Deployable loop antenna

A base, a spool, and an antenna structure coupled to the spool has ends that are affixed to the base. The antenna structure is wound about the spool in a stowed state, and unwound to form a loop antenna in the deployed state. The antenna structure may be a bistable composite tape with a cross-sectional curvature and having one or more antenna conductors embedded therein. A storage containment device holds the antenna structure in the stowed state. When in the stored state, the antenna structure generates a strain force against the spool biased to unwind and deploy the antenna structure to form a loop antenna when released. Another embodiment adds a second spool rotating in a direction opposite the first to achieve either state. A further embodiment uses two loop antennas by winding two antenna structures around two pairs of spools, respectively.

FIELD OF THE INVENTION

The present invention relates to the field of antennas, and more particularly, to deployable antennas for space vehicles.

BACKGROUND OF THE INVENTION

Antennas are used in a number of terrestrial and orbital applications. With larger apertures being attractive for their higher gain, it is desirable to deploy space-based antennas from a small storage volume. This allows large antennas to fit within the confines of the launch vehicle and more easily survive the dynamic loading of the launch vehicle.

For example, U.S. Pat. No. 5,969,695 to Bassily et al., entitled “Mesh Tensioning, Retention and Management Systems for Large Deployable Reflectors,” relates to systems for controlling and retaining tension in a mesh reflector in the deployed condition, as well as for managing the mesh during launch and transport in the stowed condition.

U.S. Pat. No. 5,313,221 to Denton entitled “Self-deployable Phased Array Radar Antenna,” is directed to a phased array monopole antenna that has a single layer membrane upon which a plurality of antenna units are attached. Each antenna unit has a flexible curved antenna blade which bends over or springs up when the membrane is rolled or unrolled on a drum.

Also, U.S. Patent Application No. 2012/0167943 to Blanchard et al., entitled “Unwindable Flat Solar Generator,” is directed to a solar generator deployment device that includes an assembly having a plurality of tape-springs supporting a windable membrane on a face of which is arranged a plurality of elements capable of converting the solar energy into electrical energy. The tape-springs and membrane are co-wound around a unique radius of curvature equal to the natural radius of curvature of folding of the tape-spring in the wound state.

Tape-springs are known as being tapes capable of changing from the wound state to the unwound state essentially by virtue of their own elastic energy. In the unwound state, tape-springs normally have a rigidity which is capable of maintaining them in that state. Conventional tape-springs are generally metallic, and it may be difficult to control their unfolding.

However, conventional tape-springs made of composite material have also been developed and make it possible to better control their winding radius. They also have a high rigidity/weight ratio and a low expansion coefficient.

Various studies indicate that it is possible to render a composite tape-spring bistable. Such studies include “Carbon Fibre Reinforced Plastic First antenna structure s”, J. C. H. Yee et al., AIAA 2004-1819, and “Analytical models for bistable cylindrical shells”, S. D. Guest et al. Such bistable tape-springs are mechanically stable both in the unwound state and in the wound state. The bistable tape-springs remain stable in the wound state around their natural radius of curvature, without external force. All that is needed is to unfold one end thereof, with a force of low intensity, exerted by a motor-drive system for example, to trigger the unwinding.

However, there may be a need for a space loop antenna that is self-deployable from a compact storage size without the use of motors or actuators.

BRIEF SUMMARY OF THE INVENTION

With the above in mind, embodiments of the present invention are related to a loop antenna for use in space that is self-deployable from a compact storage space without the use of motors or actuators.

Advantages may be provided by an embodiment that is directed to an antenna including a base, at least one spool, and an antenna structure coupled to the spool or spools having ends that are affixed at the base, the antenna structure being configured to actuate between a stowed state and a deployed state. The stowed state is defined by the antenna structure being wound or coiled about the spool(s). The deployed state is defined by the antenna structure being unwound from the spool(s) to form a loop.

The antenna structure may be a bistable composite tape having one or more antenna conductors embedded therein. The bistable composite tape has a cross-sectional curvature. The bistable composite tape may be a bistable fiber-reinforced composite tape including first and second forty-five degree (45°) biased woven layers and a unidirectional lamina layer sandwiched therebetween. Additionally, multiple loop antenna connectors may be embedded in the bistable composite tape. The connectors may lie in parallel.

