FIELD OF INVENTION

This invention relates to deployable antennae in general and to shape memory deployable dish antenna in particular.

BACKGROUND OF INVENTION

Parabolic dish antennae are desirable for space communications as they offer high so-called antenna ‘gain’ (concentration and beam width of the signal energy) and through it, extend a satellite's effective communications range. For a given electromagnetic wavelength, the larger the diameter of a dish antenna, the higher its ‘gain’.

Rigid permanent dish antennae due to their size and geometry are impractical for smaller satellites, such as ‘mini’-, ‘micro’- and ‘nano’-types of satellites presently gaining wider usage. Present deployable dish antennae have been largely unfeasible as well, due to their size, shape, weight and their deployment mechanism complexity and mechanical interface requirements.

At present, deployable reflector dish antennae used in satellites generally fall into two groups. One group comprises dish antenna assemblies with several petal-shaped rigid elements forming a paraboloid reflector when unfolded. Because these elements are rigid, they are often stowed as a stack, to be opened and deployed rotationally.

The other group includes antenna reflectors which comprise a set of supports to which a flexible reflective membrane is attached. The supporting structures, such as radial ribs, are relatively rigid and are customarily stowed as an elongated bundle folded along its longitudinal axis. Some membrane support structures when deployed take a form of complex three-dimensional lattices which unfurl/unfold in space and support the attached reflective membrane in the required paraboloid shape.

A wide variety of the dish antenna deployment mechanisms exist or have been proposed. They include mechanical gearing assemblies, cables and tensioners and some limited shape memory actuators. Majority of them are mechanically quite complex and sometimes fail to fully deploy the antennae.

The present deployable dish assemblies are also awkward to store since they have to be located and oriented in very limited and specific ways to conform to the available envelopes aboard the launch vehicles while still be a part of a satellite.

Also because of the necessity to conform to the launch vehicle's configuration and the overall satellite physical envelope, the location selection of the antenna on a satellite itself is complicated, subject to numerous constraints and trade-offs.

Additionally, the sometimes off-axis placement of the antenna deployment mechanism adversely affects the center of gravity and rotational moments of a satellite and introduces complications for its in-flight positioning and maneuvering.

The addition of the deployment mechanisms and their rigid mechanical interfaces with the antennae themselves add to the assemblies' bulk, weight and complexity, the latter leading to their reduced overall reliability.

OBJECTIVES OF THE INVENTION

Thus, it is the objective of instant invention to provide a compact deployable dish antenna assembly which prior to deployment would be stowable in a variety of locations and at various attitudes on a satellite.

Another objective is to provide an antenna whose deployment would be reliable.

Another objective is to provide an antenna with high volumetric packing efficiency.

Yet another objective is to provide an antenna which would not require separate mechanical deployment mechanism.

Another objective is to provide an antenna which would be lightweight.

Yet another objective is to provide an antenna which would be compatible with deep space environment.

Another objective is to provide an antenna whose deployment would be energy efficient.

SUMMARY OF THE INVENTION

In accordance with the present invention, shape memory based deployable reflective dish antenna is described and its several embodiments are presented.

The shape memory antenna dish is formed into its desired deployed shape during manufacturing and subsequent ‘training’ where it is mechanically restrained in the deployed geometry while being heated at—or above the phase—or glass transition temperature of the shape memory material and is allowed to cool off. Thereafter, mechanical restraints are removed at which point the dish remains in its deployed configuration. The dish then is highly radially folded/corrugated to provide for efficient storage.

The shape memory dish antenna remains in its packaged configuration until deployment. At deployment it is heated to—or above the phase—or glass transition temperature of the shape memory material, and returns to their original ‘as-trained’ shape.

In addition to the dish itself, several shape memory antenna feeds are also presented, some with telescopic waveguide elements extended by several types of shape memory actuators and some having an extendable shape memory waveguides formed from corrugated tubular shape memory preforms. These feeds can be used interchangeably with the antenna dish.

