The technical field of this disclosure concerns compact antenna system structures, and more particularly, compact deployable reflector antenna systems.
Various conventional antenna structures exist that include a reflector for directing energy into a desired pattern. One such conventional antenna structure is a hoop column reflector (HCR) type system, which is known to have a high compaction ratio. The HCR antenna system includes a hoop assembly, a collapsible mesh reflector surface and an extendible mast assembly. The hoop assembly includes a plurality of link members extending between a plurality of hinge bodies and the hoop assembly is moveable between a collapsed configuration wherein the link members extend substantially parallel to one another and an expanded configuration wherein the link members define a circumferential hoop. The reflector surface is secured to the hoop assembly and collapses and extends therewith. The hoop is secured by cords relative to top and bottom portions of a mast that maintains the hoop substantially in a plane. The mast extends to release the hoop, pull the mesh reflector surface into a shape that is intended to concentrate RF energy in a desired pattern, and tension the cords that locate the hoop. An example of an HCR type antenna system is disclosed in U.S. Pat. No. 9,608,333.
There is a market need for a low-cost, offset-fed reflector that can be easily modified for a wide variety of missions. Offset-fed reflectors are in great demand for antenna RF and system integration purposes as they potentially offer higher efficiency, reduced blockage and sidelobes, enable integration with separate feed subassemblies, and so on.
This document concerns a reflector system for an antenna. The reflector system includes a hoop assembly comprising a plurality of link members extending between a plurality of hinge bodies. The hoop assembly is configured to automatically, passively expand between a collapsed configuration wherein the link members extend substantially parallel to one another and an expanded configuration wherein the link members define a circumferential hoop.
A collapsible mesh reflector surface is secured to the hoop assembly. Consequently, when the hoop assembly is in the collapsed configuration, the reflector surface is collapsed within the hoop assembly and when the hoop assembly is in the expanded configuration, the reflector surface is expanded to a predetermined shape that is intended to concentrate RF energy in a desired pattern.
The system also includes a mast assembly, which is comprised of an extendible boom. The hoop assembly is secured by a plurality of hoop positioning cords relative to a top portion of the boom. Further, a plurality of primary catenary cords secure the hoop assembly to a bottom portion of the boom. Consequently, upon extension of the boom to a deployed condition, the hoop assembly is supported by the boom. In this deployed condition, a central axis of the hoop assembly can be substantially parallel to the central axis of the extendible boom or they may be oriented at a slight angle. Unlike certain prior art antenna systems which may be configured with the mast centered inside the hoop, the mast for this reflector system is offset in position relative to a central axis of the hoop assembly. This offset is defined by a first predetermined distance when the hoop assembly is in the collapsed configuration, and a second predetermined distance greater than the first predetermined distance when the hoop assembly is in the expanded configuration. The predetermined shape of the reflector is defined by a perimeter shape of the hoop assembly when in the deployed condition, and the perimeter shape is fixed by a plurality of hoop stability cords which extend across the hoop assembly.
In addition to being supported by the hoop positioning cords and the primary catenary cords, the hoop assembly is also secured by a plurality of secondary catenary cords. Each of these secondary catenary cords respectively extends from an intermediate portion of the extendible boom to a corresponding primary catenary cord. Each of the secondary catenary cords is advantageously aligned in a cord plane with a corresponding one of the primary catenary cords and a corresponding one of the hoop positioning cords. In this regard it may be noted that the reflector can have a reflector surface contour. The reflector surface contour is determined by a plurality of surface shaping ties. These surface shaping ties extend between the reflector surface and at least one of the primary catenary cords and the secondary catenary cords.
In some scenarios, the extendible boom is comprised of a plurality of links that slide relative to one another, such that the extendible boom automatically extends from a collapsed configuration where the links are nested together and an expanded configuration wherein the link members extend substantially end to end. In other scenarios, the extendible boom is comprised of a spoolable extensible member.
The reflector system can also include a second hoop assembly. The second hoop assembly can include a second collapsible mesh reflector surface secured to the second hoop assembly. Consequently, when the second hoop assembly is in the collapsed configuration, the second collapsible mesh reflector surface is collapsed within the second hoop assembly and when the second hoop assembly is in the expanded configuration, the second collapsible mesh reflector surface is expanded to a second predetermined shape that is intended to concentrate RF energy in a second desired pattern. The second hoop assembly can expand in a manner similar to the first hoop assembly, and may include a similar arrangement of cords to establish a desired reflector shape. Consequently, a second central axis of the second hoop assembly can in some scenarios be substantially parallel to the central axis of the extendible boom, or in the alternative may be oriented at a slight angle. Further, the second central axis can be offset in position relative to the central axis of the extendible boom and relative to the central axis of the first hoop assembly.