The ends of the antenna structure are affixed to the base such that in the stowed state, the antenna structure generates and stores a strain force applied to the spool(s) which is biased toward the deployed state. A storage containment device is configured to hold the antenna structure in the stowed state, and a release mechanism configured to release the antenna structure so that, without external assistance, the coiled antenna structure unwinds into the deployed state.

The antenna structure is comprised of two connected sections, with each having a curved cross section with a radius of curvature. The respective curved cross sections form concave surfaces facing in opposite directions when the antenna structure is in the deployed state. The cross sections are flattened when the sections are wound around the spool in the stored state.

Advantages may be provided by another embodiment of an antenna including a base, first and second spools, an antenna structure coupled to each of the spools and having ends affixed to the base, the antenna structure being configured to actuate between a stowed state and a deployed state. The stowed state is defined by respective portions of the first antenna structure being wound or coiled about the first and second spools, and the deployed state is defined by the antenna structure being unwound from about the first and second spools to form a first loop.

Additionally, or alternatively, the antenna may include third and fourth spools, and a second antenna structure coupled to each of the third and fourth spools and having ends that are affixed at the base, with the second antenna structure being configured to actuate between the stowed state and the deployed state. The stowed state is also defined by respective portions of the second antenna structure being wound about the third and fourth spools, and the deployed state is also defined by the second antenna structure being unwound from about the third and fourth spools to form a second loop. The first and second loops would lie in respective intersecting planes. The planes could intersect orthogonally.

DETAILED DESCRIPTION OF THE INVENTION

The present embodiments may provide a loop antenna that is remotely deployable from a small storage size, yet that presents a larger aperture when deployed so as to deliver high gain. Such a storage and deployment approach enables larger loop antennas to fit within the confines of a space-limited launch vehicle and more easily survive the dynamic loading of the launch vehicle, and then to deploy to a pre-determined, operable shape upon demand.

The features that deliver these advantages may be found in the rolling of the loop antenna structure around a single or double spool that is deployed in a loop (e.g. in either a diamond or circular loop configuration), and the use of thin flexible and bistable composite tape elements with electrical antenna conductors embedded therein.

A notable use of the deployable loop antenna is for a radio frequency (RF) receive antenna, either for communications or for passive measurement of RF fields or returns from an ionosphere sounding device in terrestrial and orbital applications.

Turning to the drawings,FIG. 1is a perspective view of a deployable loop antenna10according to features of the present invention. Loop antenna10includes base12, rotatable spool14, and antenna structure16coupled to spool14and having ends that are affixed at base12. End17is shown, while the other end is not. Antenna structure16is configured to actuate between a stowed state and the illustrated deployed state. The stowed state is defined by antenna structure16being wound about spool14, as will be described below. The deployed state is defined by antenna structure16being unwound from around spool14to form a loop antenna.

Storage containment device20is configured to hold antenna structure16in the stowed state, and release mechanism22is configured to release antenna structure16to allow it to transition into the deployed state. As shown, the storage containment device20is a frame with a hinged door defining the release mechanism22. Other embodiments are contemplated, for example, a tensioned strap could be severed to release antenna structure16into the deployed state, or a removeable pin could be inserted into spool14adjacent base12to hold antenna structure16in the stowed state, and withdrawn to allow its deployment. Also, a limiter24, such as a cable or cord, may be coupled between the spool14and the base12to limit the travel of spool14and, concomitantly, the deployment of antenna structure16, and aid in defining its resulting shape in the deployed state (e.g., the diamond loop inFIG. 1).

FIGS. 2-4illustrate that the common elements of the concept that can be applied to loop antennas in several different configurations.FIG. 2is a flow diagram illustrating the single spool antenna embodiment ofFIG. 1being rolled up into the stowed state.FIG. 3is a flow diagram illustrating another embodiment the present invention comprising deployable loop antenna30, including spool34and spool35. Loop antenna30is shown transitioning from the deployed state into the stowed state.

FIG. 4is a flow diagram illustrating deployable loop antenna40, another embodiment of the present invention, comprised of antenna structures42and43using first through fourth spools44-47. Loop antenna40is shown transitioning from its deployed state to its stowed state. In its deployed state, spools44and45lie in a plane orthogonal to a plane including spools46and47.FIG. 4shows a benefit of the two spool approach in that two orthogonal loops are coupled at the distal extent49of the antenna40and stowed together.

