and deploys to a configuration that supports a mesh-configured reflector surface in substantial conformity with an intended surface of revolution, having minimized recessed (e.g., ‘scalloped’) edges at its periphery.
BACKGROUND OF THE INVENTION
The use of large reflector structures for satellite communication networks is becoming more widespread as demand for mobile communications increases. As the aperture size or number of reflectors per space-deployed communication site increases, the availability of lightweight, compactly packaged antenna structures is a key element in industry growth. A non-limiting example of an umbrella type and folded rib mesh reflector include the Tracking Data Relay System (TDRS) mesh reflector antenna system, deployed by the National Aeronautics and Space Administration (NASA). In its deployed state or condition, the metallic mesh reflector structure of the TDRS system measures 4.8 meters in diameter; yet, when folded, it is readily stowed in a cylindrical volume approximately one meter in diameter and three meters in length. Each satellite in the deployed TDRS constellation employs two such antennae.
In addition to the TDRS antenna system, there are other communications systems, such as the Asian Cellular Satellite (ACeS), that employ two mesh reflectors, each having an aperture size of twelve meters. Each of these reflectors, with folding ribs, is sized to fit within a cylindrical volume approximately one meter diameter and four and one-half meters in length. By folding the ribs, the same TDRS-configured volume, moderately lengthened, can package a reflector that is more than twice the TDRS size.
There are other reflector designs in which rigid elements are oriented in either a radial direction from the reflector center or a circumferential direction at the reflector periphery, and may employ foldable rigid elements to improve packaging. Non-limiting examples of such prior art antenna structures include the following U.S. Pat. Nos.: 5,787,671; 5,635,946; 5,680,145; 5,574,472; 5,451,975; 5,446,474; 5,198,832; 5,104,211; and 4,989,015;
The basic architecture of such ‘umbrella’ mesh reflector designs is diagrammatically shown in the perspective view of
FIG. 1
, as comprising an arrangement of radially extending ribs
10
, and associated sets of circumferentially extending, mesh support cords
20
cross-connected between the ribs. When deployed from its stowed condition, this structure supports a generally mesh-configured material that serves as the intended reflective (e.g., electrically conductive, RF reflective) surface
30
of the antenna.
As shown in greater detail in the side view of
FIG. 2
, each set of circumferential cords
20
is organized into pairs, comprised of a front cord
21
and a rear cord
23
, that are joined to one another via multiple tie cords
25
therebetween. Opposite ends of the front and rear cords
21
,
23
are respectively attached to a front tie
12
, and rigid rear stand-offs
14
, supported by and extending generally orthogonally from the ribs
10
, so that each cord set
20
is placed in tension by a pair of radial ribs
10
in a generally catenary configuration. The reflective mesh
30
is retained against the underside of the front cords
21
at their attachment points
16
with the tie cords
25
. As a consequence, when the support structure is deployed, the cords sets
20
define a prescribed surface with which the attached tensioned mesh
30
conforms.
Radially outermost or ‘intercostal’ cord sets
20
RO in
FIG. 1
, to which the outer peripheral edge
32
of the mesh is attached, are connected to stand-offs at distal ends
13
of the ribs
10
. Because of the tensioning forces acting on the cord sets and on the mesh held thereby, each intercostal cord set
20
RO follows a generally ‘scalloped’ arc
34
, that is recessed radially inwardly, away from circular perimeter
35
of the surface of revolution with which the circumference of the deployed mesh surface
30
should ideally conform.
Because these scalloped arcs
34
leave (generally elliptically shaped) gap areas or openings
36
between the actual (scalloped) perimeter
34
of the deployed mesh surface
30
and the wider diameter generally circular perimeter
35
passing through the distal ends
13
of the ribs
10
, the effective area of the reflective mesh
30
is generally limited to the radius to the interiormost scalloped edges of its intercostal cord sets, rather than the longer radial lengths of the ribs
10
. In other words, due to the loss of reflective surface material in the scalloped gaps
36
, the structure supporting the mesh surface must be increased in size (diameter). The increase is such that the resulting area of the actual mesh surface, exclusive of the scallops, is equal to the area of the desired reflector.
A first shortcoming of this conventional configuration is the increased payload associated with the larger rib lengths required to stow and deploy a given mesh surface area. Secondly, since the perimeter of the actually deployed surface is scalloped rather than circular, the additional mesh reflector material in the vicinity of the distal ends of the ribs introduces anomalies into the intended radiation profile of the antenna. Although the size of the gaps could be reduced by increasing the number of ribs (thereby placing more ribs closer together), such an approach would be self-defeating by the addition of substantial weight and volume.
SUMMARY OF THE INVENTION
In accordance with the present invention, the above-discussed deficiencies of conventional ‘umbrella’ configured mesh reflector structures are substantially mitigated by a support architecture, that effectively translates the terminus of the mesh to the diametric edge of the geometric surface actually required by the antenna, rather than at the interior recessed edges of a scalloped perimeter. For this purpose, the invention employs a gap-filling structure that supports a mesh-attachment, outermost intercostal cord set that substantially conforms with the intended (e.g., circular) perimeter geometry of the deployed mesh.
The outermost intercostal cord set is supplemented by at least one, and preferably a plurality of, additional, auxiliary intercostal cord sets installed between each pair of structural support members, herein referred to as ‘ribs’. These plural intercostal cord sets are attached to intercostal and radial compression members in a manner that fills in the scallop-shaped gaps of the conventional architecture (FIG.
1
), with an auxiliary mesh attachment structure for conforming the perimeter of the mesh surface with its intended geometrical shape (e.g., generally a circle). The combination of these additional intercostal cord sets and their associated intercostal and radial compression members provides for a more accurate mesh geometry and improved reflector surface stability.
A set of such gap-filling intercostal and radial compression members employed in one of the radial sectors of the multi-rib architecture contains a first, flexible intercostal compression reactor member and a plurality of second, generally radially extending, flexible compression members that are sized to fill the shape of the scalloped gap. Each of the compression members has a cross section that is reduced considerably relative to that of the radial ribs. Also, the compression members may made of the same or similar materials as the support structure, rib members.
A flexible intercostal compression reactor member is installed between stand-offs affixed to distal ends of adjacent ribs. Interior ends of the radial compression members terminate and are attached at spaced apart locations along the intercostal compression reactor member. Secon
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Chan Shih-Chao
Harris Corporation
Wong Don
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