The solution can also concern a method of deploying a reflector of a reflector system comprising a housing, a mast assembly, and a hoop assembly as described above. The method can involve extending the boom from the housing such that a cord tension between the hinges and the mast facilitates a controlled deployment of the hoop assembly. The hoop assembly is deployed in a position adjacent to the boom such that a central axis of the hoop assembly is substantially parallel with a central axis of the boom but is offset a predetermined distance. Consequently, the central axis of the boom is maintained external of a perimeter of the hoop assembly. The hoop assembly is urged out of the housing prior to fully deploying the boom in the manner described above.
This disclosure is facilitated by reference to the following drawing figures, in which like numerals represent like items throughout the figures, and in which:
It will be readily understood that the solution described herein and illustrated in the appended figures could involve a wide variety of different configurations. Thus, the following more detailed description, as represented in the figures, is not intended to limit the scope of the present disclosure, but is merely representative of certain implementations in various different scenarios. While the various aspects are presented in the drawings, the drawings are not necessarily drawn to scale unless specifically indicated.
Reference throughout this specification to features, advantages, or similar language does not imply that all of the features and advantages that may be realized should be or are in any single embodiment of the invention. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present invention. Thus, discussions of the features and advantages, and similar language, throughout the specification may, but do not necessarily, refer to the same embodiment.
Shown in
As illustrated in
In some scenarios, the housing 101 can comprise a portion of a spacecraft which comprises various types of equipment, including radio communication equipment. The radio communication equipment can include a radio frequency (RF) feed 105 which is used for illuminating the reflector with RF energy in a transmit mode, and for receiving RF energy which is focused by the reflector on the feed 105 in a receive direction. Accordingly, the combination of the RF feed 105 and the reflector system 100 can facilitate a reflector type antenna system.
The housing 101 may have various configurations and sizes depending on the size of the reflector assembly 103. By way of example, the system 100 may include a deployable mesh reflector with a 1 meter aperture that is stowed within a housing 101 that is of 2 U cubes at packaging and having an approximately 10 cm×10 cm×20 cm volume. Alternatively, the system 100 may include a deployable mesh reflector with a 3 meter aperture that is stowed within a housing 101 that is of 12 U cubes at packaging and having an approximately 20 cm×20 cm×30 cm volume. Of course, the solution is not limited in this regard and other sizes and configurations of the systems are also possible. In some scenarios, the housing 101 is in the nanosat or microsat size range.
The hoop assembly 104 is supported on the boom 107 by means of a plurality of cords. The cords are attached to the boom by anchors 132, 134 which are located respectively at a top and bottom portion 117, 119 of the boom. Anchors 132, 134 can be any structure that is suitable for securing the ends of the cords to the top and bottom portions of the boom. The cords include a plurality of hoop positioning cords 108 which extend to the hoop assembly from anchor 132 at the top portion 117 of the boom, and a plurality of primary catenary cords 110 which extend to anchor 134 at the bottom portion 119 of the boom. In some scenarios, the hoop positioning cords and the primary catenary cords can be attached to the hoop assembly 104 at selected ones of a plurality of hinge bodies 314. These hinge bodies 314 are described below in greater detail in relation to the description of the hoop assembly.
Upon extension of the boom to a deployed condition, the hoop assembly 104 is fully supported by the boom as shown in
The mesh reflector surface 106 has a predetermined shape when the hoop assembly is deployed such that the reflector surface will concentrate RF energy in a predetermined pattern. The predetermined shape of the reflector surface 106 includes a reflector surface contour which is determined by a plurality of surface shaping tie cords 114 that extend between the reflector surface 106 and at least one of the primary catenary cords 110 and the secondary catenary cords 115. As such, the mesh reflector surface can be parabolic or can be specially shaped in accordance with the needs of a particular design. For example, in some scenarios the reflector surface can be specially shaped in accordance with a predetermined polynomial function. Further, the reflector surface 106 can be a surface of revolution, but it should be understood that this is not a requirement. There are some instances when the reflector surface can be an axisymmetric shape, for example, in order to concentrate RF energy into a predetermined non-symmetric pattern.