Some antenna embodiments presented, in addition, include deployable sub-reflectors positioned above the main reflector and facing the feeds, and some use small patch antennas instead of the feeds and sub-reflectors.

Articles made with shape memory materials, their fabrication, ‘training’ and usage are known in their respective arts.

PRIOR ART

The prior art for deployable antennae is extensive, since these antennae have been a key piece of communications equipment for satellites from the dawn of space exploration. Deployable antennae with shape memory elements are relatively new, however.

For example, U.S. Pat. No. 7,710,348 to Taylor et al. teaches a deployable antenna reflector which utilizes a shape memory element to open conventional rigid ribs supporting a flexible reflector.

U.S. Pat. Nos. 8,259,033 and 9,281,569, both to Taylor et al. teach a deployable antenna reflector with longitudinal and circumferential shape memory stiffeners supporting a reflective elastic material.

U.S. Pat. No. 10,170,843 to Thomson et al. teaches mechanically actuated foldable support conventional ribs for antenna reflector and a pleated foldable reflector itself.

None of the prior art above suggests or teaches a deployable shape memory solid reflector created from a folded/corrugated preform.

None teaches deployable shape memory antenna feeds or sub-reflector supports, or using patch antennas in conjunction with parabolic reflectors.

OBJECTS AND ADVANTAGES

In contrast to the prior art mentioned hereinabove, the instant invention describes shape memory dish antenna which offers the following advantages.

High Volumetric Storage Efficiency

The reflector of the instant antenna system is tightly folded and merely requires application of heat for its deployment. Without any mechanical deployment apparatus, the resulting assembly offers a very dense package. The required heaters can be very compact as well, or the reflector can be heated directly with electric current.

In addition, the very shapes of the deployable reflector can be optimized for both storage and for deployment. Thus, greater design latitudes exist to optimize packaging, interface with the satellite, and deployment of the antenna.

Light Weight

Due to the absence of the relatively heavy mechanical deployment drives and their associated interfaces, the weight of instant antenna system is greatly reduced. The required heaters can be very thin and lightweight and in some applications the actuating heat can be generated by passing electric current directly through the reflector and feeds themselves. A completely passive heating and subsequent antenna deployment can be achieved by exposing the antenna system elements to sunlight by appropriately maneuvering the satellite. In the vacuum of space, solar heating can be considerable.

Simplified Construction

The instant antenna system comprises a very limited number of parts. There are basically no separate ‘actuators’ per se, other than heaters, with the system elements deploying themselves upon application of heat, by utilizing elastic energy stored at the time of packaging. The deployment heaters of instant invention are much smaller and less complicated than mechanical actuators of the present deployable antennas.

Improved Reliability

With thermal actuation of instant invention replacing present electro-mechanical actuators the instant antenna system is much more reliable, since the only moving parts are the very support elements themselves. With timed heater activation specific deployment sequences are possible to minimize the risk of malfunction or interference.

Easier Redundancy Implementation

Since it is much easier to provide redundancy to an electrically heated deployment system than to a mechanical actuator(s)-based one, the shape memory based antenna systems can have enhanced redundancy of its deployment apparatus.

Heating and Deployment by Sunlight

As mentioned above, since heating of satellite components by solar radiation in space can be considerable, the instant antenna system elements can be exposed to sunlight instead of heaters for deployment. This also can be used as a backup procedure in case of a heater failure. To facilitate sunlight heating the system elements can have radiation-absorptive coating(s).

High Stored Energy

The shape memory materials used for the support elements store considerable elastic energy at the time of packaging and can generate considerable forces during deployment to overcome potential adhesions, friction and snags.

Relaxed Requirements for Placement/Orientation on Satellite or Launch Vehicle.

Due to the compact size of the antenna system its location on a satellite is not as constrained as for the present deployable antennas. This simplifies the design of a satellite itself and/or its operations. In addition, the instant antenna system can be more easily located to minimize its effect on the location of the satellite's center of gravity, which will also simplify satellite operations.