Referring toFIG. 5, antenna structure16may be a bistable composite tape50having one or more antenna conductors52embedded therein. The antenna conductors52may be embedded in parallel in the bistable composite tape50. The antenna conductors52are electrically coupled at or near the base12and may include the use of an antenna tuner, a matchbox, antenna tuning unit (ATU), antenna coupler, or feedline coupler coupled between a radio transmitter or receiver and the antenna conductors to improve power transfer between them by matching the impedance of the radio to the antenna's feedline (such features are not shown), as would be appreciated by those skilled in the art. A basic form of antenna10includes a single conductor52embedded in tape50, but multiple parallel conductors52can be embedded therein to provide additional antenna gain by wiring them to produce a system of several loops, as would be appreciated by those skilled in the antenna art.

As shown inFIG. 6, bistable composite tape50has a cross-sectional curvature, and is composed of bistable fiber-reinforced composite tape. The bistable fiber-reinforced composite tape is composed of first and second forty-five degree (45°) biased woven layers53and54and a unidirectional lamina layer56sandwiched therebetween. The utilization of bistable composite tape50for antenna structure16allows the antenna10to roll around the spool14in a way that controls the deployment of loop antenna10. More particularly, the bistability enables linear controlled unrolling of tape50along a pre-determined kinematic path without random billowing. The bistability is imparted through the composite layup as well as the curved cross-section.

Referring toFIG. 7, tape50is composed of sections58and60having respective radii of curvature represented by vectors R58and R60drawn from their centers to their curved surfaces, respectively. The vectors thus point towards the concavity in each section. In reference to antenna10shown in its deployed state inFIG. 1, sections58and60would lie on the two sides of spool14and base20, respectively. The concave surface of section58thus faces inwards toward the geometric center of the loop of antenna10, while the concavity of section60faces outwardly, away from the geometric center. The orientation of the concavities defined by the directions of R58and R60are shown for the clockwise rotation of spool14shown InFIG. 2. If spool14were to rotate in a counterclockwise direction, the orientations of R58and R60would be reversed so that the respective concave surfaces would face in the opposite direction as shown. As will be discussed below, tape50is flattened when rolled into the stored state.

In reference to antenna30inFIG. 3, section58could be considered as that section of tape50coupling spools34and35, with section60being further divided into two sub-sections, sub-section62coupling base12and spool34, and sub-section64coupling base12and spool35. The underlying principle remains as outlined with respect to antenna10; that is, the concave surface for section58would face toward the geometric center of the loop of antenna30when in its deployed state, while the concavities for the two sub-sections62and64of section60would face outwards, away from the geometric center.

Referring to antenna40inFIG. 4, antenna structure42is comprised of section58of tape50coupling spools44and45, sub-section62coupling base12and spool44, and sub-section64coupling base12and spool45. For antenna40and antenna structure42in the deployed state, the concave surface for section58would face inward, toward the geometric center of the loop of antenna structure42, while the concave surfaces of sub-sections62and64would face outward, away from the geometric center. For antenna structure43, section66couples spools46and47, with sub-section68coupling base12and spool46, and sub-section70coupling base12and spool47. The concave surface for section66would face inward, toward the geometric center of the loop of antenna structure43, while the concave surfaces of sub-sections68and70would face outward, away from the geometric center.

Strain energy is used to actuate the deployment of the antennas10,30and40. This strain energy is generated and stored by rolling and flattening curved cross sections of the respective antenna structures in the stored state. This means that the loop antennas10,30and40can deploy via their own strain energy without any external motors or actuators. A simple release mechanism22is used to initiate deployment by releasing the antenna structure from its coiled storage in storage containment device20. As such, the end17and the other end (not shown) of antenna structure16are fixed to the base12such that in the stowed state, antenna structure16stores a strain energy imparted thereto and is configured to be biased toward the deployed state. Without the clamped ends, the bi-stability might actually keep antennas10,30and40in their respective stowed states without having the strain energy necessary to deploy them.

Turning toFIG. 8, Antenna10(or antennas30and40) are preferably for use with a space vehicle72, which may be a spacecraft, space capsule, space station and/or satellite, for example. Other spacecraft are also contemplated. Space vehicle72may typically include a body74housing various electronic components, solar arrays76and deployable antenna10.

The above description provides specific details, such as material types and processing conditions to provide a thorough description of example embodiments. However, a person of ordinary skill in the art would understand that the embodiments may be practiced without using these specific details.