It can be observed in
When the hoop assembly is fully deployed as shown in
A drive train assembly 116 is positioned within the housing 101 and is configured to extend the boom 107 from the stowed configuration shown in
In other scenarios, the mast assembly 102 may include a plurality of links joined by hinges which are moveable between a collapsed configuration wherein the link members extend substantially parallel to one another and an expanded configuration wherein the link members align co-linear to one other. As another example, the extendible mast assembly may include a plurality of links that slide relative to one another such that the mast assembly automatically extends from a collapsed configuration where the links are nested together and an expanded configuration wherein the link members extend substantially end to end. These and other mast configurations are described in greater detail in U.S. Patent No. 9,608,333 which is incorporated herein by reference.
As explained hereinafter, the hoop assembly 104 is advantageously configured to be self-deploying such that the deployed hoop structure shown in
Certain details of an exemplary hoop assembly 104 are illustrated with respect to
As shown in
As shown in
The configuration of the hoop assembly 104 as shown in
The mesh reflector surface 106 is secured at its periphery to the hoop assembly 104 and collapses and extends therewith. Hoop positioning cords 108 and primary catenary cords 110 attach selected hinge bodies 314 to both top and bottom portions 117, 119 of the boom 107. Accordingly, a load path goes from one end of the boom, to the hinge bodies 314 and to the other end of the boom using the cords. The hoop positioning cords 108 and the primary catenary cords 110 maintain the hoop assembly 104 in a plane. Additional surface shaping tie cords 114 that extend between the reflector surface 106 and at least one of the primary catenary cords 110 and the secondary catenary cords 115 are used to pull the mesh down into a predetermined shape selected for the reflector surface. Accordingly, the hoop assembly 104 is not required to have depth out of plane to form the reflector into a parabola.
Unbalanced forces applied to the hoop assembly by the hoop positioning cords 108, primary catenary cords 110, secondary catenary cords 115, and tie cords 114 can tend to distort the perimeter shape of the hoop assembly 104. To prevent such distortion and maintain a predetermined perimeter shape, hoop stability cords 124 are provided which extend directly across the aperture of the hoop assembly 104 between hinge bodies 314. The exact configuration of these hoop stability cords can depend in part on the perimeter shape of the hoop assembly that is to be maintained. In some scenarios the hoop stability cords 124 can extend between offset opposing hinge bodies 314 as shown in
In some scenarios it can be advantageous to include more than one reflector as part of an antenna system. In such scenarios, a deployable mesh reflector system 200 can be provided which is similar to reflector system 100, but comprised of dual reflector assemblies 103a, 103b so as to achieve the configuration shown in
The mast assembly 202 is similar to the mast assembly 102 insofar as it includes an extendable boom 207. The extendable boom 207 is similar to extendable boom 107 but is configured to support the reflector assemblies 103a, 103b on opposing sides of its central axis 111. The reflector assemblies 103a, 103b respectively comprise collapsible, mesh reflector surfaces 106a, 106b which are respectively supported by circumferential hoop assemblies 104a, 104b. The reflector assemblies 103a, 103b and the mast assembly 202 are configured to collapse into a stowed configuration which fits within the interior space of the housing 201. When the antenna system arrives at a deployment location (e.g., an orbital location) the antenna can be transitioned to the deployed configuration shown in
Each hoop assembly 104a, 104b is supported by the boom 207 by means of a plurality of cords in a manner similar to that which has been described herein with respect to reflector system 100. Accordingly, support for each hoop assembly can include a plurality of hoop positioning cords 108 which extend to the hoop assembly from a top portion 117 of the boom, and a plurality of primary catenary cords 110 which extend to a bottom portion 119 of the boom. A plurality of secondary catenary cords 115, each respectively extends from a portion of the hoop assembly that is adjacent to the extendible boom, to a corresponding primary catenary cord 110. As may be understood with reference to
The presence of the second reflector assembly supported on the boom 207 advantageously balances the bending forces that are applied to the boom. As such, the reflector system 200 differs from reflector system 100 insofar as it does not require counterbalancing structural components such as struts 121, and stability tension cords 112 to counterbalance bending loads applied to the extendible boom 207.
Furthermore, the described features, advantages and characteristics disclosed herein may be combined in any suitable manner. One skilled in the relevant art will recognize, in light of the description herein, that the disclosed systems and/or methods can be practiced without one or more of the specific features. In other instances, additional features and advantages may be recognized in certain scenarios that may not be present in all instances.
As used in this document, the singular form “a”, “an”, and “the” include plural references unless the context clearly dictates otherwise. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. As used in this document, the term “comprising” means “including, but not limited to”.
Although the systems and methods have been illustrated and described with respect to one or more implementations, equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In addition, while a particular feature may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular application. Thus, the breadth and scope of the disclosure herein should not be limited by any of the above descriptions. Rather, the scope of the invention should be defined in accordance with the following claims and their equivalents.