Patent Description:
Small satellites have limited space to store electronics and an antenna, which becomes technically challenging when the electronics and antenna are designed to operate at the lower L-band and S-band frequencies. High performance antenna operating at those frequencies usually require significant volume. Even antennas designed to operate at the higher frequencies up to <NUM>, or above, have size constraints that make them difficult to implement into small satellites, even though the antenna at those upper frequencies are typically reduced in size. This problem becomes challenging when small satellites are built as CubeSat platforms, which are miniaturized satellites made up of multiple block units known as CubeSats, each block unit being about <NUM> by <NUM> by <NUM> inches (<NUM> by <NUM> by <NUM>). CubeSats are advantageous for smaller satellites because they are designed to use commercial off-the-shelf (COTS) components for their major circuits and can be easily implemented for custom satellite operation.

In most practical small satellite applications, a number of CubeSat units are combined together to form a CubeSat platform as a small satellite that is typically intended for Low Earth Orbit (LEO) and perform scientific research and explore new space technologies. CubeSats are advantageous because their use as block units to build small satellites shortens the satellite development cycle, permits greater diversity in satellite design since each small satellite can be designed for a specific function, and reduces the overall cost of satellite deployment. CubeSats and even larger classes of small satellites often are suitable for launch with multiple small satellites per payload, thus using the excess capacity of larger launch vehicles and reducing the risk to the rest of the launch vehicle and other payloads.

Typical CubeSat satellite platforms are formed from multiple, individual CubeSat block units combined together and include a 6U design of about <NUM> x <NUM> x <NUM> inches (<NUM> x <NUM> x <NUM>) or a 12U design of about <NUM> x <NUM> x <NUM> inches (<NUM> x <NUM> x <NUM>). Additionally, the small satellite class also envelopes larger form factors, such as EELV Secondary Payload Adapter (ESPA) each forming a satellite in the <NUM> to about <NUM> class. Small satellites can be propelled by cold gas, chemical promotion, electric propulsion, or solar sails. Most CubeSats and similar small satellites have internal batteries for power, which preferably include solar cells.

Many Low Earth Orbit (LEO) small satellites require an antenna for communicating in the L-band and S-band, and also X-band and Ka-band can be used for higher data rate communications. These higher frequency bands allow the use of smaller antennae due to the higher frequencies, but the constraints of small satellites, such as CubeSats, still make it difficult to implement workable antennas, even at the higher frequencies. These small satellites have limited volume and designing an antenna that can be compactly stored and deployed once orbit is reached is a challenge.

For example, horn and sinuous antennas are often used on small satellites, but take up a relatively large volume, especially at the lower L-band and S-band frequencies. Wideband antennas and communication modems offer the valuable potential to communicate with various ground stations or even perhaps other satellites directly. A log periodic parasitic monopole antenna (LPPMA) operates as a high performance antenna and may be used for many satellite communication applications because of its wideband performance, multi-polarization, excellent directivity, and other features. A technical drawback of this antenna, however, is it takes up a large volume, making that type of antenna difficult to implement in small satellites. For example, a log periodic parasitic monopole antenna may have a wide <NUM>:<NUM> bandwidth and operate up to <NUM> and provide six arms for multi-polarization in both transmit and receive applications, making it useful for a variety of CubeSat and other Small Satellite applications. Those positive operating benefits, however, may make it difficult to implement that antenna onto small satellites since the antenna requires a relatively large volume compared to the size of the satellite. As a result, deployment of most antennas, including a log periodic parasitic monopole antenna, is difficult on small satellites.

Prior art can be found in <CIT> which generally relates to a stowable, deployable, retractable antenna and in <CIT> which generally relates to foldable dipole array antennas.

In general, an outer space deployable antenna includes a support shaft, a plurality of antenna fins, and an actuator. At least one draw cord is coupled between the plurality of antenna fins and the actuator so that the plurality of antenna fins are moveable from a flat stored configuration to a fanned-out deployed configuration surrounding the support shaft.

The plurality of antenna fins may be in spaced relation about the support shaft in the fanned-out deployed configuration. A respective fin support may be coupled to a radially inner edge of each antenna fin to maintain the plurality of antenna fins in spaced relation. An electrical conductive layer may be between adjacent antenna fins.

In some embodiments, one of the plurality of antenna fins may be fixed to the support shaft. The support shaft may have a passageway therethrough and the draw cord extends through the passageway. The actuator may comprise an electric motor. Each fin may comprise a rigid dielectric layer and a conductive layer thereon. Each fin may have a tapered shape.

In yet another embodiment, a satellite may include a satellite housing and a satellite transceiver carried by the satellite housing. An outer space deployable antenna may be carried by the satellite housing and coupled to the satellite transceiver. The outer space deployable antenna comprises a support shaft, a plurality of antenna fins, and an actuator. At least one draw cord is coupled between the plurality of antenna fins and the actuator so that the plurality of antenna fins are moveable from a flat stored configuration to a fanned-out deployed configuration surrounding the support shaft.

Another aspect is directed to a method for making an outer space deployable antenna. The method assembling a support shaft and a plurality of antenna fins adjacent the support shaft. The method includes coupling at least one draw cord between the plurality of antenna fins and an actuator so that the plurality of antenna fins are moveable from a flat stored configuration to a fanned-out deployed configuration surrounding the support shaft.

The present description is made with reference to the accompanying drawings, in which exemplary embodiments are shown. However, many different embodiments may be used, and thus, the description should not be construed as limited to the particular embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete. Like numbers refer to like elements throughout, and prime notation is used to indicate similar elements in different embodiments.

Referring initially to <FIG>, a satellite is illustrated generally at <NUM> and shown orbiting Earth (E) in a Low Earth Orbit (LEO) as typical for small satellites, although any orbit altitude may be established depending on satellite functions. The satellite <NUM> includes a satellite housing <NUM> shown partially cut away and a satellite transceiver <NUM> carried by the satellite housing <NUM> and solar panels <NUM>. The satellite <NUM> is a small form factor satellite, which could be formed by one or more CubeSats, but not limited to this implementation. The satellite transceiver <NUM> and any associated electronic components and circuits may be formed from Conventional Off-The-Shelf (OTS) components as is typical for those smaller satellites formed from CubeSats.

An outer space deployable antenna is indicated generally at <NUM> and carried by the satellite housing <NUM> and coupled to the satellite transceiver <NUM>. Basic components of the antenna <NUM> are shown in better detail in <FIG>. The antenna <NUM> includes a support shaft <NUM> and plurality of antenna fins <NUM>, and in this example, six antenna fins, and an actuator <NUM>. As explained in greater detail relative to <FIG> and shown in the fragmentary, perspective view of <FIG>, at least one draw cord <NUM> is coupled between the plurality of antenna fins <NUM> and the actuator <NUM> so that the plurality of antenna fins are movable from a flat stored configuration, such as shown in <FIG>, to the fanned-out deployed configuration surrounding the support shaft <NUM> as shown in <FIG> and <FIG>. Although the antenna <NUM> may be configured and sized to operate at different radio frequencies and wavelengths depending on end-use application, in this example, the antenna is formed as a log periodic parasitic monopole antenna, and operative in a wideband frequency of about <NUM>:<NUM> bandwidth and operative at about UHF frequencies as low as <NUM> up to and above frequencies as high as <NUM>. The six antenna fins <NUM> in this example operating as antenna arms may provide multi-polarization for transmit and receive functions via the satellite transceiver <NUM> carried by the satellite housing <NUM>.

Each antenna fin <NUM> cooperates with the other antenna fins and each may include antenna elements <NUM> (<FIG>) connected in parallel to an antenna feed element <NUM>, usually with an alternating phase, and in an example may simulate a series of multiple element YAGI antennas connected together, each tuned to a different frequency. The different antenna elements <NUM> for each antenna fin <NUM> operate together and may increase the frequency response or bandwidth. Each antenna fin <NUM> may include a support structure <NUM> (<FIG>), such as formed from thin diameter and lightweight plastic or metal tubes or other support members that can add support and rigidity to each antenna fin. In <FIG>, a portion of the first antenna fin <NUM> is partially exposed to show a support structure <NUM> that may be incorporated into each antenna fin <NUM>. As explained in greater detail below, it is possible to incorporate a rigid dielectric layer into each antenna fin <NUM> such that a support structure <NUM> is not necessary.

The plurality of antenna fins <NUM> are positioned in spaced relation about the support shaft <NUM> when the plurality of antenna fins are moved from the flat stored configuration shown in <FIG>, into the fanned-out deployed configuration surrounding the support shaft (<FIG>). In this fanned-out deployed configuration of the antenna <NUM>, each antenna fin <NUM> is spaced equidistantly from each other at the same angle. In this example, the six antenna fins <NUM> are spaced <NUM>° apart from an adjacent antenna fin surrounding the support shaft <NUM>. Each antenna fin <NUM> in this example has a tapered shape, such that the antenna <NUM> is formed overall in a conical shape similar to a "Christmas tree" configuration.

As best shown with reference to the top plan view of the antenna <NUM> in <FIG>, an electrically conductive layer <NUM> is positioned between adjacent antenna fins <NUM> for the antenna function, and operates as a ground plane and is shown stretched between the antenna fins. In an example, this electrical conductive layer <NUM> may be formed as a thin web film or mesh material, and in an example, is a gossamer material formed of a very thin mesh and operates as the ground plane. In an example, the electrical conductive layer <NUM> may be formed from a polymer material of <NUM> or <NUM> mil (<NUM> or <NUM>) thickness or other thin film laminate material. In another example, the electrical conductive layer may be formed from Mylar that is folded up when the antenna <NUM> is in the flat stored configuration as in <FIG>, and then stretched out when the antenna is moved into its fanned-out deployed configuration surrounding the support shaft <NUM>. Mylar as metallized BoPET (Biaxially-Oriented Polyethylene Terephthalate) has been found advantageous to use since it has high tensile strength, chemical and dimensional stability, good barrier resistance and insulator properties, and excellent reflectivity. In an example, one electrical signal feed coaxial cable may attach to one end or the other of each antenna fin <NUM>, which is used to connect this antenna <NUM> to other electronics for transmit or receive operation.

Each antenna fin <NUM> may include a rigid dielectric layer as a substrate <NUM> and a conductive layer <NUM> thereon (<FIG> and <FIG>). It is possible for the conductive layer <NUM> to operate as an active antenna element and include another layer opposite the conductive layer to operate as a parasitic element. The antenna fin <NUM> could include a Mylar layer or other thin material layer that may be supported by the support structure <NUM> if it is used. It is possible for the rigid dielectric layer <NUM> to provide support as a substrate without use of a separate support structure <NUM> when it is made rigid and thick to act as a support.

In an example best shown in <FIG>, a respective fin support <NUM> is coupled to a radially inner edge of each antenna fin <NUM> to maintain the plurality of antenna fins, in this example, the six antenna fins, in spaced relation to each other. Each fin support <NUM> may include a beveled edge <NUM> at the end proximate to the support shaft <NUM> so that in the deployed condition, the beveled edges <NUM> meet and position each antenna fin <NUM> sixty degrees apart. One of the plurality of antenna fin supports <NUM> is fixed to the support shaft (<FIG> and <FIG>) to operate as a stable antenna fin when the actuator <NUM>, formed as an electric motor in this example, pulls the one or more draw cords <NUM> and moves the antenna fins <NUM> into their fanned-out deployed condition. In the example of <FIG>, the antenna fin <NUM> marked number <NUM> is fixed.

Referring now to the schematic sequence diagrams of <FIG>, there is illustrated how the antenna <NUM> may be moved from its flat stored configuration in <FIG> to its fanned-out deployed configuration surrounding the support shaft <NUM> in <FIG>. For example, when the satellite <NUM> carrying the antenna <NUM> reaches Low Earth Orbit or other desired orbit where it will become operational, a support rod <NUM> connected to an antenna mounting plate (<FIG>) may be pivoted <NUM>° by a spring or drive mechanism, and thus, extend the flat and stored antenna fins <NUM> from their flat stored configuration shown schematically in <FIG> into their vertical position shown in <FIG>. At that time, the actuator <NUM> that is coupled to the at least one draw cord <NUM> will actuate and pull the draw cord so that the antenna fins <NUM> move from the stored configuration where they are stacked to each other to their fanned-out deployed configuration surrounding the support shaft <NUM> (<FIG> and <FIG>). Although use of a draw cord <NUM> and associated actuator is one mechanism for moving the antenna fins <NUM> into their fanned-out deployed configuration, other mechanisms may be used such as spring actuated mechanisms or similar biasing mechanisms or a system of gears to deploy the fins similar to a draw cord.

Referring now to <FIG>, there is illustrated an example of a mechanism using at least one draw cord <NUM> to move the antenna fins <NUM> into their fanned-out deployed configuration. At least one draw cord <NUM> is coupled between the plurality of antenna fins <NUM> and the actuator <NUM> to move the plurality of antenna fins from their flat stored configuration into a fanned-out deployed configuration surrounding the support shaft <NUM>. In one example, the antenna fins <NUM> are coupled to the respective fin support <NUM> via the radially inner edge of each antenna fin and five of the antenna fins are stacked together in a free-floating manner, while one of the antenna fins, in this example, antenna fin number <NUM> in <FIG>, is fixed to the support shaft <NUM> via its fin support. In an example, this fixed fin support <NUM> may be formed integral with the support shaft <NUM>. Each antenna fin support <NUM> may be formed as an elongate lightweight metal or plastic rectangular configured support member that could be used as a rigid support for each antenna fin <NUM>, thus making the separate support structure <NUM> unnecessary in some cases. In this example, the support shaft <NUM> is formed as a hollow rod, for example, formed from a rigid plastic or lightweight metal material. Each respective fin support <NUM> includes the beveled edge <NUM> such that when the actuator <NUM> pulls the draw cord <NUM>, the five free-floating antenna fins <NUM> are moved around the support shaft <NUM> from the flat stowed position such that the beveled edges of adjacent support fins <NUM> are in contact with each other and each antenna fin <NUM> is spaced <NUM>° apart as best shown in <FIG>.

In an example best illustrated in <FIG> and <FIG>, the draw cord <NUM> may pass through each respective fin support <NUM> via a transverse hole <NUM> in each of the floating antenna fin supports <NUM> and routed down the hollow interior support shaft <NUM> and secured to a collar <NUM> contained in an actuator housing <NUM> as shown in <FIG> at the base of the support shaft <NUM>. The collar <NUM> includes an internally threaded orifice <NUM> that receives a threaded output shaft <NUM> from the actuator <NUM>, which is an electric motor in this example, and the collar is displaced axially upon electric motor actuation. As the actuator <NUM>, e.g., the electric motor, slowly rotates its threaded output shaft <NUM>, the internally threaded collar <NUM> is displaced axially and moved toward the actuator <NUM>. The draw cord <NUM> is secured to this internally threaded collar <NUM>, which may accommodate multiple draw cords, with individual draw cords extending through the five floating antenna assemblies and into the interior of the support shaft <NUM> back to the collar <NUM>.

Internal pins <NUM> on the collar <NUM> are received in a slot <NUM> and used to constrain rotation of the collar <NUM> in the actuator housing <NUM>, and as a result, motion of the collar is confined in the axial direction when the actuator <NUM> as the electric motor is actuated. The draw cord <NUM> in the example of <FIG> and <FIG> passes through the transverse holes <NUM> in each respective fin support <NUM> and is illustrated with both ends of the draw cord <NUM> entering the support shaft <NUM> and will attach to the internally threaded collar <NUM> so that when the collar <NUM> is displaced toward the actuator <NUM> as the electric motor and its output shaft <NUM> rotates, the antenna fins <NUM> are moved from the flat stored configuration to their fanned-out deployed configuration surrounding the support shaft <NUM>. It is possible to have one end of a draw cord <NUM> connected to that antenna fin <NUM> fixed to the support shaft <NUM> and the other end of the draw cord fixed to the internally threaded collar <NUM>. The draw cord may pass through holes (not shown) in each antenna fin <NUM> so that when the collar <NUM> is moved axially toward the actuator <NUM> as the electric motor, the antenna fins are moved into their fanned-out deployed configuration surrounding the support shaft.

In the example shown in <FIG>, the electrical conductive layer <NUM> between adjacent antenna fins <NUM> is formed as a gossamer or mesh grounding material and affixed to the respective fin supports <NUM> at their edge forming the bevel <NUM> and packs between the antenna fins <NUM> when the antenna <NUM> is in its flat stored configuration. When the antenna <NUM> is deployed, this electrical conductor layer <NUM> stretches to fill the triangular gap or pyramid face when the antenna is deployed in its fanned-out deployed configuration as best shown in <FIG> and <FIG>. It is possible that this electrical conductive layer <NUM> forming the ground plane between the first and sixth antenna fins as shown in <FIG> can be stretched via a spring-deployed gossamer material since tension is not provided between these two positions in this particular example.

In the example such as shown in <FIG>, the antenna <NUM> is about <NUM> centimeters (<NUM> inches) thick shown by the dimension "X" in the flat stored configuration and each antenna fin <NUM> may be about <NUM> inches long extending from its tip to the end of respective fin support <NUM> near the bevel <NUM>. The antenna fins <NUM> are shown cut in <FIG> and shortened for purposes of illustration. These dimensions are only representative of a specific log periodic parasitic monopole antenna operative as a deployable broadband antenna and operating in a range from the low UHF up to about <NUM> and above. The respective size of the antenna fins <NUM> and other components can vary depending on specific frequency and bandwidth ranges desired for operation of the antenna.

The antenna <NUM> as described provides a competitive advantage in the small satellite market, such as satellites manufactured from one or more CubeSat block units. This antenna <NUM> provides wideband communications and may be less expensive to launch. It may be stowed in a small satellite package. This antenna <NUM> may be used for remote sensing such as for Hawkeye <NUM> implementations and wireless applications in voice, machine-to-machine and special communications. By exploring a specific design as a log periodic parasitic monopole antenna, the antenna <NUM> may be used with an offset perimeter truss antenna for a wide range of applications from <NUM> to <NUM>. One reason for this advantage is its larger surface area and it can be used at higher frequencies.

It is also possible to use wire frame assemblies and inflatable membranes to move components or pivot the flat stored antenna vertically from its position shown in <FIG> to its vertical position in <FIG>.

Different manufacturing techniques may be used and in an example shown in the high-level flowchart of <FIG>, a method for making the outer space deployable antenna <NUM> is illustrated generally at <NUM>. The process starts (Block <NUM>) and a support shaft <NUM> and plurality of antenna fins <NUM> are assembled together (Block <NUM>) adjacent the support shaft. The at least one draw cord <NUM> is coupled between the plurality of antenna fins <NUM> and actuator <NUM> (Block <NUM>). The draw cord <NUM> is then tied down to the respective endpoints, which could be both ends tied and connected to the collar <NUM> that displaces axially upon electric motor activation (Block <NUM>). The process ends at Block <NUM>.

Claim 1:
An outer space deployable antenna (<NUM>) comprising:
a support shaft (<NUM>);
a plurality of antenna fins (<NUM>);
an actuator (<NUM>); and
at least one draw cord (<NUM>) coupled between the plurality of antenna fins (<NUM>) and the actuator (<NUM>) so that the plurality of antenna fins (<NUM>) are moveable from a flat stored configuration to a fanned-out deployed configuration surrounding the support shaft (<NUM>).